Materials

12 pages, 3789 KiB

Open AccessArticle

Functionalization of Cellulose Nanocrystals in Choline Lactate Ionic Liquid

by Sarah Montes^1,*

, Itxaso Azcune¹, Germán Cabañero¹, Hans-Jürgen Grande¹, Ibon Odriozola¹ and Jalel Labidi²

¹ Materials Division, IK4-CIDETEC Research Centre, Paseo de Miramón 196, 20009 San Sebastián, Spain

² Chemical and Environmental Engineering Department, University of the Basque Country, Plaza Europa 1, 20018 San Sebastian, Spain

Materials 2016, 9(7), 499; https://doi.org/10.3390/ma9070499 - 23 Jun 2016

Cited by 18 | Viewed by 6855

Abstract

Cellulose nanocrystals (CNCs) are valuable nanomaterials obtained from renewable resources. Their properties make them suitable for a wide range of applications, including polymer reinforcement. However, due to their highly hydrophilic character, it is necessary to modify their surface with non-polar functional groups before [...] Read more.

Cellulose nanocrystals (CNCs) are valuable nanomaterials obtained from renewable resources. Their properties make them suitable for a wide range of applications, including polymer reinforcement. However, due to their highly hydrophilic character, it is necessary to modify their surface with non-polar functional groups before their incorporation into a hydrophobic polymer matrix. In this work, cellulose nanocrystals were modified using a silane coupling agent and choline lactate, an ionic liquid derived from renewable resources, as a reaction medium. Modified cellulose nanocrystals were characterized by infrared spectroscopy, showing new peaks associated to the modification performed. X-ray diffraction was used to analyze the crystalline structure of functionalized cellulose nanocrystals and to optimize the amount of silane for functionalization. Poly(lactic acid) (PLA) nanocomposites containing 1 wt % of functionalized cellulose nanocrystals were prepared. They were characterized by field-emission scanning electron microscopy (FE-SEM) and mechanical tests. The use of choline lactate as reaction media has been shown to be an alternative method for the dispersion and silanization of the cellulose nanocrystals without the addition of an external catalyst. Full article

(This article belongs to the Special Issue Advances in Functionalization of Lignocellulosic Materials)

▼ Show Figures

Figure 1

8 pages, 4905 KiB

Open AccessArticle

A Stress-Induced Martensitic Transformation in Aged Ti₄₉Ni₅₁ Alloy after High-Velocity Impact

by Yingying Zhu, Haizhen Wang, Zhiyong Gao^* and Wei Cai

Science and Technology on Materials Performance Evaluation in Space Environment Laboratory, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China

Materials 2016, 9(7), 500; https://doi.org/10.3390/ma9070500 - 23 Jun 2016

Cited by 1 | Viewed by 4998

Abstract

The effects of a high-velocity impact on the microstructure, phase transformation and mechanical property of aged Ti₄₉Ni₅₁ alloy are investigated. The transformation behavior and microstructure along the impact direction after impact emerge with regionalization characteristics, including a deformed region near [...] Read more.

The effects of a high-velocity impact on the microstructure, phase transformation and mechanical property of aged Ti₄₉Ni₅₁ alloy are investigated. The transformation behavior and microstructure along the impact direction after impact emerge with regionalization characteristics, including a deformed region near the crater (0–4 mm) and an un-deformed region of the distal crater (5–6 mm). Stress-induced martensite is the main deformation mechanism in the deforming region of aged Ti₄₉Ni₅₁ alloy under high-velocity impact. Full article

(This article belongs to the Special Issue Computational Multiscale Modeling and Simulation in Materials Science)

▼ Show Figures

Figure 1

8 pages, 1820 KiB

Open AccessArticle

Silk Fiber as the Support and Reductant for the Facile Synthesis of Ag–Fe₃O₄ Nanocomposites and Its Antibacterial Properties

by Xiaonan Liu^1,2, Guangfu Yin^1,*, Zao Yi² and Tao Duan²

¹ College of Materials Science and Engineering, Sichuan University, Chengdu 610064, China

² Joint Laboratory for Extreme Conditions Matter Properties, Southwest University of Science and Technology, Mianyang 621010, China

Materials 2016, 9(7), 501; https://doi.org/10.3390/ma9070501 - 23 Jun 2016

Cited by 12 | Viewed by 5620

Abstract

We report a facile and environmentally friendly approach to prepare Ag–Fe₃O₄–silk fiber nanocomposites. The Ag–Fe₃O₄–silk fiber acts as: (i) a biocompatible support for the silver nanoparticles; and (ii) a reducing agent for the silver ions. [...] Read more.

We report a facile and environmentally friendly approach to prepare Ag–Fe₃O₄–silk fiber nanocomposites. The Ag–Fe₃O₄–silk fiber acts as: (i) a biocompatible support for the silver nanoparticles; and (ii) a reducing agent for the silver ions. Neither additional reducing agents nor toxic organic solvents were used during the preparation process. The Ag–Fe₃O₄–silk fiber nanocomposites can be actuated by a small household magnet and have high antibacterial activities against both Escherichia coli and Staphylococcus aureus. These nanocomposites could be easily recycled without a decrease in their antibacterial activities due to the synergistic effects between the Ag NPs and Fe₃O₄ NPs with large amounts of active sites. Full article

(This article belongs to the Section Advanced Composites)

▼ Show Figures

Figure 1

8 pages, 1089 KiB

Open AccessReview

Coating Methods for Surface Modification of Ammonium Nitrate: A Mini-Review

by Baha I. Elzaki^1,2 and Yue Jun Zhang^1,*

¹ School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu, China

² Department of Chemical Engineering, College of Engineering, Karary University, Omdurman 12304, Sudan

Materials 2016, 9(7), 502; https://doi.org/10.3390/ma9070502 - 23 Jun 2016

Cited by 32 | Viewed by 8083

Abstract

Using ammonium nitrate (AN) as a propellant oxidizer is limited due to its hygroscopicity. This review consolidated the available information of various issues pertaining to the coating methods of the surface modification of ammonium nitrate for reducing its hygroscopicity. Moreover this review summarizes [...] Read more.

Using ammonium nitrate (AN) as a propellant oxidizer is limited due to its hygroscopicity. This review consolidated the available information of various issues pertaining to the coating methods of the surface modification of ammonium nitrate for reducing its hygroscopicity. Moreover this review summarizes the recent advances and issues involved in ammonium nitrate surface modification by physical, chemical and encapsulation coating methods to reduce the hygroscopicity. Furthermore, coating materials, process conditions, and the hygroscopicity test conditions are extensively discussed along, with summaries of the advantages and disadvantages of each coating method. Our findings indicated that the investigation and development of anti-hygroscopicity of AN, and the mechanisms of surface modification by coating urgently require further research in order to further reduce the hygroscopicity. Therefore, this review is useful to researchers concerned with the improvement of ammonium salts’ anti-hygroscopicity. Full article

(This article belongs to the Special Issue Thin-Film Deposition, Characterization and Advanced Surface Engineering)

▼ Show Figures

Figure 1

23 pages, 27636 KiB

Open AccessArticle

Wood Sawdust/Natural Rubber Ecocomposites Cross-Linked by Electron Beam Irradiation

by Elena Manaila¹, Maria Daniela Stelescu², Gabriela Craciun^1,* and Daniel Ighigeanu¹

¹ National Institute for Laser, Plasma and Radiation Physics, Electron Accelerators Laboratory, 409 Atomistilor St., Magurele 077125, Romania

² National R&D Institute for Textile and Leather—Leather and Footwear Research Institute, 93 Ion Minulescu St., Bucharest 031215, Romania

Materials 2016, 9(7), 503; https://doi.org/10.3390/ma9070503 - 23 Jun 2016

Cited by 44 | Viewed by 9306

Abstract

The obtaining and characterization of some polymeric eco-composites based on wood sawdust and natural rubber is presented. The natural rubber was cross-linked using the electron beam irradiation. The irradiation doses were of 75, 150, 300 and 600 kGy and the concentrations of wood [...] Read more.

The obtaining and characterization of some polymeric eco-composites based on wood sawdust and natural rubber is presented. The natural rubber was cross-linked using the electron beam irradiation. The irradiation doses were of 75, 150, 300 and 600 kGy and the concentrations of wood sawdust were of 10 and 20 phr, respectively. As a result of wood sawdust adding, the physical and mechanical properties such as hardness, modulus at 100% elongation and tensile strength, showed significant improvements. The presence of wood sawdust fibers has a reinforcing effect on natural rubber, similar or better than of mineral fillers. An increase in the irradiation dose leads to the increasing of cross-link density, which is reflected in the improvement of hardness, modulus at 100% elongation and tensile strength of blends. The cross-linking rates, appreciated using the Flory-Rehner equation, have increased with the amount of wood sawdust in blends and with the irradiation dose. Even if the gel fraction values have varied irregularly with the amount of wood sawdust and irradiation dose it was over 90% for all blends, except for the samples without wood sawdust irradiated with 75 kGy. The water uptake increased with increasing of fiber content and decreased with the irradiation dose. Full article

(This article belongs to the Special Issue Advances in Research on Elastomers)

▼ Show Figures

Graphical abstract

8 pages, 7357 KiB

Open AccessArticle

Incorporation of Rutin in Electrospun Pullulan/PVA Nanofibers for Novel UV-Resistant Properties

by Yongfang Qian^1,2, Mengjie Qi¹, Laijiu Zheng¹, Martin W. King², Lihua Lv¹ and Fang Ye^1,*

¹ School of Textile and Material Engineering, Dalian Polytechnic University, Dalian 116034, China

² College of Textiles, North Carolina State University, Raleigh, NC 27695, USA

Materials 2016, 9(7), 504; https://doi.org/10.3390/ma9070504 - 23 Jun 2016

Cited by 38 | Viewed by 7085

Abstract

This study aimed to investigate the incorporation of rutin into electrospun pullulan and poly(vinyl alcohol) (PVA) nanofibers to obtain ultraviolet (UV)-resistant properties. The effect of weight ratios between pullulan and PVA, and the addition of rutin on the nanofibers’ morphology and diameters were [...] Read more.

This study aimed to investigate the incorporation of rutin into electrospun pullulan and poly(vinyl alcohol) (PVA) nanofibers to obtain ultraviolet (UV)-resistant properties. The effect of weight ratios between pullulan and PVA, and the addition of rutin on the nanofibers’ morphology and diameters were studied and characterized by scanning electron microscopy (SEM). Fourier transform infrared (FTIR) analysis was utilized to investigate the interaction between pullulan and PVA, as well as with rutin. The results showed that the inclusion of PVA results in the increase in the fiber’s diameter. The addition of rutin had no obvious effect on the fibers’ average diameters when the content of rutin was less than 7.41%. FTIR results indicated that a hydrogen bond formed between pullulan and PVA, also between these polymers and rutin. Moreover, the addition of rutin could enhance the mechanical properties due to its stiff structure and could decrease the transmittance of UVA and UVB to be fewer than 5%; meanwhile, the value of ultraviolet protection factor (UPF) reached more than 40 and 50 when the content of rutin was 4.46% and 5.67%, respectively. Therefore, the electrospun pullulan/PVA/rutin nanofibrous mats showed excellent UV resistance and have potential applications in anti-ultraviolet packaging and dressing materials. Full article

▼ Show Figures

Graphical abstract

13 pages, 10246 KiB

Open AccessArticle

Characterization of Aluminum-Based-Surface Matrix Composites with Iron and Iron Oxide Fabricated by Friction Stir Processing

by Essam R. I. Mahmoud^1,2 and Mahmoud M. Tash^3,4,*

¹ Mechanical Engineering, King Khalid University, Abha 61413, Saudi Arabia

² Welding and NDT Laboratory, Manufacturing Technology Department, Central Metallurgical Research and Development Institute (CMRDI), Cairo 11421, Egypt

³ Industrial Engineering Program, Department of Mechanical Engineering, University of Prince Sattam bin Abdulaziz, AlKharj 11942, Saudi Arabia

⁴ On Leave from the Mining, Petroleum and Metallurgical Engineering Department, Cairo University, Giza 12613, Egypt

Materials 2016, 9(7), 505; https://doi.org/10.3390/ma9070505 - 23 Jun 2016

Cited by 18 | Viewed by 5126

Abstract

Surface composite layers were successfully fabricated on an A 1050-H24 aluminum plate by dispersed iron (Fe) and magnetite (Fe₃O₄) particles through friction stir processing (FSP). Fe and Fe₃O₄ powders were packed into a groove of 3 [...] Read more.

Surface composite layers were successfully fabricated on an A 1050-H24 aluminum plate by dispersed iron (Fe) and magnetite (Fe₃O₄) particles through friction stir processing (FSP). Fe and Fe₃O₄ powders were packed into a groove of 3 mm in width and 1.5 mm in depth, cut on the aluminum plate, and covered with an aluminum sheet that was 2-mm thick. A friction stir processing (FSP) tool of square probe shape, rotated at a rate of 1000–2000 rpm, was plunged into the plate through the cover sheet and the groove, and moved along the groove at a travelling speed of 1.66 mm/s. Double and triple passes were applied. As a result, it is found that the Fe particles were homogenously distributed in the whole nugget zone at a rotation speed of 1000 rpm after triple FSP passes. Limited interfacial reactions occurred between the Fe particles and the aluminum matrix. On the other hand, the lower rotation speed (1000 rpm) was not enough to form a sound nugget when the dispersed particles were changed to the larger Fe₃O₄. The Fe₃O₄ particles were dispersed homogenously in a sound nugget zone when the rotation speed was increased to 1500 rpm. No reaction products could be detected between the Fe₃O₄ particles and the aluminum matrix. The saturation magnetization (Ms) of the Fe-dispersed nugget zone was higher than that of the Fe₃O₄-dispersed nugget zone. Moreover, there were good agreement between the obtained saturation magnetization values relative to that of pure Fe and Fe₃O₄ materials and the volume content of the dispersed particles in the nugget zone. Full article

(This article belongs to the Special Issue Materials' 2016 (Montreal, Canada: June 20 - 24, 2016) - Advances and Trends in Engineering Materials and their Applications)

▼ Show Figures

Figure 1

14 pages, 3478 KiB

Open AccessArticle

Microwave Crystallization of Lithium Aluminum Germanium Phosphate Solid-State Electrolyte

by Morsi M. Mahmoud^1,2,*

, Yuantao Cui¹, Magnus Rohde¹, Carlos Ziebert¹

, Guido Link³ and Hans Juergen Seifert¹

¹ Institute for Applied Materials—Applied Materials Physics (IAM-AWP), Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen 76344, Germany

² Department of Fabrication Technology, Advanced Technology and New Materials Research Institute (ATNMRI), City of Scientific Research and Technological Application (SRTA), New Borg Al-Arab City, Alexandria 21934, Egypt

³ Institute for Pulsed Power and Microwave Technology (IHM), Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen 76344, Germany

Materials 2016, 9(7), 506; https://doi.org/10.3390/ma9070506 - 23 Jun 2016

Cited by 21 | Viewed by 8105

Abstract

Lithium aluminum germanium phosphate (LAGP) glass-ceramics are considered as promising solid-state electrolytes for Li-ion batteries. LAGP glass was prepared via the regular conventional melt-quenching method. Thermal, chemical analyses and X-ray diffraction (XRD) were performed to characterize the prepared glass. The crystallization of the [...] Read more.

Lithium aluminum germanium phosphate (LAGP) glass-ceramics are considered as promising solid-state electrolytes for Li-ion batteries. LAGP glass was prepared via the regular conventional melt-quenching method. Thermal, chemical analyses and X-ray diffraction (XRD) were performed to characterize the prepared glass. The crystallization of the prepared LAGP glass was done using conventional heating and high frequency microwave (MW) processing. Thirty GHz microwave (MW) processing setup were used to convert the prepared LAGP glass into glass-ceramics and compared with the conventionally crystallized LAGP glass-ceramics that were heat-treated in an electric conventional furnace. The ionic conductivities of the LAGP samples obtained from the two different routes were measured using impedance spectroscopy. These samples were also characterized using XRD and scanning electron microscopy (SEM). Microwave processing was successfully used to crystallize LAGP glass into glass-ceramic without the aid of susceptors. The MW treated sample showed higher total, grains and grain boundary ionic conductivities values, lower activation energy and relatively larger-grained microstructure with less porosity compared to the corresponding conventionally treated sample at the same optimized heat-treatment conditions. The enhanced total, grains and grain boundary ionic conductivities values along with the reduced activation energy that were observed in the MW treated sample was considered as an experimental evidence for the existence of the microwave effect in LAGP crystallization process. MW processing is a promising candidate technology for the production of solid-state electrolytes for Li-ion battery. Full article

(This article belongs to the Special Issue Microwave Materials Processing)

▼ Show Figures

Graphical abstract

12 pages, 3456 KiB

Open AccessArticle

The Effect of High Concentration and Small Size of Nanodiamonds on the Strength of Interface and Fracture Properties in Epoxy Nanocomposite

by Yasir A. Haleem¹, Pin Song², Daobin Liu¹, Changda Wang¹, Wei Gan¹, Muhammad Farooq Saleem¹

and Li Song^1,*

¹ National Synchrotron Radiation Laboratory, CAS Center for Excellence in Nanoscience, University of Science and Technology of China, Hefei 230029, Anhui, China

² School of Chemistry and Chemical Engineering, Hefei University of Technology, Hefei 230029, Anhui, China

Materials 2016, 9(7), 507; https://doi.org/10.3390/ma9070507 - 23 Jun 2016

Cited by 14 | Viewed by 4986

Abstract

The concentration and small size of nanodiamonds (NDs) plays a crucial role in the mechanical performance of epoxy-based nanocomposites by modifying the interface strength. Herein, we systemically analyzed the relation between the high concentration and small size of ND and the fracture properties [...] Read more.

The concentration and small size of nanodiamonds (NDs) plays a crucial role in the mechanical performance of epoxy-based nanocomposites by modifying the interface strength. Herein, we systemically analyzed the relation between the high concentration and small size of ND and the fracture properties of its epoxy-based nanocomposites. It was observed that there is a two-fold increase in fracture toughness and a three-fold increase in fracture energy. Rationally, functionalized-NDs (F-NDs) showed a much better performance for the nanocomposite than pristine NDs (P-NDs) because of additional functional groups on its surface. The F-ND/epoxy nanocomposites exhibited rougher surface in contrast with the P-ND/epoxy, indicating the presence of a strong interface. We found that the interfaces in F-ND/epoxy nanocomposites at high concentrations of NDs overlap by making a web, which can efficiently hinder further crack propagation. In addition, the de-bonding in P-ND/epoxy nanocomposites occurred at the interface with the appearance of plastic voids or semi-naked particles, whereas the de-bonding for F-ND/epoxy nanocomposites happened within the epoxy molecular network instead of the interface. Because of the strong interface in F-ND/epoxy nanocomposites, at high concentrations the de-bonding within the epoxy molecular network may lead to subsequent cracks, parallel to the parent crack, via crack splitting which results in a fiber-like structure on the fracture surface. The plastic void growth, crack deflection and subsequent crack growth were correlated to higher values of fracture toughness and fracture energy in F-ND/epoxy nanocomposites. Full article

(This article belongs to the Special Issue The Properties and Applications of Nanodiamonds)

▼ Show Figures

Figure 1

38 pages, 24047 KiB

Open AccessFeature PaperArticle

Calibration Methods of Acoustic Emission Sensors

by Kanji Ono

Department of Materials Science and Engineering, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA

Materials 2016, 9(7), 508; https://doi.org/10.3390/ma9070508 - 24 Jun 2016

Cited by 56 | Viewed by 10884 | Correction

Abstract

This study examined outstanding issues of sensitivity calibration methods for ultrasonic and acoustic emission transducers and provides workable solutions based on physically measureable quantities, laser-based displacement measurement in particular. This leads to mutually consistent determination of transmitting and receiving sensitivities of sensors and [...] Read more.

This study examined outstanding issues of sensitivity calibration methods for ultrasonic and acoustic emission transducers and provides workable solutions based on physically measureable quantities, laser-based displacement measurement in particular. This leads to mutually consistent determination of transmitting and receiving sensitivities of sensors and transducers. Methods of circumventing problems of extraneous vibrations on free transmitters are used, giving the foundation for face-to-face calibration methods. Working on many ultrasonic and acoustic emission transducers, their receiving and transmitting sensitivities are found to be always different, while their ratios exhibit unexpected similarity. This behavior is attributed to monopolar pulse generation and bipolar received signals due to electrical charge transfer during elastic wave motion and reflection on the back face. This is verified through a quantitative piezoelectric sensing experiment. Displacement vs. velocity calibration terminology is clarified, redefining the “V/µbar” reference for contact sensor calibration. With demonstrated differences in the transmitting and receiving sensitivities of transducers, the requirement of the Hill-Adams equation invalidates the basic premise of the currently formulated reciprocity calibration methods for acoustic emission transducers. In addition, the measured reciprocity parameter for the case of through-transmission significantly deviates from the approximate theoretical prediction. It is demonstrated that three methods provide reliable sensor calibration results that are complimentary among them. Full article

(This article belongs to the Special Issue Acoustic Waves in Advanced Materials)

▼ Show Figures

Figure 1

12 pages, 3973 KiB

Open AccessArticle

Pulsed Laser Porosification of Silicon Thin Films

by Christian Sämann^*

, Jürgen R. Köhler, Morris Dahlinger, Markus B. Schubert and Jürgen H. Werner

Institute for Photovoltaics and Research Center SCoPE, University of Stuttgart, Pfaffenwaldring 47, 70569 Stuttgart, Germany

Materials 2016, 9(7), 509; https://doi.org/10.3390/ma9070509 - 24 Jun 2016

Cited by 8 | Viewed by 6722

Abstract

We present a new and simple laser-based process to porosify thin film silicon using a pulsed laser. During deposition, we incorporate gas atoms or molecules into the Si thin film. Pulsed laser radiation of wavelength

λ = 532 nm

heats up thin film [...] Read more.

We present a new and simple laser-based process to porosify thin film silicon using a pulsed laser. During deposition, we incorporate gas atoms or molecules into the Si thin film. Pulsed laser radiation of wavelength

λ = 532 nm

heats up thin film Si beyond its melting point. Upon heating, gas atoms or molecules form nm-sized thermally expanding gas bubbles in the silicon melt, until they explosively exit the film, leaving pores behind. Rapid heating and fast cooling during pulsed laser processing enable re-solidification of the liquid Si before the created pores contract and pore closure occurs within the liquid phase. Optimized plasma-enhanced chemical vapor deposition or sputtering of amorphous Si thin films on stainless steel substrate incorporates the necessary concentration of gas atoms or molecules. We are able to tailor the pore size between 50 and 550 nm by changing laser pulse energy density and film deposition parameters. Evaporated silicon containing no gas atoms forms only a few very large

μ

m-sized gas bubbles due to laser-induced vapor formation of evaporated solid material at the substrate–silicon interface. Full article

(This article belongs to the Section Porous Materials)

▼ Show Figures

Figure 1

24 pages, 5508 KiB

Open AccessArticle

Experimental and Finite Element Investigations of Damage Resistance in Biomimetic Composite Sandwich T-Joints

by Ali A. Saeid¹ and Steven L. Donaldson^2,*

¹ Department of Mechanical and Aerospace Engineering, University of Dayton, 300 College Park, Dayton, OH 45469-0243, USA

² Department of Civil and Environmental Engineering and Engineering Mechanics, University of Dayton, 300 College Park, Dayton, OH 45469-0243, USA

Materials 2016, 9(7), 510; https://doi.org/10.3390/ma9070510 - 24 Jun 2016

Cited by 11 | Viewed by 7717

Abstract

Composite sandwich structural joints, such as T-joints, are used in many different composite applications to transfers the load orthogonally between two sandwich elements. However, these joints connecting the sections can represent the weakest link in sandwich composite structures due to the lack of [...] Read more.

Composite sandwich structural joints, such as T-joints, are used in many different composite applications to transfers the load orthogonally between two sandwich elements. However, these joints connecting the sections can represent the weakest link in sandwich composite structures due to the lack of reinforcement in the out-of-plane direction. Therefore, this paper presents a new methodology for the design and analysis of composite sandwich T-joints using new biomimetic fabrication methods. The fabricated idea comes from biological fixed joints as an evolutionary alteration processes of trunk-branches of trees. It offers unique attributes to optimize the continuous fiber paths for minimum stress concentrations and multi-sandwich layers to increase the bending stiffness and strength. The focus is on how the biomimetic technique can improve sandwich T-joint structures by increasing their strength and load carrying capability without adding a significant weight penalty. The major attention is to investigate the comprehensive failure modes in the joint numerically and verified by experiments. Investigations were conducted on three different designs of biomimetic composite sandwich T-joints under tension and bending loads. The results show significant improvements to the ultimate load up to 68% in the case of bending load and 40% in the case of pull-off load in the biomimetic sandwich T-joints compared to the reference conventional T-joint design. The final failure was significantly deferred in both load status. The FE models provided important insights into the core failure and delamination of multi-interface biomimetic T-joints. Full article

(This article belongs to the Special Issue Bioinspired and Biomimetic Materials)

▼ Show Figures

Figure 1

6 pages, 927 KiB

Open AccessArticle

Tunable Emission Wavelength Stacked InAs/GaAs Quantum Dots by Chemical Beam Epitaxy for Optical Coherence Tomography

by Bouraoui Ilahi^2,1,*

, Jihene Zribi¹, Maxime Guillotte¹, Richard Arès¹, Vincent Aimez¹ and Denis Morris¹

¹ Université de Sherbrooke, Laboratoire Nanotechnologies Nanosystèmes (LN2)–CNRS UMI-3463, Institut Interdisciplinaire d’Innovation Technologique (3IT), Sherbrooke, QC J1K OA5, Canada

² King Saud University, Department of Physics & Astronomy, College of Sciences, Riyadh 11451, Saudi Arabia

Materials 2016, 9(7), 511; https://doi.org/10.3390/ma9070511 - 24 Jun 2016

Cited by 3 | Viewed by 8486

Abstract

We report on Chemical Beam Epitaxy (CBE) growth of wavelength tunable InAs/GaAs quantum dots (QD) based superluminescent diode’s active layer suitable for Optical Coherence Tomography (OCT). The In-flush technique has been employed to fabricate QD with controllable heights, from 5 nm down to [...] Read more.

We report on Chemical Beam Epitaxy (CBE) growth of wavelength tunable InAs/GaAs quantum dots (QD) based superluminescent diode’s active layer suitable for Optical Coherence Tomography (OCT). The In-flush technique has been employed to fabricate QD with controllable heights, from 5 nm down to 2 nm, allowing a tunable emission band over 160 nm. The emission wavelength blueshift has been ensured by reducing both dots’ height and composition. A structure containing four vertically stacked height-engineered QDs have been fabricated, showing a room temperature broad emission band centered at 1.1 µm. The buried QD layers remain insensitive to the In-flush process of the subsequent layers, testifying the reliability of the process for broadband light sources required for high axial resolution OCT imaging. Full article

(This article belongs to the Special Issue Materials and Nanomaterials for Environmental and Bio-Medical Applications)

▼ Show Figures

Figure 1

17 pages, 984 KiB

Open AccessArticle

Two Independent Prospectively Planned Blinded Weibull Statistical Analyses of Flexural Strength Data of Zirconia Materials

by Malgorzata Roos^1,*, Christine Schatz² and Bogna Stawarczyk²

¹ Department of Biostatistics, Epidemiology Biostatistics and Prevention Institute, University of Zurich, Hirschengraben 84, 8001 Zurich, Switzerland

² Department of Prosthodontics, Dental School, Ludwig-Maximilians-University Munich, Goethestrasse 70, 80336 Munich, Germany

Materials 2016, 9(7), 512; https://doi.org/10.3390/ma9070512 - 24 Jun 2016

Cited by 7 | Viewed by 4835

Abstract

Zirconia as a restoration dental material are gaining attention because of their high mechanical properties and good biocompatibility. Therefore, investigation of the flexural strength of zirconia is of great interest. For this purpose, Weibull statistics for description of the material reliability are frequently [...] Read more.

Zirconia as a restoration dental material are gaining attention because of their high mechanical properties and good biocompatibility. Therefore, investigation of the flexural strength of zirconia is of great interest. For this purpose, Weibull statistics for description of the material reliability are frequently used. The aim of this work was to present a blinded data set to two independent statisticians for two parallel statistical analyses in order to find an optimal statistical approach for analysis of in-vitro measured flexural strength data of zirconia materials. A prospectively planned independent blinded statistical analysis implementing three quality control actions “blinded data set”, “independent statistical analyses” and “parallel manuscript writing” was designed. Statistical analysis paths taken by both biostatisticians differed. They arrived at complementary results. The major difference was caused by two alternative distributional assumptions (Weibull/Normal) and alternative fitting methods (LS/ML). The parallel statistical analysis and manuscript writing approach on a blinded data set greatly supported our choice of statistical methods for analysis of flexural strength results of zirconia materials. Full article

▼ Show Figures

Figure 1

13 pages, 6018 KiB

Open AccessArticle

TiO₂-Based Photocatalytic Geopolymers for Nitric Oxide Degradation

by Alberto Strini^1,*

, Giuseppina Roviello^2,3,*, Laura Ricciotti^2,3, Claudio Ferone^2,3

, Francesco Messina^2,3, Luca Schiavi¹, Davide Corsaro¹ and Raffaele Cioffi^2,3

¹ Construction Technologies Institute-National Research Council of Italy (ITC-CNR), via Lombardia 49, San Giuliano Milanese I-20098, Italy

² Department of Engineering, University of Naples “Parthenope”, INSTM Research Unit Napoli Parthenope, Centro Direzionale Isola C4, Naples I-80143, Italy

³ INSTM, Consorzio Interuniversitario per la Scienza e Tecnologia dei Materiali, Via G. Giusti, 9, Firenze I-50121, Italy

Materials 2016, 9(7), 513; https://doi.org/10.3390/ma9070513 - 24 Jun 2016

Cited by 68 | Viewed by 7281

Abstract

This study presents an experimental overview for the development of photocatalytic materials based on geopolymer binders as catalyst support matrices. Particularly, geopolymer matrices obtained from different solid precursors (fly ash and metakaolin), composite systems (siloxane-hybrid, foamed hybrid), and curing temperatures (room temperature and [...] Read more.

This study presents an experimental overview for the development of photocatalytic materials based on geopolymer binders as catalyst support matrices. Particularly, geopolymer matrices obtained from different solid precursors (fly ash and metakaolin), composite systems (siloxane-hybrid, foamed hybrid), and curing temperatures (room temperature and 60 °C) were investigated for the same photocatalyst content (i.e., 3% TiO₂ by weight of paste). The geopolymer matrices were previously designed for different applications, ranging from insulating (foam) to structural materials. The photocatalytic activity was evaluated as NO degradation in air, and the results were compared with an ordinary Portland cement reference. The studied matrices demonstrated highly variable photocatalytic performance depending on both matrix constituents and the curing temperature, with promising activity revealed by the geopolymers based on fly ash and metakaolin. Furthermore, microstructural features and titania dispersion in the matrices were assessed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDS) analyses. Particularly, EDS analyses of sample sections indicated segregation effects of titania in the surface layer, with consequent enhancement or depletion of the catalyst concentration in the active sample region, suggesting non-negligible transport phenomena during the curing process. The described results demonstrated that geopolymer binders can be interesting catalyst support matrices for the development of photocatalytic materials and indicated a large potential for the exploitation of their peculiar features. Full article

(This article belongs to the Special Issue Advances in Geopolymers and Alkali-Activated Materials)

▼ Show Figures

Figure 1

10 pages, 2038 KiB

Open AccessArticle

Mechanical Properties and Atomic Explanation of Plastic Deformation for Diamond-Like BC₂

by Baobing Zheng^*

, Meiguang Zhang and Shaomei Chang

College of Physics and Optoelectronics Technology, Nonlinear Research Institute, Baoji University of Arts and Sciences, Baoji 721016, China

Materials 2016, 9(7), 514; https://doi.org/10.3390/ma9070514 - 24 Jun 2016

Cited by 3 | Viewed by 5757

Abstract

Motivated by a recently predicted structure of diamond-like BC₂ with a high claimed hardness of 56 GPa (J. Phys. Chem. C 2010, 114, 22688–22690), we focus on whether this tetragonal BC₂ (t-BC₂) is superhard [...] Read more.

Motivated by a recently predicted structure of diamond-like BC₂ with a high claimed hardness of 56 GPa (J. Phys. Chem. C 2010, 114, 22688–22690), we focus on whether this tetragonal BC₂ (t-BC₂) is superhard or not in spite of such an ultrahigh theoretical hardness. The mechanical properties of t-BC₂ were thus further extended by using the first principles in the framework of density functional theory. Our results suggest that the Young’s and shear moduli of t-BC₂ exhibit a high degree of anisotropy. For the weakest shear direction, t-BC₂ undergoes an electronic instability and structural collapse upon a shear strain of about 0.11, with its theoretically ideal strength of only 36.2 GPa. Specifically, the plastic deformation under shear strain along the (110)[001] direction can be attributed to the breaking of d1 B–C bonds. Full article

(This article belongs to the Special Issue Computational Multiscale Modeling and Simulation in Materials Science)

▼ Show Figures

Figure 1

24 pages, 3886 KiB

Open AccessReview

Non-Equilibrium Plasma Processing for the Preparation of Antibacterial Surfaces

by Eloisa Sardella^1,*

, Fabio Palumbo¹

, Giuseppe Camporeale^2,*

and Pietro Favia^1,2

¹ Istituto di Nanotecnologia, Consiglio Nazionale delle Ricerche, Via Orabona 4, 70126 Bari, Italy

² Dipartimento di Chimica Università degli Studi di Bari “Aldo Moro”, Via Orabona 4, 70126 Bari, Italy

Materials 2016, 9(7), 515; https://doi.org/10.3390/ma9070515 - 25 Jun 2016

Cited by 47 | Viewed by 8430

Abstract

Non-equilibrium plasmas offer several strategies for developing antibacterial surfaces that are able to repel and/or to kill bacteria. Due to the variety of devices, implants, and materials in general, as well as of bacteria and applications, plasma assisted antibacterial strategies need to be [...] Read more.

Non-equilibrium plasmas offer several strategies for developing antibacterial surfaces that are able to repel and/or to kill bacteria. Due to the variety of devices, implants, and materials in general, as well as of bacteria and applications, plasma assisted antibacterial strategies need to be tailored to each specific surface. Nano-composite coatings containing inorganic (metals and metal oxides) or organic (drugs and biomolecules) compounds can be deposited in one step, and used as drug delivery systems. On the other hand, functional coatings can be plasma-deposited and used to bind antibacterial molecules, for synthesizing surfaces with long lasting antibacterial activity. In addition, non-fouling coatings can be produced to inhibit the adhesion of bacteria and reduce the formation of biofilm. This paper reviews plasma-based strategies aimed to reduce bacterial attachment and proliferation on biomedical materials and devices, but also onto materials used in other fields. Most of the activities described have been developed in the lab of the authors. Full article

(This article belongs to the Special Issue Advances and Applications of Nano-antimicrobial Treatments)

▼ Show Figures

Figure 1

8 pages, 2391 KiB

Open AccessArticle

A Photonic 1 × 4 Power Splitter Based on Multimode Interference in Silicon–Gallium-Nitride Slot Waveguide Structures

by Dror Malka^1,2,*, Yossef Danan¹, Yehonatan Ramon¹ and Zeev Zalevsky¹

¹ Faculty of Engineering, Department of Electro-Optics, Bar-Ilan University, Ramat-Gan 52900, Israel

² Faculty of Engineering Holon Institute of Technology (HIT), Holon 5810201, Israel

Materials 2016, 9(7), 516; https://doi.org/10.3390/ma9070516 - 25 Jun 2016

Cited by 42 | Viewed by 9932

Abstract

In this paper, a design for a 1 × 4 optical power splitter based on the multimode interference (MMI) coupler in a silicon (Si)–gallium nitride (GaN) slot waveguide structure is presented—to our knowledge, for the first time. Si and GaN were found as [...] Read more.

In this paper, a design for a 1 × 4 optical power splitter based on the multimode interference (MMI) coupler in a silicon (Si)–gallium nitride (GaN) slot waveguide structure is presented—to our knowledge, for the first time. Si and GaN were found as suitable materials for the slot waveguide structure. Numerical optimizations were carried out on the device parameters using the full vectorial-beam propagation method (FV-BPM). Simulation results show that the proposed device can be useful to divide optical signal energy uniformly in the C-band range (1530–1565 nm) into four output ports with low insertion losses (0.07 dB). Full article

(This article belongs to the Special Issue Silicon Nanophotonics)

▼ Show Figures

Figure 1

13 pages, 2174 KiB

Open AccessArticle

Physicochemical Characterization of Functional Lignin–Silica Hybrid Fillers for Potential Application in Abrasive Tools

by Beata Strzemiecka^1,*, Łukasz Klapiszewski¹

, Artur Jamrozik¹, Tadeusz J. Szalaty¹, Danuta Matykiewicz², Tomasz Sterzyński², Adam Voelkel¹ and Teofil Jesionowski^1,*

¹ Faculty of Chemical Technology, Institute of Chemical Technology and Engineering, Poznan University of Technology, Berdychowo 4, Poznan PL-60965, Poland

² Faculty of Construction Engineering and Management, Institute of Materials Technology, Poznan University of Technology, Piotrowo 3, Poznan PL-61138, Poland

Materials 2016, 9(7), 517; https://doi.org/10.3390/ma9070517 - 25 Jun 2016

Cited by 41 | Viewed by 7072

Abstract

Functional lignin–SiO₂ hybrid fillers were prepared for potential application in binders for phenolic resins, and their chemical structure was characterized. The properties of these fillers and of composites obtained from them with phenolic resin were compared with those of systems with lignin [...] Read more.

Functional lignin–SiO₂ hybrid fillers were prepared for potential application in binders for phenolic resins, and their chemical structure was characterized. The properties of these fillers and of composites obtained from them with phenolic resin were compared with those of systems with lignin or silica alone. The chemical structure of the materials was investigated by Fourier transform infrared spectroscopy (FT-IR) and carbon-13 nuclear magnetic resonance spectroscopy (¹³C CP MAS NMR). The thermal stability of the new functional fillers was examined by thermogravimetric analysis–mass spectrometry (TG-MS). Thermo-mechanical properties of the lignin–silica hybrids and resin systems were investigated by dynamic mechanical thermal analysis (DMTA). The DMTA results showed that abrasive composites with lignin–SiO₂ fillers have better thermo-mechanical properties than systems with silica alone. Thus, fillers based on lignin might provide new, promising properties for the abrasive industry, combining the good properties of lignin as a plasticizer and of silica as a filler improving mechanical properties. Full article

(This article belongs to the Special Issue Advances in Functionalization of Lignocellulosic Materials)

▼ Show Figures

Figure 1

14 pages, 4527 KiB

Open AccessArticle

Influence of Pre-Sintered Zirconia Surface Conditioning on Shear Bond Strength to Resin Cement

by Tomofumi Sawada^1,2,*

, Sebastian Spintzyk¹

, Christine Schille¹, Judit Zöldföldi³, Angelos Paterakis², Ernst Schweizer¹, Ingrid Stephan¹, Frank Rupp¹ and Jürgen Geis-Gerstorfer¹

¹ Section Medical Materials Science & Technology, University Hospital Tübingen, Osiander Strasse 2-8, Tübingen 72076, Germany

² Department of Prosthodontics, Center of Dentistry, Oral Medicine, and Maxillofacial Surgery, University Hospital Tübingen, Osianderstrasse 2-8, Tübingen 72076, Germany

³ Institute for Materials Science, University of Stuttgart, Pfaffenwaldring 2b, Stuttgart 70569, Germany

Materials 2016, 9(7), 518; https://doi.org/10.3390/ma9070518 - 25 Jun 2016

Cited by 14 | Viewed by 6962

Abstract

This study analyzed the shear bond strength (SBS) of resin composite on zirconia surface to which a specific conditioner was applied before sintering. After sintering of either conditioner-coated or uncoated specimens, both groups were divided into three subgroups by their respective surface modifications [...] Read more.

This study analyzed the shear bond strength (SBS) of resin composite on zirconia surface to which a specific conditioner was applied before sintering. After sintering of either conditioner-coated or uncoated specimens, both groups were divided into three subgroups by their respective surface modifications (n = 10 per group): no further treatment; etched with hydrofluoric acid; and sandblasted with 50 µm Al₂O₃ particles. Surfaces were characterized by measuring different surface roughness parameters (e.g., R_a and R_max) and water contact angles. Half of the specimens underwent thermocycling (10,000 cycles, 5–55 °C) after self-adhesive resin cement build-up. The SBSs were measured using a universal testing machine, and the failure modes were analyzed by microscopy. Data were analyzed by nonparametric and parametric tests followed by post-hoc comparisons (α = 0.05). Conditioner-coated specimens increased both surface roughness and hydrophilicity (p < 0.01). In the non-thermocycled condition, sandblasted surfaces showed higher SBSs than other modifications, irrespective of conditioner application (p < 0.05). Adhesive fractures were commonly observed in the specimens. Thermocycling favored debonding and decreased SBSs. However, conditioner-coated specimens upon sandblasting showed the highest SBS (p < 0.05) and mixed fractures were partially observed. The combination of conditioner application before sintering and sandblasting after sintering showed the highest shear bond strength and indicated improvements concerning the failure mode. Full article

(This article belongs to the Section Biomaterials)

▼ Show Figures

Figure 1

10 pages, 595 KiB

Open AccessArticle

Vaccinium meridionale Swartz Supercritical CO₂ Extraction: Effect of Process Conditions and Scaling Up

by Alexis López-Padilla¹, Alejandro Ruiz-Rodriguez¹, Claudia Estela Restrepo Flórez², Diana Marsela Rivero Barrios², Guillermo Reglero¹

and Tiziana Fornari^1,*

¹ Institute of Food Science Research CIAL (CSIC-UAM)—CEI UAM + CSIC, Madrid 28049, Spain

² INTAL Foundation Cra 50 G N° 12 Sur 91, Itagüí 050023, Colombia

Materials 2016, 9(7), 519; https://doi.org/10.3390/ma9070519 - 25 Jun 2016

Cited by 19 | Viewed by 5533

Abstract

Vaccinium meridionale Swartz (Mortiño or Colombian blueberry) is one of the Vaccinium species abundantly found across the Colombian mountains, which are characterized by high contents of polyphenolic compounds (anthocyanins and flavonoids). The supercritical fluid extraction (SFE) of Vaccinium species has mainly focused on [...] Read more.

Vaccinium meridionale Swartz (Mortiño or Colombian blueberry) is one of the Vaccinium species abundantly found across the Colombian mountains, which are characterized by high contents of polyphenolic compounds (anthocyanins and flavonoids). The supercritical fluid extraction (SFE) of Vaccinium species has mainly focused on the study of V. myrtillus L. (blueberry). In this work, the SFE of Mortiño fruit from Colombia was studied in a small-scale extraction cell (273 cm³) and different extraction pressures (20 and 30 MPa) and temperatures (313 and 343 K) were investigated. Then, process scaling-up to a larger extraction cell (1350 cm³) was analyzed using well-known semi-empirical engineering approaches. The Broken and Intact Cell (BIC) model was adjusted to represent the kinetic behavior of the low-scale extraction and to simulate the large-scale conditions. Extraction yields obtained were in the range 0.1%–3.2%. Most of the Mortiño solutes are readily accessible and, thus, 92% of the extractable material was recovered in around 30 min. The constant CO₂ residence time criterion produced excellent results regarding the small-scale kinetic curve according to the BIC model, and this conclusion was experimentally validated in large-scale kinetic experiments. Full article

(This article belongs to the Special Issue Optimisation and Scale-Up of Supercritical Fluid Extraction Processes)

▼ Show Figures

Figure 1

16 pages, 1813 KiB

Open AccessFeature PaperReview

Curcumin and Osteosarcoma: Can Invertible Polymeric Micelles Help?

by Avudaiappan Maran¹, Michael J. Yaszemski¹, Ananiy Kohut² and Andriy Voronov^3,*

¹ Department of Orthopedics, Mayo Clinic, 200 1st St SW, Rochester, MN 55905, USA

² Department of Organic Chemistry, Lviv Polytechnic National University, vul. S. Bandery, 12, Lviv 79013, Ukraine

³ Department of Coatings and Polymeric Materials, North Dakota State University, NDSU Dept. 2760, P.O. Box 6050, Fargo, ND 58108-6050, USA

Materials 2016, 9(7), 520; https://doi.org/10.3390/ma9070520 - 27 Jun 2016

Cited by 27 | Viewed by 7540

Abstract

Systematic review of experimental and clinical data on the use of curcumin in the treatment of osteosarcoma is presented. The current status of curcumin’s therapeutic potential against bone cancer is analyzed in regard to using polymeric micelles (including recently developed invertible, responsive, micelles) [...] Read more.

Systematic review of experimental and clinical data on the use of curcumin in the treatment of osteosarcoma is presented. The current status of curcumin’s therapeutic potential against bone cancer is analyzed in regard to using polymeric micelles (including recently developed invertible, responsive, micelles) as a platform for curcumin delivery to treat osteosarcoma. The potential of micellar assemblies from responsive macromolecules in a controlled delivery of curcumin to osteosarcoma cells, and the release using a new inversion mechanism is revealed. Full article

(This article belongs to the Special Issue Selected papers from ISN2A2016)

▼ Show Figures

Figure 1

17 pages, 9560 KiB

Open AccessArticle

Uncertainty Evaluation of Weibull Estimators through Monte Carlo Simulation: Applications for Crack Initiation Testing

by Jae Phil Park

and Chi Bum Bahn^*

School of Mechanical Engineering, Pusan National University, Busan 46241, Korea

Materials 2016, 9(7), 521; https://doi.org/10.3390/ma9070521 - 27 Jun 2016

Cited by 8 | Viewed by 5640

Abstract

The typical experimental procedure for testing stress corrosion cracking initiation involves an interval-censored reliability test. Based on these test results, the parameters of a Weibull distribution, which is a widely accepted crack initiation model, can be estimated using maximum likelihood estimation or median [...] Read more.

The typical experimental procedure for testing stress corrosion cracking initiation involves an interval-censored reliability test. Based on these test results, the parameters of a Weibull distribution, which is a widely accepted crack initiation model, can be estimated using maximum likelihood estimation or median rank regression. However, it is difficult to determine the appropriate number of test specimens and censoring intervals required to obtain sufficiently accurate Weibull estimators. In this study, we compare maximum likelihood estimation and median rank regression using a Monte Carlo simulation to examine the effects of the total number of specimens, test duration, censoring interval, and shape parameters of the true Weibull distribution on the estimator uncertainty. Finally, we provide the quantitative uncertainties of both Weibull estimators, compare them with the true Weibull parameters, and suggest proper experimental conditions for developing a probabilistic crack initiation model through crack initiation tests. Full article

▼ Show Figures

Figure 1

17 pages, 11033 KiB

Open AccessArticle

Soldering Characteristics and Mechanical Properties of Sn-1.0Ag-0.5Cu Solder with Minor Aluminum Addition

by Yee Mei Leong and A.S.M.A. Haseeb^*

Centre for Advanced Materials, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia

Materials 2016, 9(7), 522; https://doi.org/10.3390/ma9070522 - 28 Jun 2016

Cited by 27 | Viewed by 8203

Abstract

Driven by the trends towards miniaturization in lead free electronic products, researchers are putting immense efforts to improve the properties and reliabilities of Sn based solders. Recently, much interest has been shown on low silver (Ag) content solder SAC105 (Sn-1.0Ag-0.5Cu) because of economic [...] Read more.

Driven by the trends towards miniaturization in lead free electronic products, researchers are putting immense efforts to improve the properties and reliabilities of Sn based solders. Recently, much interest has been shown on low silver (Ag) content solder SAC105 (Sn-1.0Ag-0.5Cu) because of economic reasons and improvement of impact resistance as compared to SAC305 (Sn-3.0Ag-0.5Cu. The present work investigates the effect of minor aluminum (Al) addition (0.1–0.5 wt.%) to SAC105 on the interfacial structure between solder and copper substrate during reflow. The addition of minor Al promoted formation of small, equiaxed Cu-Al particle, which are identified as Cu₃Al₂. Cu₃Al₂ resided at the near surface/edges of the solder and exhibited higher hardness and modulus. Results show that the minor addition of Al does not alter the morphology of the interfacial intermetallic compounds, but they substantially suppress the growth of the interfacial Cu₆Sn₅ intermetallic compound (IMC) after reflow. During isothermal aging, minor alloying Al has reduced the thickness of interfacial Cu₆Sn₅ IMC but has no significant effect on the thickness of Cu₃Sn. It is suggested that of atoms of Al exert their influence by hindering the flow of reacting species at the interface. Full article

▼ Show Figures

Figure 1

14 pages, 3793 KiB

Open AccessArticle

Preparation and Properties of Electrospun Poly (Vinyl Pyrrolidone)/Cellulose Nanocrystal/Silver Nanoparticle Composite Fibers

by Siwei Huang¹, Ling Zhou², Mei-Chun Li³, Qinglin Wu^3,*, Yoichi Kojima⁴

and Dingguo Zhou^1,*

¹ College of Materials Science and Engineering, Nanjing Forestry University, Nanjing 210037, China

² School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China

³ School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA

⁴ Department of Environment & Forest Resources Science Faculty of Agriculture, Shizuoka University, Shizuoka 422-8529, Japan

Materials 2016, 9(7), 523; https://doi.org/10.3390/ma9070523 - 28 Jun 2016

Cited by 116 | Viewed by 9892

Abstract

Poly (vinyl pyrrolidone) (PVP)/cellulose nanocrystal (CNC)/silver nanoparticle composite fibers were prepared via electrospinning using N,N′-dimethylformamide (DMF) as a solvent. Rheology, morphology, thermal properties, mechanical properties, and antimicrobial activity of nanocomposites were characterized as a function of material composition. The PVP/CNC/Ag [...] Read more.

Poly (vinyl pyrrolidone) (PVP)/cellulose nanocrystal (CNC)/silver nanoparticle composite fibers were prepared via electrospinning using N,N′-dimethylformamide (DMF) as a solvent. Rheology, morphology, thermal properties, mechanical properties, and antimicrobial activity of nanocomposites were characterized as a function of material composition. The PVP/CNC/Ag electrospun suspensions exhibited higher conductivity and better rheological properties compared with those of the pure PVP solution. The average diameter of the PVP electrospun fibers decreased with the increase in the amount of CNCs and Ag nanoparticles. Thermal stability of electrospun composite fibers was decreased with the addition of CNCs. The CNCs help increase the composite tensile strength, while the elongation at break decreased. The composite fibers included Ag nanoparticles showed improved antimicrobial activity against both the Gram-negative bacterium Escherichia coli (E. coli) and the Gram-positive bacterium Staphylococcus aureus (S. aureus). The enhanced strength and antimicrobial performances of PVP/CNC/Ag electrospun composite fibers make the mat material an attractive candidate for application in the biomedical field. Full article

(This article belongs to the Section Advanced Composites)

▼ Show Figures

Graphical abstract

18 pages, 5929 KiB

Open AccessArticle

Optimization of Supercritical Fluid Extraction of Total Alkaloids, Peimisine, Peimine and Peiminine from the Bulb of Fritillaria thunbergii Miq, and Evaluation of Antioxidant Activities of the Extracts

by Xiao Ruan, Li Yang, Wen-Xia Cui, Men-Xing Zhang, Zhao-Hui Li, Ben Liu and Qiang Wang^*

Ningbo Institute of Technology, Zhejiang University, Ningbo 315100, China

Materials 2016, 9(7), 524; https://doi.org/10.3390/ma9070524 - 29 Jun 2016

Cited by 32 | Viewed by 6452

Abstract

Supercritical fluid extraction (SFE) was used to extract total alkaloids, peimisine, peimine and peiminine from the bulb of Fritillaria thunbergii Miq. The antioxidant capacity of the extracts was evaluated by DPPH radical scavenging activity (DPPH-RSA), ABTS radical scavenging activity (ABTS-RSA) and ferric reducing [...] Read more.

Supercritical fluid extraction (SFE) was used to extract total alkaloids, peimisine, peimine and peiminine from the bulb of Fritillaria thunbergii Miq. The antioxidant capacity of the extracts was evaluated by DPPH radical scavenging activity (DPPH-RSA), ABTS radical scavenging activity (ABTS-RSA) and ferric reducing capacity (FRAP) assay. A central composite design (CCD) with four variables and five levels was employed for optimization of process parameters, and response surface plots were constructed in accordance with a second order polynomial model. Under optimal conditions of 3.0 h, 60.4 °C, 26.5 MPa and 89.3% ethanol, the highest yields were predicted to be 3.8 mg/g for total alkaloids, 0.5 mg/g for peimisine, 1.3 mg/g for peimine and 1.3 mg/g for peiminine, and the antioxidant capacity of extracts displayed EC_{50, DPPH} value of 5.5 mg/mL, EC_{50, ABTS} value of 0.3 mg/mL and FRAP value of 118.2 mg ascorbic acid equivalent (AAE)/100 g. Full article

(This article belongs to the Special Issue Optimisation and Scale-Up of Supercritical Fluid Extraction Processes)

▼ Show Figures

Figure 1

11 pages, 4842 KiB

Open AccessArticle

Photoresist Design for Elastomeric Light Tunable Photonic Devices

by Sara Nocentini^1,†

, Daniele Martella^1,2,†, Camilla Parmeggiani^1,3,* and Diederik S. Wiersma¹

¹ European Laboratory for Non-Linear Spectroscopy (LENS), University of Florence, via Nello Carrara 1, 50019 Sesto Fiorentino, Italy

² Department of Chemistry “Ugo Schiff”, University of Florence, via Della Lastruccia 3-13, 50019 Sesto Fiorentino, Italy

³ CNR-INO, Sede Secondaria di Sesto Fiorentino, via Nello Carrara 1, 50019 Sesto Fiorentino, Italy

^† These authors contributed equally.

Materials 2016, 9(7), 525; https://doi.org/10.3390/ma9070525 - 29 Jun 2016

Cited by 39 | Viewed by 7747

Abstract

An increasing interest in tunable photonic structures is growing within the photonic community. The usage of Liquid Crystalline Elastomer (LCE) structures in the micro-scale has been motivated by the potential to remotely control their properties. In order to design elastic photonic structures with [...] Read more.

An increasing interest in tunable photonic structures is growing within the photonic community. The usage of Liquid Crystalline Elastomer (LCE) structures in the micro-scale has been motivated by the potential to remotely control their properties. In order to design elastic photonic structures with a three-dimensional lithographic technique, an analysis of the different mixtures used in the micro-printing process is required. Previously reported LCE microstructures suffer damage and strong swelling as a limiting factor of resolution. In this article, we reported a detailed study on the writing process with four liquid crystalline photoresists, in which the percentage of crosslinker is gradually increased. The experiments reveal that exploiting the crosslinking degree is a possible means in which to obtain suspended lines with good resolution, quite good rigidity, and good elasticity, thereby preserving the possibility of deformation by light irradiation. Full article

(This article belongs to the Special Issue Advances in Research on Elastomers)

▼ Show Figures

Graphical abstract

12 pages, 3742 KiB

Open AccessArticle

Copper-Zinc-Tin-Sulfur Thin Film Using Spin-Coating Technology

by Min-Yen Yeh¹, Po-Hsun Lei^2,*, Shao-Hsein Lin² and Chyi-Da Yang¹

¹ Department of Microelectronic Engineering, National Kaohsiung Marine University, Kaohsiung 811, Taiwan

² Institute of Electro-Optical and Materials Science, National Formosa University, 64 Wen-Hwa Rd, Hu-Wei, Yun-Lin 632, Taiwan

Materials 2016, 9(7), 526; https://doi.org/10.3390/ma9070526 - 29 Jun 2016

Cited by 68 | Viewed by 10344

Abstract

Cu₂ZnSnS₄ (CZTS) thin films were deposited on glass substrates by using spin-coating and an annealing process, which can improve the crystallinity and morphology of the thin films. The grain size, optical gap, and atomic contents of copper (Cu), zinc (Zn), [...] Read more.

Cu₂ZnSnS₄ (CZTS) thin films were deposited on glass substrates by using spin-coating and an annealing process, which can improve the crystallinity and morphology of the thin films. The grain size, optical gap, and atomic contents of copper (Cu), zinc (Zn), tin (Sn), and sulfur (S) in a CZTS thin film absorber relate to the concentrations of aqueous precursor solutions containing copper chloride (CuCl₂), zinc chloride (ZnCl₂), tin chloride (SnCl₂), and thiourea (SC(NH₂)₂), whereas the electrical properties of CZTS thin films depend on the annealing temperature and the atomic content ratios of Cu/(Zn + Sn) and Zn/Sn. All of the CZTS films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDXS), Raman spectroscopy, and Hall measurements. Furthermore, CZTS thin film was deposited on an n-type silicon substrate by using spin-coating to form an Mo/p-CZTS/n-Si/Al heterostructured solar cell. The p-CZTS/n-Si heterostructured solar cell showed a conversion efficiency of 1.13% with V_oc = 520 mV, J_sc = 3.28 mA/cm², and fill-factor (FF) = 66%. Full article

(This article belongs to the Special Issue Selected Papers from ICASI 2016)

▼ Show Figures

Figure 1

12 pages, 2590 KiB

Open AccessArticle

Influence of Rubber Size on Properties of Crumb Rubber Mortars

by Yong Yu^1,2

and Han Zhu^1,2,*

¹ Department of Civil Engineering, Tianjin University, Tianjin 300350, China

² Key Laboratory of Coast Civil Structure Safety, Tianjin University, Ministry of Education, Tianjin 300072, China

Materials 2016, 9(7), 527; https://doi.org/10.3390/ma9070527 - 29 Jun 2016

Cited by 59 | Viewed by 7426

Abstract

Studies on the properties and applications of rubber cement-based materials are well documented. The sizes of rubbers used in these materials varied. However, information about the effects of rubber size on the properties of rubber cement-based materials, especially pore structure, mechanical strengths, and [...] Read more.

Studies on the properties and applications of rubber cement-based materials are well documented. The sizes of rubbers used in these materials varied. However, information about the effects of rubber size on the properties of rubber cement-based materials, especially pore structure, mechanical strengths, and drying shrinkage properties, remains limited. Three groups of rubber with major particle sizes of 2–4 mm, 1–3 mm, and 0–2 mm were selected in this study. This paper presents experimental studies on the effects of rubber size on the consistency, fresh density, pore structure, mechanical properties, and drying shrinkage properties of crumb rubber mortars (CRMs). Results demonstrated that the consistency and fresh density of CRMs decreased with the rubber size. As to the pore structure, the total pore volume increased with the decrease of the rubber size. By contrast, the influence of the rubber size on the mesopore (<50 nm) volume is not as significant as that of the rubber content. The mechanical properties of CRMs decreased with the rubber size. Low rubber stiffness and large pore volumes, especially those of small sized rubbers, contribute to the reduction of CRMs strength. The drying shrinkage of CRM increases as the rubber size decreases. The influences of rubber size on capillary tension are not significant. Thus, the shrinkage increases with the decrease of rubber size mainly because of its function in the deformation modulus reduction of CRMs. Full article

▼ Show Figures

Figure 1

11 pages, 3931 KiB

Open AccessArticle

Exopolysaccharide-Based Bioflocculant Matrix of Azotobacter chroococcum XU1 for Synthesis of AgCl Nanoparticles and Its Application as a Novel Biocidal Nanobiomaterial

by Bakhtiyor A. Rasulov¹, Parhat Rozi^2,3, Mohichehra A. Pattaeva⁴, Abulimiti Yili²

and Haji Akber Aisa^2,*

¹ Institute of Genetics and Plant Experimental Biology, Uzbekistan Academy of Sciences, Yukori Yuz, Kybray District 111226, Uzbekistan

² Key Laboratory of Plant Resources and Chemistry in Arid Region, Xinjiang Technical Institute of Chemistry and Physics, Chinese Academy of Sciences, Urumqi 830011, China

³ University of Chinese Academy of Sciences, Beijing 100039, China

⁴ Institute of Microbiology, Uzbekistan Academy of Sciences, Tashkent 100128, Uzbekistan

Materials 2016, 9(7), 528; https://doi.org/10.3390/ma9070528 - 29 Jun 2016

Cited by 20 | Viewed by 5810

Abstract

A simple and green method was developed for the biosynthesis of AgCl nanoparticles, free from Ag nanoparticles, using the exopolysaccharide-based bioflocculant of nitrogen fixing Azotobacter chroococcum XU1 strain. AgCl nanoparticles were characterized by UV-Vis, X-ray diffraction (XRD), Fourier Transform-Infra Red (FT-IR) and Scanning [...] Read more.

A simple and green method was developed for the biosynthesis of AgCl nanoparticles, free from Ag nanoparticles, using the exopolysaccharide-based bioflocculant of nitrogen fixing Azotobacter chroococcum XU1 strain. AgCl nanoparticles were characterized by UV-Vis, X-ray diffraction (XRD), Fourier Transform-Infra Red (FT-IR) and Scanning electron microscopy-energy dispersive X-ray (SEM-EDX). The concentration-dependent and controllable method for the synthesis of AgCl nanoparticles of a certain size and morphology was developed. As-synthesized AgCl nanoparticles were characterized bya high content of AgCl and exhibited strong antimicrobial activity towards pathogenic microorganisms such as E. coli, S. aureus and C. albicans. The biofabricated AgCl nanoparticles can be exploited as a promising new biocidalbionanocomposite against pathogenic microorganisms. Full article

(This article belongs to the Special Issue Advances and Applications of Nano-antimicrobial Treatments)

▼ Show Figures

Figure 1

13 pages, 4034 KiB

Open AccessArticle

Ceramic Spheres—A Novel Solution to Deep Sea Buoyancy Modules

by Bo Jiang^1,*, Gurdial Blugan¹, Philip N. Sturzenegger², Urs T. Gonzenbach², Michael Misson³, John Thornberry⁴, Runar Stenerud⁵, David Cartlidge⁶

and Jakob Kuebler^1,*

¹ Laboratory for High Performance Ceramics, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf 8600, Switzerland

² De Cavis AG, Dübendorf 8600, Switzerland

³ Almath Crucibles Ltd., Newmarket, Suffolk CB8 9NE, UK

⁴ Moulded Foams, Blackwood, Gwent South Wales NP12 2EU, UK

⁵ Plasto AS, Andalsnes 6300, Norway

⁶ Pera Technology, Melton Mowbray, Leicestershire LE13 0PB, UK

Materials 2016, 9(7), 529; https://doi.org/10.3390/ma9070529 - 29 Jun 2016

Cited by 19 | Viewed by 9484

Abstract

Ceramic-based hollow spheres are considered a great driving force for many applications such as offshore buoyancy modules due to their large diameter to wall thickness ratio and uniform wall thickness geometric features. We have developed such thin-walled hollow spheres made of alumina using [...] Read more.

Ceramic-based hollow spheres are considered a great driving force for many applications such as offshore buoyancy modules due to their large diameter to wall thickness ratio and uniform wall thickness geometric features. We have developed such thin-walled hollow spheres made of alumina using slip casting and sintering processes. A diameter as large as 50 mm with a wall thickness of 0.5–1.0 mm has been successfully achieved in these spheres. Their material and structural properties were examined by a series of characterization tools. Particularly, the feasibility of these spheres was investigated with respect to its application for deep sea (>3000 m) buoyancy modules. These spheres, sintered at 1600 °C and with 1.0 mm of wall thickness, have achieved buoyancy of more than 54%. As the sphere’s wall thickness was reduced (e.g., 0.5 mm), their buoyancy reached 72%. The mechanical performance of such spheres has shown a hydrostatic failure pressure above 150 MPa, corresponding to a rating depth below sea level of 5000 m considering a safety factor of 3. The developed alumina-based ceramic spheres are feasible for low cost and scaled-up production and show great potential at depths greater than those achievable by the current deep-sea buoyancy module technologies. Full article

(This article belongs to the Section Energy Materials)

▼ Show Figures

Graphical abstract

11 pages, 1084 KiB

Open AccessFeature PaperArticle

Recovery of Butanol by Counter-Current Carbon Dioxide Fractionation with its Potential Application to Butanol Fermentation

by Miriam Solana^1,2,*, Nasib Qureshi^3,*, Alberto Bertucco¹ and Fred Eller²

¹ Department of Industrial Engineering DII, University of Padua, Via Marzolo 9, Padua 35131, Italy

² United States Department of Agriculture (USDA), National Center for Agricultural Utilization Research (NCAUR), Functional Foods Research Unit, 1815 North University Street, Peoria, IL 61604, USA

³ United States Department of Agriculture (USDA), National Center for Agricultural Utilization Research (NCAUR), Bioenergy Research Unit, 1815 North University Street, Peoria, IL 61604, USA

Materials 2016, 9(7), 530; https://doi.org/10.3390/ma9070530 - 30 Jun 2016

Cited by 9 | Viewed by 5472

Abstract

A counter-current CO₂ fractionation method was applied as a mean to recover n-butanol and other compounds that are typically obtained from biobutanol fermentation broth from aqueous solutions. The influence of operating variables, such as solvent-to-feed ratio, temperature, pressure and feed solution composition [...] Read more.

A counter-current CO₂ fractionation method was applied as a mean to recover n-butanol and other compounds that are typically obtained from biobutanol fermentation broth from aqueous solutions. The influence of operating variables, such as solvent-to-feed ratio, temperature, pressure and feed solution composition was experimentally studied in terms of separation efficiency, butanol removal rate, total removal and butanol concentration in the extract at the end of the continuous cycle. With respect to the temperature and pressure conditions investigated, results show that the highest separation efficiency was obtained at 35 °C and 10.34 MPa. At these operating conditions, 92.3% of the butanol present in the feed solution was extracted, and a concentration of 787.5 g·L⁻¹ of butanol in the extract was obtained, starting from a feed solution of 20 g·L⁻¹. Selectivity was calculated from experimental data, concluding that our column performs much better than a single equilibrium stage. When adding ethanol and acetone to the feed solution, ethanol was detected in the water-rich fraction (raffinate), whereas the highest concentration of acetone was found in the butanol rich fraction (extract). Full article

(This article belongs to the Special Issue Optimisation and Scale-Up of Supercritical Fluid Extraction Processes)

▼ Show Figures

Figure 1

19 pages, 805 KiB

Open AccessArticle

Hard-Rock Stability Analysis for Span Design in Entry-Type Excavations with Learning Classifiers

by Esperanza García-Gonzalo^1,*

, Zulima Fernández-Muñiz¹, Paulino José García Nieto¹

, Antonio Bernardo Sánchez²

and Marta Menéndez Fernández²

¹ Mathematics Department, Universidad de Oviedo, Oviedo 33007, Spain

² Department of Mining Technology, Topography and Structures, University of León, León 24071, Spain

Materials 2016, 9(7), 531; https://doi.org/10.3390/ma9070531 - 29 Jun 2016

Cited by 49 | Viewed by 6772

Abstract

The mining industry relies heavily on empirical analysis for design and prediction. An empirical design method, called the critical span graph, was developed specifically for rock stability analysis in entry-type excavations, based on an extensive case-history database of cut and fill mining in [...] Read more.

The mining industry relies heavily on empirical analysis for design and prediction. An empirical design method, called the critical span graph, was developed specifically for rock stability analysis in entry-type excavations, based on an extensive case-history database of cut and fill mining in Canada. This empirical span design chart plots the critical span against rock mass rating for the observed case histories and has been accepted by many mining operations for the initial span design of cut and fill stopes. Different types of analysis have been used to classify the observed cases into stable, potentially unstable and unstable groups. The main purpose of this paper is to present a new method for defining rock stability areas of the critical span graph, which applies machine learning classifiers (support vector machine and extreme learning machine). The results show a reasonable correlation with previous guidelines. These machine learning methods are good tools for developing empirical methods, since they make no assumptions about the regression function. With this software, it is easy to add new field observations to a previous database, improving prediction output with the addition of data that consider the local conditions for each mine. Full article

(This article belongs to the Section Advanced Materials Characterization)

▼ Show Figures

Figure 1

17 pages, 3236 KiB

Open AccessArticle

Biomimetic Multispiked Connecting Ti-Alloy Scaffold Prototype for Entirely-Cementless Resurfacing Arthroplasty Endoprostheses—Exemplary Results of Implantation of the Ca-P Surface-Modified Scaffold Prototypes in Animal Model and Osteoblast Culture Evaluation

by Ryszard Uklejewski^1,2,*

, Piotr Rogala³, Mariusz Winiecki^1,2

, Renata Tokłowicz², Piotr Ruszkowski⁴ and Maria Wołuń-Cholewa⁵

¹ Department of Medical Bioengineering Fundamentals, Institute of Technology, Casimir the Great University, Karola Chodkiewicza Street 30, Bydgoszcz 85-064, Poland

² Department of Process Engineering, Institute of Technology and Chemical Engineering, Poznan University of Technology, Marii Sklodowskiej-Curie 2, Poznan 60-965, Poland

³ Department of Spine Surgery, Oncologic Orthopaedics and Traumatology, Poznan University of Medical Sciences, 28 Czerwca 1956 135/147, Poznan 61-545, Poland

⁴ Department of Pharmacology, Poznan University of Medical Sciences, Rokietnicka 5A, Poznan 60-806, Poland

⁵ Department of Cell Biology, Poznan University of Medical Sciences, Rokietnicka 5D, Poznan 60-806, Poland

Materials 2016, 9(7), 532; https://doi.org/10.3390/ma9070532 - 29 Jun 2016

Cited by 15 | Viewed by 6399

Abstract

We present here—designed, manufactured, and tested by our research team—the Ti-alloy prototype of the multispiked connecting scaffold (MSC-Scaffold) interfacing the components of resurfacing arthroplasty (RA) endoprostheses with bone. The spikes of the MSC-Scaffold prototype mimic the interdigitations of the articular subchondral bone, which [...] Read more.

We present here—designed, manufactured, and tested by our research team—the Ti-alloy prototype of the multispiked connecting scaffold (MSC-Scaffold) interfacing the components of resurfacing arthroplasty (RA) endoprostheses with bone. The spikes of the MSC-Scaffold prototype mimic the interdigitations of the articular subchondral bone, which is the natural biostructure interfacing the articular cartilage with the periarticular trabecular bone. To enhance the osteoinduction/osteointegration potential of the MSC-Scaffold, the attempts to modify its bone contacting surfaces by the process of electrochemical cathodic deposition of Ca-P was performed with further immersion of the MSC-Scaffold prototypes in SBF in order to transform the amorphous calcium-phosphate coating in hydroxyapatite-like (HA-like) coating. The pilot experimental study of biointegration of unmodified and Ca-P surface-modified MSC-Scaffold prototypes was conducted in an animal model (swine) and in osteoblast cell culture. On the basis of a microscope-histological method the biointegration was proven by the presence of trabeculae in the interspike spaces of the MSC-Scaffold prototype on longitudinal and cross-sections of bone-implant specimens. The percentage of trabeculae in the area between the spikes of specimen containing Ca-P surface modified scaffold prototype observed in microCT reconstructions of the explanted joints was visibly higher than in the case of unmodified MSC-Scaffold prototypes. Significantly higher Alkaline Phosphatase (ALP) activity and the cellular proliferation in the case of Ca-P-modified MSC-Scaffold pre-prototypes, in comparison with unmodified pre-prototypes, was found in osteoblast cell cultures. The obtained results of experimental implantation in an animal model and osteoblast cell culture evaluations of Ca-P surface-modified and non-modified biomimetic MSC-Scaffold prototypes for biomimetic entirely-cementless RA endoprostheses indicate the enhancement of the osteoinduction/osteointegration potential by the Ca-P surface modification of the Ti-alloy MSC-Scaffold prototype. Planned further research on the prototype of this biomimetic MSC-Scaffold for a new generation of RA endoprostheses is also given. Full article

(This article belongs to the Special Issue Metallic Scaffolds for Bone Regeneration)

▼ Show Figures

Figure 1

9 pages, 3855 KiB

Open AccessArticle

The Characterization of Fixation of Ba, Pb, and Cu in Alkali-Activated Fly Ash/Blast Furnace Slag Matrix

by Jan Koplík^*

, Lukáš Kalina

, Jiří Másilko

and František Šoukal

Materials Research Centre, Faculty of Chemistry, Brno University of Technology, Purkyňova 118, Brno 61200, Czech Republic

Materials 2016, 9(7), 533; https://doi.org/10.3390/ma9070533 - 30 Jun 2016

Cited by 28 | Viewed by 7231

Abstract

The fixation of heavy metals (Ba, Cu, Pb) in an alkali-activated matrix was investigated. The matrix consisted of fly ash and blast furnace slag (BFS). The mixture of NaOH and Na-silicate was used as alkaline activator. Three analytical techniques were used to describe [...] Read more.

The fixation of heavy metals (Ba, Cu, Pb) in an alkali-activated matrix was investigated. The matrix consisted of fly ash and blast furnace slag (BFS). The mixture of NaOH and Na-silicate was used as alkaline activator. Three analytical techniques were used to describe the fixation of heavy metals—X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), and X-ray powder diffraction (XRD). All heavy metals formed insoluble salts after alkaline activation. Ba was fixed as BaSO₄, and only this product was crystalline. EDS mapping showed that Ba was cumulated in some regions and formed clusters. Pb was present in the form of Pb(OH)₂ and was dispersed throughout the matrix on the edges of BFS grains. Cu was fixed as Cu(OH)₂ and also was cumulated in some regions and formed clusters. Cu was present in two different chemical states; apart from Cu(OH)₂, a Cu–O bond was also identified. Full article

(This article belongs to the Special Issue Advances in Geopolymers and Alkali-Activated Materials)

▼ Show Figures

Figure 1

10 pages, 4895 KiB

Open AccessArticle

The Development of High-Density Vertical Silicon Nanowires and Their Application in a Heterojunction Diode

by Wen-Chung Chang¹, Sheng-Chien Su¹ and Chia-Ching Wu^2,*

¹ Department of Electronic Engineering, Southern Taiwan University of Science and Technology, Tainan 71005, Taiwan

² Department of Electronic Engineering, Kao Yuan University, Kaohsiung 82151, Taiwan

Materials 2016, 9(7), 534; https://doi.org/10.3390/ma9070534 - 30 Jun 2016

Cited by 7 | Viewed by 7363

Abstract

Vertically aligned p-type silicon nanowire (SiNW) arrays were fabricated through metal-assisted chemical etching (MACE) of Si wafers. An indium tin oxide/indium zinc oxide/silicon nanowire (ITO/IZO/SiNW) heterojunction diode was formed by depositing ITO and IZO thin films on the vertically aligned SiNW arrays. The [...] Read more.

Vertically aligned p-type silicon nanowire (SiNW) arrays were fabricated through metal-assisted chemical etching (MACE) of Si wafers. An indium tin oxide/indium zinc oxide/silicon nanowire (ITO/IZO/SiNW) heterojunction diode was formed by depositing ITO and IZO thin films on the vertically aligned SiNW arrays. The structural and electrical properties of the resulting ITO/IZO/SiNW heterojunction diode were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and current−voltage (I−V) measurements. Nonlinear and rectifying I−V properties confirmed that a heterojunction diode was successfully formed in the ITO/IZO/SiNW structure. The diode had a well-defined rectifying behavior, with a rectification ratio of 550.7 at 3 V and a turn-on voltage of 2.53 V under dark conditions. Full article

(This article belongs to the Special Issue Green Nanotechnology)

▼ Show Figures

Figure 1

13 pages, 6914 KiB

Open AccessArticle

Thermal Behaviour of Metakaolin/Fly Ash Geopolymers with Chamotte Aggregate

by Pavel Rovnaník^* and Kristýna Šafránková

Faculty of Civil Engineering, Brno University of Technology, Veveří 95, Brno 602 00, Czech Republic

Materials 2016, 9(7), 535; https://doi.org/10.3390/ma9070535 - 30 Jun 2016

Cited by 68 | Viewed by 7222

Abstract

Geopolymers are generally appreciated for their good resistance against high temperatures. This paper compares the influence of thermal treatment with temperatures ranging from 200 to 1200 °C on the mechanical properties and microstructure of geopolymers based on two different aluminosilicate precursors, metakaolin and [...] Read more.

Geopolymers are generally appreciated for their good resistance against high temperatures. This paper compares the influence of thermal treatment with temperatures ranging from 200 to 1200 °C on the mechanical properties and microstructure of geopolymers based on two different aluminosilicate precursors, metakaolin and fly ash. Moreover, the paper is also aimed at characterizing the effect of chamotte aggregate on the performance of geopolymers subjected to high temperatures. Thermal treatment leads to a deterioration in the strength of metakaolin geopolymer, whereas fly ash geopolymer gains strength upon heating. The formation of albite above 900 °C is responsible for the fusion of geopolymer matrix during exposure to 1200 °C, which leads to the deformation of the geopolymer samples. Chamotte aggregate improves the performance of geopolymer material by increasing the thermal stability of geopolymers via sintering of the aggregate particles with the geopolymer matrix in the contact zone. Full article

(This article belongs to the Special Issue Advances in Geopolymers and Alkali-Activated Materials)

▼ Show Figures

Figure 1

13 pages, 4487 KiB

Open AccessArticle

Modeling the Effects of Cu Content and Deformation Variables on the High-Temperature Flow Behavior of Dilute Al-Fe-Si Alloys Using an Artificial Neural Network

by Mohammad Shakiba^1,*, Nick Parson² and X.-Grant Chen¹

¹ Department of Applied Science, University of Québec at Chicoutimi, Saguenay, QC G7H 2B1, Canada

² Arvida Research and Development Centre, Rio Tinto Alcan, Saguenay, QC G7S 4K8, Canada

Materials 2016, 9(7), 536; https://doi.org/10.3390/ma9070536 - 30 Jun 2016

Cited by 44 | Viewed by 5351

Abstract

The hot deformation behavior of Al-0.12Fe-0.1Si alloys with varied amounts of Cu (0.002–0.31 wt %) was investigated by uniaxial compression tests conducted at different temperatures (400 °C–550 °C) and strain rates (0.01–10 s⁻¹). The results demonstrated that flow stress decreased with [...] Read more.

The hot deformation behavior of Al-0.12Fe-0.1Si alloys with varied amounts of Cu (0.002–0.31 wt %) was investigated by uniaxial compression tests conducted at different temperatures (400 °C–550 °C) and strain rates (0.01–10 s⁻¹). The results demonstrated that flow stress decreased with increasing deformation temperature and decreasing strain rate, while flow stress increased with increasing Cu content for all deformation conditions studied due to the solute drag effect. Based on the experimental data, an artificial neural network (ANN) model was developed to study the relationship between chemical composition, deformation variables and high-temperature flow behavior. A three-layer feed-forward back-propagation artificial neural network with 20 neurons in a hidden layer was established in this study. The input parameters were Cu content, temperature, strain rate and strain, while the flow stress was the output. The performance of the proposed model was evaluated using the K-fold cross-validation method. The results showed excellent generalization capability of the developed model. Sensitivity analysis indicated that the strain rate is the most important parameter, while the Cu content exhibited a modest but significant influence on the flow stress. Full article

▼ Show Figures

Graphical abstract

9 pages, 2645 KiB

Open AccessArticle

In Situ AFM Imaging of Microstructural Changes Associated with The Spin Transition in [Fe(Htrz)₂(Trz)](Bf₄) Nanoparticles

by María D. Manrique-Juárez^1,2, Iurii Suleimanov^1,3, Edna M. Hernández⁴, Lionel Salmon¹, Gábor Molnár^1,* and Azzedine Bousseksou^1,*

¹ LCC, CNRS & Université de Toulouse (UPS, INP), Toulouse 31077, France

² LAAS, CNRS & Université de Toulouse (INSA, UPS), Toulouse 31077, France

³ Department of Chemistry, National Taras Shevchenko University, Kiev 01601, Ukraine

⁴ Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico

Materials 2016, 9(7), 537; https://doi.org/10.3390/ma9070537 - 30 Jun 2016

Cited by 17 | Viewed by 5740

Abstract

Topographic images of [Fe(Htrz)₂(trz)](BF₄) nanoparticles were acquired across the first-order spin transition using variable-temperature atomic force microscopy (AFM) in amplitude modulation mode. These studies revealed a complex morphology of the particles consisting of aggregates of small nanocrystals, which expand, [...] Read more.

Topographic images of [Fe(Htrz)₂(trz)](BF₄) nanoparticles were acquired across the first-order spin transition using variable-temperature atomic force microscopy (AFM) in amplitude modulation mode. These studies revealed a complex morphology of the particles consisting of aggregates of small nanocrystals, which expand, separate and re-aggregate due to the mechanical stress during the spin-state switching events. Both reversible (prompt or slow recovery) and irreversible effects (fatigue) on the particle morphology were evidenced and correlated with the spin crossover properties. Full article

(This article belongs to the Special Issue Advances in Molecular Magnets and related Phenomena)

▼ Show Figures

Figure 1

8 pages, 5012 KiB

Open AccessArticle

Effects of Stress Relaxation Aging with Electrical Pulses on Microstructures and Properties of 2219 Aluminum Alloy

by Jingsheng Tan^1,2, Lihua Zhan^1,2,*, Jiao Zhang^1,2, Zhan Yang^1,2 and Ziyao Ma^1,2

¹ State Key Laboratory of High Performance Complex Manufacturing, Central South University, Changsha 410083, China

² School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China

Materials 2016, 9(7), 538; https://doi.org/10.3390/ma9070538 - 1 Jul 2016

Cited by 10 | Viewed by 5341

Abstract

To realize the high-efficiency and high-performance manufacture of complex high-web panels, this paper introduced electric pulse current (EPC) into the stress relaxation aging forming process of 2219 aluminum alloy and systematically studied the effects of EPC, stress, and aging time upon the microstructure [...] Read more.

To realize the high-efficiency and high-performance manufacture of complex high-web panels, this paper introduced electric pulse current (EPC) into the stress relaxation aging forming process of 2219 aluminum alloy and systematically studied the effects of EPC, stress, and aging time upon the microstructure and properties of 2219 aluminum alloy. It is discovered that: (a) EPC greatly enhanced the mechanical properties after stress relaxation aging and reduced the sensitivity of the yield strength for the initial stress under the aging system of 165 °C/11 h; (b) compared with general aging, stress relaxation aging instead delayed the aging process of 2219 aluminum alloy and greatly increased the peak strength value; (c) EPC accelerated the aging precipitation behavior of 2219 aluminum alloy and reduced transgranular and grain-boundary energy difference, thus leading to a more diffused distribution of the transgranular precipitated phase and the absence of a significant precipitation-free zone (PFZ) and grain-boundary stable phase in the grain boundary, further improving the mechanical properties of the alloy. Full article

▼ Show Figures

Graphical abstract

19 pages, 5650 KiB

Open AccessArticle

Formability Analysis of Bamboo Fabric Reinforced Poly (Lactic) Acid Composites

by Nurul Fazita M. R.^1,2,*, Krishnan Jayaraman¹ and Debes Bhattacharyya¹

¹ Centre for Advanced Composite Materials (CACM), Department of Mechanical Engineering, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand

² School of Industrial Technology, Universiti Sains Malaysia, Penang 11800, Malaysia

Materials 2016, 9(7), 539; https://doi.org/10.3390/ma9070539 - 2 Jul 2016

Cited by 18 | Viewed by 7571

Abstract

Poly (lactic) acid (PLA) composites have made their way into various applications that may require thermoforming to produce 3D shapes. Wrinkles are common in many forming processes and identification of the forming parameters to prevent them in the useful part of the mechanical [...] Read more.

Poly (lactic) acid (PLA) composites have made their way into various applications that may require thermoforming to produce 3D shapes. Wrinkles are common in many forming processes and identification of the forming parameters to prevent them in the useful part of the mechanical component is a key consideration. Better prediction of such defects helps to significantly reduce the time required for a tooling design process. The purpose of the experiment discussed here is to investigate the effects of different test parameters on the occurrence of deformations during sheet forming of double curvature shapes with bamboo fabric reinforced-PLA composites. The results demonstrated that the domes formed using hot tooling conditions were better in quality than those formed using cold tooling conditions. Wrinkles were more profound in the warp direction of the composite domes compared to the weft direction. Grid Strain Analysis (GSA) identifies the regions of severe deformation and provides useful information regarding the optimisation of processing parameters. Full article

(This article belongs to the Special Issue Bio- and Natural-Fiber Composites)

▼ Show Figures

Figure 1

8 pages, 2224 KiB

Open AccessArticle

Effects of Carbonization Temperature and Component Ratio on Electromagnetic Interference Shielding Effectiveness of Woodceramics

by Yubo Tao¹, Peng Li^1,*

and Sheldon Q. Shi²

¹ College of Material Science and Engineering, Northeast Forestry University, Harbin 150040, China

² Department of Electrical Engineering, University of North Texas, Denton, TX 76203, USA

Materials 2016, 9(7), 540; https://doi.org/10.3390/ma9070540 - 2 Jul 2016

Cited by 30 | Viewed by 5647

Abstract

Woodceramics were fabricated in a vacuum through carbonization of wood powder impregnated with phenol formaldehyde (PF) resin. The effects of carbonization temperature and mass ratio of wood/resin on electromagnetic interference (EMI) shielding effectiveness (SE) and morphology of woodceramics were explored. The PF resin [...] Read more.

Woodceramics were fabricated in a vacuum through carbonization of wood powder impregnated with phenol formaldehyde (PF) resin. The effects of carbonization temperature and mass ratio of wood/resin on electromagnetic interference (EMI) shielding effectiveness (SE) and morphology of woodceramics were explored. The PF resin made wood cell walls have the characteristics of glassy carbon. Wood axial tracheid and ray cells were filled with more glassy carbon by increasing addition of PF resin. Moreover, the increase of carbonization temperature was beneficial to improving SE. Woodceramics (mass ratio 1:1) obtained at 1000 °C presented a medium SE level between 30 MHz and 1.5 GHz. Full article

▼ Show Figures

Figure 1

15 pages, 33914 KiB

Open AccessArticle

Self-Assembly and Drug Release Capacities of Organogels via Some Amide Compounds with Aromatic Substituent Headgroups

by Lexin Zhang¹, Tifeng Jiao^1,2,*

, Kai Ma¹, Ruirui Xing¹, Yamei Liu¹, Yong Xiao³, Jingxin Zhou¹, Qingrui Zhang¹ and Qiuming Peng²

¹ Hebei Key Laboratory of Applied Chemistry, School of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, China

² State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China

³ Environmental Protection Sciences Research Institute of Qinhuangdao City, Qinhuangdao 066001, China

Materials 2016, 9(7), 541; https://doi.org/10.3390/ma9070541 - 4 Jul 2016

Cited by 14 | Viewed by 5870

Abstract

In this work, some amide compounds with different aromatic substituent headgroups were synthesized and their gelation self-assembly behaviors in 22 solvents were characterized as new gelators. The obtained results indicated that the size of aromatic substituent headgroups in molecular skeletons in gelators showed [...] Read more.

In this work, some amide compounds with different aromatic substituent headgroups were synthesized and their gelation self-assembly behaviors in 22 solvents were characterized as new gelators. The obtained results indicated that the size of aromatic substituent headgroups in molecular skeletons in gelators showed crucial effect in the gel formation and self-assembly behavior of all compounds in the solvents used. Larger aromatic headgroups in molecular structures in the synthesized gelator molecules are helpful to form various gel nanostructures. Morphological investigations showed that the gelator molecules can self-assembly and stack into various organized aggregates with solvent change, such as wrinkle, belt, rod, and lamella-like structures. Spectral characterizations suggested that there existed various weak interactions including π-π stacking, hydrogen bonding, and hydrophobic forces due to aromatic substituent headgroups and alkyl substituent chains in molecular structures. In addition, the drug release capacities experiments demonstrated that the drug release rate in present obtained gels can be tuned by adjusting the concentrations of dye. The present work would open up enormous insight to design and investigate new kind of soft materials with designed molecular structures and tunable drug release performance. Full article

▼ Show Figures

Figure 1

15 pages, 8190 KiB

Open AccessArticle

In Vitro Corrosion Study of Friction Stir Processed WE43 Magnesium Alloy in a Simulated Body Fluid

by Genghua Cao, Datong Zhang^*, Weiwen Zhang and Wen Zhang

National Engineering Research Center of Near-Net Shape Forming for Metallic Materials, South China University of Technology, Guangzhou 510640, Guangdong, China

Materials 2016, 9(7), 542; https://doi.org/10.3390/ma9070542 - 7 Jul 2016

Cited by 21 | Viewed by 5264

Abstract

Corrosion behavior of friction stir processing (FSP) WE43 alloy in a simulated body fluid (SBF) was investigated. Micro-galvanic corrosion was the dominated corrosion behavior, and the corrosion resistance of FSP WE43 alloy was improved compared to the cast counterpart. Furthermore, due to the [...] Read more.

Corrosion behavior of friction stir processing (FSP) WE43 alloy in a simulated body fluid (SBF) was investigated. Micro-galvanic corrosion was the dominated corrosion behavior, and the corrosion resistance of FSP WE43 alloy was improved compared to the cast counterpart. Furthermore, due to the fine-grained and homogeneous microstructure, uniform corrosion morphology was observed on FSP WE43 alloy. According to the tensile properties of specimens with different immersion time intervals, FSP WE43 alloy shows better performance to maintain the mechanical integrity in SBF as compared to the as-cast alloy. Full article

▼ Show Figures

Figure 1

12 pages, 1395 KiB

Open AccessArticle

Electrochemical Study and Characterization of an Amperometric Biosensor Based on the Immobilization of Laccase in a Nanostructure of TiO₂ Synthesized by the Sol-Gel Method

by Mariana Romero-Arcos¹, Ma. Guadalupe Garnica-Romo^2,* and Héctor Eduardo Martínez-Flores³

¹ Programa Institucional de Doctorado en Ciencias Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Santiago Tapia 403, col. Centro, Morelia, Mich. cp 58000, Mexico

² Facultad de Ingeniería Civil, Universidad Michoacana de San Nicolás de Hidalgo, Santiago Tapia 403, col. Centro, Morelia, Mich cp 58000, Mexico

³ Facultad de Químico Farmacobiología, Universidad Michoacana de San Nicolás de Hidalgo, Santiago Tapia 403, col. Centro, Morelia, Mich cp 58000, Mexico

Materials 2016, 9(7), 543; https://doi.org/10.3390/ma9070543 - 7 Jul 2016

Cited by 37 | Viewed by 6834

Abstract

Laccase amperometric biosensors were developed to detect the catechol compound. The laccase enzyme (LAC) immobilization was performed on nanostructures of (a) titania (TiO₂); (b) titania/Nafion (TiO₂/NAF) (both immobilized by the sol-gel method) and a third nanostructure, which consisted of [...] Read more.

Laccase amperometric biosensors were developed to detect the catechol compound. The laccase enzyme (LAC) immobilization was performed on nanostructures of (a) titania (TiO₂); (b) titania/Nafion (TiO₂/NAF) (both immobilized by the sol-gel method) and a third nanostructure, which consisted of a single biosensor composite of Nafion and laccase enzyme denoted as NAF/LAC. The Nafion was deposited on a graphite electrode and used to avoid “cracking” on the matrix. The TiO₂ particle size was an average of 66 nm. FTIR spectroscopy vibration modes of different composites were determined. The electrochemical behavior of the biosensor was studied using electrochemical spectroscopy (EIS) and cyclic voltammetry (CV). The biosensor based on TiO₂/NAF/LAC presented the best electro-chemical properties with regard to sensitivity, stability and detection limit after a period of 22 days. Full article

▼ Show Figures

Figure 1

13 pages, 4176 KiB

Open AccessArticle

Investigation of Industrial Polyurethane Foams Modified with Antimicrobial Copper Nanoparticles

by Maria Chiara Sportelli¹

, Rosaria Anna Picca¹

, Roberto Ronco¹, Elisabetta Bonerba², Giuseppina Tantillo², Mauro Pollini³, Alessandro Sannino³, Antonio Valentini⁴, Tommaso R.I. Cataldi¹

and Nicola Cioffi^1,*

¹ Dipartimento di Chimica, Università Degli Studi di Bari “Aldo Moro”, via E. Orabona 4, Bari (BA) 70126, Italy

² Dipartimento di Medicina Veterinaria, Università Degli Studi di Bari “Aldo Moro”, St.da P.le per Casamassima Km 3, Valenzano (BA) 70010, Italy

³ Dipartimento di Ingegneria dell’Innovazione, Università del Salento, via per Monteroni, Lecce (LE) 73100, Italy

⁴ Dipartimento Interateneo di Fisica, Università Degli Studi di Bari “Aldo Moro”, via Amendola 173, Bari (BA) 70126, Italy

Materials 2016, 9(7), 544; https://doi.org/10.3390/ma9070544 - 7 Jul 2016

Cited by 31 | Viewed by 7123

Abstract

Antimicrobial copper nanoparticles (CuNPs) were electrosynthetized and applied to the controlled impregnation of industrial polyurethane foams used as padding in the textile production or as filters for air conditioning systems. CuNP-modified materials were investigated and characterized morphologically and spectroscopically, by means of Transmission [...] Read more.

Antimicrobial copper nanoparticles (CuNPs) were electrosynthetized and applied to the controlled impregnation of industrial polyurethane foams used as padding in the textile production or as filters for air conditioning systems. CuNP-modified materials were investigated and characterized morphologically and spectroscopically, by means of Transmission Electron Microscopy (TEM), and X-ray Photoelectron Spectroscopy (XPS). The release of copper ions in solution was studied by Electro-Thermal Atomic Absorption Spectroscopy (ETAAS). Finally, the antimicrobial activity of freshly prepared, as well as aged samples—stored for two months—was demonstrated towards different target microorganisms. Full article

(This article belongs to the Special Issue Advances and Applications of Nano-antimicrobial Treatments)

▼ Show Figures

Figure 1

10 pages, 3046 KiB

Open AccessArticle

Tailoring the Dielectric Layer Structure for Enhanced Performance of Organic Field-Effect Transistors: The Use of a Sandwiched Polar Dielectric Layer

by Shijiao Han¹

, Xin Yang², Xinming Zhuang¹, Junsheng Yu^1,2,*

and Lu Li^2,*

¹ State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054, China

² Co-Innovation Center for Micro/Nano Optoelectronic Materials and Devices, Research Institute for New Materials and Technology, Chongqing University of Arts and Sciences, Chongqing 402160, China

Materials 2016, 9(7), 545; https://doi.org/10.3390/ma9070545 - 7 Jul 2016

Cited by 16 | Viewed by 8676

Abstract

To investigate the origins of hydroxyl groups in a polymeric dielectric and its applications in organic field-effect transistors (OFETs), a polar polymer layer was inserted between two polymethyl methacrylate (PMMA) dielectric layers, and its effect on the performance as an organic field-effect transistor [...] Read more.

To investigate the origins of hydroxyl groups in a polymeric dielectric and its applications in organic field-effect transistors (OFETs), a polar polymer layer was inserted between two polymethyl methacrylate (PMMA) dielectric layers, and its effect on the performance as an organic field-effect transistor (OFET) was studied. The OFETs with a sandwiched dielectric layer of poly(vinyl alcohol) (PVA) or poly(4-vinylphenol) (PVP) containing hydroxyl groups had shown enhanced characteristics compared to those with only PMMA layers. The field-effect mobility had been raised more than 10 times in n-type devices (three times in the p-type one), and the threshold voltage had been lowered almost eight times in p-type devices (two times in the n-type). The on-off ratio of two kinds of devices had been enhanced by almost two orders of magnitude. This was attributed to the orientation of hydroxyl groups from disordered to perpendicular to the substrate under gate-applied voltage bias, and additional charges would be induced by this polarization at the interface between the semiconductor and dielectrics, contributing to the accumulation of charge transfer. Full article

▼ Show Figures

Graphical abstract

12 pages, 10548 KiB

Open AccessArticle

Acid-Alkali Resistance of New Reclaimed Tiles Containing Sewage Sludge Ash and Waste Glass

by Deng-Fong Lin, Kuo-Liang Lin^*, Huan-Lin Luo and Jia-Qin Xu

Department of Civil and Ecological Engineering, I-Shou University, Kaohsiung 84001, Taiwan

Materials 2016, 9(7), 546; https://doi.org/10.3390/ma9070546 - 7 Jul 2016

Cited by 8 | Viewed by 5826

Abstract

In this study, properties of newly developed reclaimed tiles in a harmful environment were investigated. A portion of clay used to manufacture tiles was replaced with sewage sludge ash (SSA) and waste glass to produce the new reclaimed tiles. To investigate the effects [...] Read more.

In this study, properties of newly developed reclaimed tiles in a harmful environment were investigated. A portion of clay used to manufacture tiles was replaced with sewage sludge ash (SSA) and waste glass to produce the new reclaimed tiles. To investigate the effects of SSA and waste glass on the properties of the tiles, different specimens were blended and placed in acid-alkali solutions. The reclaimed tile specimens were manufactured by clay, 10% SSA, and five different mixes of waste glass replacement, namely, 0%, 10%, 20%, 40%, and 60%. These specimens were calcined at 1000 °C and subsequently underwent a series of tests, including TGA/DTA (thermogravimetric analysis/differential thermal analysis), SEM (scanning electron microscopy), XRD (X-ray diffraction), bending strength, weight loss, and porosity. Test results show that shortcomings associated with the introduction of the sludge ash were improved by the admixture of waste glass, especially in the aspects of shrinkage and bending strength. The study showed that the new reclaimed tiles performed relatively well in acid-alkali resistance tests but appeared to have better alkali resistance than acid resistance. It was also found that the optimal mix of such reclaimed tiles was 10% SSA, 10% waste glass, and 80% clay. Full article

(This article belongs to the Special Issue Selected Papers from ICASI 2016)

▼ Show Figures

Figure 1

12 pages, 3044 KiB

Open AccessArticle

Repair Bond Strength of Aged Resin Composite after Different Surface and Bonding Treatments

by Michael Wendler^1,2, Renan Belli¹, Reinhard Panzer¹, Daniel Skibbe¹, Anselm Petschelt¹ and Ulrich Lohbauer^1,*

¹ Dental Clinic 1-Operative Dentistry and Periodontology, Research Laboratory for Dental Biomaterials, Friedrich-Alexander University Erlangen-Nuremberg, Erlangen 91054, Germany

² Department of Restorative Dentistry, Faculty of Dentistry, University of Concepción, Concepción 4070369, Chile

Materials 2016, 9(7), 547; https://doi.org/10.3390/ma9070547 - 7 Jul 2016

Cited by 60 | Viewed by 8299

Abstract

The aim of this study was to compare the effect of different mechanical surface treatments and chemical bonding protocols on the tensile bond strength (TBS) of aged composite. Bar specimens were produced using a nanohybrid resin composite and aged in distilled water for [...] Read more.

The aim of this study was to compare the effect of different mechanical surface treatments and chemical bonding protocols on the tensile bond strength (TBS) of aged composite. Bar specimens were produced using a nanohybrid resin composite and aged in distilled water for 30 days. Different surface treatments (diamond bur, phosphoric acid, silane, and sandblasting with Al₂O₃ or CoJet Sand), as well as bonding protocols (Primer/Adhesive) were used prior to application of the repair composite. TBS of the specimens was measured and the results were analyzed using analysis of variance (ANOVA) and the Student–Newman–Keuls test (α = 0.05). Mechanically treated surfaces were characterized under SEM and by profilometry. The effect of water aging on the degree of conversion was measured by means of FTIR-ATR spectroscopy. An important increase in the degree of conversion was observed after aging. No significant differences in TBS were observed among the mechanical surface treatments, despite variations in surface roughness profiles. Phosphoric acid etching significantly improved repair bond strength values. The cohesive TBS of the material was only reached using resin bonding agents. Application of an intermediate bonding system plays a key role in achieving reliable repair bond strengths, whereas the kind of mechanical surface treatment appears to play a secondary role. Full article

(This article belongs to the Section Biomaterials)

▼ Show Figures

Figure 1

12 pages, 3627 KiB

Open AccessArticle

Preliminary Design and Experimental Investigation of a Novel Pneumatic Conveying Method to Disperse Natural Fibers in Thermoset Polymers

by Mahi Fahimian¹, Mark Kortschot^1,*

and Mohini Sain²

¹ Advanced Materials Group, Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College St., Toronto, ON M5S 3E5, Canada

² Center for Biocomposites and Biomaterials Processing, Faculty of Forestry, University of Toronto, 33 Willcocks Street, Toronto, ON M5S 3B3, Canada

Materials 2016, 9(7), 548; https://doi.org/10.3390/ma9070548 - 7 Jul 2016

Cited by 1 | Viewed by 8754

Abstract

Natural fibers can be attractive reinforcing materials in thermosetting polymers due to their low density and high specific mechanical properties. Although the research effort in this area has grown substantially over the last 20 years, manufacturing technologies to make use of short natural [...] Read more.

Natural fibers can be attractive reinforcing materials in thermosetting polymers due to their low density and high specific mechanical properties. Although the research effort in this area has grown substantially over the last 20 years, manufacturing technologies to make use of short natural fibers in high volume fraction composites; are still limited. Natural fibers, after retting and preprocessing, are discontinuous and easily form entangled bundles. Dispersion and mixing these short fibers with resin to manufacture high quality, high volume fraction composites presents a significant challenge. In this paper, a novel pneumatic design for dispersion of natural fibers in their original discontinuous form is described. In this design, compressed air is used to create vacuum to feed and convey fibres while breaking down fibre clumps and dispersing them in an aerosolized resin stream. Model composite materials, made using proof-of-concept prototype equipment, were imaged with both optical and X-ray tomography to evaluate fibre and resin dispersion. The images indicated that the system was capable of providing an intimate mixture of resin and detangled fibres for two different resin viscosities. The new pneumatic process could serve as the basis of a system to produce well-dispersed high-volume fraction composites containing discontinuous natural fibres drawn directly from a loosely packed source. Full article

(This article belongs to the Special Issue Bio- and Natural-Fiber Composites)

▼ Show Figures

Figure 1

7 pages, 3144 KiB

Open AccessArticle

Low Cost Local Contact Opening by Using Polystyrene Spheres Spin-Coating Method for PERC Solar Cells

by Chia-Hsun Hsu¹, Chih-Hsiang Yang², Yi-Han Wang³, Chun-Wei Huang⁴, Shui-Yang Lien^1,*

, Chung-Yuan Kung² and Jen-Chung Lou³

¹ Department of Materials Science and Engineering, Da-Yeh University, Chunghua 51591, Taiwan

² Department of Electrical Engineering, National Chung Hsing University, Taichung 40227, Taiwan

³ Electronics and Communication Engineering, Peking University, Wuxi 214125, China

⁴ Department of Electrical Engineering, Da-Yeh University, Chunghua 51591, Taiwan

Materials 2016, 9(7), 549; https://doi.org/10.3390/ma9070549 - 8 Jul 2016

Cited by 4 | Viewed by 5785

Abstract

The passivated emitter and rear cell (PERC) concept is one of the most promising technologies for increasing crystalline silicon solar cell efficiency. Instead of using the traditional laser ablation process, this paper demonstrates spin-coated polystyrene spheres (PS) to create local openings on the [...] Read more.

The passivated emitter and rear cell (PERC) concept is one of the most promising technologies for increasing crystalline silicon solar cell efficiency. Instead of using the traditional laser ablation process, this paper demonstrates spin-coated polystyrene spheres (PS) to create local openings on the rear side of PERCs. Effects of PS concentration and post-annealing temperature on PERC performance are investigated. The experimental results show that the PS are randomly distributed on wafers and no PS are joined together at a spin rate of 2000 rpm. The PS can be removed at a temperature of 350 °C, leaving holes on the passivation layers without damaging the wafer surfaces. As compared to the laser opening technique with the same contact fraction, the PS opening technique can yield a higher minority effective lifetime, a higher implied open-circuit voltage, and a slightly higher short-circuit current. Although the fill factor of the PS opening technique is lower owing to non-optimized distribution of the openings, the conversion efficiency of the devices is comparable to that of devices prepared via the laser opening process. Full article

(This article belongs to the Special Issue Selected Papers from ICASI 2016)

▼ Show Figures

Figure 1

25 pages, 7533 KiB

Open AccessFeature PaperArticle

Bimetallic Nanoparticles as Efficient Catalysts: Facile and Green Microwave Synthesis

by Magda Blosi¹, Simona Ortelli¹

, Anna Luisa Costa¹, Michele Dondi¹, Alice Lolli², Sara Andreoli², Patricia Benito² and Stefania Albonetti^2,*

¹ ISTEC-CNR, Institute of Science and Technology for Ceramics, National Research Council, Via Granarolo 64, Faenza 48018, Italy

² Department Industrial Chemistry “Toso Montanari”, Bologna University, Viale Risorgimento 4, Bologna 40136, Italy

Materials 2016, 9(7), 550; https://doi.org/10.3390/ma9070550 - 8 Jul 2016

Cited by 38 | Viewed by 8042

Abstract

This work deals with the development of a green and versatile synthesis of stable mono- and bi-metallic colloids by means of microwave heating and exploiting ecofriendly reagents: water as the solvent, glucose as a mild and non-toxic reducer and polyvinylpirrolidone (PVP) as the [...] Read more.

This work deals with the development of a green and versatile synthesis of stable mono- and bi-metallic colloids by means of microwave heating and exploiting ecofriendly reagents: water as the solvent, glucose as a mild and non-toxic reducer and polyvinylpirrolidone (PVP) as the chelating agent. Particle size-control, total reaction yield and long-term stability of colloids were achieved with this method of preparation. All of the materials were tested as effective catalysts in the reduction of p-nitrophenol in the presence of NaBH₄ as the probe reaction. A synergistic positive effect of the bimetallic phase was assessed for Au/Cu and Pd/Au alloy nanoparticles, the latter showing the highest catalytic performance. Moreover, monoand bi-metallic colloids were used to prepare TiO₂- and CeO₂-supported catalysts for the liquid phase oxidation of 5-hydroxymethylfufural (HMF) to 2,5-furandicarboxylic acid (FDCA). The use of Au/Cu and Au/Pd bimetallic catalysts led to an increase in FDCA selectivity. Finally, preformed Pd/Cu nanoparticles were incorporated into the structure of MCM-41-silica. The resulting Pd/Cu MCM-41 catalysts were tested in the hydrodechlorination of CF₃OCFClCF₂Cl to CF₃OCF=CF₂. The effect of Cu on the hydrogenating properties of Pd was demonstrated. Full article

(This article belongs to the Special Issue Nanoparticle Synthesis and Applications in Catalysis)

▼ Show Figures

Figure 1

9 pages, 1162 KiB

Open AccessArticle

The Resistive Switching Characteristics in ZrO₂ and Its Filamentary Conduction Behavior

by Chun-Hung Lai¹, Hung-Wei Chen^1,* and Chih-Yi Liu²

¹ Department of Electronic Engineering, National United University, Miaoli 36063, Taiwan

² Department and Institute of Electronic Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung 80778, Taiwan

Materials 2016, 9(7), 551; https://doi.org/10.3390/ma9070551 - 8 Jul 2016

Cited by 10 | Viewed by 5479

Abstract

This study investigated the conduction properties of sputtered ZrO₂ exhibiting reversible and stable resistance change. Similar current distributions in on/off conduction and set/reset switching were observed in top electrodes with a diameter of 150, 250, and 350 µm. The size independence of [...] Read more.

This study investigated the conduction properties of sputtered ZrO₂ exhibiting reversible and stable resistance change. Similar current distributions in on/off conduction and set/reset switching were observed in top electrodes with a diameter of 150, 250, and 350 µm. The size independence of current magnitude implied the presence of an uneven filamentary path over the electrode area. Increased current compliance was imposed on the turn-on process, and the observed increase in on-state current and turn-off threshold was attributed to incremental filament diameter. Variations in current conduction and resistance switching were analyzed by monitoring sweeping bias limits in both positive and negative polarities. These experimental observations were interpreted based on the aspect ratio of channels comprising conductive and oxidized filament portions, thereby elucidating the characteristics of filamentary resistive switching. Full article

(This article belongs to the Special Issue Selected Papers from ICASI 2016)

▼ Show Figures

Figure 1

13 pages, 3209 KiB

Open AccessArticle

The First 20 Hours of Geopolymerization: An in Situ WAXS Study of Flyash-Based Geopolymers

by Ross P. Williams^* and Arie Van Riessen

John de Laeter Centre, Curtin University of Technology, GPO Box U1987, Perth WA 6845, Australia

Materials 2016, 9(7), 552; https://doi.org/10.3390/ma9070552 - 8 Jul 2016

Cited by 14 | Viewed by 5611

Abstract

This study followed the first 20 h of flyash geopolymerization at 70 °C using time resolved Wide Angle X-ray Scattering (WAXS). The extent of dissolution of the amorphous phase of the flyash was determined to range from 29% to 54% for the different [...] Read more.

This study followed the first 20 h of flyash geopolymerization at 70 °C using time resolved Wide Angle X-ray Scattering (WAXS). The extent of dissolution of the amorphous phase of the flyash was determined to range from 29% to 54% for the different formulations trialed. The dissolution rate of the flyash significantly reduced after the first 5 h for all samples. During the formation stage of the geopolymer there were significant temporal variations in the chemistry of the dissolved solution due to the rate of flyash dissolution, with a relative standard deviation of 20%, 57% and 24% for the Si/Al, Na/Al and H/Si ratios, respectively. Utilizing the Power Law, scattering in the low angle region of the WAXS pattern combined with the geopolymer peak area yielded a measure which correlated with the compressive strength—providing a new method to measure the flyash dissolution and geopolymer formation processes independently. The evolution of several zeolite-like phases was followed, noting there are different formation mechanisms involved even within the same sample. Four samples were examined with compressive strengths ranging from 14(2)–50(9) MPa, each was synthesized with flyash from Collie Power Station (Western Australia) activated with sodium silicate solution of varying concentrations. Full article

(This article belongs to the Special Issue Advances in Geopolymers and Alkali-Activated Materials)

▼ Show Figures

Figure 1

13 pages, 2663 KiB

Open AccessArticle

Cationic Site-Preference in the Yb_14-xCa_xAlSb₁₁ (4.81 ≤ x ≤ 10.57) Series: Theoretical and Experimental Studies

by Gnu Nam^1,†, Eunyoung Jang^1,†, Hongil Jo²

, Mi-Kyung Han³, Sung-Jin Kim³, Kang Min Ok²

and Tae-Soo You^1,*

¹ Department of Chemistry, Chungbuk National University, Cheongju, Chungbuk 28644, Korea

² Department of Chemistry, Chung-Ang University, Seoul 06974, Korea

³ Department of Chemistry and Nano Science, Ewha Woman University, Seoul 03760, Korea

^† These authors are equally contributed to this work.

Materials 2016, 9(7), 553; https://doi.org/10.3390/ma9070553 - 8 Jul 2016

Cited by 16 | Viewed by 4425

Abstract

Four quaternary Zintl phases with mixed-cations in the Yb_14-xCa_xAlSb₁₁ (4.81 ≤ x ≤ 10.57) series have been synthesized by using the arc-melting and the Sn metal-flux reaction methods, and the isotypic crystal structures of the title compounds have [...] Read more.

Four quaternary Zintl phases with mixed-cations in the Yb_14-xCa_xAlSb₁₁ (4.81 ≤ x ≤ 10.57) series have been synthesized by using the arc-melting and the Sn metal-flux reaction methods, and the isotypic crystal structures of the title compounds have been characterized by both powder and single-crystal X-ray diffraction (PXRD and SXRD) analyses. The overall crystal structure adopting the Ca₁₄AlSb₁₁-type can be described as a pack of four different types of the spiral-shaped one-dimensional octahedra chains with various turning radii, each of which is formed by the distorted ((Yb/Ca)Sb₆) octahedra. Four symmetrically-independent cationic sites contain mixed occupations of Yb²⁺ and Ca²⁺ with different mixing ratios and display a particular site preference by two cationic elements. Two hypothetical structural models of Yb₄Ca₁₀AlSb₁₁ with different cationic arrangements were designed and exploited to study the details of site and bond energies. QVAL values provided the rationale for the observed site preference based on the electronegativity of each atom. Density of states (DOS) curves indicated a semiconducting property of the title compounds, and crystal orbital Hamilton population (COHP) plots explained individual chemical bonding between components. Thermal conductivity measurement was performed for Yb_8.42(4)Ca_5.58AlSb₁₁, and the result was compared to compounds without mixed cations. Full article

▼ Show Figures

Figure 1

10 pages, 14071 KiB

Open AccessFeature PaperArticle

Tunability of Size and Magnetic Moment of Iron Oxide Nanoparticles Synthesized by Forced Hydrolysis

by Ben Sutens^1,†, Tom Swusten^1,†, Kuo Zhong¹, Johanna K. Jochum², Margriet J. Van Bael², Erik V. Van der Eycken³, Ward Brullot¹, Maarten Bloemen¹ and Thierry Verbiest^1,*

¹ Department of Chemistry, Laboratory for Molecular Electronics and Photonics, KU Leuven, Celestijnenlaan 200D, Box 2425, 3001 Leuven, Belgium

² Department of Physics and Astronomy, Laboratory of Solid State Physics and Magnetism, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium

³ Department of Chemistry, Laboratory for Organic & Microwave-Assisted Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium

^† These authors contributed equally to this work.

Materials 2016, 9(7), 554; https://doi.org/10.3390/ma9070554 - 8 Jul 2016

Cited by 18 | Viewed by 7131

Abstract

To utilize iron oxide nanoparticles in biomedical applications, a sufficient magnetic moment is crucial. Since this magnetic moment is directly proportional to the size of the superparamagnetic nanoparticles, synthesis methods of superparamagnetic iron oxide nanoparticles with tunable size are desirable. However, most existing [...] Read more.

To utilize iron oxide nanoparticles in biomedical applications, a sufficient magnetic moment is crucial. Since this magnetic moment is directly proportional to the size of the superparamagnetic nanoparticles, synthesis methods of superparamagnetic iron oxide nanoparticles with tunable size are desirable. However, most existing protocols are plagued by several drawbacks. Presented here is a one-pot synthesis method resulting in monodisperse superparamagnetic iron oxide nanoparticles with a controllable size and magnetic moment using cost-effective reagents. The obtained nanoparticles were thoroughly characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) measurements. Furthermore, the influence of the size on the magnetic moment of the nanoparticles is analyzed by superconducting quantum interference device (SQUID) magnetometry. To emphasize the potential use in biomedical applications, magnetic heating experiments were performed. Full article

(This article belongs to the Special Issue Selected papers from ISN2A2016)

▼ Show Figures

Figure 1

20 pages, 7228 KiB

Open AccessArticle

Crack Healing Performance of PVA-Coated Granules Made of Cement, CSA, and Na₂CO₃ in the Cement Matrix

by Yong-Soo Lee and Jae-Suk Ryou^*

Department of Civil & Environmental Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 133-791, Korea

Materials 2016, 9(7), 555; https://doi.org/10.3390/ma9070555 - 9 Jul 2016

Cited by 30 | Viewed by 6515

Abstract

Various self-healing methods for concrete, such as the use of supplementary cementitious materials, adhesive agents, mineral admixtures, and bacteria, have been suggested to date, and each of these has merits and demerits. Among these, however, the use of cementitious materials may be appropriate [...] Read more.

Various self-healing methods for concrete, such as the use of supplementary cementitious materials, adhesive agents, mineral admixtures, and bacteria, have been suggested to date, and each of these has merits and demerits. Among these, however, the use of cementitious materials may be appropriate due to their good healing efficiency, low cost, and compatibility with the cement matrix. In this study, granulation and coating methods were applied to a new cementitious composite material. The self-healing property of these materials was controlled by the polyvinyl alcohol (PVA) coating until cracks were created. Water dissolved the PVA coating after entering through the cracks, and reacted with the healing materials to generate healing products. The self-healing performance was evaluated at various elapsed times through the measurement of the crack widths, visual observation, and examination of the microscopic images. Simultaneously, a water permeability test was performed and the dynamic modulus of elasticity was measured to verify the recovery of the cracks. In addition, the healing products that had been formed in the cracks were analyzed via X-ray diffraction (XRD) and scanning electron microscopy (SEM). Full article

▼ Show Figures

Graphical abstract

8 pages, 3588 KiB

Open AccessArticle

Enhanced Visible Transmittance of Thermochromic VO₂ Thin Films by SiO₂ Passivation Layer and Their Optical Characterization

by Jung-Hoon Yu¹, Sang-Hun Nam², Ji Won Lee^1,2 and Jin-Hyo Boo^1,2,*

¹ Department of Chemistry, Sungkyunkwan University, Suwon 440-746, Korea

² Institute of Basic Science, Sungkyunkwan University, Suwon 440-746, Korea

Materials 2016, 9(7), 556; https://doi.org/10.3390/ma9070556 - 9 Jul 2016

Cited by 36 | Viewed by 9453

Abstract

This paper presents the preparation of high-quality vanadium dioxide (VO₂) thermochromic thin films with enhanced visible transmittance (T_vis) via radio frequency (RF) sputtering and plasma enhanced chemical vapor deposition (PECVD). VO₂ thin films with high T_vis and [...] Read more.

This paper presents the preparation of high-quality vanadium dioxide (VO₂) thermochromic thin films with enhanced visible transmittance (T_vis) via radio frequency (RF) sputtering and plasma enhanced chemical vapor deposition (PECVD). VO₂ thin films with high T_vis and excellent optical switching efficiency (E_os) were successfully prepared by employing SiO₂ as a passivation layer. After SiO₂ deposition, the roughness of the films was decreased 2-fold and a denser structure was formed. These morphological changes corresponded to the results of optical characterization including the haze, reflectance and absorption spectra. In spite of SiO₂ coating, the phase transition temperature (T_c) of the prepared films was not affected. Compared with pristine VO₂, the total layer thickness after SiO₂ coating was 160 nm, which is an increase of 80 nm. Despite the thickness change, the VO₂ thin films showed a higher T_vis value (λ 650 nm, 58%) compared with the pristine samples (λ 650 nm, 43%). This enhancement of T_vis while maintaining high E_os is meaningful for VO₂-based smart window applications. Full article

(This article belongs to the Special Issue Selected Papers from ICASI 2016)

▼ Show Figures

Graphical abstract

9 pages, 13143 KiB

Open AccessArticle

Solvent-Free Esterification of Carboxylic Acids Using Supported Iron Oxide Nanoparticles as an Efficient and Recoverable Catalyst

by Fatemeh Rajabi^1,*, Mohammad Abdollahi¹ and Rafael Luque²

¹ Department of Science, Payame Noor University, P.O. Box 19395-4697, Tehran 19569, Iran

² Departamento de Química Orgánica, Universidad de Córdoba, Campus de Rabanales, Edificio Marie Curie (C-3), Ctra Nnal IV-A, km 396, Cordoba 14014, Spain

Materials 2016, 9(7), 557; https://doi.org/10.3390/ma9070557 - 12 Jul 2016

Cited by 24 | Viewed by 8037

Abstract

Supported iron oxide nanoparticles on mesoporous materials (FeNP@SBA-15) have been successfully utilized in the esterification of a variety carboxylic acids including aromatic, aliphatic, and long-chain carboxylic acids under convenient reaction conditions. The supported catalyst could be easily recovered after reaction completion and reused [...] Read more.

Supported iron oxide nanoparticles on mesoporous materials (FeNP@SBA-15) have been successfully utilized in the esterification of a variety carboxylic acids including aromatic, aliphatic, and long-chain carboxylic acids under convenient reaction conditions. The supported catalyst could be easily recovered after reaction completion and reused several times without any loss in activity after up to 10 runs. Full article

(This article belongs to the Special Issue Nanocatalysts: Preparation and applications in Catalysis)

▼ Show Figures

Figure 1

11 pages, 5815 KiB

Open AccessFeature PaperArticle

Bonding of TRIP-Steel/Al₂O₃-(3Y)-TZP Composites and (3Y)-TZP Ceramic by a Spark Plasma Sintering (SPS) Apparatus

by Aslan Miriyev¹, Steffen Grützner², Lutz Krüger², Sergey Kalabukhov³ and Nachum Frage^3,*

¹ Department of Mechanical Engineering, Columbia University, New York, NY 10027, USA

² Institute of Materials Engineering, TU Bergakademie Freiberg, Freiberg 09599, Germany

³ Department of Materials Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer Sheva 8410501, Israel

Materials 2016, 9(7), 558; https://doi.org/10.3390/ma9070558 - 9 Jul 2016

Cited by 10 | Viewed by 6815

Abstract

A combination of the high damage tolerance of TRIP-steel and the extremely low thermal conductivity of partially stabilized zirconia (PSZ) can provide controlled thermal-mechanical properties to sandwich-shaped composite specimens comprising these materials. Sintering the (TRIP-steel-PSZ)/PSZ sandwich in a single step is very difficult [...] Read more.

A combination of the high damage tolerance of TRIP-steel and the extremely low thermal conductivity of partially stabilized zirconia (PSZ) can provide controlled thermal-mechanical properties to sandwich-shaped composite specimens comprising these materials. Sintering the (TRIP-steel-PSZ)/PSZ sandwich in a single step is very difficult due to differences in the sintering temperature and densification kinetics of the composite and the ceramic powders. In the present study, we successfully applied a two-step approach involving separate SPS consolidation of pure (3Y)-TZP and composites containing 20 vol % TRIP-steel, 40 vol % Al₂O₃ and 40 vol % (3Y)-TZP ceramic phase, and subsequent diffusion joining of both sintered components in an SPS apparatus. The microstructure and properties of the sintered and bonded specimens were characterized. No defects at the interface between the TZP and the composite after joining in the 1050–1150 °C temperature range were observed. Only limited grain growth occurred during joining, while crystallite size, hardness, shear strength and the fraction of the monoclinic phase in the TZP ceramic virtually did not change. The slight increase of the TZP layer’s fracture toughness with the joining temperature was attributed to the effect of grain size on transformation toughening. Full article

(This article belongs to the Collection Spark-Plasma Sintering and Related Field-Assisted Powder Consolidation Technologies)

▼ Show Figures

Figure 1

15 pages, 4775 KiB

Open AccessArticle

Preparation of a Carbon Doped Tissue-Mimicking Material with High Dielectric Properties for Microwave Imaging Application

by Siang-Wen Lan¹, Min-Hang Weng², Ru-Yuan Yang^3,*

, Shoou-Jinn Chang¹, Yaoh-Sien Chung³, Tsung-Chih Yu² and Chun-Sen Wu²

¹ Department of Electrical Engineering and Advanced Optoelectronic Technology Center, Institute of Microelectronics, National Cheng Kung University, Tainan 701, Taiwan

² Medical Devices and Opto-Electronics Equipment Department, Metal Industries Research and Development Center, Kaohsiung City 811, Taiwan

³ Graduate Institute of Materials Engineering, National Pingtung University of Science and Technology, Pingtung County 912, Taiwan

Materials 2016, 9(7), 559; https://doi.org/10.3390/ma9070559 - 9 Jul 2016

Cited by 8 | Viewed by 5992

Abstract

In this paper, the oil-in-gelatin based tissue-mimicking materials (TMMs) doped with carbon based materials including carbon nanotube, graphene ink or lignin were prepared. The volume percent for gelatin based mixtures and oil based mixtures were both around 50%, and the doping amounts were [...] Read more.

In this paper, the oil-in-gelatin based tissue-mimicking materials (TMMs) doped with carbon based materials including carbon nanotube, graphene ink or lignin were prepared. The volume percent for gelatin based mixtures and oil based mixtures were both around 50%, and the doping amounts were 2 wt %, 4 wt %, and 6 wt %. The effect of doping material and amount on the microwave dielectric properties including dielectric constant and conductivity were investigated over an ultra-wide frequency range from 2 GHz to 20 GHz. The coaxial open-ended reflection technology was used to evaluate the microwave dielectric properties. Six measured values in different locations of each sample were averaged and the standard deviations of all the measured dielectric properties, including dielectric constant and conductivity, were less than one, indicating a good uniformity of the prepared samples. Without doping, the dielectric constant was equal to 23 ± 2 approximately. Results showed with doping of carbon based materials that the dielectric constant and conductivity both increased about 5% to 20%, and the increment was dependent on the doping amount. By proper selection of doping amount of the carbon based materials, the prepared material could map the required dielectric properties of special tissues. The proposed materials were suitable for the phantom used in the microwave medical imaging system. Full article

(This article belongs to the Special Issue Bioinspired and Biomimetic Materials)

▼ Show Figures

Figure 1

13 pages, 3223 KiB

Open AccessFeature PaperCommunication

Biomineralization of Engineered Spider Silk Protein-Based Composite Materials for Bone Tissue Engineering

by John G. Hardy¹

, Jose Guillermo Torres-Rendon², Aldo Leal-Egaña¹, Andreas Walther², Helmut Schlaad³, Helmut Cölfen^4,*

and Thomas R. Scheibel^1,*

¹ Lehrstuhl Biomaterialien, Universität Bayreuth, Universitätsstraße 30, Bayreuth 95447, Germany

² DWI Leibniz Institute for Interactive Materials, Forckenbeckstr. 50, Aachen 52056, Germany

³ Institute of Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, Potsdam 14476, Germany

⁴ Physical Chemistry, Department of Chemistry, University of Konstanz, Universitätsstr. 10, Konstanz D-78457, Germany

Materials 2016, 9(7), 560; https://doi.org/10.3390/ma9070560 - 11 Jul 2016

Cited by 33 | Viewed by 9145

Abstract

Materials based on biodegradable polyesters, such as poly(butylene terephthalate) (PBT) or poly(butylene terephthalate-co-poly(alkylene glycol) terephthalate) (PBTAT), have potential application as pro-regenerative scaffolds for bone tissue engineering. Herein, the preparation of films composed of PBT or PBTAT and an engineered spider silk [...] Read more.

Materials based on biodegradable polyesters, such as poly(butylene terephthalate) (PBT) or poly(butylene terephthalate-co-poly(alkylene glycol) terephthalate) (PBTAT), have potential application as pro-regenerative scaffolds for bone tissue engineering. Herein, the preparation of films composed of PBT or PBTAT and an engineered spider silk protein, (eADF4(C16)), that displays multiple carboxylic acid moieties capable of binding calcium ions and facilitating their biomineralization with calcium carbonate or calcium phosphate is reported. Human mesenchymal stem cells cultured on films mineralized with calcium phosphate show enhanced levels of alkaline phosphatase activity suggesting that such composites have potential use for bone tissue engineering. Full article

(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)

▼ Show Figures

Graphical abstract

17 pages, 2048 KiB

Open AccessArticle

Structural Transitions in Nanosized Zn_0.97Al_0.03O Powders under High Pressure Analyzed by in Situ Angle-Dispersive X-ray Diffraction

by Chih-Ming Lin^1,*, Hsin-Tzu Liu^2,3, Shi-Yao Zhong¹, Chia-Hung Hsu¹, Yi-Te Chiu¹, Ming-Fong Tai^4,*, Jenh-Yih Juang^5,*

, Yu-Chun Chuang⁶

and Yen-Fa Liao⁶

¹ Department of Applied Science, National Hsinchu University of Education, Hsinchu 30014, Taiwan

² Department of Chemical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan

³ Chemical Systems Research Division, Chung-Shan Institute of Science & Technology, Taoyuan 32546, Taiwan

⁴ Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan

⁵ Department of Electrophysics, National Chiao Tung University, Hsinchu 33013, Taiwan

⁶ National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan

Materials 2016, 9(7), 561; https://doi.org/10.3390/ma9070561 - 12 Jul 2016

Cited by 4 | Viewed by 5478

Abstract

Nanosized aluminum-doped zinc oxide Zn_1−xAl_xO (AZO) powders (AZO-NPs) with x = 0.01, 0.03, 0.06, 0.09 and 0.11 were synthesized by chemical precipitation method. The thermogravimetric analysis (TGA) indicated that the precursors were converted to oxides from hydroxides near [...] Read more.

Nanosized aluminum-doped zinc oxide Zn_1−xAl_xO (AZO) powders (AZO-NPs) with x = 0.01, 0.03, 0.06, 0.09 and 0.11 were synthesized by chemical precipitation method. The thermogravimetric analysis (TGA) indicated that the precursors were converted to oxides from hydroxides near 250 °C, which were then heated to 500 °C for subsequent thermal processes to obtain preliminary powders. The obtained preliminary powders were then calcined at 500 °C for three hours. The structure and morphology of the products were measured and characterized by angle-dispersive X-ray diffraction (ADXRD) and scanning electron microscopy (SEM). ADXRD results showed that AZO-NPs with Al content less than 11% exhibited würtzite zinc oxide structure and there was no other impurity phase in the AZO-NPs, suggesting substitutional doping of Al on Zn sites. The Zn_0.97Al_0.03O powders (A₃ZO-NPs) with grain size of about 21.4 nm were used for high-pressure measurements. The in situ ADXRD measurements revealed that, for loading run, the pressure-induced würtzite (B4)-to-rocksalt (B1) structural phase transition began at 9.0(1) GPa. Compared to the predicted phase-transition pressure of ~12.7 GPa for pristine ZnO nanocrystals of similar grain size (~21.4 nm), the transition pressure for the present A₃ZO-NPs exhibited a reduction of ~3.7 GPa. The significant reduction in phase-transition pressure is attributed to the effects of highly selective site occupation, namely Zn²⁺ and Al³⁺, were mainly found in tetrahedral and octahedral sites, respectively. Full article

(This article belongs to the Special Issue Computational Multiscale Modeling and Simulation in Materials Science)

▼ Show Figures

Figure 1

13 pages, 3863 KiB

Open AccessArticle

Enrichment of Cellulosic Waste Hemp (Cannabis sativa) Hurd into Non-Toxic Microfibres

by Reinu E. Abraham¹, Cynthia S. Wong² and Munish Puri^1,3,*

¹ Centre for Chemistry and Biotechnology, School of Life and Environment Science, Deakin University, Waurn Ponds, Geelong 3217, Australia

² Institute for Frontier Materials, Geelong Technology Precinct, Deakin University, Geelong 3217, Australia

³ Bioprocessing Laboratory, CCB, Deakin University, Geelong3217, Australia

Materials 2016, 9(7), 562; https://doi.org/10.3390/ma9070562 - 11 Jul 2016

Cited by 25 | Viewed by 7992

Abstract

In this study a largely available lignocellulose feedstock hemp (Cannabis sativa), obtained as an industrial waste, was used for cellulose extraction. The extraction of cellulose microfibres from hemp biomass was conducted by alkaline treatment and an acidification process. The extracted cellulose [...] Read more.

In this study a largely available lignocellulose feedstock hemp (Cannabis sativa), obtained as an industrial waste, was used for cellulose extraction. The extraction of cellulose microfibres from hemp biomass was conducted by alkaline treatment and an acidification process. The extracted cellulose microfibres were characterised using Fourier-transformed infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). The viability of the study was determined by growing human fibroblasts on the preparation which resulted in being non-toxic; indicating its potential in preparing biological scaffolds. Upon enzymatic hydrolysis of the cellulose microfibre using cellulase from Trichoderma reesei, a maximum of 909 mg/g of reducing sugars were obtained, which endorses its suitability for biofuel production. Full article

(This article belongs to the Special Issue Advances in Functionalization of Lignocellulosic Materials)

▼ Show Figures

Figure 1

22 pages, 1383 KiB

Open AccessArticle

LCA of 1,4-Butanediol Produced via Direct Fermentation of Sugars from Wheat Straw Feedstock within a Territorial Biorefinery

by Annachiara Forte^1,*, Amalia Zucaro¹, Riccardo Basosi²

and Angelo Fierro^1,3

¹ Dipartimento di Biologia, Università di Napoli Federico II, Napoli 80126, Italy

² Dipartimento di Biotecnologie, Chimica e Farmacia, Università di Siena, Siena 53100, Italy

³ Laboratorio di Urbanistica e di Pianificazione del Territorio (LUPT), Università di Napoli Federico II, Napoli 80138, Italy

Materials 2016, 9(7), 563; https://doi.org/10.3390/ma9070563 - 12 Jul 2016

Cited by 65 | Viewed by 10213

Abstract

The bio-based industrial sector has been recognized by the European Union as a priority area toward sustainability, however, the environmental profile of bio-based products needs to be further addressed. This study investigated, through the Life Cycle Assessment (LCA) approach, the environmental performance of [...] Read more.

The bio-based industrial sector has been recognized by the European Union as a priority area toward sustainability, however, the environmental profile of bio-based products needs to be further addressed. This study investigated, through the Life Cycle Assessment (LCA) approach, the environmental performance of bio-based 1,4-butanediol (BDO) produced via direct fermentation of sugars from wheat straw, within a hypothetical regional biorefinery (Campania Region, Southern Italy). The aim was: (i) to identify the hotspots along the production chain; and (ii) to assess the potential environmental benefits of this bio-based polymer versus the reference conventional product (fossil-based BDO). Results identified the prevailing contribution to the total environmental load of bio-based BDO in the feedstock production and in the heat requirement at the biorefinery plant. The modeled industrial bio-based BDO supply chain, showed a general reduction of the environmental impacts compared to the fossil-based BDO. The lowest benefits were gained in terms of acidification and eutrophication, due to the environmental load of the crop phase for feedstock cultivation. Full article

(This article belongs to the Special Issue Advances in Functionalization of Lignocellulosic Materials)

▼ Show Figures

Figure 1

17 pages, 9306 KiB

Open AccessArticle

Characterizations of Rapid Sintered Nanosilver Joint for Attaching Power Chips

by Shuang-Tao Feng^1,2, Yun-Hui Mei^1,2,*

, Gang Chen³, Xin Li^1,2 and Guo-Quan Lu^1,4

¹ Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University, 135# Yaguan Road, Jinnan District, Tianjin 300350, China

² Tianjin Key Laboratory of Advanced Joining Technology and School of Materials Science and Engineering, Tianjin University, Tianjin 300350, China

³ School of Chemical Engineering and Technology, Tianjin University, Tianjin 300350, China

⁴ Department of Materials Science and Engineering, Virginia Tech, Blacksburg, VA 24061, USA

Materials 2016, 9(7), 564; https://doi.org/10.3390/ma9070564 - 12 Jul 2016

Cited by 26 | Viewed by 8157

Abstract

Sintering of nanosilver paste has been extensively studied as a lead-free die-attach solution for bonding semiconductor power chips, such as the power insulated gated bipolar transistor (IGBT). However, for the traditional method of bonding IGBT chips, an external pressure of a few MPa [...] Read more.

Sintering of nanosilver paste has been extensively studied as a lead-free die-attach solution for bonding semiconductor power chips, such as the power insulated gated bipolar transistor (IGBT). However, for the traditional method of bonding IGBT chips, an external pressure of a few MPa is reported necessary for the sintering time of ~1 h. In order to shorten the processing duration time, we developed a rapid way to sinter nanosilver paste for bonding IGBT chips in less than 5 min using pulsed current. In this way, we firstly dried as-printed paste at about 100 °C to get rid of many volatile solvents because they may result in defects or voids during the out-gassing from the paste. Then, the pre-dried paste was further heated by pulse current ranging from 1.2 kA to 2.4 kA for several seconds. The whole procedure was less than 3 min and did not require any gas protection. We could obtain robust sintered joint with shear strength of 30–35 MPa for bonding 1200-V, 25-A IGBT and superior thermal properties. Static and dynamic electrical performance of the as-bonded IGBT assemblies was also characterized to verify the feasibility of this rapid sintering method. The results indicate that the electrical performance is comparable or even partially better than that of commercial IGBT modules. The microstructure evolution of the rapid sintered joints was also studied by scanning electron microscopy (SEM). This work may benefit the wide usage of nanosilver paste for rapid bonding IGBT chips in the future. Full article

(This article belongs to the Collection Spark-Plasma Sintering and Related Field-Assisted Powder Consolidation Technologies)

▼ Show Figures

Figure 1

19 pages, 4772 KiB

Open AccessFeature PaperArticle

Rapeseed and Raspberry Seed Cakes as Inexpensive Raw Materials in the Production of Activated Carbon by Physical Activation: Effect of Activation Conditions on Textural and Phenol Adsorption Characteristics

by Koen Smets¹, Mats De Jong¹, Iwona Lupul², Grazyna Gryglewicz², Sonja Schreurs³, Robert Carleer¹ and Jan Yperman^1,*

¹ Research Group of Applied and Analytical Chemistry, CMK, Hasselt University, Agoralaan Gebouw D, Diepenbeek 3590, Belgium

² Division of Polymer and Carbonaceous Materials, Faculty of Chemistry, Wroclaw University of Technology, ul. Gdañska 7/9, Wroclaw 50-344, Poland

³ NuTeC, CMK, Hasselt University, Agoralaan Gebouw H, Diepenbeek 3590, Belgium

Materials 2016, 9(7), 565; https://doi.org/10.3390/ma9070565 - 12 Jul 2016

Cited by 21 | Viewed by 6467

Abstract

The production of activated carbons (ACs) from rapeseed cake and raspberry seed cake using slow pyrolysis followed by physical activation of the obtained solid residues is the topic of this study. The effect of activation temperature (850, 900 and 950 °C), activation time [...] Read more.

The production of activated carbons (ACs) from rapeseed cake and raspberry seed cake using slow pyrolysis followed by physical activation of the obtained solid residues is the topic of this study. The effect of activation temperature (850, 900 and 950 °C), activation time (30, 60, 90 and 120 min) and agent (steam and CO₂) on the textural characteristics of the ACs is investigated by N₂ adsorption. In general, higher activation temperatures and longer activation times increase the BET specific surface area and the porosity of the ACs, regardless of the activation agent or raw material. Steam is more reactive than CO₂ in terms of pore development, especially in the case of raspberry seed cake. The performance of the ACs in liquid adsorption is evaluated by batch phenol adsorption tests. Experimental data are best fitted by the Freundlich isotherm model. Based on total yield, textural characteristics and phenol adsorption, steam activation at 900 °C for 90 min and CO₂ activation at 900 °C for 120 min are found as the best activation conditions. Raspberry seed cake turns out to be a better raw material than rapeseed cake. Moreover, AC from raspberry seed cake produced by steam activation at 900 °C for 90 min performs as well as commercial AC (Norit GAC 1240) in phenol adsorption. The adsorption kinetics of the selected ACs are best fitted by the pseudo-second-order model. Full article

(This article belongs to the Special Issue Advances in Functionalization of Lignocellulosic Materials)

▼ Show Figures

Figure 1

22 pages, 3862 KiB

Open AccessArticle

A Review of Natural Joint Systems and Numerical Investigation of Bio-Inspired GFRP-to-Steel Joints

by Evangelos I. Avgoulas and Michael P. F. Sutcliffe^*

Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK

Materials 2016, 9(7), 566; https://doi.org/10.3390/ma9070566 - 12 Jul 2016

Cited by 7 | Viewed by 9217

Abstract

There are a great variety of joint types used in nature which can inspire engineering joints. In order to design such biomimetic joints, it is at first important to understand how biological joints work. A comprehensive literature review, considering natural joints from a [...] Read more.

There are a great variety of joint types used in nature which can inspire engineering joints. In order to design such biomimetic joints, it is at first important to understand how biological joints work. A comprehensive literature review, considering natural joints from a mechanical point of view, was undertaken. This was used to develop a taxonomy based on the different methods/functions that nature successfully uses to attach dissimilar tissues. One of the key methods that nature uses to join dissimilar materials is a transitional zone of stiffness at the insertion site. This method was used to propose bio-inspired solutions with a transitional zone of stiffness at the joint site for several glass fibre reinforced plastic (GFRP) to steel adhesively bonded joint configurations. The transition zone was used to reduce the material stiffness mismatch of the joint parts. A numerical finite element model was used to identify the optimum variation in material stiffness that minimises potential failure of the joint. The best bio-inspired joints showed a 118% increase of joint strength compared to the standard joints. Full article

(This article belongs to the Special Issue Bioinspired and Biomimetic Materials)

▼ Show Figures

Figure 1

12 pages, 12784 KiB

Open AccessArticle

Modelling and Microstructural Characterization of Sintered Metallic Porous Materials

by Wojciech Depczynski^1,*, Robert Kazala²

, Krzysztof Ludwinek² and Katarzyna Jedynak³

¹ Faculty of Mechatronics and Mechanical Engineering, Kielce University of Technology, Al. Tysiaclecia P.P. 7, Kielce 25-314, Poland

² Faculty of Electrical Engineering, Automatic Control and Computer Science, Kielce University of Technology, Al. Tysiaclecia P.P. 7, Kielce 25-314, Poland

³ Institute of Chemistry, Jan Kochanowski University in Kielce, Swietokrzyska 15G, Kielce 25-406, Poland

Materials 2016, 9(7), 567; https://doi.org/10.3390/ma9070567 - 12 Jul 2016

Cited by 14 | Viewed by 7501

Abstract

This paper presents selected characteristics of the metallic porous materials produced by the sintering of metal powders. The authors focus on materials produced from the iron powder (Fe) of ASC 100.29 and Distaloy SE. ASC 100.29 is formed by atomization and has a [...] Read more.

This paper presents selected characteristics of the metallic porous materials produced by the sintering of metal powders. The authors focus on materials produced from the iron powder (Fe) of ASC 100.29 and Distaloy SE. ASC 100.29 is formed by atomization and has a characteristic morphology. It consists of spherical particles of different sizes forming agglomerates. Distaloy SE is also based on the sponge-iron. The porous material is prepared using the patented method of sintering the mixture of iron powder ASC 100.29, Fe(III) oxide, Distaloy SE and Fe(III) oxide in the reducing atmosphere of dissociated ammonia. As a result, the materials with open pores of micrometer sizes are obtained. The pores are formed between iron particles bonded by diffusion bridges. The modelling of porous materials containing diffusion bridges that allows for three-dimensional (3D) imaging is presented. Full article

(This article belongs to the Section Porous Materials)

▼ Show Figures

Figure 1

13 pages, 4777 KiB

Open AccessFeature PaperArticle

Rotation Disk Process to Assess the Influence of Metals and Voltage on the Growth of Biofilm

by Dana M. Barry^1,2,3,* and Paul B. McGrath²

¹ Departments of Chemical & Biomolecular Engineering, Clarkson University, Potsdam, NY 13699, USA

² Department of Electrical and Computer Engineering, Clarkson University, Potsdam, NY 13699, USA

³ Center for Advanced Materials Processing (CAMP), Clarkson University, Potsdam, NY 13699, USA

Materials 2016, 9(7), 568; https://doi.org/10.3390/ma9070568 - 12 Jul 2016

Cited by 3 | Viewed by 5586

Abstract

Biofilms consist of not only bacteria but also extracellular polymer substrates (EPS). They are groups of microorganisms that adhere to each other on a surface, especially as a result of exposure to water and bacteria. They can pose health risks to humans as [...] Read more.

Biofilms consist of not only bacteria but also extracellular polymer substrates (EPS). They are groups of microorganisms that adhere to each other on a surface, especially as a result of exposure to water and bacteria. They can pose health risks to humans as they grow in hospital settings that include medical supplies and devices. In a previous study, the researchers discovered that bacteria/biofilm grew well on wetted external latex, male catheters. These results concerned the investigators and encouraged them to find ways for prohibiting the growth of bacteria/biofilm on the male catheters (which are made of natural rubber). They carried out a new study to assess the influence of metals and voltage for the growth of bacteria on these latex samples. For this purpose, a unique Rotation Disk Reactor was used to accelerate biofilm formation on external male catheter samples. This setup included a dip tank containing water and a rotating wheel with the attached latex samples (some of which had single electrodes while others had paired electrodes with applied voltage). The process allowed the samples to become wetted and also exposed them to microorganisms in the ambient air during each revolution of the wheel. The results (as viewed from SEM images) showed that when compared to the control sample, the presence of metals (brass, stainless steel, and silver) was generally effective in preventing bacterial growth. Also the use of voltage (9.5 volt battery) essentially eliminated the appearance of rod shaped bacteria in some of the samples. It can be concluded that the presence of metals significantly reduced bacterial growth on latex and the application of voltage was able to essentially eliminate bacteria, providing appropriate electrode combinations were used. Full article

(This article belongs to the Special Issue Biofilm and Materials Science)

▼ Show Figures

Figure 1

9 pages, 3396 KiB

Open AccessArticle

Influence of Growth Rate and Magnetic Field on Microstructure and Properties of Directionally Solidified Ag-Cu Eutectic Alloy

by Xiaowei Zuo^1,2,*

, Congcong Zhao^1,3, Lin Zhang^1,2 and Engang Wang^1,2,*

¹ Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110004, China

² School of Metallurgy, Northeastern University, Shenyang 110004, China

³ School of Materials Science and Engineering, Northeastern University, Shenyang 110004, China

Materials 2016, 9(7), 569; https://doi.org/10.3390/ma9070569 - 13 Jul 2016

Cited by 15 | Viewed by 7260

Abstract

We report the influence of growth rate and external magnetic field on the eutectic lamellar spacing and properties of directionally-solidified Ag-Cu eutectic alloys. The results indicated that the relationship between the lamellar spacing of directionally-solidified Ag-Cu alloys and the growth rate matched the [...] Read more.

We report the influence of growth rate and external magnetic field on the eutectic lamellar spacing and properties of directionally-solidified Ag-Cu eutectic alloys. The results indicated that the relationship between the lamellar spacing of directionally-solidified Ag-Cu alloys and the growth rate matched the prediction of the Jackson-Hunt model, and the constant was 5.8 µm³/s. The increasing external magnetic field during solidification tilted the growth direction of the lamellar eutectics, and coarsened the eutectic lamellar spacing. These decreased the microhardness and strength of Ag-Cu alloys, but increased their electrical conductivity. The competitive strengthening contributions between the refinement of the eutectic lamellar spacing and the change in growth direction of the eutectics resulted in higher strength in the as-rolled sample with a 0.8 T magnetic field than with other samples, which was confirmed from higher relieved deformation energy using differential scanning calorimetry. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

▼ Show Figures

Figure 1

13 pages, 2637 KiB

Open AccessArticle

Crystal Structures and Mechanical Properties of Ca₂C at High Pressure

by Qun Wei^1,*

, Quan Zhang² and Meiguang Zhang^3,*

¹ School of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071, China

² School of Microelectronics, Xidian University, Xi’an 710071, China

³ College of Physics and Optoelectronic Technology, Baoji University of Arts and Sciences, Baoji 721016, China

Materials 2016, 9(7), 570; https://doi.org/10.3390/ma9070570 - 14 Jul 2016

Cited by 16 | Viewed by 7005

Abstract

Recently, a new high-pressure semiconductor phase of Ca₂C (space group Pnma) was successfully synthesized, it has a low-pressure metallic phase (space group C2/m). In this paper, a systematic investigation of the pressure-induced phase transition of Ca₂ [...] Read more.

Recently, a new high-pressure semiconductor phase of Ca₂C (space group Pnma) was successfully synthesized, it has a low-pressure metallic phase (space group C2/m). In this paper, a systematic investigation of the pressure-induced phase transition of Ca₂C is studied on the basis of first-principles calculations. The calculated enthalpy reveals that the phase transition which transforms from C2/m-Ca₂C to Pnma-Ca₂C occurs at 7.8 GPa, and it is a first-order phase transition with a volume drop of 26.7%. The calculated elastic constants show that C2/m-Ca₂C is mechanically unstable above 6.4 GPa, indicating that the structural phase transition is due to mechanical instability. Both of the two phases exhibit the elastic anisotropy. The semiconductivity of Pnma-Ca₂C and the metallicity of C2/m-Ca₂C have been demonstrated by the electronic band structure calculations. The quasi-direct band gap of Pnma-Ca₂C at 0 GPa is 0.86 eV. Furthermore, the detailed analysis of the total and partial density of states is performed to show the specific contribution to the Fermi level. Full article

(This article belongs to the Special Issue Computational Multiscale Modeling and Simulation in Materials Science)

▼ Show Figures

Figure 1

15 pages, 8953 KiB

Open AccessArticle

An Experimental Study on Micro Clinching of Metal Foils with Cutting by Laser Shock Forming

by Xiao Wang^*, Cong Li, Youjuan Ma, Zongbao Shen, Xianqing Sun, Chaofei Sha, Shuai Gao, Liyin Li and Huixia Liu

School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, China

Materials 2016, 9(7), 571; https://doi.org/10.3390/ma9070571 - 13 Jul 2016

Cited by 21 | Viewed by 6393

Abstract

This paper describes a novel technique for joining similar and dissimilar metal foils, namely micro clinching with cutting by laser shock forming. A series of experiments were conducted to study the deformation behavior of single layer material, during which many important process parameters [...] Read more.

This paper describes a novel technique for joining similar and dissimilar metal foils, namely micro clinching with cutting by laser shock forming. A series of experiments were conducted to study the deformation behavior of single layer material, during which many important process parameters were determined. The process window of the 1060 pure aluminum foils and annealed copper foils produced by micro clinching with cutting was analyzed. Moreover, similar material combination (annealed copper foils) and dissimilar material combination (1060 pure aluminum foils and 304 stainless steel foils) were successfully achieved. The effect of laser energy on the interlock and minimum thickness of upper foils was investigated. In addition, the mechanical strength of different material combinations joined by micro clinching with cutting was measured in single lap shearing tests. According to the achieved results, this novel technique is more suitable for material combinations where the upper foil is thicker than lower foil. With the increase of laser energy, the interlock increased while the minimum thickness of upper foil decreased gradually. The shear strength of 1060 pure aluminum foils and 304 stainless steel foils combination was three times as large as that of 1060 pure aluminum foils and annealed copper foils combination. Full article

(This article belongs to the Special Issue Ultrafast Laser-Based Manufacturing)

▼ Show Figures

Graphical abstract

9 pages, 2259 KiB

Open AccessFeature PaperArticle

Pickering Emulsion-Based Marbles for Cellular Capsules

by Guangzhao Zhang and Chaoyang Wang^*

Research Institute of Materials Science, South China University of Technology, Guangzhou 510640, China

Materials 2016, 9(7), 572; https://doi.org/10.3390/ma9070572 - 14 Jul 2016

Cited by 10 | Viewed by 7064

Abstract

The biodegradable cellular capsule, being prepared from simple vaporization of liquid marbles, is an ideal vehicle for the potential application of drug encapsulation and release. This paper reports the fabrication of cellular capsules via facile vaporization of Pickering emulsion marbles in an ambient [...] Read more.

The biodegradable cellular capsule, being prepared from simple vaporization of liquid marbles, is an ideal vehicle for the potential application of drug encapsulation and release. This paper reports the fabrication of cellular capsules via facile vaporization of Pickering emulsion marbles in an ambient atmosphere. Stable Pickering emulsion (water in oil) was prepared while utilizing dichloromethane (containing poly(l-lactic acid)) and partially hydrophobic silica particles as oil phase and stabilizing agents respectively. Then, the Pickering emulsion marbles were formed by dropping emulsion into a petri dish containing silica particles with a syringe followed by rolling. The cellular capsules were finally obtained after the complete vaporization of both oil and water phases. The technique of scanning electron microscope (SEM) was employed to research the microstructure and surface morphology of the prepared capsules and the results showed the cellular structure as expected. An in vitro drug release test was implemented which showed a sustained release property of the prepared cellular capsules. In addition, the use of biodegradable poly(l-lactic acid) and the biocompatible silica particles also made the fabricated cellular capsules of great potential in the application of sustained drug release. Full article

(This article belongs to the Special Issue Pickering Emulsion and Derived Materials)

▼ Show Figures

Figure 1

10 pages, 6012 KiB

Open AccessArticle

Residual Tensile Property of Plain Woven Jute Fiber/Poly(Lactic Acid) Green Composites during Thermal Cycling

by Hideaki Katogi^*, Kenichi Takemura and Motoki Akiyama

Department of Mechanical Engineering, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama, Kanagawa 221-8686, Japan

Materials 2016, 9(7), 573; https://doi.org/10.3390/ma9070573 - 14 Jul 2016

Cited by 9 | Viewed by 5909

Abstract

This study investigated the residual tensile properties of plain woven jute fiber reinforced poly(lactic acid) (PLA) during thermal cycling. Temperature ranges of thermal cycling tests were 35–45 °C and 35–55 °C. The maximum number of cycles was 10³ cycles. The quasi-static tensile [...] Read more.

This study investigated the residual tensile properties of plain woven jute fiber reinforced poly(lactic acid) (PLA) during thermal cycling. Temperature ranges of thermal cycling tests were 35–45 °C and 35–55 °C. The maximum number of cycles was 10³ cycles. The quasi-static tensile tests of jute fiber, PLA, and composite were conducted after thermal cycling tests. Thermal mechanical analyses of jute fiber and PLA were conducted after thermal cycling tests. Results led to the following conclusions. For temperatures of 35–45 °C, tensile strength of composite at 10³ cycles decreased 10% compared to that of composite at 0 cycles. For temperatures of 35–55 °C, tensile strength and Young’s modulus of composite at 10³ cycles decreased 15% and 10%, respectively, compared to that of composite at 0 cycles. Tensile properties and the coefficient of linear expansion of PLA and jute fiber remained almost unchanged after thermal cycling tests. From observation of a fracture surface, the length of fiber pull out in the fracture surface of composite at 10³ cycles was longer than that of composite at 0 cycles. Therefore, tensile properties of the composite during thermal cycling were decreased, probably because of the decrease of interfacial adhesion between the fiber and resin. Full article

(This article belongs to the Special Issue Bio- and Natural-Fiber Composites)

▼ Show Figures

Graphical abstract

37 pages, 15832 KiB

Open AccessReview

Physico-Chemical Alternatives in Lignocellulosic Materials in Relation to the Kind of Component for Fermenting Purposes

by Alberto Coz^1,*

, Tamara Llano¹

, Eva Cifrián¹, Javier Viguri¹, Edmond Maican² and Herbert Sixta³

¹ Green Engineering and Resources, Department of Chemistry and Process and Resource Engineering, University of Cantabria, Avda. Los Castros s/n, Santander 39005, Spain

² Faculty of Biotechnical Systems Engineering, Politehnica University of Bucharest, 313 Splaiul Independentei, Sector 6, Bucuresti 060042, Romania

³ Department of Forest Products Technology, School of Chemistry, Aalto University, P.O. Box 16300, Aalto FI-00076, Finland

Materials 2016, 9(7), 574; https://doi.org/10.3390/ma9070574 - 15 Jul 2016

Cited by 32 | Viewed by 7358

Abstract

The complete bioconversion of the carbohydrate fraction is of great importance for a lignocellulosic-based biorefinery. However, due to the structure of the lignocellulosic materials, and depending basically on the main parameters within the pretreatment steps, numerous byproducts are generated and they act as [...] Read more.

The complete bioconversion of the carbohydrate fraction is of great importance for a lignocellulosic-based biorefinery. However, due to the structure of the lignocellulosic materials, and depending basically on the main parameters within the pretreatment steps, numerous byproducts are generated and they act as inhibitors in the fermentation operations. In this sense, the impact of inhibitory compounds derived from lignocellulosic materials is one of the major challenges for a sustainable biomass-to-biofuel and -bioproduct industry. In order to minimise the negative effects of these compounds, numerous methodologies have been tested including physical, chemical, and biological processes. The main physical and chemical treatments have been studied in this work in relation to the lignocellulosic material and the inhibitor in order to point out the best mechanisms for fermenting purposes. In addition, special attention has been made in the case of lignocellulosic hydrolysates obtained by chemical processes with SO₂, due to the complex matrix of these materials and the increase in these methodologies in future biorefinery markets. Recommendations of different detoxification methods have been given. Full article

▼ Show Figures

Graphical abstract

19 pages, 9129 KiB

Open AccessArticle

A 3D Lattice Modelling Study of Drying Shrinkage Damage in Concrete Repair Systems

by Mladena Luković^*, Branko Šavija

, Erik Schlangen

, Guang Ye

and Klaas Van Breugel

Faculty of Civil Engineering and Geosciences, Delft 2628 CN, The Netherlands

Materials 2016, 9(7), 575; https://doi.org/10.3390/ma9070575 - 14 Jul 2016

Cited by 48 | Viewed by 7114

Abstract

Differential shrinkage between repair material and concrete substrate is considered to be the main cause of premature failure of repair systems. The magnitude of induced stresses depends on many factors, for example the degree of restraint, moisture gradients caused by curing and drying [...] Read more.

Differential shrinkage between repair material and concrete substrate is considered to be the main cause of premature failure of repair systems. The magnitude of induced stresses depends on many factors, for example the degree of restraint, moisture gradients caused by curing and drying conditions, type of repair material, etc. Numerical simulations combined with experimental observations can be of great use when determining the influence of these parameters on the performance of repair systems. In this work, a lattice type model was used to simulate first the moisture transport inside a repair system and then the resulting damage as a function of time. 3D simulations were performed, and damage patterns were qualitatively verified with experimental results and cracking tendencies in different brittle and ductile materials. The influence of substrate surface preparation, bond strength between the two materials, and thickness of the repair material were investigated. Benefits of using a specially tailored fibre reinforced material, namely strain hardening cementitious composite (SHCC), for controlling the damage development due to drying shrinkage in concrete repairs was also examined. Full article

(This article belongs to the Special Issue Numerical Analysis of Concrete using Discrete Elements)

▼ Show Figures

Figure 1

17 pages, 7233 KiB

Open AccessArticle

Numerical Study of Laminar Flow and Convective Heat Transfer Utilizing Nanofluids in Equilateral Triangular Ducts with Constant Heat Flux

by Hsien-Hung Ting and Shuhn-Shyurng Hou^*

Department of Mechanical Engineering, Kun Shan University, Tainan 71070, Taiwan

Materials 2016, 9(7), 576; https://doi.org/10.3390/ma9070576 - 15 Jul 2016

Cited by 22 | Viewed by 7806

Abstract

This study numerically investigates heat transfer augmentation using water-based Al₂O₃ and CuO nanofluids flowing in a triangular cross-sectional duct under constant heat flux in laminar flow conditions. The Al₂O₃/water nanofluids with different volume fractions (0.1%, 0.5%, [...] Read more.

This study numerically investigates heat transfer augmentation using water-based Al₂O₃ and CuO nanofluids flowing in a triangular cross-sectional duct under constant heat flux in laminar flow conditions. The Al₂O₃/water nanofluids with different volume fractions (0.1%, 0.5%, 1%, 1.5%, and 2%) and CuO/water nanofluids with various volume fractions (0.05%, 0.16%, 0.36%, 0.5%, and 0.8%) are employed, and Reynolds numbers in the range of 700 to 1900 in a laminar flow are considered. The heat transfer rate becomes more remarkable when employing nanofluids. As compared with pure water, at a Peclet number of 7000, a 35% enhancement in the convective heat transfer coefficient, is obtained for an Al₂O₃/water nanofluid with 2% particle volume fraction; at the same Peclet number, a 41% enhancement in the convective heat transfer coefficient is achieved for a CuO/water nanofluid with 0.8% particle volume concentration. Heat transfer enhancement increases with increases in particle volume concentration and Peclet number. Moreover, the numerical results are found to be in good agreement with published experimental data. Full article

(This article belongs to the Special Issue Selected Papers from ICASI 2016)

▼ Show Figures

Figure 1

16 pages, 5666 KiB

Open AccessArticle

Zirconium Carbide Produced by Spark Plasma Sintering and Hot Pressing: Densification Kinetics, Grain Growth, and Thermal Properties

by Xialu Wei^1,*

, Christina Back², Oleg Izhvanov², Christopher D. Haines³ and Eugene A. Olevsky^1,4

¹ Department of Mechanical Engineering, San Diego State University, 5500 Campanile Dr., San Diego, CA 92182, USA

² General Atomics, 3350 General Atomics Ct., San Diego, CA 92121, USA

³ US Army Armament Research Development Engineering Center, Picatinny Arsenal, NJ 07806, USA

⁴ Department of NanoEngineering, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92037, USA

Materials 2016, 9(7), 577; https://doi.org/10.3390/ma9070577 - 14 Jul 2016

Cited by 27 | Viewed by 10003

Abstract

Spark plasma sintering (SPS) has been employed to consolidate a micron-sized zirconium carbide (ZrC) powder. ZrC pellets with a variety of relative densities are obtained under different processing parameters. The densification kinetics of ZrC powders subjected to conventional hot pressing and SPS are [...] Read more.

Spark plasma sintering (SPS) has been employed to consolidate a micron-sized zirconium carbide (ZrC) powder. ZrC pellets with a variety of relative densities are obtained under different processing parameters. The densification kinetics of ZrC powders subjected to conventional hot pressing and SPS are comparatively studied by applying similar heating and loading profiles. Due to the lack of electric current assistance, the conventional hot pressing appears to impose lower strain rate sensitivity and higher activation energy values than those which correspond to the SPS processing. A finite element simulation is used to analyze the temperature evolution within the volume of ZrC specimens subjected to SPS. The control mechanism for grain growth during the final SPS stage is studied via a recently modified model, in which the grain growth rate dependence on porosity is incorporated. The constant pressure specific heat and thermal conductivity of the SPS-processed ZrC are determined to be higher than those reported for the hot-pressed ZrC and the benefits of applying SPS are indicated accordingly. Full article

(This article belongs to the Collection Spark-Plasma Sintering and Related Field-Assisted Powder Consolidation Technologies)

▼ Show Figures

Figure 1

12 pages, 2621 KiB

Open AccessArticle

H₂ Adsorbed Site-to-Site Electronic Delocalization within IRMOF-1: Understanding Non-Negligible Interactions at High Pressure

by Jian Wu, Mustafa U. Kucukkal and Aurora E. Clark^*

Department of Chemistry, Washington State University, Pullman, WA 99164, USA

Materials 2016, 9(7), 578; https://doi.org/10.3390/ma9070578 - 15 Jul 2016

Cited by 5 | Viewed by 4553

Abstract

Isoreticular metal organic frameworks (IRMOFs) have shown high uptake capabilities for storage of H₂ (11.5 wt % at 77 K and 170 bar). A significant literature has employed fragment models and a single adsorbed H₂ to identify adsorption sites within IRMOFs, [...] Read more.

Isoreticular metal organic frameworks (IRMOFs) have shown high uptake capabilities for storage of H₂ (11.5 wt % at 77 K and 170 bar). A significant literature has employed fragment models and a single adsorbed H₂ to identify adsorption sites within IRMOFs, as well as the necessary adsorbate–adsorbent interactions needed to reach sufficient adsorption enthalpy for practical usage, however at high pressures it remains to be seen if H₂···H₂ intermolecular interactions may influence the energetics. This study focuses upon IRMOF-1 (also known as MOF-5), and examines the individual H₂ stabilization energies at different sites using Möller–Plesset perturbation theory and density functional theory alongside chemical models that consist of isolated fragment models and a cubic super cell cluster consisting of both the face- and edge-cube’s of IRMOF-1. Optimization of twenty stable configurations of singly adsorbed H₂ in the super-cell cluster is observed to be essential to obtain energy ordering of the five primary sites consistent with experiment and prior benchmark calculations (α >> β > γ > δ ≈ ε). To examine site-to-site interactions that may occur in the high-pressure regime, 64 co-adsorbed H₂ within a super-cell cluster have been studied (a theoretical maximum of all adsorption sites, 14 wt %). There, delocalization and/or charge transfer of electrons is observed from the σ orbitals of the H₂ bound at the γ positions into the σ* orbitals of H₂ bound at the α sites leads to stabilization of the interaction of H₂ at the γ, by 1.4 kJ/mol, respectively (using M06-2X/LANL2DZ). This effect has been confirmed to be charge transfer, and not a manifestation of enhanced dispersion at high loading, through natural bond order (NBO) analysis and by comparisons of the square of off-diagonal NBO Fock matrix elements for both density functionals that account for dispersion interactions and Hartree–Fock calculations that ignore dispersion. Full article

(This article belongs to the Section Energy Materials)

▼ Show Figures

Graphical abstract

12 pages, 2925 KiB

Open AccessArticle

Nb⁵⁺-Doped SrCoO_3−δ Perovskites as Potential Cathodes for Solid-Oxide Fuel Cells

by Vanessa Cascos^1,*

, José Antonio Alonso¹ and María Teresa Fernández-Díaz²

¹ Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid, Spain

² Institut Laue Langevin, BP 156X, 38042 Grenoble, France

Materials 2016, 9(7), 579; https://doi.org/10.3390/ma9070579 - 15 Jul 2016

Cited by 28 | Viewed by 7136

Abstract

SrCoO_3−δ outperforms as cathode material in solid-oxide fuel cells (SOFC) when the three-dimensional (3C-type) perovskite structure is stabilized by the inclusion of highly-charged transition-metal ions at the octahedral positions. In a previous work we studied the Nb incorporation at the Co [...] Read more.

SrCoO_3−δ outperforms as cathode material in solid-oxide fuel cells (SOFC) when the three-dimensional (3C-type) perovskite structure is stabilized by the inclusion of highly-charged transition-metal ions at the octahedral positions. In a previous work we studied the Nb incorporation at the Co positions in the SrCo_1−xNb_xO_3−δ system, in which the stabilization of a tetragonal P4/mmm perovskite superstructure was described for the x = 0.05 composition. In the present study we extend this investigation to the x = 0.10–0.15 range, also observing the formation of the tetragonal P4/mmm structure instead of the unwanted hexagonal phase corresponding to the 2H polytype. We also investigated the effect of Nb⁵⁺ doping on the thermal, electrical, and electrochemical properties of SrCo_1−xNb_xO_3−δ (x = 0.1 and 0.15) perovskite oxides performing as cathodes in SOFC. In comparison with the undoped hexagonal SrCoO_3−δ phase, the resulting compounds present high thermal stability and an increase of the electrical conductivity. The single-cell tests for these compositions (x = 0.10 and 0.15) with La_0.8Sr_0.2Ga_0.83Mg_0.17O_3−δ (LSGM) as electrolyte and SrMo_0.8Fe_0.2CoO_3−δ as anode gave maximum power densities of 693 and 550 mW∙cm⁻² at 850 °C respectively, using pure H₂ as fuel and air as oxidant. Full article

(This article belongs to the Special Issue Recent Advances in Materials for Solid Oxide Cells)

▼ Show Figures

Figure 1

30 pages, 7966 KiB

Open AccessArticle

Optimizing and Characterizing Geopolymers from Ternary Blend of Philippine Coal Fly Ash, Coal Bottom Ash and Rice Hull Ash

by Martin Ernesto Kalaw^1,*

, Alvin Culaba¹, Hirofumi Hinode², Winarto Kurniawan², Susan Gallardo³ and Michael Angelo Promentilla³

¹ Mechanical Engineering Department, De La Salle University, Manila 1004, Philippines

² International Development Engineering, Tokyo Institute of Technology, Tokyo 152-8550, Japan

³ Chemical Engineering Department, De La Salle University, Manila 1004, Philippines

Materials 2016, 9(7), 580; https://doi.org/10.3390/ma9070580 - 15 Jul 2016

Cited by 43 | Viewed by 11772

Abstract

Geopolymers are inorganic polymers formed from the alkaline activation of amorphous alumino-silicate materials resulting in a three-dimensional polymeric network. As a class of materials, it is seen to have the potential of replacing ordinary Portland cement (OPC), which for more than a hundred [...] Read more.

Geopolymers are inorganic polymers formed from the alkaline activation of amorphous alumino-silicate materials resulting in a three-dimensional polymeric network. As a class of materials, it is seen to have the potential of replacing ordinary Portland cement (OPC), which for more than a hundred years has been the binder of choice for structural and building applications. Geopolymers have emerged as a sustainable option vis-à-vis OPC for three reasons: (1) their technical properties are comparable if not better; (2) they can be produced from industrial wastes; and (3) within reasonable constraints, their production requires less energy and emits significantly less CO₂. In the Philippines, the use of coal ash, as the alumina- and silica- rich geopolymer precursor, is being considered as one of the options for sustainable management of coal ash generation from coal-fired power plants. However, most geopolymer mixes (and the prevalent blended OPC) use only coal fly ash. The coal bottom ash, having very few applications, remains relegated to dumpsites. Rice hull ash, from biomass-fired plants, is another silica-rich geopolymer precursor material from another significantly produced waste in the country with only minimal utilization. In this study, geopolymer samples were formed from the mixture of coal ash, using both coal fly ash (CFA) and coal bottom ash (CBA), and rice hull ash (RHA). The raw materials used for the geopolymerization process were characterized using X-ray fluorescence spectroscopy (XRF) for elemental and X-ray diffraction (XRD) for mineralogical composition. The raw materials’ thermal stability and loss on ignition (LOI) were determined using thermogravimetric analysis (TGA) and reactivity via dissolution tests and inductively-coupled plasma mass spectrometry (ICP) analysis. The mechanical, thermal and microstructural properties of the geopolymers formed were analyzed using compression tests, Fourier transform infra-red spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Using a Scheffé-based mixture design, targeting applications with low thermal conductivity, light weight and moderate strength and allowing for a maximum of five percent by mass of rice hull ash in consideration of the waste utilization of all three components, it has been determined that an 85-10-5 by weight ratio of CFA-CBA-RHA activated with 80-20 by mass ratio of 12 M NaOH and sodium silicate (55% H₂O, modulus = 3) produced geopolymers with a compressive strength of 18.5 MPa, a volumetric weight of 1660 kg/m³ and a thermal conductivity of 0.457 W/m-°C at 28-day curing when pre-cured at 80 °C for 24 h. For this study, the estimates of embodied energy and CO₂ were all below 1.7 MJ/kg and 0.12 kg CO₂/kg, respectively. Full article

(This article belongs to the Special Issue Advances in Geopolymers and Alkali-Activated Materials)

▼ Show Figures

Figure 1

16 pages, 5971 KiB

Open AccessArticle

Mechanical Behavior of Dowel-Type Joints Made of Wood Scrimber Composite

by Minjuan He¹, Duo Tao¹, Zheng Li^1,* and Maolin Li²

¹ Department of Structural Engineering, Tongji University, Shanghai 200092, China

² Tianjin Hualin (Group) Co., Ltd., 88 Nanhuan Road, Tianjin 300350, China

Materials 2016, 9(7), 581; https://doi.org/10.3390/ma9070581 - 15 Jul 2016

Cited by 19 | Viewed by 9001

Abstract

As a renewable building material with low embodied energy characteristics, wood has gained more and more attention in the green and sustainable building industry. In terms of material resource and physical properties, scrimber composite not only makes full use of fast-growing wood species, [...] Read more.

As a renewable building material with low embodied energy characteristics, wood has gained more and more attention in the green and sustainable building industry. In terms of material resource and physical properties, scrimber composite not only makes full use of fast-growing wood species, but also has better mechanical performance and less inherent variability than natural wood material. In this study, the mechanical behavior of bolted beam-to-column joints built with a kind of scrimber composite was investigated both experimentally and numerically. Two groups of specimens were tested under monotonic and low frequency cyclic loading protocols. The experimental results showed that the bolted joints built with scrimber composite performed well in initial stiffness, ductility, and energy dissipation. A three-dimensional (3D) non-linear finite element model (FEM) for the bolted beam-to-column joints was then developed and validated by experimental results. The validated model was further used to investigate the failure mechanism of the bolted joints through stress analysis. This study can contribute to the application of the proposed scrimber composite in structural engineering, and the developed FEM can serve as a useful tool to evaluate the mechanical behavior of such bolted beam-to-column joints with different configurations in future research. Full article

▼ Show Figures

Figure 1

15 pages, 6715 KiB

Open AccessArticle

Adsorption of Heavy Metals by Graphene Oxide/Cellulose Hydrogel Prepared from NaOH/Urea Aqueous Solution

by Xiong Chen, Sukun Zhou, Liming Zhang, Tingting You and Feng Xu^*

Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China

Materials 2016, 9(7), 582; https://doi.org/10.3390/ma9070582 - 16 Jul 2016

Cited by 144 | Viewed by 12902

Abstract

By taking advantage of cellulose, graphene oxide (GO), and the process for crosslinking using epichlorohydrin (ECH), we propose a simple and novel method to prepare GO/cellulose hydrogel with good potential to adsorb metal ions. GO nanosheets containing carboxyl and hydroxyl groups were introduced [...] Read more.

By taking advantage of cellulose, graphene oxide (GO), and the process for crosslinking using epichlorohydrin (ECH), we propose a simple and novel method to prepare GO/cellulose hydrogel with good potential to adsorb metal ions. GO nanosheets containing carboxyl and hydroxyl groups were introduced into the surface of the cellulose hydrogel with retention of the gel structure and its nanoporous property. Due to the introduction of GO, the GO/cellulose composite hydrogels exhibited good compressive strength. Adsorption capacity of Cu²⁺ significantly increases with an increase in the GO/cellulose ratio and GO/cellulose hydrogel showed high adsorption rates. The calculated adsorption capacities at equilibrium (

q_{e}^{cal}

) for GO/cellulose hydrogel (GO:cellulose = 20:100 in weight) was up to 94.34 mg·g⁻¹, which was much higher than that of the pristine cellulose hydrogels. Furthermore, GO/cellulose hydrogel exhibited high efficient regeneration and metal ion recovery, and high adsorption capacity for Zn²⁺, Fe³⁺, and Pb²⁺. Full article

▼ Show Figures

Graphical abstract

12 pages, 2107 KiB

Open AccessArticle

UV-Assisted 3D Printing of Glass and Carbon Fiber-Reinforced Dual-Cure Polymer Composites

by Marta Invernizzi

, Gabriele Natale, Marinella Levi, Stefano Turri and Gianmarco Griffini^*

Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano 20133, Italy

Materials 2016, 9(7), 583; https://doi.org/10.3390/ma9070583 - 16 Jul 2016

Cited by 152 | Viewed by 19968

Abstract

Glass (GFR) and carbon fiber-reinforced (CFR) dual-cure polymer composites fabricated by UV-assisted three-dimensional (UV-3D) printing are presented. The resin material combines an acrylic-based photocurable resin with a low temperature (140 °C) thermally-curable resin system based on bisphenol A diglycidyl ether as base component, [...] Read more.

Glass (GFR) and carbon fiber-reinforced (CFR) dual-cure polymer composites fabricated by UV-assisted three-dimensional (UV-3D) printing are presented. The resin material combines an acrylic-based photocurable resin with a low temperature (140 °C) thermally-curable resin system based on bisphenol A diglycidyl ether as base component, an aliphatic anhydride (hexahydro-4-methylphthalic anhydride) as hardener and (2,4,6,-tris(dimethylaminomethyl)phenol) as catalyst. A thorough rheological characterization of these formulations allowed us to define their 3D printability window. UV-3D printed macrostructures were successfully demonstrated, giving a clear indication of their potential use in real-life structural applications. Differential scanning calorimetry and dynamic mechanical analysis highlighted the good thermal stability and mechanical properties of the printed parts. In addition, uniaxial tensile tests were used to assess the fiber reinforcing effect on the UV-3D printed objects. Finally, an initial study was conducted on the use of a sizing treatment on carbon fibers to improve the fiber/matrix interfacial adhesion, giving preliminary indications on the potential of this approach to improve the mechanical properties of the 3D printed CFR components. Full article

(This article belongs to the Special Issue Materials for Photolithography and 3D Printing)

▼ Show Figures

Graphical abstract

7 pages, 1196 KiB

Open AccessCommunication

Anomalous Halo Formation in an Arc-Melted ScNi-Sc₂Ni Off-Eutectic Binary Alloy

by Kai Wang, Ming Wei and Lijun Zhang^*

State Key Laboratory of Powder Metallugy, Central South University, Changsha 410083, China

Materials 2016, 9(7), 584; https://doi.org/10.3390/ma9070584 - 18 Jul 2016

Cited by 7 | Viewed by 4819

Abstract

Diverse non-equilibrium eutectic structures have attracted numerous experimental and theoretical studies. One special type is the formation of a halo of one phase around a primary dendrite of another phase. In our experiments, it was occasionally observed that ScNi halos grow as dendritic [...] Read more.

Diverse non-equilibrium eutectic structures have attracted numerous experimental and theoretical studies. One special type is the formation of a halo of one phase around a primary dendrite of another phase. In our experiments, it was occasionally observed that ScNi halos grow as dendritic morphology around the primary Sc

_{2}

Ni dendrites in an arc-melted ScNi-Sc

_{2}

Ni off-eutectic binary alloy. The formation of this anomalous halo structure was then well reproduced by employing quantitative phase-field simulations. Based on the phase-field simulation, It was found that (i) the large undercooling and growth velocity of the ScNi phase during solidification causes the formation of halos; and (ii) the released latent heat induces the recalescence phenomenon, and changes the solidification sequence largely, resulting in the anomalous halo structure in the Sc-34 at % Ni alloy. Full article

▼ Show Figures

Figure 1

10 pages, 1702 KiB

Open AccessFeature PaperArticle

Solvent-Induced Polymorphism of Iron(II) Spin Crossover Complexes

by Ivan Šalitroš^1,2,*, Olaf Fuhr^1,3 and Mario Ruben^1,4,*

¹ Institut für Nanotechnologie, Karlsruher Institut für Technologie, Postfach 3640, Karlsruhe 76021, Germany

² Faculty of Chemical and Food Technology, Institute of Inorganic Chemistry, Technology and Materials, Slovak University of Technology, Bratislava 812 37, Slovakia

³ Karlsruhe Nano Micro Facility (KNMF), Karlsruher Institut für Technologie, Postfach 3640, Karlsruhe 76021, Germany

⁴ Institute de Physique et Chimie de Matériaux de Strasbourg (IPCMS), CNRS-Université de Strasbourg, 23, rue du Loess BP 43, F-67034 Strasbourg cedex 2, France

Materials 2016, 9(7), 585; https://doi.org/10.3390/ma9070585 - 19 Jul 2016

Cited by 23 | Viewed by 6241

Abstract

Two new mononuclear iron(II) compounds (1) and (2) of the general formula [Fe(L)₂](BF₄)₂·nCH₃CN (L = 4-(2-bromoethyn-1-yl)-2,6-bis(pyrazol-1-yl)pyridine, n = 1 for (1) and n = 2 for [...] Read more.

Two new mononuclear iron(II) compounds (1) and (2) of the general formula [Fe(L)₂](BF₄)₂·nCH₃CN (L = 4-(2-bromoethyn-1-yl)-2,6-bis(pyrazol-1-yl)pyridine, n = 1 for (1) and n = 2 for compound (2)), were synthesized. The room temperature crystallization afforded concomitant formation of two different solvent analogues: compound (1) exhibiting triclinic P-1 and compound (2) monoclinic C2/c symmetry. Single-crystal X-ray studies confirmed the presence of the LS (low-spin) state for both compounds at 180 K and of the HS (high-spin) state for compound (2) at 293 K, in full agreement with the magnetic investigations for both solvent polymorphs. Compound (1) exhibits spin transition above 293 K followed by subsequent solvent liberation, while the spin transition of (2) takes already place at 237 K. After complete solvent removal from the crystal lattice, compound (1d) (the desolvated polymorph derived from (1)) exhibits spin transition centered at 342 K accompanied by a thermal hysteresis loop, while the analogous compound (2d) (the desolvated derivate of compound (2)) remains blocked in the HS state over all the investigated temperature range. Full article

(This article belongs to the Special Issue Advances in Molecular Magnets and related Phenomena)

▼ Show Figures

Figure 1

15 pages, 3885 KiB

Open AccessArticle

Superplasticizer Addition to Carbon Fly Ash Geopolymers Activated at Room Temperature

by Lorenza Carabba^*, Stefania Manzi and Maria Chiara Bignozzi

Department of Civil, Chemical, Environmental and Materials Engineering, University of Bologna, via Terracini, 28, Bologna 40131, Italy

Materials 2016, 9(7), 586; https://doi.org/10.3390/ma9070586 - 18 Jul 2016

Cited by 31 | Viewed by 9342

Abstract

Present concerns about global warming due to the greenhouse emissions in the atmosphere have pushed the cement industry to research alternatives to ordinary Portland cement (OPC). Geopolymer binder may constitute a possible breakthrough in the development of sustainable materials: understanding the effectiveness and [...] Read more.

Present concerns about global warming due to the greenhouse emissions in the atmosphere have pushed the cement industry to research alternatives to ordinary Portland cement (OPC). Geopolymer binder may constitute a possible breakthrough in the development of sustainable materials: understanding the effectiveness and the influences of superplasticizers on geopolymer systems is one of the essential requirements for its large-scale implementation. This study aims to investigate the possibility of using commercially available chemical admixtures designed for OPC concrete, to improve fresh properties of fly ash-based geopolymers and mortars. A special emphasis is laid upon evaluating their influence on mechanical and microstructural characteristics of the hardened material realized under room-temperature curing conditions. Results indicate that the addition of a polycarboxylic ether-based superplasticizer, in the amount of 1.0 wt. % by mass of fly ash, promotes an improvement in workability without compromising the final strength of the hardened material. Moreover, the addition of the polycarboxylic ether- and acrylic-based superplasticizers induces a refinement in the pore structure of hardened mortar leading to a longer water saturation time. Full article

(This article belongs to the Special Issue Advances in Geopolymers and Alkali-Activated Materials)

▼ Show Figures

Figure 1

13 pages, 4304 KiB

Open AccessFeature PaperArticle

Effect of Transition Metal Substitution on the Structure and Properties of a Clathrate-Like Compound Eu₇Cu₄₄As₂₃

by Igor V. Plokhikh¹, Dmitri O. Charkin¹, Valeriy Yu. Verchenko^1,2

, Ivan A. Ignatyev¹, Sergey M. Kazakov¹, Alexey V. Sobolev¹, Igor A. Presniakov¹, Alexander A. Tsirlin³ and Andrei V. Shevelkov^1,*

¹ Department of Chemistry, Lomonosov Moscow State University, Moscow 119991, Russia

² National Institute of Chemical Physics and Biophysics, Tallinn 12618, Estonia

³ Experimental Physics VI, Center for Correlations and Magnetism, Institute of Physics, University of Augsburg, Augsburg 86135, Germany

Materials 2016, 9(7), 587; https://doi.org/10.3390/ma9070587 - 19 Jul 2016

Cited by 3 | Viewed by 5458

Abstract

A series of substitutional solid solutions—Eu₇Cu_44−xT_xAs₂₃ (T = Fe, Co, Ni)—based on a recently discovered clathrate-like compound (Eu₇Cu₄₄As₂₃) were synthesized from the elements at 800 °C. Almost up to [...] Read more.

A series of substitutional solid solutions—Eu₇Cu_44−xT_xAs₂₃ (T = Fe, Co, Ni)—based on a recently discovered clathrate-like compound (Eu₇Cu₄₄As₂₃) were synthesized from the elements at 800 °C. Almost up to 50% of Cu can be substituted by Ni, resulting in a linear decrease of the cubic unit cell parameter from a = 16.6707(1) Å for the ternary compound to a = 16.3719(1) Å for the sample with the nominal composition Eu₇Cu₂₄Ni₂₀As₂₃. In contrast, Co and Fe can only substitute less than 20% of Cu. Crystal structures of six samples of different composition were refined from powder diffraction data. Despite very small differences in scattering powers of Cu, Ni, Co, and Fe, we were able to propose a reasonable model of dopant distribution over copper sites based on the trends in interatomic distances as well as on Mössbauer spectra for the iron-substituted compound Eu₇Cu₃₆Fe₈As₂₃. Ni doping increases the Curie temperature to 25 K with respect to the parent compound, which is ferromagnetically ordered below 17.5 K, whereas Fe doping suppresses the ferromagnetic ordering in the Eu sublattice. Full article

(This article belongs to the Special Issue Inorganic Clathrate Materials)

▼ Show Figures

Graphical abstract

14 pages, 5291 KiB

Open AccessArticle

Novel Mg-Doped SrMoO₃ Perovskites Designed as Anode Materials for Solid Oxide Fuel Cells

by Vanessa Cascos^1,*

, José Antonio Alonso¹ and María Teresa Fernández-Díaz²

¹ Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid, Spain

² Institut Laue Langevin, BP 156X, Grenoble 38042, France

Materials 2016, 9(7), 588; https://doi.org/10.3390/ma9070588 - 19 Jul 2016

Cited by 22 | Viewed by 6779

Abstract

SrMo_1−xM_xO_3−δ (M = Fe and Cr, x = 0.1 and 0.2) oxides have been recently described as excellent anode materials for solid oxide fuel cells at intermediate temperatures (IT-SOFC) with LSGM as the electrolyte. In this work, we [...] Read more.

SrMo_1−xM_xO_3−δ (M = Fe and Cr, x = 0.1 and 0.2) oxides have been recently described as excellent anode materials for solid oxide fuel cells at intermediate temperatures (IT-SOFC) with LSGM as the electrolyte. In this work, we have improved their properties by doping with aliovalent Mg ions at the B-site of the parent SrMoO₃ perovskite. SrMo_1−xMg_xO₃₋_δ (x = 0.1, 0.2) oxides have been prepared, characterized and tested as anode materials in single solid-oxide fuel cells, yielding output powers near 900 mW/cm⁻² at 850 °C using pure H₂ as fuel. We have studied its crystal structure with an “in situ” neutron power diffraction (NPD) experiment at temperatures as high as 800 °C, emulating the working conditions of an SOFC. Adequately high oxygen deficiencies, observed by NPD, together with elevated disk-shaped anisotropic displacement factors suggest a high ionic conductivity at the working temperatures. Furthermore, thermal expansion measurements, chemical compatibility with the LSGM electrolyte, electronic conductivity and reversibility upon cycling in oxidizing-reducing atmospheres have been carried out to find out the correlation between the excellent performance as an anode and the structural features. Full article

(This article belongs to the Special Issue Recent Advances in Materials for Solid Oxide Cells)

▼ Show Figures

Figure 1

11 pages, 3153 KiB

Open AccessFeature PaperArticle

In Situ Thermal Generation of Silver Nanoparticles in 3D Printed Polymeric Structures

by Erika Fantino¹, Annalisa Chiappone^2,*, Flaviana Calignano², Marco Fontana¹, Fabrizio Pirri^1,2

and Ignazio Roppolo²

¹ Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi, 24, Torino 10129, Italy

² Center for Sustainable Futures@PoliTo, Istituto Italiano di Tecnologia, Corso Trento, 21, Torino 10129, Italy

Materials 2016, 9(7), 589; https://doi.org/10.3390/ma9070589 - 19 Jul 2016

Cited by 84 | Viewed by 11134

Abstract

Polymer nanocomposites have always attracted the interest of researchers and industry because of their potential combination of properties from both the nanofillers and the hosting matrix. Gathering nanomaterials and 3D printing could offer clear advantages and numerous new opportunities in several application fields. [...] Read more.

Polymer nanocomposites have always attracted the interest of researchers and industry because of their potential combination of properties from both the nanofillers and the hosting matrix. Gathering nanomaterials and 3D printing could offer clear advantages and numerous new opportunities in several application fields. Embedding nanofillers in a polymeric matrix could improve the final material properties but usually the printing process gets more difficult. Considering this drawback, in this paper we propose a method to obtain polymer nanocomposites by in situ generation of nanoparticles after the printing process. 3D structures were fabricated through a Digital Light Processing (DLP) system by disolving metal salts in the starting liquid formulation. The 3D fabrication is followed by a thermal treatment in order to induce in situ generation of metal nanoparticles (NPs) in the polymer matrix. Comprehensive studies were systematically performed on the thermo-mechanical characteristics, morphology and electrical properties of the 3D printed nanocomposites. Full article

(This article belongs to the Special Issue Materials for Photolithography and 3D Printing)

▼ Show Figures

Graphical abstract

16 pages, 8626 KiB

Open AccessArticle

Microscale Simulation on Mechanical Properties of Al/PTFE Composite Based on Real Microstructures

by Chao Ge, Yongxiang Dong^* and Wubuliaisan Maimaitituersun

State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081, China

Materials 2016, 9(7), 590; https://doi.org/10.3390/ma9070590 - 19 Jul 2016

Cited by 50 | Viewed by 8274

Abstract

A novel numerical method at the microscale for studying the mechanical behavior of an aluminum-particle-reinforced polytetrafluoroethylene (Al/PTFE) composite is proposed and validated experimentally in this paper. Two types of 2D representative volume elements (RVEs), real microstructure-based and simulated microstructures, are established by following [...] Read more.

A novel numerical method at the microscale for studying the mechanical behavior of an aluminum-particle-reinforced polytetrafluoroethylene (Al/PTFE) composite is proposed and validated experimentally in this paper. Two types of 2D representative volume elements (RVEs), real microstructure-based and simulated microstructures, are established by following a series of image processing procedures and on a statistical basis considering the geometry and the distribution of particles and microvoids, respectively. Moreover, 3D finite element modelling based on the same statistical information as the 2D simulated microstructure models is conducted to show the efficiency and effectiveness of the 2D models. The results of all simulations and experiments indicate that real microstructure-based models and simulated microstructure models are efficient methods to predict elastic and plastic constants of particle-reinforced composites. Full article

(This article belongs to the Section Advanced Materials Characterization)

▼ Show Figures

Figure 1

17 pages, 5460 KiB

Open AccessArticle

Stereocomplexation in Copolymer Networks Incorporating Enantiomeric Glycerol-Based 3-Armed Lactide Oligomers and a 2-Armed ɛ-Caprolactone Oligomer

by Ayaka Shibita, Seina Kawasaki, Toshiaki Shimasaki, Naozumi Teramoto and Mitsuhiro Shibata^*

Department of Life and Environmental Sciences, Faculty of Engineering, Chiba Institute of Technology, 2-17-1, Tsudanuma, Narashino, Chiba 275-0016, Japan

Materials 2016, 9(7), 591; https://doi.org/10.3390/ma9070591 - 19 Jul 2016

Cited by 5 | Viewed by 5250

Abstract

The reactions of enantiomeric glycerol-based 3-armed lactide oligomers (H3DLAO and H3LLAO) and a diethylene glycol-based 2-armed ɛ-caprolactone oligomer (H2CLO) with hexamethylene diisocyanate (HDI) produced polyesterurethane copolymer networks (PEU-3scLAO/2CLOs 100/0, 75/25, 50/50, 25/75 and 0/100) with different feed ratios of stereocomplex (sc) lactide oligomer [...] Read more.

The reactions of enantiomeric glycerol-based 3-armed lactide oligomers (H3DLAO and H3LLAO) and a diethylene glycol-based 2-armed ɛ-caprolactone oligomer (H2CLO) with hexamethylene diisocyanate (HDI) produced polyesterurethane copolymer networks (PEU-3scLAO/2CLOs 100/0, 75/25, 50/50, 25/75 and 0/100) with different feed ratios of stereocomplex (sc) lactide oligomer (H3scLAO = H3DLAO + H3LLAO, H3DLAO/H3LLAO = 1/1) and H2CLO. Thermal and mechanical properties of the copolymer networks were compared with those of a simple homochiral (hc) network (PEU-3DLAO) produced by the reaction of H3DLAO and HDI. X-ray diffraction and differential scanning calorimetric analyses revealed that sc crystallites are formed without any hc crystallization for PEU-3scLAO/2CLOs, and that PEU-3DLAO is amorphous. The melting temperatures of sc crystallites for PEU-3scLAO/2CLOs were much higher than that of hc crystallites of H3DLAO. The polarized optical microscopic analysis revealed that the nucleation efficiency is enhanced with increasing feed of H3scLAO fraction, whereas the spherulite growth rate is accelerated with increasing feed H2CLO fraction over 100/0-50/50 networks. PEU-3scLAO/2CLO 100/0 (i.e., PEU-3scLAO) exhibited a higher tensile strength and modulus than PEU-3DLAO. The elongation at break and tensile toughness for PEU-3scLAO/2CLOs increased with an increasing feed amount of H2CLO. Full article

(This article belongs to the Section Biomaterials)

▼ Show Figures

Graphical abstract

22 pages, 7624 KiB

Open AccessArticle

Acoustic Performance of Resilient Materials Using Acrylic Polymer Emulsion Resin

by Haseog Kim, Sangki Park^*

and Seahyun Lee

Building and Urban Research Institute, Korea Institute of Civil Engineering and Building Technology, 283, Goyang-daero, Ilsanseo-gu, Goyang-si, Gyeonngi-do 10223, Korea

Materials 2016, 9(7), 592; https://doi.org/10.3390/ma9070592 - 19 Jul 2016

Cited by 4 | Viewed by 6701

Abstract

There have been frequent cases of civil complaints and disputes in relation to floor impact noises over the years. To solve these issues, a substantial amount of sound resilient material is installed between the concrete slab and the foamed concrete during construction. A [...] Read more.

There have been frequent cases of civil complaints and disputes in relation to floor impact noises over the years. To solve these issues, a substantial amount of sound resilient material is installed between the concrete slab and the foamed concrete during construction. A new place-type resilient material is made from cement, silica powder, sodium sulfate, expanded-polystyrene, anhydrite, fly ash, and acrylic polymer emulsion resin. Its physical characteristics such as density, compressive strength, dynamic stiffness, and remanent strain are analyzed to assess the acoustic performance of the material. The experimental results showed the density and the dynamic stiffness of the proposed resilient material is increased with proportional to the use of cement and silica powder due to the high contents of the raw materials. The remanent strain, related to the serviceability of a structure, is found to be inversely proportional to the density and strength. The amount of reduction in the heavyweight impact noise is significant in a material with high density, high strength, and low remanent strain. Finally, specimen no. R4, having the reduction level of 3 dB for impact ball and 1 dB for bang machine in the single number quantity level, respectively, is the best product to obtain overall acoustic performance. Full article

(This article belongs to the Section Advanced Composites)

▼ Show Figures

Figure 1

10 pages, 3359 KiB

Open AccessArticle

Binary Alkali-Metal Silicon Clathrates by Spark Plasma Sintering: Preparation and Characterization

by Igor Veremchuk¹

, Matt Beekman², Iryna Antonyshyn¹, Walter Schnelle¹, Michael Baitinger¹, George S. Nolas^3,* and Yuri Grin^1,*

¹ Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany

² Department of Physics, California Polytechnic State University, San Luis Obispo, CA 93407, USA

³ Department of Physics, University of South Florida, Tampa, FL 33620, USA

Materials 2016, 9(7), 593; https://doi.org/10.3390/ma9070593 - 19 Jul 2016

Cited by 11 | Viewed by 5803

Abstract

The binary intermetallic clathrates K_8-xSi₄₆ (x = 0.4; 1.2), Rb_6.2Si₄₆, Rb_11.5Si₁₃₆ and Cs_7.8Si₁₃₆ were prepared from M₄Si₄ (M = K, Rb, Cs) precursors by [...] Read more.

The binary intermetallic clathrates K_8-xSi₄₆ (x = 0.4; 1.2), Rb_6.2Si₄₆, Rb_11.5Si₁₃₆ and Cs_7.8Si₁₃₆ were prepared from M₄Si₄ (M = K, Rb, Cs) precursors by spark-plasma route (SPS) and structurally characterized by Rietveld refinement of PXRD data. The clathrate-II phase Rb_11.5Si₁₃₆ was synthesized for the first time. Partial crystallographic site occupancy of the alkali metals, particularly for the smaller Si₂₀ dodecahedra, was found in all compounds. SPS preparation of Na₂₄Si₁₃₆ with different SPS current polarities and tooling were performed in order to investigate the role of the electric field on clathrate formation. The electrical and thermal transport properties of K_7.6Si₄₆ and K_6.8Si₄₆ in the temperature range 4–700 K were investigated. Our findings demonstrate that SPS is a novel tool for the synthesis of intermetallic clathrate phases that are not easily accessible by conventional synthesis techniques. Full article

(This article belongs to the Special Issue Inorganic Clathrate Materials)

▼ Show Figures

Graphical abstract

12 pages, 1305 KiB

Open AccessArticle

Spectroscopic Study of Plasma Polymerized a-C:H Films Deposited by a Dielectric Barrier Discharge

by Thejaswini Halethimmanahally Chandrashekaraiah¹, Robert Bogdanowicz^1,2, Eckart Rühl³, Vladimir Danilov¹, Jürgen Meichsner¹, Steffen Thierbach³ and Rainer Hippler^1,*

¹ Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald, Felix-Hausdorff-Str. 6, Greifswald 17489, Germany

² Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology, 11/12 G. Narutowicza St., Gdansk 80-233, Poland

³ Institut für Chemie und Biochemie-Physikalische und Theoretische Chemie, Freie Universität Berlin, Takustr. 3, Berlin 14195, Germany

Materials 2016, 9(7), 594; https://doi.org/10.3390/ma9070594 - 19 Jul 2016

Cited by 11 | Viewed by 6467

Abstract

Plasma polymerized a-C:H thin films have been deposited on Si (100) and aluminum coated glass substrates by a dielectric barrier discharge (DBD) operated at medium pressure using C₂H_m/Ar (m = 2, 4, 6) gas mixtures. The deposited films [...] Read more.

Plasma polymerized a-C:H thin films have been deposited on Si (100) and aluminum coated glass substrates by a dielectric barrier discharge (DBD) operated at medium pressure using C₂H_m/Ar (m = 2, 4, 6) gas mixtures. The deposited films were characterized by Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS), Raman spectroscopy, and ellipsometry. FT-IRRAS revealed the presence of sp³ and sp² C–H stretching and C–H bending vibrations of bonds in the films. The presence of D and G bands was confirmed by Raman spectroscopy. Thin films obtained from C₂H₄/Ar and C₂H₆/Ar gas mixtures have I_D/I_G ratios of 0.45 and 0.3, respectively. The refractive indices were 2.8 and 3.1 for C₂H₄/Ar and C₂H₆/Ar films, respectively, at a photon energy of 2 eV. Full article

(This article belongs to the Special Issue Thin-Film Deposition, Characterization and Advanced Surface Engineering)

▼ Show Figures

Figure 1

26 pages, 9507 KiB

Open AccessReview

Optimization of Layered Cathode Materials for Lithium-Ion Batteries

by Christian Julien^1,*

, Alain Mauger², Karim Zaghib³ and Henri Groult¹

¹ Physicochimie des Electrolytes et Nanosystèmes Interfaciaux (PHENIX), Sorbonne Universités, UPMC Univ. Paris 06, CNRS UMR 8234, 4 place Jussieu, Paris 75005, France

² Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Sorbonne Universités, UPMC Univ. Paris 06, CNRS UMR 7590, 4 place Jussieu, Paris 75005, France

³ Institut de Recherche d’Hydro-Québec (IREQ), Stockage and Conversion d’Energie, 1800 Lionel-Boulet, Varennes, QC J3X 1S1, Canada

Materials 2016, 9(7), 595; https://doi.org/10.3390/ma9070595 - 19 Jul 2016

Cited by 101 | Viewed by 15768

Abstract

This review presents a survey of the literature on recent progress in lithium-ion batteries, with the active sub-micron-sized particles of the positive electrode chosen in the family of lamellar compounds LiMO₂, where M stands for a mixture of Ni, [...] Read more.

This review presents a survey of the literature on recent progress in lithium-ion batteries, with the active sub-micron-sized particles of the positive electrode chosen in the family of lamellar compounds LiMO₂, where M stands for a mixture of Ni, Mn, Co elements, and in the family of yLi₂MnO₃•(1 − y)LiNi_½Mn_½O₂ layered-layered integrated materials. The structural, physical, and chemical properties of these cathode elements are reported and discussed as a function of all the synthesis parameters, which include the choice of the precursors and of the chelating agent, and as a function of the relative concentrations of the M cations and composition y. Their electrochemical properties are also reported and discussed to determine the optimum compositions in order to obtain the best electrochemical performance while maintaining the structural integrity of the electrode lattice during cycling. Full article

(This article belongs to the Special Issue Advances in Renewable Energy Conversion Materials)

▼ Show Figures

Graphical abstract

14 pages, 9456 KiB

Open AccessArticle

Microstructures and Mechanical Properties of Co-Cr Dental Alloys Fabricated by Three CAD/CAM-Based Processing Techniques

by Hae Ri Kim¹, Seong-Ho Jang¹, Young Kyung Kim², Jun Sik Son³, Bong Ki Min^4,*, Kyo-Han Kim⁵ and Tae-Yub Kwon^5,*

¹ Department of Dental Science, Graduate School, Kyungpook National University, Daegu 700-412, Korea

² Department of Conservative Dentistry, School of Dentistry, Kyungpook National University, Daegu 700-412, Korea

³ Korea Textile Development Institute, Daegu 703-712, Korea

⁴ Center for Research Facilities, Yeungnam University, Gyeongsan 712-749, Korea

⁵ Department of Dental Biomaterials, School of Dentistry, Kyungpook National University, Daegu 700-412, Korea

Materials 2016, 9(7), 596; https://doi.org/10.3390/ma9070596 - 20 Jul 2016

Cited by 130 | Viewed by 9287

Abstract

The microstructures and mechanical properties of cobalt-chromium (Co-Cr) alloys produced by three CAD/CAM-based processing techniques were investigated in comparison with those produced by the traditional casting technique. Four groups of disc- (microstructures) or dumbbell- (mechanical properties) specimens made of Co-Cr alloys were prepared [...] Read more.

The microstructures and mechanical properties of cobalt-chromium (Co-Cr) alloys produced by three CAD/CAM-based processing techniques were investigated in comparison with those produced by the traditional casting technique. Four groups of disc- (microstructures) or dumbbell- (mechanical properties) specimens made of Co-Cr alloys were prepared using casting (CS), milling (ML), selective laser melting (SLM), and milling/post-sintering (ML/PS). For each technique, the corresponding commercial alloy material was used. The microstructures of the specimens were evaluated via X-ray diffractometry, optical and scanning electron microscopy with energy-dispersive X-ray spectroscopy, and electron backscattered diffraction pattern analysis. The mechanical properties were evaluated using a tensile test according to ISO 22674 (n = 6). The microstructure of the alloys was strongly influenced by the manufacturing processes. Overall, the SLM group showed superior mechanical properties, the ML/PS group being nearly comparable. The mechanical properties of the ML group were inferior to those of the CS group. The microstructures and mechanical properties of Co-Cr alloys were greatly dependent on the manufacturing technique as well as the chemical composition. The SLM and ML/PS techniques may be considered promising alternatives to the Co-Cr alloy casting process. Full article

▼ Show Figures

Graphical abstract

14 pages, 7222 KiB

Open AccessArticle

A Numerical Study on the Effect of Debris Layer on Fretting Wear

by Tongyan Yue¹ and Magd Abdel Wahab^2,3,4,*

¹ Department of Electrical Energy, Systems and Automation, Faculty of Engineering and Architecture, Ghent University, Zwijnaarde B-9052, Belgium

² Division of Computational Mechanics, Ton Duc Thang University, Ho Chi Minh City, Vietnam

³ Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam

⁴ Soete Laboratory, Faculty of Engineering and Architecture, Ghent University, Technologiepark Zwijnaarde 903, Zwijnaarde B-9052, Belgium

Materials 2016, 9(7), 597; https://doi.org/10.3390/ma9070597 - 20 Jul 2016

Cited by 81 | Viewed by 8226

Abstract

Fretting wear is the material damage of two contact surfaces caused by micro relative displacement. Its characteristic is that debris is trapped on the contact surfaces. Depending on the material properties, the shapes of the debris, and the dominant wear mechanisms, debris can [...] Read more.

Fretting wear is the material damage of two contact surfaces caused by micro relative displacement. Its characteristic is that debris is trapped on the contact surfaces. Depending on the material properties, the shapes of the debris, and the dominant wear mechanisms, debris can play different roles that either protect or harm interfaces. Due to the micro scale of the debris, it is difficult to obtain instantaneous information and investigate debris behavior in experiments. The Finite Element Method (FEM) has been used to model the process of fretting wear and calculate contact variables, such as contact stress and relative slip during the fretting wear process. In this research, a 2D fretting wear model with a debris layer was developed to investigate the influence of debris on fretting wear. Effects of different factors such as thickness of the debris layer, Young’s modulus of the debris layer, and the time of importing the layer into the FE model were considered in this study. Based on FE results, here we report that: (a) the effect of Young’s modulus of the debris layer on the contact pressure is not significant; (b) the contact pressure between the debris layer and the flat specimen decreases with increasing thickness of the layer and (c) by importing the debris layer in different fretting wear cycles, the debris layer shows different roles in the wear process. At the beginning of the wear cycle, the debris layer protects the contact surfaces of the first bodies (cylindrical pad and flat specimen). However, in the final cycle, the wear volumes of the debris layers exhibit slightly higher damage compared to the model without the debris layer in all considered cases. Full article

(This article belongs to the Special Issue Numerical Analysis of Tribology Behavior of Materials)

▼ Show Figures

Figure 1

11 pages, 2979 KiB

Open AccessArticle

Benefits of Sealed-Curing on Compressive Strength of Fly Ash-Based Geopolymers

by Sujeong Lee^1,2, Arie Van Riessen^3,* and Chul-Min Chon¹

¹ Korea Institute of Geoscience and Mineral Resources, Daejeon 34132, Korea

² Department of Resources Recycling Engineering, University of Science and Technology, Daejeon 34113, Korea

³ John de Laeter Centre, Curtin University, Perth 6845, Western Australia, Australia

Materials 2016, 9(7), 598; https://doi.org/10.3390/ma9070598 - 20 Jul 2016

Cited by 35 | Viewed by 5595

Abstract

There is no standardized procedure for producing geopolymers; therefore, many researchers develop their own procedures for mixing and curing to achieve good workability and strength development. The curing scheme adopted is important in achieving maximum performance of resultant geopolymers. In this study, we [...] Read more.

There is no standardized procedure for producing geopolymers; therefore, many researchers develop their own procedures for mixing and curing to achieve good workability and strength development. The curing scheme adopted is important in achieving maximum performance of resultant geopolymers. In this study, we evaluated the impact of sealed and unsealed curing on mechanical strength of geopolymers. Fly ash-based geopolymers cured in sealed and unsealed moulds clearly revealed that retention of water during curing resulted in superior strength development. The average compressive strength of sealed-cured geopolymers measured after 1 day of curing was a modest 50 MPa, while after 7 day curing the average compressive strength increased to 120~135 MPa. In the unsealed specimens the average compressive strength of geopolymers was lower; ranging from 60 to 90 MPa with a slight increase as the curing period increased. Microcracking caused by dehydration is postulated to cause the strength decrease in the unsealed cured samples. These results show that water is a crucial component for the evolution of high strength three-dimensional cross-linked networks in geopolymers. Full article

(This article belongs to the Special Issue Advances in Geopolymers and Alkali-Activated Materials)

▼ Show Figures

Figure 1

33 pages, 3243 KiB

Open AccessFeature PaperReview

Recent Developments in Antimicrobial Polymers: A Review

by Madson R. E. Santos¹, Ana C. Fonseca¹, Patrícia V. Mendonça¹, Rita Branco², Arménio C. Serra¹, Paula V. Morais²

and Jorge F. J. Coelho^1,*

¹ CEMUC, Department of Chemical Engineering, University of Coimbra, Coimbra 3030-790, Portugal

² CEMUC, Department of Life Sciences, University of Coimbra, Coimbra 3001-401, Portugal

Materials 2016, 9(7), 599; https://doi.org/10.3390/ma9070599 - 20 Jul 2016

Cited by 177 | Viewed by 13961

Abstract

Antimicrobial polymers represent a very promising class of therapeutics with unique characteristics for fighting microbial infections. As the classic antibiotics exhibit an increasingly low capacity to effectively act on microorganisms, new solutions must be developed. The importance of this class of materials emerged [...] Read more.

Antimicrobial polymers represent a very promising class of therapeutics with unique characteristics for fighting microbial infections. As the classic antibiotics exhibit an increasingly low capacity to effectively act on microorganisms, new solutions must be developed. The importance of this class of materials emerged from the uncontrolled use of antibiotics, which led to the advent of multidrug-resistant microbes, being nowadays one of the most serious public health problems. This review presents a critical discussion of the latest developments involving the use of different classes of antimicrobial polymers. The synthesis pathways used to afford macromolecules with antimicrobial properties, as well as the relationship between the structure and performance of these materials are discussed. Full article

(This article belongs to the Special Issue Self-Cleaning and Antimicrobial Surfaces)

▼ Show Figures

Graphical abstract

18 pages, 4254 KiB

Open AccessArticle

Investigation of the Self-Healing Behaviors of Microcapsules/Bitumen Composites by a Repetitive Direct Tension Test

by Jun-Feng Su^1,*, Peng Yang², Ying-Yuan Wang¹, Shan Han¹, Ning-Xu Han³ and Wei Li¹

¹ Department of Polymer Materials, School of Material Science and Engineering, Tianjin Polytechnic University, Tianjin 300387, China

² School of Navigational Engineering, Guangzhou Maritime Institute, Guangzhou 510725, China

³ Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen University, Shenzhen 518060, China

Materials 2016, 9(7), 600; https://doi.org/10.3390/ma9070600 - 21 Jul 2016

Cited by 33 | Viewed by 8251

Abstract

The aim of this work was to evaluate the self-healing behaviors of bitumen using microcapsules containing rejuvenator by a modified fracture healing–refracture method through a repetitive tension test. Microcapsules had mean size values of 10, 20 and 30 μm with a same core/shell [...] Read more.

The aim of this work was to evaluate the self-healing behaviors of bitumen using microcapsules containing rejuvenator by a modified fracture healing–refracture method through a repetitive tension test. Microcapsules had mean size values of 10, 20 and 30 μm with a same core/shell ratio of 1/1. Various microcapsules/bitumen samples were fabricated with microcapsule contents of 1.0, 3.0 and 5.0 wt. %, respectively. Tension strength values of microcapsules/bitumen samples were measured by a reparative fracture-healing process under different temperatures. It was found that these samples had tensile strength values larger than the data of pure bitumen samples under the same conditions after the four tensile fracture-healing cycles. Fracture morphology investigation and mechanism analysis indicated that the self-healing process was a process consisting of microcapsules being broken, penetrated and diffused. Moreover, the crack healing of bitumen can be considered as a viscosity driven process. The self-healing ability partly repaired the damage of bitumen during service life by comparing the properties of virgin and rejuvenated bitumen. Full article

(This article belongs to the Section Advanced Materials Characterization)

▼ Show Figures

Graphical abstract

17 pages, 2611 KiB

Open AccessArticle

Gas Diffusion Electrodes Manufactured by Casting Evaluation as Air Cathodes for Microbial Fuel Cells (MFC)

by Sandipam Srikanth, Deepak Pant, Xochitl Dominguez-Benetton, Inge Genné, Karolien Vanbroekhoven, Philippe Vermeiren and Yolanda Alvarez-Gallego^*

Separation and Conversion Technology, Flemish Institute for Technological Research (VITO), Boeretang 200, MOL B-2400, Belgium

Materials 2016, 9(7), 601; https://doi.org/10.3390/ma9070601 - 21 Jul 2016

Cited by 24 | Viewed by 7981

Abstract

One of the most intriguing renewable energy production methods being explored currently is electrical power generation by microbial fuel cells (MFCs). However, to make MFC technology economically feasible, cost efficient electrode manufacturing processes need to be proposed and demonstrated. In this context, VITO [...] Read more.

One of the most intriguing renewable energy production methods being explored currently is electrical power generation by microbial fuel cells (MFCs). However, to make MFC technology economically feasible, cost efficient electrode manufacturing processes need to be proposed and demonstrated. In this context, VITO has developed an innovative electrode manufacturing process based on film casting and phase inversion. The screening and selection process of electrode compositions was done based on physicochemical properties of the active layer, which in turn maintained a close relation with their composition A dual hydrophilic-hydrophobic character in the active layer was achieved with values of ε_hydrophilic up to 10% while ε_TOTAL remained in the range 65 wt % to 75 wt %. Eventually, selected electrodes were tested as air cathodes for MFC in half cell and full cell modes. Reduction currents, up to −0.14 mA·cm²⁻ at −100 mV (vs. Ag/AgCl) were reached in long term experiments in the cathode half-cell. In full MFC, a maximum power density of 380 mW·m⁻² was observed at 100 Ω external load. Full article

(This article belongs to the Special Issue Advances in Renewable Energy Conversion Materials)

▼ Show Figures

Graphical abstract

19 pages, 6489 KiB

Open AccessArticle

Guided Wave Based Crack Detection in the Rivet Hole Using Global Analytical with Local FEM Approach

by Md Yeasin Bhuiyan¹

, Yanfeng Shen² and Victor Giurgiutiu^1,*

¹ Department of Mechanical Engineering, University of South Carolina, Columbia, SC 29208, USA

² University of Michigan-Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai 200240, China

Materials 2016, 9(7), 602; https://doi.org/10.3390/ma9070602 - 21 Jul 2016

Cited by 58 | Viewed by 7441

Abstract

In this article, ultrasonic guided wave propagation and interaction with the rivet hole cracks has been formulated using closed-form analytical solution while the local damage interaction, scattering, and mode conversion have been obtained from finite element analysis. The rivet hole cracks (damage) in [...] Read more.

In this article, ultrasonic guided wave propagation and interaction with the rivet hole cracks has been formulated using closed-form analytical solution while the local damage interaction, scattering, and mode conversion have been obtained from finite element analysis. The rivet hole cracks (damage) in the plate structure gives rise to the non-axisymmetric scattering of Lamb wave, as well as shear horizontal (SH) wave, although the incident Lamb wave source (primary source) is axisymmetric. The damage in the plate acts as a non-axisymmetric secondary source of Lamb wave and SH wave. The scattering of Lamb and SH waves are captured using wave damage interaction coefficient (WDIC). The scatter cubes of complex-valued WDIC are formed that can describe the 3D interaction (frequency, incident direction, and azimuth direction) of Lamb waves with the damage. The scatter cubes are fed into the exact analytical framework to produce the time domain signal. This analysis enables us to obtain the optimum design parameters for better detection of the cracks in a multiple-rivet-hole problem. The optimum parameters provide the guideline of the design of the sensor installation to obtain the most noticeable signals that represent the presence of cracks in the rivet hole. Full article

(This article belongs to the Special Issue Advances in Structural Health Monitoring for Aerospace Structures)

▼ Show Figures

Figure 1

17 pages, 7872 KiB

Open AccessArticle

Fiberglass Grids as Sustainable Reinforcement of Historic Masonry

by Luca Righetti¹, Vikki Edmondson¹, Marco Corradi^1,2,*

and Antonio Borri²

¹ Department of Mechanical and Construction Engineering, Northumbria University, 209 Wynne-Jones Building, Newcastle upon Tyne NE1 8ST, UK

² Department of Engineering, University of Perugia, 92 Via Duranti, Perugia 06125, Italy

Materials 2016, 9(7), 603; https://doi.org/10.3390/ma9070603 - 21 Jul 2016

Cited by 18 | Viewed by 6927

Abstract

Fiber-reinforced composite (FRP) materials have gained an increasing success, mostly for strengthening, retrofitting and repair of existing historic masonry structures and may cause a significant enhancement of the mechanical properties of the reinforced members. This article summarizes the results of previous experimental activities [...] Read more.

Fiber-reinforced composite (FRP) materials have gained an increasing success, mostly for strengthening, retrofitting and repair of existing historic masonry structures and may cause a significant enhancement of the mechanical properties of the reinforced members. This article summarizes the results of previous experimental activities aimed at investigating the effectiveness of GFRP (Glass Fiber Reinforced Polymers) grids embedded into an inorganic mortar to reinforce historic masonry. The paper also presents innovative results on the relationship between the durability and the governing material properties of GFRP grids. Measurements of the tensile strength were made using specimens cut off from GFRP grids before and after ageing in aqueous solution. The tensile strength of a commercially available GFRP grid has been tested after up 450 days of storage in deionized water and NaCl solution. A degradation in tensile strength and Young’s modulus up to 30.2% and 13.2% was recorded, respectively. This degradation indicated that extended storage in a wet environment may cause a decrease in the mechanical properties. Full article

(This article belongs to the Section Advanced Composites)

▼ Show Figures

Figure 1

12 pages, 4004 KiB

Open AccessArticle

Thermal Stability and Flammability of Styrene-Butadiene Rubber-Based (SBR) Ceramifiable Composites

by Rafał Anyszka^1,*

, Dariusz M. Bieliński¹, Zbigniew Pędzich²

, Przemysław Rybiński³

, Mateusz Imiela¹, Mariusz Siciński¹, Magdalena Zarzecka-Napierała², Tomasz Gozdek¹ and Paweł Rutkowski²

¹ Institute of Polymer and Dye Technology, Faculty of Chemistry, Lodz University of Technology, Stefanowskiego 12/16, Lódź 90-924, Poland

² Department of Ceramics and Refractory Materials, Faculty of Materials Science & Ceramics, AGH–University of Science & Technology, Al. Mickiewicza 30, Kraków 30-045, Poland

³ Management of Environment Protection and Modeling, The Jan Kochanowski University, Żeromskiego 5, Kielce 25-369, Poland

Materials 2016, 9(7), 604; https://doi.org/10.3390/ma9070604 - 21 Jul 2016

Cited by 18 | Viewed by 10370

Abstract

Ceramifiable styrene-butadiene (SBR)-based composites containing low-softening-point-temperature glassy frit promoting ceramification, precipitated silica, one of four thermally stable refractory fillers (halloysite, calcined kaolin, mica or wollastonite) and a sulfur-based curing system were prepared. Kinetics of vulcanization and basic mechanical properties were analyzed and added [...] Read more.

Ceramifiable styrene-butadiene (SBR)-based composites containing low-softening-point-temperature glassy frit promoting ceramification, precipitated silica, one of four thermally stable refractory fillers (halloysite, calcined kaolin, mica or wollastonite) and a sulfur-based curing system were prepared. Kinetics of vulcanization and basic mechanical properties were analyzed and added as Supplementary Materials. Combustibility of the composites was measured by means of cone calorimetry. Their thermal properties were analyzed by means of thermogravimetry and specific heat capacity determination. Activation energy of thermal decomposition was calculated using the Flynn-Wall-Ozawa method. Finally, compression strength of the composites after ceramification was measured and their micromorphology was studied by scanning electron microscopy. The addition of a ceramification-facilitating system resulted in the lowering of combustibility and significant improvement of the thermal stability of the composites. Moreover, the compression strength of the mineral structure formed after ceramification is considerably high. The most promising refractory fillers for SBR-based ceramifiable composites are mica and halloysite. Full article

(This article belongs to the Special Issue Advances in Research on Elastomers)

▼ Show Figures

Figure 1

16 pages, 2747 KiB

Open AccessFeature PaperArticle

Hydration of Hybrid Alkaline Cement Containing a Very Large Proportion of Fly Ash: A Descriptive Model

by Inés Garcia-Lodeiro^*, Shane Donatello

, Ana Fernández-Jiménez

and Ángel Palomo

Cement and Recycling Materials Department, Eduardo Torroja Institute (IETcc-CSIC), Madrid 28033, Spain

Materials 2016, 9(7), 605; https://doi.org/10.3390/ma9070605 - 22 Jul 2016

Cited by 128 | Viewed by 11093

Abstract

In hybrid alkaline fly ash cements, a new generation of binders, hydration, is characterized by features found in both ordinary portland cement (OPC) hydration and the alkali activation of fly ash (AAFA). Hybrid alkaline fly ash cements typically have a high fly ash [...] Read more.

In hybrid alkaline fly ash cements, a new generation of binders, hydration, is characterized by features found in both ordinary portland cement (OPC) hydration and the alkali activation of fly ash (AAFA). Hybrid alkaline fly ash cements typically have a high fly ash (70 wt % to 80 wt %) and low clinker (20 wt % to 30 wt %) content. The clinker component favors curing at ambient temperature. A hydration mechanism is proposed based on the authors’ research on these hybrid binders over the last five years. The mechanisms for OPC hydration and FA alkaline activation are summarized by way of reference. In hybrid systems, fly ash activity is visible at very early ages, when two types of gel are formed: C–S–H from the OPC and N–A–S–H from the fly ash. In their mutual presence, these gels tend to evolve, respectively, into C–A–S–H and (N,C)–A–S–H. The use of activators with different degrees of alkalinity has a direct impact on reaction kinetics but does not modify the main final products, a mixture of C–A–S–H and (N,C)–A–S–H gels. The proportion of each gel in the mix does, however, depend on the alkalinity generated in the medium. Full article

(This article belongs to the Special Issue Advances in Geopolymers and Alkali-Activated Materials)

▼ Show Figures

Graphical abstract

15 pages, 11275 KiB

Open AccessArticle

Transformation and Precipitation Reactions by Metal Active Gas Pulsed Welded Joints from X2CrNiMoN22-5-3 Duplex Stainless Steels

by Ion-Dragos Utu

, Ion Mitelea^*, Sorin Dumitru Urlan and Corneliu Marius Crăciunescu

Department of Materials and Manufacturing Engineering, University Politehnica Timisoara, Pta Victoriei, No. 2, Timisoara 300006, Romania

Materials 2016, 9(7), 606; https://doi.org/10.3390/ma9070606 - 21 Jul 2016

Cited by 13 | Viewed by 6429

Abstract

The high alloying degree of Duplex stainless steels makes them susceptible to the formation of intermetallic phases during their exposure to high temperatures. Precipitation of these phases can lead to a decreasing of the corrosion resistance and sometimes of the toughness. Starting from [...] Read more.

The high alloying degree of Duplex stainless steels makes them susceptible to the formation of intermetallic phases during their exposure to high temperatures. Precipitation of these phases can lead to a decreasing of the corrosion resistance and sometimes of the toughness. Starting from the advantages of the synergic Metal Active Gas (MAG) pulsed welding process, this paper analyses the structure formation particularities of homogeneous welded joints from Duplex stainless steel. The effect of linear welding energy on the structure morphology of the welded joints was revealed by macro- and micrographic examinations, X-ray energy dispersion analyses, measurements of ferrite proportion and X-ray diffraction analysis. The results obtained showed that the transformation of ferrite into austenite is associated with the chromium, nickel, molybdenum and nitrogen distribution between these two phases and their redistribution degree is closely linked to the overall heat cycle of the welding process. The adequate control of the energy inserted in the welded components provides an optimal balance between the two microstructural constituents (Austenite and Ferrite) and avoids the formation of undesirable intermetallic phases. Full article

(This article belongs to the Section Advanced Materials Characterization)

▼ Show Figures

Figure 1

17 pages, 6396 KiB

Open AccessArticle

Influence of Network Structure on Glass Transition Temperature of Elastomers

by Katarzyna Bandzierz^1,*, Louis Reuvekamp², Jerzy Dryzek³, Wilma Dierkes²

, Anke Blume² and Dariusz Bielinski¹

¹ Institute of Polymer and Dye Technology, Lodz University of Technology, Lodz 90-924, Poland

² Elastomer Technology & Engineering, University of Twente, Enschede 7500 AE, The Netherlands

³ Institute of Nuclear Physics, Polish Academy of Sciences, Krakow 31-342, Poland

Materials 2016, 9(7), 607; https://doi.org/10.3390/ma9070607 - 22 Jul 2016

Cited by 108 | Viewed by 12804

Abstract

It is generally believed that only intermolecular, elastically-effective crosslinks influence elastomer properties. The role of the intramolecular modifications of the polymer chains is marginalized. The aim of our study was the characterization of the structural parameters of cured elastomers, and determination of their [...] Read more.

It is generally believed that only intermolecular, elastically-effective crosslinks influence elastomer properties. The role of the intramolecular modifications of the polymer chains is marginalized. The aim of our study was the characterization of the structural parameters of cured elastomers, and determination of their influence on the behavior of the polymer network. For this purpose, styrene-butadiene rubbers (SBR), cured with various curatives, such as DCP, TMTD, TBzTD, Vulcuren^®, DPG/S₈, CBS/S₈, MBTS/S₈ and ZDT/S₈, were investigated. In every series of samples a broad range of crosslink density was obtained, in addition to diverse crosslink structures, as determined by equilibrium swelling and thiol-amine analysis. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were used to study the glass transition process, and positron annihilation lifetime spectroscopy (PALS) to investigate the size of the free volumes. For all samples, the values of the glass transition temperature (T_g) increased with a rise in crosslink density. At the same time, the free volume size proportionally decreased. The changes in T_g and free volume size show significant differences between the series crosslinked with various curatives. These variations are explained on the basis of the curatives’ structure effect. Furthermore, basic structure-property relationships are provided. They enable the prediction of the effect of curatives on the structural parameters of the network, and some of the resulting properties. It is proved that the applied techniques—DSC, DMA, and PALS—can serve to provide information about the modifications to the polymer chains. Moreover, on the basis of the obtained results and considering the diversified curatives available nowadays, the usability of “part per hundred rubber” (phr) unit is questioned. Full article

(This article belongs to the Special Issue Advances in Research on Elastomers)

▼ Show Figures

Figure 1

16 pages, 9084 KiB

Open AccessArticle

Design and Fabrication of a Precision Template for Spine Surgery Using Selective Laser Melting (SLM)

by Di Wang^1,†, Yimeng Wang^1,†, Jianhua Wang^2,*, Changhui Song^1,†, Yongqiang Yang^1,*, Zimian Zhang¹, Hui Lin¹, Yongqiang Zhen² and Suixiang Liao²

¹ School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China

² Hospital of Orthopedics, Guangzhou General Hospital of Guangzhou Military Command, Liuhua Road, Guangzhou 510010, China

^† These authors contributed equally to this work.

Materials 2016, 9(7), 608; https://doi.org/10.3390/ma9070608 - 22 Jul 2016

Cited by 41 | Viewed by 11763

Abstract

In order to meet the clinical requirements of spine surgery, this paper proposes the fabrication of the customized template for spine surgery through computer-aided design. A 3D metal printing-selective laser melting (SLM) technique was employed to directly fabricate the 316L stainless steel template, [...] Read more.

In order to meet the clinical requirements of spine surgery, this paper proposes the fabrication of the customized template for spine surgery through computer-aided design. A 3D metal printing-selective laser melting (SLM) technique was employed to directly fabricate the 316L stainless steel template, and the metal template with tiny locating holes was used as an auxiliary tool to insert spinal screws inside the patient’s body. To guarantee accurate fabrication of the template for cervical vertebra operation, the contact face was placed upwards to improve the joint quality between the template and the cervical vertebra. The joint surface of the printed template had a roughness of Ra = 13 ± 2 μm. After abrasive blasting, the surface roughness was Ra = 7 ± 0.5 μm. The surgical metal template was bound with the 3D-printed Acrylonitrile Butadiene Styrene (ABS) plastic model. The micro-hardness values determined at the cross-sections of SLM-processed samples varied from HV0.3 250 to HV0.3 280, and the measured tensile strength was in the range of 450 MPa to 560 MPa, which showed that the template had requisite strength. Finally, the metal template was clinically used in the patient’s surgical operation, and the screws were inserted precisely as the result of using the auxiliary template. The geometrical parameters of the template hole (e.g., diameter and wall thickness) were optimized, and measures were taken to optimize the key geometrical units (e.g., hole units) in metal 3D printing. Compared to the traditional technology of screw insertion, the use of the surgical metal template enabled the screws to be inserted more easily and accurately during spinal surgery. However, the design of the high-quality template should fully take into account the clinical demands of surgeons, as well as the advice of the designing engineers and operating technicians. Full article

(This article belongs to the Special Issue 3D Printing for Biomedical Engineering)

▼ Show Figures

Graphical abstract

Journal Menu

Journal Browser

Materials, Volume 9, Issue 7 (July 2016) – 111 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI