Materials

19 pages, 5301 KiB

Open AccessArticle

Analysis of the Shear Behavior of Stubby Y-Type Perfobond Rib Shear Connectors for a Composite Frame Structure

by Sang-Hyo Kim, Kun-Soo Kim

, Do-Hoon Lee, Jun-Seung Park and Oneil Han^*

School of Civil & Environmental Engineering, Yonsei University, Yonsei-Ro 50, Seodaemun-Gu, Seoul 03722, Korea

Materials 2017, 10(11), 1340; https://doi.org/10.3390/ma10111340 - 22 Nov 2017

Cited by 21 | Viewed by 5785

Abstract

Shear connectors are used in steel beam–concrete slabs of composite frame and bridge structures to transfer shear force according to design loads. The existing Y-type perfobond rib shear connectors are designed for girder slabs of composite bridges. Therefore, the rib and transverse rebars [...] Read more.

Shear connectors are used in steel beam–concrete slabs of composite frame and bridge structures to transfer shear force according to design loads. The existing Y-type perfobond rib shear connectors are designed for girder slabs of composite bridges. Therefore, the rib and transverse rebars of the conventional Y-type perfobond rib shear connectors are extremely large for the composite frames of building structures. Thus, this paper proposes stubby Y-type perfobond rib shear connectors, redefining the existing connectors, for composite frames of building structures; these were used to perform push-out tests. These shear connectors have relatively small ribs compared to the conventional Y-type perfobond rib shear connectors. To confirm the shear resistance of these stubby shear connectors, we performed an experiment by using transverse rebars D13 and D16. The results indicate that these shear connectors have suitable shear strength and ductility for application in composite frame structures. The shear strengths obtained using D13 and D16 were not significantly different. However, the ductility of the shear connectors with D16 was 45.1% higher than that of the shear connectors with D13. Full article

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19 pages, 9068 KiB

Open AccessArticle

Environmentally Friendly Compatibilizers from Soybean Oil for Ternary Blends of Poly(lactic acid)-PLA, Poly(ε-caprolactone)-PCL and Poly(3-hydroxybutyrate)-PHB

by María Jesús Garcia-Campo¹, Luis Quiles-Carrillo¹

, Jaime Masia², Miguel Jorge Reig-Pérez¹

, Nestor Montanes¹ and Rafael Balart^1,*

¹ Institute of Materials Technology (ITM), Universitat Politècnica de València (UPV), Plaza Ferrándiz y Carbonell 1, 03801 Alcoy, Alicante, Spain

² Institute of Design and Manufacturing (IDF), Universitat Politècnica de València (UPV), Plaza Ferrándiz y Carbonell 1, 03801 Alcoy, Alicante, Spain

Materials 2017, 10(11), 1339; https://doi.org/10.3390/ma10111339 - 22 Nov 2017

Cited by 65 | Viewed by 8028

Abstract

Ternary blends of poly(lactic acid) (PLA), poly(3-hydroxybutyrate) (PHB) and poly(ε-caprolactone) (PCL) with a constant weight percentage of 60%, 10% and 30% respectively were compatibilized with soybean oil derivatives epoxidized soybean oil (ESO), maleinized soybean oil (MSO) and acrylated epoxidized soybean oil (AESO). The [...] Read more.

Ternary blends of poly(lactic acid) (PLA), poly(3-hydroxybutyrate) (PHB) and poly(ε-caprolactone) (PCL) with a constant weight percentage of 60%, 10% and 30% respectively were compatibilized with soybean oil derivatives epoxidized soybean oil (ESO), maleinized soybean oil (MSO) and acrylated epoxidized soybean oil (AESO). The potential compatibilization effects of the soybean oil-derivatives was characterized in terms of mechanical, thermal and thermomechanical properties. The effects on morphology were studied by field emission scanning electron microscopy (FESEM). All three soybean oil-based compatibilizers led to a noticeable increase in toughness with a remarkable improvement in elongation at break. On the other hand, both the tensile modulus and strength decreased, but in a lower extent to a typical plasticization effect. Although phase separation occurred, all three soybean oil derivatives led somewhat to compatibilization through reaction between terminal hydroxyl groups in all three biopolyesters (PLA, PHB and PCL) and the readily reactive groups in the soybean oil derivatives, that is, epoxy, maleic anhydride and acrylic/epoxy functionalities. In particular, the addition of 5 parts per hundred parts of the blend (phr) of ESO gave the maximum elongation at break while the same amount of MSO and AESO gave the maximum toughness, measured through Charpy’s impact tests. In general, the herein-developed materials widen the potential of ternary PLA formulations by a cost effective blending method with PHB and PCL and compatibilization with vegetable oil-based additives. Full article

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12 pages, 5084 KiB

Open AccessArticle

Auxeticity of Yukawa Systems with Nanolayers in the (111) Crystallographic Plane

by Paweł M. Pigłowski¹, Jakub W. Narojczyk^1,*

, Artur A. Poźniak², Krzysztof W. Wojciechowski¹

and Konstantin V. Tretiakov¹

¹ Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17/19, 60-179 Poznan, Poland

² Department of Technical Physics, Poznan University of Technology, Piotrowo 3, 60-695 Poznan, Poland

Materials 2017, 10(11), 1338; https://doi.org/10.3390/ma10111338 - 22 Nov 2017

Cited by 19 | Viewed by 5328

Abstract

Elastic properties of model crystalline systems, in which the particles interact via the hard potential (infinite when any particles overlap and zero otherwise) and the hard-core repulsive Yukawa interaction, were determined by Monte Carlo simulations. The influence of structural modifications, in the form [...] Read more.

Elastic properties of model crystalline systems, in which the particles interact via the hard potential (infinite when any particles overlap and zero otherwise) and the hard-core repulsive Yukawa interaction, were determined by Monte Carlo simulations. The influence of structural modifications, in the form of periodic nanolayers being perpendicular to the crystallographic axis [111], on auxetic properties of the crystal was investigated. It has been shown that the hard sphere nanolayers introduced into Yukawa crystals allow one to control the elastic properties of the system. It has been also found that the introduction of the Yukawa monolayers to the hard sphere crystal induces auxeticity in the

[11 \bar{1}] [112]

-direction, while maintaining the negative Poisson’s ratio in the

[110] [1 \bar{1} 0]

-direction, thus expanding the partial auxeticity of the system to an additional important crystallographic direction. Full article

(This article belongs to the Special Issue Auxetic Materials 2017-2018)

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14 pages, 3540 KiB

Open AccessFeature PaperArticle

In-Doped ZnO Hexagonal Stepped Nanorods and Nanodisks as Potential Scaffold for Highly-Sensitive Phenyl Hydrazine Chemical Sensors

by Ahmad Umar^1,2,*

, Sang Hoon Kim^1,2, Rajesh Kumar³, Mohammad S. Al-Assiri^2,4, A. E. Al-Salami⁵, Ahmed A. Ibrahim^1,2,6 and Sotirios Baskoutas^6,*

¹ Department of Chemistry, Faculty of Science and Arts, Najran University, P.O. Box 1988, Najran 11001, Saudi Arabia

² Promising Centre for Sensors and Electronic Devices (PCSED), Najran University, P.O. Box-1988, Najran 11001, Saudi Arabia

³ PG Department of Chemistry, JCDAV College, Dasuya 144205, India

⁴ Department of Physics, Faculty of Science and Arts, Najran University, P.O. Box 1988, Najran 11001, Saudi Arabia

⁵ Department of Physics, Faculty of Science, King Khalid University, P.O. Box-9004, Abha 61413, Saudi Arabia

⁶ Department of Materials Science, University of Patras, 26504 Patras, Greece

Materials 2017, 10(11), 1337; https://doi.org/10.3390/ma10111337 - 21 Nov 2017

Cited by 30 | Viewed by 5930

Abstract

Herein, we report the growth of In-doped ZnO (IZO) nanomaterials, i.e., stepped hexagonal nanorods and nanodisks by the thermal evaporation process using metallic zinc and indium powders in the presence of oxygen. The as-grown IZO nanomaterials were investigated by several techniques in order [...] Read more.

Herein, we report the growth of In-doped ZnO (IZO) nanomaterials, i.e., stepped hexagonal nanorods and nanodisks by the thermal evaporation process using metallic zinc and indium powders in the presence of oxygen. The as-grown IZO nanomaterials were investigated by several techniques in order to examine their morphological, structural, compositional and optical properties. The detailed investigations confirmed that the grown nanomaterials, i.e., nanorods and nanodisks possess well-crystallinity with wurtzite hexagonal phase and grown in high density. The room-temperature PL spectra exhibited a suppressed UV emissions with strong green emissions for both In-doped ZnO nanomaterials, i.e., nanorods and nanodisks. From an application point of view, the grown IZO nanomaterials were used as a potential scaffold to fabricate sensitive phenyl hydrazine chemical sensors based on the I–V technique. The observed sensitivities of the fabricated sensors based on IZO nanorods and nanodisks were 70.43 μA·mM⁻¹·cm⁻² and 130.18 μA·mM⁻¹·cm⁻², respectively. For both the fabricated sensors, the experimental detection limit was 0.5 μM, while the linear range was 0.5 μM–5.0 mM. The observed results revealed that the simply grown IZO nanomaterials could efficiently be used to fabricate highly sensitive chemical sensors. Full article

(This article belongs to the Special Issue Zinc Oxide Nanostructures: Synthesis and Characterization)

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12 pages, 9921 KiB

Open AccessArticle

Multifunctional Carbon Aerogels Derived by Sol–Gel Process of Natural Polysaccharides of Different Botanical Origin

by Monika Bakierska^1,*, Agnieszka Chojnacka¹, Michał Świętosławski¹, Piotr Natkański¹, Marta Gajewska², Małgorzata Rutkowska¹ and Marcin Molenda^1,*

¹ Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Krakow, Poland

² Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, Mickiewicza 30, 30-059 Krakow, Poland

Materials 2017, 10(11), 1336; https://doi.org/10.3390/ma10111336 - 21 Nov 2017

Cited by 30 | Viewed by 6159

Abstract

In this manuscript, we describe the results of our recent studies on carbon aerogels derived from natural starches. A facile method for the fabrication of carbon aerogels is presented. Moreover, the complete analysis of the carbonization process of different starch aerogels (potato, maize, [...] Read more.

In this manuscript, we describe the results of our recent studies on carbon aerogels derived from natural starches. A facile method for the fabrication of carbon aerogels is presented. Moreover, the complete analysis of the carbonization process of different starch aerogels (potato, maize, and rice) was performed using thermogravimetric studies combined with a detailed analysis of evolved decomposition products. The prepared carbon aerogels were studied in terms of their morphology and electrical properties to relate the origin of starch precursor with final properties of carbon materials. The obtained results confirmed the differences in carbon aerogels’ morphology, especially in materials’ specific surface areas, depending on the botanical origin of precursors. The electrical conductivity measurements suggest that carbon aerogels with the best electrical properties can be obtained from potato starch. Full article

(This article belongs to the Special Issue Novel Electrochemical Materials for Energy Storage and Conversion)

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16 pages, 8828 KiB

Open AccessFeature PaperArticle

Time-Resolved Photoluminescence Microscopy for the Analysis of Semiconductor-Based Paint Layers

by Daniela Comelli^1,*

, Alessia Artesani¹

, Austin Nevin²

, Sara Mosca¹, Victor Gonzalez^3,4, Myriam Eveno³ and Gianluca Valentini¹

¹ Physics Department, Politecnico di Milano, Piazza Leonardo da Vinci, 20133 Milano, Italy

² Istituto di Fotonica e Nanotecnologie-Consiglio Nazionale delle Ricerche (IFN-CNR), Piazza Leonardo da Vinci, 20133 Milano, Italy

³ Centre de Recherche et de Restauration des Musées de France (C2RMF), Palais du Louvre, F-75001 Paris, France

⁴ Chimie Paris-Tech, PSL Research University, CNRS, Institut de Recherche de Chimie Paris (IRCP), F-75005 Paris, France

Materials 2017, 10(11), 1335; https://doi.org/10.3390/ma10111335 - 21 Nov 2017

Cited by 20 | Viewed by 6748

Abstract

In conservation, science semiconductors occur as the constituent matter of the so-called semiconductor pigments, produced following the Industrial Revolution and extensively used by modern painters. With recent research highlighting the occurrence of various degradation phenomena in semiconductor paints, it is clear that their [...] Read more.

In conservation, science semiconductors occur as the constituent matter of the so-called semiconductor pigments, produced following the Industrial Revolution and extensively used by modern painters. With recent research highlighting the occurrence of various degradation phenomena in semiconductor paints, it is clear that their detection by conventional optical fluorescence imaging and microscopy is limited by the complexity of historical painting materials. Here, we illustrate and prove the capabilities of time-resolved photoluminescence (TRPL) microscopy, equipped with both spectral and lifetime sensitivity at timescales ranging from nanoseconds to hundreds of microseconds, for the analysis of cross-sections of paint layers made of luminescent semiconductor pigments. The method is sensitive to heterogeneities within micro-samples and provides valuable information for the interpretation of the nature of the emissions in samples. A case study is presented on micro samples from a painting by Henri Matisse and serves to demonstrate how TRPL can be used to identify the semiconductor pigments zinc white and cadmium yellow, and to inform future investigations of the degradation of a cadmium yellow paint. Full article

(This article belongs to the Special Issue Techniques and Methods for Advanced Characterization of Luminescent Materials)

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27 pages, 14017 KiB

Open AccessArticle

Underlying Physics of Conductive Polymer Composites and Force Sensing Resistors (FSRs). A Study on Creep Response and Dynamic Loading

by Leonel Paredes-Madrid^1,*

, Arnaldo Matute¹

, Jorge O. Bareño¹, Carlos A. Parra Vargas² and Elkin I. Gutierrez Velásquez³

¹ Faculty of Electronic and Biomedical Engineering, Universidad Antonio Nariño, Tunja 150001, Colombia

² Grupo de Física de Materiales (GFM), Universidad Pedagógica y Tecnológica de Colombia, Tunja 150003, Colombia

³ Faculty of Mechanical Engineering, Universidad Antonio Nariño, Tunja 150001, Colombia

Materials 2017, 10(11), 1334; https://doi.org/10.3390/ma10111334 - 21 Nov 2017

Cited by 47 | Viewed by 7553

Abstract

Force Sensing Resistors (FSRs) are manufactured by sandwiching a Conductive Polymer Composite (CPC) between metal electrodes. The piezoresistive property of FSRs has been exploited to perform stress and strain measurements, but the rheological property of polymers has undermined the repeatability of measurements causing [...] Read more.

Force Sensing Resistors (FSRs) are manufactured by sandwiching a Conductive Polymer Composite (CPC) between metal electrodes. The piezoresistive property of FSRs has been exploited to perform stress and strain measurements, but the rheological property of polymers has undermined the repeatability of measurements causing creep in the electrical resistance of FSRs. With the aim of understanding the creep phenomenon, the drift response of thirty two specimens of FSRs was studied using a statistical approach. Similarly, a theoretical model for the creep response was developed by combining the Burger’s rheological model with the equations for the quantum tunneling conduction through thin insulating films. The proposed model and the experimental observations showed that the sourcing voltage has a strong influence on the creep response; this observation—and the corresponding model—is an important contribution that has not been previously accounted. The phenomenon of sensitivity degradation was also studied. It was found that sensitivity degradation is a voltage-related phenomenon that can be avoided by choosing an appropriate sourcing voltage in the driving circuit. The models and experimental observations from this study are key aspects to enhance the repeatability of measurements and the accuracy of FSRs. Full article

(This article belongs to the Section Advanced Composites)

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10 pages, 9306 KiB

Open AccessArticle

Residual Endodontic Filling Material after Post Space Preparation: A Confocal Microscopic Study

by Yu-Yao Teoh^*

and Laurence J. Walsh

School of Dentistry, The University of Queensland, Herston, Brisbane QLD 4006, Australia

Materials 2017, 10(11), 1333; https://doi.org/10.3390/ma10111333 - 21 Nov 2017

Cited by 8 | Viewed by 5300

Abstract

This laboratory study assessed removability of endodontic alkaline cements and resin sealers using coronal cross-sectional slices of roots with single canals. Materials were labelled with 0.1% (w/w) sodium fluorescein prior to mixing so that confocal microscopy could be used [...] Read more.

This laboratory study assessed removability of endodontic alkaline cements and resin sealers using coronal cross-sectional slices of roots with single canals. Materials were labelled with 0.1% (w/w) sodium fluorescein prior to mixing so that confocal microscopy could be used to quantify material remaining on the walls of post spaces, to assess cleanliness. Roots of extracted teeth were prepared using rotary NiTi instruments then obturated using lateral condensation with gutta percha and epoxy resin sealers (AH-Plus™ or Zirmix™), or were filled by injecting mineral trioxide aggregate (MTA) cement (GC Nex™ MTA or MTAmix™) or a hard-setting calcium hydroxide cement (Supercal™). Brown (#3) ParaPost™ drills were used at 600 rpm with a torque setting of 3 N cm⁻¹ for 2 min to remove 5 mm of the root filling. Roots were embedded and coronal slices examined by confocal microscopy, with the perimeter of the drill channel divided into clean, unclean and non-accessible regions. The choice of material affects cleanliness, with MTA being the most difficult and calcium hydroxide cement the easiest to remove. With epoxy resin-based sealers, almost half of the accessible canal walls remained coated with remnants of sealer after post space preparation. Full article

(This article belongs to the Special Issue Dental Biomaterials 2017)

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10 pages, 4367 KiB

Open AccessArticle

Solution Growth of Two-Dimensional Bi₂Se₃ Nanosheets for Two-Color All-Optical Switching

by Xinghua Wu^1,2, Chao Tan³, Qingkai Wang²

, Yanyan Guo¹, Dianyuan Wang², Yongqian Wang¹ and Dawei Meng^1,*

¹ Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, China

² College of Science, Key Laboratory for Microstructural Functional Materials of Jiangxi Province, Jiujiang University, Jiujiang 332005, China

³ School of Information and Electrical Engineering, Hunan University of Science and Technology, Xiangtan 411201, China

Materials 2017, 10(11), 1332; https://doi.org/10.3390/ma10111332 - 21 Nov 2017

Cited by 8 | Viewed by 5080

Abstract

Two-dimensional Bi₂Se₃ nanosheets with hexagonal shape are synthesized by a solution synthetic route. The Bi₂Se₃ nanosheets are 120 nm in edge width and 7 nm in thickness. The size of the Bi₂Se₃ nanosheets can [...] Read more.

Two-dimensional Bi₂Se₃ nanosheets with hexagonal shape are synthesized by a solution synthetic route. The Bi₂Se₃ nanosheets are 120 nm in edge width and 7 nm in thickness. The size of the Bi₂Se₃ nanosheets can be controlled by choosing different kinds of reducing agents including hydroxylamine and ethylenediamine. Subsequently, we demonstrate a configuration of two-color all-optical switching based on plasma channels effect using the as-synthesized Bi₂Se₃ nanosheets as an optical media. The signal light can be modulated as two states including dot and ring shape by changing the intensity of control light. The modulated signal light exhibits excellent spatial propagation properties. As a type of interesting optical material, ultrathin two-dimensional Bi₂Se₃ nanosheets might provide an effective option for photoelectric applications. Full article

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10 pages, 16030 KiB

Open AccessCommunication

Warm Pre-Strain: Strengthening the Metastable 304L Austenitic Stainless Steel without Compromising Its Hydrogen Embrittlement Resistance

by Yanfei Wang^1,*, Zhiling Zhou¹, Weijie Wu² and Jianming Gong²

¹ School of Chemical Engineering & Technology, China University of Mining and Technology, Xuzhou 221116, China

² School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, China

Materials 2017, 10(11), 1331; https://doi.org/10.3390/ma10111331 - 21 Nov 2017

Cited by 5 | Viewed by 4473

Abstract

Plastic pre-strains were applied to the metastable 304L austenitic stainless steel at both room temperature (20 °C) and higher temperatures (i.e., 50, 80 and 100 °C), and then the hydrogen embrittlement (HE) susceptibility of the steel was evaluated by cathodically hydrogen-charging and tensile [...] Read more.

Plastic pre-strains were applied to the metastable 304L austenitic stainless steel at both room temperature (20 °C) and higher temperatures (i.e., 50, 80 and 100 °C), and then the hydrogen embrittlement (HE) susceptibility of the steel was evaluated by cathodically hydrogen-charging and tensile testing. The 20 °C pre-strain greatly strengthened the steel, but simultaneously significantly increased the HE susceptibility of the steel, since α′ martensite was induced by the pre-strain, causing the pre-existence of α′ martensite, which provided “highways” for hydrogen to transport deep into the steel during the hydrogen-charging. Although the warm pre-strains did not strengthen the steel as significantly as the 20 °C pre-strain, they retained the HE resistance of the steel. This is because the higher temperatures, particularly 80 and 100 °C, suppressed the α′ martensite transformation during the pre-straining. Pre-strain at a temperature slightly higher than room temperature has a potential to strengthen the metastable 304L austenitic stainless steel without compromising its initial HE resistance. Full article

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11 pages, 3784 KiB

Open AccessArticle

Facile Control of the Porous Structure of Larch-Derived Mesoporous Carbons via Self-Assembly for Supercapacitors

by Xin Zhao^1,2,*

, Wei Li²

, Honglei Chen¹, Shoujuan Wang¹, Fangong Kong¹ and Shouxin Liu^2,*

¹ Key Lab of Pulp and Paper Science and Technology of Ministry of Education (Shandong Province), Qilu University of Technology, Jinan 250353, China

² College of Material Science and Engineering, Northeast Forestry University, Harbin 150040, China

Materials 2017, 10(11), 1330; https://doi.org/10.3390/ma10111330 - 20 Nov 2017

Cited by 9 | Viewed by 4183

Abstract

Mesoporous carbons have been successfully synthesized via self-assembly using larch-based resins as precursors and triblock copolymers as soft templates. The porous structure of mesoporous carbons can be tailored by adjusting the ratio of hydrophilic/hydrophobic (EO/PO) units owing to interfacial curvature. Interestingly, the porous [...] Read more.

Mesoporous carbons have been successfully synthesized via self-assembly using larch-based resins as precursors and triblock copolymers as soft templates. The porous structure of mesoporous carbons can be tailored by adjusting the ratio of hydrophilic/hydrophobic (EO/PO) units owing to interfacial curvature. Interestingly, the porous structures show a distinct change from vortex-like to worm-like pores, to stripe-like pores, and to ordered two-dimensional hexagonal pores as the ratio of hydrophilic/hydrophobic units increases, indicating the significant effect of EO/PO ratio on the porous structure. The mesoporous carbons as supercapacitor electrodes exhibit superior electrochemical capacitive performance and a high degree of reversibility after 2000 cycles for supercapacitors due to the well-defined mesoporosity of the carbon materials. Meanwhile, the superior carbon has a high specific capacitance of 107 F·g⁻¹ in 6 M KOH at a current density of 10 A·g⁻¹. Full article

(This article belongs to the Section Porous Materials)

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9 pages, 2654 KiB

Open AccessCommunication

Morphology and Mechanical Properties of Polyimide Films: The Effects of UV Irradiation on Microscale Surface

by Changzi Qu¹, Junsong Hu¹, Xing Liu¹, Zheng Li^1,*

and Yanhuai Ding^1,2,*

¹ Institute of Rheological Mechanics, Xiangtan University, Xiangtan 411105, China

² Key Laboratory of Intelligent Computing & Information Processing of Ministry of Education, Xiangtan University, Xiangtan 411105, China

Materials 2017, 10(11), 1329; https://doi.org/10.3390/ma10111329 - 20 Nov 2017

Cited by 68 | Viewed by 8177

Abstract

As an attractive dielectric material, polyimide has been widely used in the field of electronics, aerospace, and automobiles due to its useful mechanical properties and good chemical resistance. UV irradiation was considered to be the main factor related to the damage and failure [...] Read more.

As an attractive dielectric material, polyimide has been widely used in the field of electronics, aerospace, and automobiles due to its useful mechanical properties and good chemical resistance. UV irradiation was considered to be the main factor related to the damage and failure of polyimide. Here the effects of UV irradiation on the surface morphology and microscale mechanical properties of polyimide films are characterized by atomic force microscopy (AFM). The surface roughness of the UV-irradiated samples developed and the mechanical properties degraded with the radiation dose increased. For comparison, uniaxial tensile test was performed to obtain the macroscale Young’s modulus of polyimide film. The UV-irradiated damaging depth was simulated with finite element method (FEM). Full article

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9 pages, 1577 KiB

Open AccessArticle

Tuning the Photoluminescence of Graphene Quantum Dots by Photochemical Doping with Nitrogen

by Xiaofen Xu¹, Fuhua Gao¹, Xiaohua Bai¹, Fuchi Liu^1,*, Wenjie Kong^1,* and Ming Li²

¹ College of Physics and Technology, Guangxi Normal University, Guilin 541004, China

² College of Science, Guilin University of Technology, Guilin 541004, China

Materials 2017, 10(11), 1328; https://doi.org/10.3390/ma10111328 - 20 Nov 2017

Cited by 44 | Viewed by 7684

Abstract

Nitrogen-doped graphene quantum dots (NGQDs) were synthesized by irradiating graphene quantum dots (GQDs) in an NH₃ atmosphere. The photoluminescence (PL) properties of the GQDs and the NGQDs samples were investigated. Compared with GQDs, a clear PL blue-shift of NGQDs could be achieved [...] Read more.

Nitrogen-doped graphene quantum dots (NGQDs) were synthesized by irradiating graphene quantum dots (GQDs) in an NH₃ atmosphere. The photoluminescence (PL) properties of the GQDs and the NGQDs samples were investigated. Compared with GQDs, a clear PL blue-shift of NGQDs could be achieved by regulating the irradiating time. The NGQDs obtained by irradiation of GQDs for 70 min had a high N content of 15.34 at % and a PL blue-shift of about 47 nm. This may be due to the fact that photochemical doping of GQDs with nitrogen can significantly enhance the contents of pyridine-like nitrogen, and also effectively decrease the contents of oxygen functional groups of NGQDs, thus leading to the observed obvious PL blue-shift. Full article

(This article belongs to the Special Issue Luminescent Materials 2017)

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8 pages, 5499 KiB

Open AccessArticle

Structural, Electrical, Magnetic and Resistive Switching Properties of the Multiferroic/Ferroelectric Bilayer Thin Films

by Ming-Cheng Kao^1,*

, Hone-Zern Chen^1,*, San-Lin Young¹, Kai-Huang Chen², Jung-Lung Chiang³

and Jen-Bin Shi⁴

¹ Department of Electronic Engineering, Hsiuping University of Science and Technology, Taichung 41280, Taiwan

² Department of Electrical Engineering and Computer Science, Tung Fang Design Institute, Kaohsiung 82941, Taiwan

³ Department of Mobile Technology, Toko University, Chiayi 61363, Taiwan

⁴ Department of Electronic Engineering, Feng Chia University, Taichung 40724, Taiwan

Materials 2017, 10(11), 1327; https://doi.org/10.3390/ma10111327 - 20 Nov 2017

Cited by 9 | Viewed by 4506

Abstract

Bi_0.8Pr_0.2Fe_0.95Mn_0.05O₃/Bi_3.96Gd_0.04Ti_2.95W_0.05O₁₂ (BPFMO/BGTWO) bilayer thin films with Multiferroic/Ferroelectric (MF/FE) structures were deposited onto Pt(111)/Ti/SiO₂/Si(100) substrates by using the sol-gel method with rapid thermal [...] Read more.

Bi_0.8Pr_0.2Fe_0.95Mn_0.05O₃/Bi_3.96Gd_0.04Ti_2.95W_0.05O₁₂ (BPFMO/BGTWO) bilayer thin films with Multiferroic/Ferroelectric (MF/FE) structures were deposited onto Pt(111)/Ti/SiO₂/Si(100) substrates by using the sol-gel method with rapid thermal annealing. The BPFMO/BGTWO thin films exhibited well-saturated ferromagnetic and ferroelectric hysteresis loops because of the electro-magnetic coupling induced by the MF/FE structure. The remnant magnetization (2Mr) and remnant polarization (2Pr) were 4.6 emu/cm³ and 62 μC/cm², respectively. Moreover, the bipolar I-V switching curves of BPFMO/BGTWO bilayer thin films resistive random access memory (RRAM) devices were discussed, and investigated for LRS/HRS. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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16 pages, 3100 KiB

Open AccessArticle

Novel Montmorillonite/TiO₂/MnAl-Mixed Oxide Composites Prepared from Inverse Microemulsions as Combustion Catalysts

by Bogna D. Napruszewska¹, Alicja Michalik-Zym¹, Melania Rogowska¹, Elżbieta Bielańska¹, Wojciech Rojek¹, Adam Gaweł², Monika Wójcik-Bania², Krzysztof Bahranowski² and Ewa M. Serwicka^1,*

¹ Jerzy Haber Institute of Catalysis and Surface Chemistry, Niezapominajek 8, 30-239 Krakow, Poland

² Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow, Poland

Materials 2017, 10(11), 1326; https://doi.org/10.3390/ma10111326 - 19 Nov 2017

Cited by 10 | Viewed by 4622

Abstract

A novel design of combustion catalysts is proposed, in which clay/TiO₂/MnAl-mixed oxide composites are formed by intermixing exfoliated organo-montmorillonite with oxide precursors (hydrotalcite-like in the case of Mn-Al oxide) obtained by an inverse microemulsion method. In order to assess the catalysts’ [...] Read more.

A novel design of combustion catalysts is proposed, in which clay/TiO₂/MnAl-mixed oxide composites are formed by intermixing exfoliated organo-montmorillonite with oxide precursors (hydrotalcite-like in the case of Mn-Al oxide) obtained by an inverse microemulsion method. In order to assess the catalysts’ thermal stability, two calcination temperatures were employed: 450 and 600 °C. The composites were characterized with XRF (X-ray fluorescence), XRD (X-ray diffraction), HR SEM (high resolution scanning electron microscopy, N₂ adsorption/desorption at −196 °C, and H₂ TPR (temperature programmed reduction). Profound differences in structural, textural and redox properties of the materials were observed, depending on the presence of the TiO₂ component, the type of neutralization agent used in the titania nanoparticles preparation (NaOH or NH₃ (aq)), and the temperature of calcination. Catalytic tests of toluene combustion revealed that the clay/TiO₂/MnAl-mixed oxide composites prepared with the use of ammonia showed excellent activity, the composites obtained from MnAl hydrotalcite nanoparticles trapped between the organoclay layers were less active, but displayed spectacular thermal stability, while the clay/TiO₂/MnAl-mixed oxide materials obtained with the aid of NaOH were least active. The observed patterns of catalytic activity bear a direct relation to the materials’ composition and their structural, textural, and redox properties. Full article

(This article belongs to the Special Issue Advances in Pillared Clays and Similar Materials: Synthesis, Characterization and Applications)

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31 pages, 21321 KiB

Open AccessFeature PaperArticle

On the Piezoelectric Detection of Guided Ultrasonic Waves

by Kanji Ono

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

Materials 2017, 10(11), 1325; https://doi.org/10.3390/ma10111325 - 18 Nov 2017

Cited by 10 | Viewed by 5872

Abstract

In order to quantify the wave motion of guided ultrasonic waves, the characteristics of piezoelectric detectors, or ultrasonic transducers and acoustic emission sensors, have been evaluated systematically. Such guided waves are widely used in structural health monitoring and nondestructive evaluation, but methods of [...] Read more.

In order to quantify the wave motion of guided ultrasonic waves, the characteristics of piezoelectric detectors, or ultrasonic transducers and acoustic emission sensors, have been evaluated systematically. Such guided waves are widely used in structural health monitoring and nondestructive evaluation, but methods of calibrating piezoelectric detectors have been inadequate. This study relied on laser interferometry for the base displacement measurement of bar waves, from which eight different guided wave test set-ups are developed with known wave motion using piezoelectric transmitters. Both plates and bars of 12.7 and 6.4 mm thickness were used as wave propagation media. The upper frequency limit was 2 MHz. Output of guided wave detectors were obtained on the test set-ups and their receiving sensitivities were characterized and averaged. While each sensitivity spectrum was noisy for a detector, the averaged spectrum showed a good convergence to a unique receiving sensitivity. Twelve detectors were evaluated and their sensitivity spectra determined in absolute units. Generally, these showed rapidly dropping sensitivity with increasing frequency due to waveform cancellation on their sensing areas. This effect contributed to vastly different sensitivities to guided wave and to normally incident wave for each one of the 12 detectors tested. Various other effects are discussed and recommendations on methods of implementing the approach developed are provided. Full article

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15 pages, 1972 KiB

Open AccessArticle

Effect of Alumina Incorporation on the Surface Mineralization and Degradation of a Bioactive Glass (CaO-MgO-SiO₂-Na₂O-P₂O₅-CaF₂)-Glycerol Paste

by Dilshat Tulyaganov¹

, Khasan Abdukayumov¹, Olim Ruzimuradov¹, Mirabbos Hojamberdiev¹, Emanuel Ionescu^2,*

and Ralf Riedel²

¹ Turin Polytechnic University in Tashkent, 17, Niyazova 100095, Uzbekistan

² Institute for Materials Science, Technische Universität Darmstadt, Jovanka-Bontschits-Strasse 2, D-64287 Darmstadt, Germany

Materials 2017, 10(11), 1324; https://doi.org/10.3390/ma10111324 - 18 Nov 2017

Cited by 13 | Viewed by 6568

Abstract

This study investigates the dissolution behavior as well as the surface biomineralization in simulated body fluid (SBF) of a paste composed of glycerol (gly) and a bioactive glass in the system CaO-MgO-SiO₂-Na₂O-P₂O₅-CaF₂ (BG). The [...] Read more.

This study investigates the dissolution behavior as well as the surface biomineralization in simulated body fluid (SBF) of a paste composed of glycerol (gly) and a bioactive glass in the system CaO-MgO-SiO₂-Na₂O-P₂O₅-CaF₂ (BG). The synthesis of the bioactive glass in an alumina crucible has been shown to significantly affect its bioactivity due to the incorporation of aluminum (ca. 1.3–1.4 wt %) into the glass network. Thus, the kinetics of the hydroxyapatite (HA) mineralization on the glass prepared in the alumina crucible was found to be slower than that reported for the same glass composition prepared in a Pt crucible. It is considered that the synthesis conditions lead to the incorporation of small amount of aluminum into the BG network and thus delay the HA mineralization. Interestingly, the BG-gly paste was shown to have significantly higher bioactivity than that of the as-prepared BG. Structural analysis of the paste indicate that glycerol chemically interacts with the glass surface and strongly alter the glass network architecture, thus generating a more depolymerized network, as well as an increased amount of silanol groups at the surface of the glass. In particular, BG-gly paste features early intermediate calcite precipitation during immersion in SBF, followed by hydroxyapatite formation after ca. seven days of SBF exposure; whereas the HA mineralization seems to be suppressed in BG, probably a consequence of the incorporation of aluminum into the glass network. The results obtained within the present study reveal the positive effect of using pastes based on bioactive glasses and organic carriers (here alcohols) which may be of interest not only due to their advantageous visco-elastic properties, but also due to the possibility of enhancing the glass bioactivity upon surface interactions with the organic carrier. Full article

(This article belongs to the Special Issue Bioactive Glasses 2017)

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17 pages, 2365 KiB

Open AccessArticle

Efficiency of True-Green Light Emitting Diodes: Non-Uniformity and Temperature Effects

by Ilya E. Titkov^1,2,*, Sergey Yu. Karpov³, Amit Yadav², Denis Mamedov¹, Vera L. Zerova^2,4 and Edik Rafailov²

¹ Ostendo Technologies Inc., 6185 Paseo del Norte, Carlsbad, CA 92011, USA

² Optoelectronics and Biomedical Photonics Group, Aston Institute of Photonic Technologies, Aston University, Birmingham B4 7ET, UK

³ STR Group—Soft-Impact, Ltd., P.O. Box 83, 27 Engels Ave., 194156 Saint-Petersburg, Russia

⁴ Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK

Materials 2017, 10(11), 1323; https://doi.org/10.3390/ma10111323 - 18 Nov 2017

Cited by 17 | Viewed by 6751

Abstract

External quantum efficiency of industrial-grade green InGaN light-emitting diodes (LEDs) has been measured in a wide range of operating currents at various temperatures from 13 K to 300 K. Unlike blue LEDs, the efficiency as a function of current is found to have [...] Read more.

External quantum efficiency of industrial-grade green InGaN light-emitting diodes (LEDs) has been measured in a wide range of operating currents at various temperatures from 13 K to 300 K. Unlike blue LEDs, the efficiency as a function of current is found to have a multi-peak character, which could not be fitted by a simple ABC-model. This observation correlated with splitting of LED emission spectra into two peaks at certain currents. The characterization data are interpreted in terms of non-uniformity of the LED active region, which is tentatively attributed to extended defects like V-pits. We suggest a new approach to evaluation of temperature-dependent light extraction and internal quantum efficiencies taking into account the active region non-uniformity. As a result, the temperature dependence of light extraction and internal quantum efficiencies have been evaluated in the temperature range mentioned above and compared with those of blue LEDs. Full article

(This article belongs to the Special Issue Light Emitting Diodes and Laser Diodes: Materials and Devices)

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14 pages, 6725 KiB

Open AccessArticle

Co-Precipitation Synthesis and Optical Properties of Mn⁴⁺-Doped Hexafluoroaluminate w-LED Phosphors

by Tim Senden^*

, Robin G. Geitenbeek and Andries Meijerink

Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, P.O. Box 80000, 3508 TA Utrecht, The Netherlands

Materials 2017, 10(11), 1322; https://doi.org/10.3390/ma10111322 - 17 Nov 2017

Cited by 33 | Viewed by 6168

Abstract

Mn⁴⁺-activated hexafluoroaluminates are promising red-emitting phosphors for white light emitting diodes (w-LEDs). Here, we report the synthesis of Na₃AlF₆:Mn⁴⁺, K₃AlF₆:Mn⁴⁺ and K₂NaAlF₆:Mn⁴⁺ phosphors through a [...] Read more.

Mn⁴⁺-activated hexafluoroaluminates are promising red-emitting phosphors for white light emitting diodes (w-LEDs). Here, we report the synthesis of Na₃AlF₆:Mn⁴⁺, K₃AlF₆:Mn⁴⁺ and K₂NaAlF₆:Mn⁴⁺ phosphors through a simple two-step co-precipitation method. Highly monodisperse large (~20 μm) smoothed-octahedron shaped crystallites are obtained for K₂NaAlF₆:Mn⁴⁺. The large size, regular shape and small size distribution are favorable for application in w-LEDs. All Mn⁴⁺-doped hexafluoroaluminates show bright red Mn⁴⁺ luminescence under blue light excitation. We compare the optical properties of Na₃AlF₆:Mn⁴⁺, K₃AlF₆:Mn⁴⁺ and K₂NaAlF₆:Mn⁴⁺ at room temperature and 4 K. The luminescence measurements reveal that multiple Mn⁴⁺ sites exist in M₃AlF₆:Mn⁴⁺ (M = Na, K), which is explained by the charge compensation that is required for Mn⁴⁺ on Al³⁺ sites. Thermal cycling experiments show that the site distribution changes after annealing. Finally, we investigate thermal quenching and show that the luminescence quenching temperature is high, around 460–490 K, which makes these Mn⁴⁺-doped hexafluoroaluminates interesting red phosphors for w-LEDs. The new insights reported on the synthesis and optical properties of Mn⁴⁺ in the chemically and thermally stable hexafluoroaluminates can contribute to the optimization of red-emitting Mn⁴⁺ phosphors for w-LEDs. Full article

(This article belongs to the Special Issue Luminescent Materials 2017)

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16 pages, 5034 KiB

Open AccessArticle

The Biological Properties of OGI Surfaces Positively Act on Osteogenic and Angiogenic Commitment of Mesenchymal Stem Cells

by Paolo Ghensi^1,2, Eriberto Bressan¹, Chiara Gardin³, Letizia Ferroni³, Maria Costanza Soldini⁴, Federico Mandelli⁵, Claudio Soldini^1,6 and Barbara Zavan^3,7,*

¹ Department of Neurosciences, Dental School, University of Padova, Via Giustiniani 2, 35100 Padova, Italy

² Centre for Integrative Biology (CIBIO), University of Trento, 38122 Trento, Italy

³ Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58, 35100 Padova, Italy

⁴ Department of Public Health, Experimental and Forensic Medicine, University of Pavia, 27100 Pavia, Italy

⁵ Private Practice, 09100 Milano, Italy

⁶ CLC Scientific, via Vecchia Ferriera 18, 36100 Vicenza, Italy

⁷ Maria Cecilia Hospital, GVM Care & Research, 48033 Cotignola (RA), Italy

Materials 2017, 10(11), 1321; https://doi.org/10.3390/ma10111321 - 17 Nov 2017

Cited by 13 | Viewed by 4287

Abstract

Osteogenesis process displays a fundamental role during dental implant osteointegration. In the present work, we studied the influence of Osteon Growth Induction (OGI) surface properties on the angiogenic and osteogenic behaviors of Mesenchymal Stem cells (MSC). MSC derived from dental pulp and HUVEC [...] Read more.

Osteogenesis process displays a fundamental role during dental implant osteointegration. In the present work, we studied the influence of Osteon Growth Induction (OGI) surface properties on the angiogenic and osteogenic behaviors of Mesenchymal Stem cells (MSC). MSC derived from dental pulp and HUVEC (Human Umbilical Vein Endothelial Cells) were grown in on OGI titanium surfaces, and cell proliferation and DNA synthesis were evaluated by MTT [3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide] test and DNA quantification. Gene expression has been performed in order to evaluate the presence of mRNA related to endothelial and osteogenesis markers. Moreover, morphological and biochemical analyses of osteogenesis commitments has been performed. On OGI surfaces, MSC and HUVEC are able to proliferate. Gene expression profiler confirms that MSC on OGI surfaces are able to express endothelial and osteogenic markers, and that these expression are higher compared the expression on control surfaces. In conclusion On OGI surfaces proliferation, expression and morphological analyses of angiogenesis-associated markers in MSC are promoted. This process induces an increasing on their osteogenesis commitment. Full article

(This article belongs to the Special Issue Dental Implant Materials)

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18 pages, 4861 KiB

Open AccessArticle

Calcined Chitosan-Supported Layered Double Hydroxides: An Efficient and Recyclable Adsorbent for the Removal of Fluoride from an Aqueous Solution

by Hanjun Wu¹, Huali Zhang², Qingxue Yang¹, Dongsheng Wang^1,3, Weijun Zhang^4,* and Xiaofang Yang^3,*

¹ Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, China

² School of Chemistry and Environmental Engineering, Wuhan Institute of Technology, Wuhan 430074, China

³ State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China

⁴ School of Environmental Studies, China University of Geosciences, Wuhan 430074, China

Materials 2017, 10(11), 1320; https://doi.org/10.3390/ma10111320 - 17 Nov 2017

Cited by 14 | Viewed by 5413

Abstract

In this work, calcined chitosan-supported layered double hydroxides (CSLDO) were synthesized through a co-precipitation method that restrained the particles’ aggregation of LDHs and exhibited huge specific surface areas, which can enhance the fluoride adsorption capacity. CSLDOs were characterized by physical and chemical methods [...] Read more.

In this work, calcined chitosan-supported layered double hydroxides (CSLDO) were synthesized through a co-precipitation method that restrained the particles’ aggregation of LDHs and exhibited huge specific surface areas, which can enhance the fluoride adsorption capacity. CSLDOs were characterized by physical and chemical methods and used for fluoride adsorption in an aqueous solution. The results indicated that the nanoparticles were constructed first and then assembled to form a porous and layered structure, and chitosan-supported layered double hydroxides (CSLDHs) calcined at 400 °C (CSLDO400) showed the highest specific surface area of 116.98 m²·g⁻¹ and the largest pore volume of 0.411 cm³·g⁻¹. CSLDO400 exhibited excellent adsorption performance at a wide pH range from 5 to 9 for fluoride. The adsorption kinetics indicated that the adsorption reached equilibrium after 120 min, and followed a pseudo-first-order model. It agreed well with the Langmuir isotherm with maximum adsorption amounts of 27.56 mg·g⁻¹. The adsorption of fluoride ions was spontaneous and endothermic. Furthermore, CSLDO400 showed a high stability for fluoride removal; it could still achieve 68% removal for fluoride after repeating five times of adsorption–desorption cycles. This study demonstrated that CSLDO400 is a promising functional material to remove fluoride from surface/ground water. Full article

(This article belongs to the Section Porous Materials)

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14 pages, 2013 KiB

Open AccessArticle

Temperature Uncertainty Analysis of Injection Mechanism Based on Kriging Modeling

by Dongdong You^1,*

, Dehui Liu¹, Xiaomo Jiang^2,*, Xueyu Cheng³ and Xiang Wang¹

¹ National Engineering Research Center of Near-Net-Shape Forming for Metallic Materials, South China University of Technology, Guangzhou 510640, China

² College of Engineering, Tongji University, Shanghai 200092, China

³ Applied Science, Clayton State University, Morrow, GA 30260, USA

Materials 2017, 10(11), 1319; https://doi.org/10.3390/ma10111319 - 17 Nov 2017

Cited by 6 | Viewed by 3687

Abstract

A kriging modeling method is proposed to conduct the temperature uncertainty analysis of an injection mechanism in squeeze casting. A mathematical model of temperature prediction with multi input and single output is employed to estimate the temperature spatiotemporal distributions of the injection mechanism. [...] Read more.

A kriging modeling method is proposed to conduct the temperature uncertainty analysis of an injection mechanism in squeeze casting. A mathematical model of temperature prediction with multi input and single output is employed to estimate the temperature spatiotemporal distributions of the injection mechanism. The kriging model applies different weights to the independent variables according to spatial location of sample points and their correlation, thus reducing the estimation variance. The predicted value of the kriging model is compared with the sample data at the corresponding position to investigate the influence of the temperature uncertainty of the injection mechanism on the injection process including friction. The results indicate that the significant error is observed at a few sample points in the early injection due to the impact of the uncertainty facts. The variance mean and standard deviation obtained by the model calibrated by experimental samples reduce largely in comparison to those obtained from the initial kriging model. This study indicates that model calibration produces more accurate prediction. Full article

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

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9 pages, 1768 KiB

Open AccessArticle

Multiferroic Hysteresis Loop

by Alexander Ruff^*, Alois Loidl

and Stephan Krohns^*

Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany

Materials 2017, 10(11), 1318; https://doi.org/10.3390/ma10111318 - 17 Nov 2017

Cited by 14 | Viewed by 7665

Abstract

Multiferroics, showing both ferroelectric and magnetic order, are promising candidates for future electronic devices. Especially, the fundamental understanding of ferroelectric switching is of key relevance for further improvements, which however is rarely reported in literature. On a prime example for a spin-driven multiferroic, [...] Read more.

Multiferroics, showing both ferroelectric and magnetic order, are promising candidates for future electronic devices. Especially, the fundamental understanding of ferroelectric switching is of key relevance for further improvements, which however is rarely reported in literature. On a prime example for a spin-driven multiferroic, LiCuVO₄, we present an extensive study of the ferroelectric order and the switching behavior as functions of external electric and magnetic fields. From frequency-dependent polarization switching and using the Ishibashi-Orihara theory, we deduce the existence of ferroelectric domains and domain-walls. These have to be related to counterclockwise and clockwise spin-spirals leading to the formation of multiferroic domains. A novel measurement—multiferroic hysteresis loop—is established to analyze the electrical polarization simultaneously as a function of electrical and magnetic fields. This technique allows characterizing the complex coupling between ferroelectric and magnetic order in multiferroic LiCuVO₄. Full article

(This article belongs to the Special Issue Physics, Measurements and Applications of Multiferroic and Magnetoelectric Materials)

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10 pages, 2863 KiB

Open AccessArticle

Growth of Anisotropic Gold Nanoparticle Assemblies via Liposome Fusion

by Kouta Sugikawa^1,*, Tatsuya Kadota¹, Kotaro Matsuo¹, Kazuma Yasuhara² and Atsushi Ikeda^1,*

¹ Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan

² Graduate School of Materials Science, Nara Institute of Science and Technology, Nara 630-0192, Japan

Materials 2017, 10(11), 1317; https://doi.org/10.3390/ma10111317 - 17 Nov 2017

Cited by 5 | Viewed by 5247

Abstract

Anisotropic assembly of nanoparticles (NPs) has attracted extensive attention because of the potential applications in materials science, biology, and medicine. However, assembly control (e.g., the number of assembled NPs) has not been adequately studied. Here, the growth of anisotropic gold NP assemblies on [...] Read more.

Anisotropic assembly of nanoparticles (NPs) has attracted extensive attention because of the potential applications in materials science, biology, and medicine. However, assembly control (e.g., the number of assembled NPs) has not been adequately studied. Here, the growth of anisotropic gold NP assemblies on a liposome surface is reported. Citrate-coated gold NPs adsorbed on liposome surfaces were assembled in one dimension at temperatures above the phase transition temperature of the lipid bilayer. Growth of the anisotropic assemblies depended on the heating time. Absorption spectroscopy and transmission electron microscopy revealed that the gradual growth was attributed to liposome fusion, which was strongly affected by the size of the gold NPs. This method enabled us to precisely control the number of NPs in each anisotropic assembly. These results will enable the fabrication of functional materials based on NP assemblies and enable investigations of cell functions and disease causality. Full article

(This article belongs to the Special Issue Designed Colloidal Self-Assembly)

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11 pages, 995 KiB

Open AccessReview

Resistance of Magnesium Alloys to Corrosion Fatigue for Biodegradable Implant Applications: Current Status and Challenges

by R. K. Singh Raman^1,2,* and Shervin Eslami Harandi¹

¹ Department of Mechanical & Aerospace Engineering, Monash University, Melbourne, VIC 3800, Australia

² Department of Chemical Engineering, Monash University, Melbourne, VIC 3800, Australia

Materials 2017, 10(11), 1316; https://doi.org/10.3390/ma10111316 - 16 Nov 2017

Cited by 28 | Viewed by 7075

Abstract

Magnesium (Mg) alloys are attracting increasing interest as the most suitable metallic materials for construction of biodegradable and bio-absorbable temporary implants. However, Mg-alloys can suffer premature and catastrophic fracture under the synergy of cyclic loading and corrosion (i.e., corrosion fatigue (CF)). Though Mg [...] Read more.

Magnesium (Mg) alloys are attracting increasing interest as the most suitable metallic materials for construction of biodegradable and bio-absorbable temporary implants. However, Mg-alloys can suffer premature and catastrophic fracture under the synergy of cyclic loading and corrosion (i.e., corrosion fatigue (CF)). Though Mg alloys are reported to be susceptible to CF also in the corrosive human body fluid, there are very limited studies on this topic. Furthermore, the in vitro test parameters employed in these investigations have not properly simulated the actual conditions in the human body. This article presents an overview of the findings of available studies on the CF of Mg alloys in pseudo-physiological solutions and the employed testing procedures, as well as identifying the knowledge gap. Full article

(This article belongs to the Section Biomaterials)

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9 pages, 4359 KiB

Open AccessArticle

Wear Behavior and Microstructure of Mg-Sn Alloy Processed by Equal Channel Angular Extrusion

by Jung-Hsuan Chen¹, Yen-Chen Shen², Chuen-Guang Chao^2,* and Tzeng-Feng Liu²

¹ Department of Industrial Education, National Taiwan Normal University, Taipei 106, Taiwan

² Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan

Materials 2017, 10(11), 1315; https://doi.org/10.3390/ma10111315 - 16 Nov 2017

Cited by 11 | Viewed by 4208

Abstract

Mg-5wt.% Sn alloy is often used in portable electronic devices and automobiles. In this study, mechanical properties of Mg-5wt.% Sn alloy processed by Equal Channel Angular Extrusion (ECAE) were characterized. More precisely, its hardness and wear behavior were measured using Vickers hardness test [...] Read more.

Mg-5wt.% Sn alloy is often used in portable electronic devices and automobiles. In this study, mechanical properties of Mg-5wt.% Sn alloy processed by Equal Channel Angular Extrusion (ECAE) were characterized. More precisely, its hardness and wear behavior were measured using Vickers hardness test and a pin-on-disc wear test. The microstructures of ECAE-processed Mg-Sn alloys were investigated by scanning electron microscope and X-ray diffraction. ECAE process refined the grain sizes of the Mg-Sn alloy from 117.6 μm (as-cast) to 88.0 μm (one pass), 49.5 μm (two passes) and 24.4 μm (four passes), respectively. Meanwhile, the hardness of the alloy improved significantly. The maximum wear resistance achieved in the present work was around 73.77 m/mm³, which was obtained from the Mg-Sn alloy treated with a one-pass ECAE process with a grain size of 88.0 μm. The wear resistance improvement was caused by the grain size refinement and the precipitate of the second phase, Mg₂Sn against the oxidation of the processed alloy. The as-cast Mg-Sn alloy with the larger grain size, i.e., 117.6 μm, underwent wear mechanisms, mainly adhesive wear and abrasive wear. In ECAE-processed Mg-Sn alloy, high internal energy occurred due to the high dislocation density and the stress field produced by the plastic deformation, which led to an increased oxidation rate of the processed alloy during sliding. Therefore, the oxidative wear and a three-body abrasive wear in which the oxide debris acted as the three-body abrasive components became the dominant factors in the wear behavior, and as a result, reduced the wear resistance in the multi-pass ECAE-processed alloy. Full article

(This article belongs to the Special Issue Selected Papers from IEEE ICICE 2017)

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22 pages, 6956 KiB

Open AccessFeature PaperArticle

Experimental Exploration of Metal Cable as Reinforcement in 3D Printed Concrete

by Freek P. Bos^1,*, Zeeshan Y. Ahmed¹, Evgeniy R. Jutinov¹ and Theo A. M. Salet^1,2

¹ Department of the Built Environment, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands

² Witteveen+Bos, P.O. Box 233, 7400 AE Deventer, The Netherlands

Materials 2017, 10(11), 1314; https://doi.org/10.3390/ma10111314 - 16 Nov 2017

Cited by 216 | Viewed by 14837

Abstract

The Material Deposition Method (MDM) is enjoying increasing attention as an additive method to create concrete mortar structures characterised by a high degree of form-freedom, a lack of geometrical repetition, and automated construction. Several small-scale structures have been realised around the world, or [...] Read more.

The Material Deposition Method (MDM) is enjoying increasing attention as an additive method to create concrete mortar structures characterised by a high degree of form-freedom, a lack of geometrical repetition, and automated construction. Several small-scale structures have been realised around the world, or are under preparation. However, the nature of this construction method is unsuitable for conventional reinforcement methods to achieve ductile failure behaviour. Sometimes, this is solved by combining printing with conventional casting and reinforcing techniques. This study, however, explores an alternative strategy, namely to directly entrain a metal cable in the concrete filament during printing to serve as reinforcement. A device is introduced to apply the reinforcement. Several options for online reinforcement media are compared for printability. Considerations specific to the manufacturing process are discussed. Subsequently, pull-out tests on cast and printed specimens provide an initial characterisation of bond behaviour. Bending tests furthermore show the potential of this reinforcement method. The bond stress of cables in printed concrete was comparable to values reported for smooth rebar but lower than that of the same cables in cast concrete. The scatter in experimental results was high. When sufficient bond length is available, ductile failure behaviour for tension parallel to the filament direction can be achieved, even though cable slip occurs. Further improvements to the process should pave the way to achieve better post-crack resistance, as the concept in itself is feasible. Full article

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

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11 pages, 9263 KiB

Open AccessFeature PaperArticle

Selective Laser Sintering of Porous Silica Enabled by Carbon Additive

by Shuai Chang^1,2, Liqun Li¹, Li Lu² and Jerry Ying Hsi Fuh^2,*

¹ State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China

² Department of Mechanical Engineering and Centre for Additive Manufacturing, National University of Singapore (NUS), Singapore 117576, Singapore

Materials 2017, 10(11), 1313; https://doi.org/10.3390/ma10111313 - 16 Nov 2017

Cited by 32 | Viewed by 12951

Abstract

The aim of this study is to investigate the possibility of a freeform fabrication of porous ceramic parts through selective laser sintering (SLS). SLS was proposed to manufacture ceramic green parts because this additive manufacturing technique can be used to fabricate three-dimensional objects [...] Read more.

The aim of this study is to investigate the possibility of a freeform fabrication of porous ceramic parts through selective laser sintering (SLS). SLS was proposed to manufacture ceramic green parts because this additive manufacturing technique can be used to fabricate three-dimensional objects directly without a mold, and the technique has the capability of generating porous ceramics with controlled porosity. However, ceramic printing has not yet fully achieved its 3D fabrication capabilities without using polymer binder. Except for the limitations of high melting point, brittleness, and low thermal shock resistance from ceramic material properties, the key obstacle lies in the very poor absorptivity of oxide ceramics to fiber laser, which is widely installed in commercial SLS equipment. An alternative solution to overcome the poor laser absorptivity via improving material compositions is presented in this study. The positive effect of carbon additive on the absorptivity of silica powder to fiber laser is discussed. To investigate the capabilities of the SLS process, 3D porous silica structures were successfully prepared and characterized. Full article

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

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11 pages, 4667 KiB

Open AccessArticle

Microstructure, Mechanical and Tribological Properties of Oxide Dispersion Strengthened High-Entropy Alloys

by Xinyu Liu, Hangboce Yin and Yi Xu^*

School of materials Science & Engineering, Southwest Jiaotong University, Chengdu 610031, China

Materials 2017, 10(11), 1312; https://doi.org/10.3390/ma10111312 - 15 Nov 2017

Cited by 59 | Viewed by 5891

Abstract

A novel metal matrix composite CrMnFeCoNi with Y₂O₃ as reinforcement phase was designed and manufactured by mechanical alloying and spark plasma sintering. After sintering at 900 °C for 5 min, the microstructure consisted of a FCC matrix and Y₂ [...] Read more.

A novel metal matrix composite CrMnFeCoNi with Y₂O₃ as reinforcement phase was designed and manufactured by mechanical alloying and spark plasma sintering. After sintering at 900 °C for 5 min, the microstructure consisted of a FCC matrix and Y₂O₃ nanoparticles. The addition of 0.25 wt % Y₂O₃ increased the room temperature tensile strength of the CrMnFeCoNi base from 868 MPa to 1001 MPa, while the mechanical properties of the addition of 0.5 wt % Y₂O₃ composite decreased. In the meantime, the addition of Y₂O₃ had no significant influence on the coefficient of friction, while the addition of 0.25 wt % Y₂O₃ composite shows excellent wear-resistance. Full article

(This article belongs to the Special Issue Contact Mechanics and Elastomer Friction of Materials)

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14 pages, 5060 KiB

Open AccessArticle

Magnetic Material Assessment of a Novel Ultra-High Step-Up Converter with Single Semiconductor Switch and Galvanic Isolation for Fuel-Cell Power System

by Chih-Lung Shen^* and Heng Liou

Department of Electronic Engineering, National Kaohsiung First University of Science and Technology, Kaohsiung 82445, Taiwan

Materials 2017, 10(11), 1311; https://doi.org/10.3390/ma10111311 - 15 Nov 2017

Cited by 1 | Viewed by 5128

Abstract

In this paper, a novel step-up converter is proposed, which has the particular features of single semiconductor switch, ultra-high conversion ratio, galvanic isolation, and easy control. Therefore, the proposed converter is suitable for the applications of fuel-cell power system. Coupled inductors and switched [...] Read more.

In this paper, a novel step-up converter is proposed, which has the particular features of single semiconductor switch, ultra-high conversion ratio, galvanic isolation, and easy control. Therefore, the proposed converter is suitable for the applications of fuel-cell power system. Coupled inductors and switched capacitors are incorporated in the converter to obtain an ultra-high voltage ratio that is much higher than that of a conventional high step-up converter. Even if the turns ratio of coupled inductor and duty ratio are only to be 1 and 0.5, respectively, the converter can readily achieve a voltage gain of up to 18. Owing to this outstanding performance, it can also be applied to any other low voltage source for voltage boosting. In the power stage, only one active switch is used to handle the converter operation. In addition, the leakage energy of the two couple inductors can be totally recycled without any snubber, which simplifies the control mechanism and improves the conversion efficiency. Magnetic material dominates the conversion performance of the converter. Different types of iron cores are discussed for the possibility to serve as a coupled inductor. A 200 W prototype with 400 V output voltage is built to validate the proposed converter. In measurement, it indicates that the highest efficiency can be up to 94%. Full article

(This article belongs to the Special Issue Selected Papers from IEEE ICASI 2017)

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