Materials

11 pages, 2964 KiB

Open AccessArticle

Microscopic View of Defect Evolution in Thermal Treated AlGaInAs Quantum Well Revealed by Spatially Resolved Cathodoluminescence

by Yue Song^1,2

, Ligong Zhang^1,*, Yugang Zeng^1,*, Li Qin¹, Yinli Zhou¹, Yongqiang Ning¹ and Lijun Wang¹

¹ State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China

² Daheng College, University of Chinese Academy of Sciences, Beijing 100049, China

Materials 2018, 11(6), 1049; https://doi.org/10.3390/ma11061049 - 20 Jun 2018

Cited by 6 | Viewed by 4475

Abstract

An aluminum gallium indium arsenic (AlGaInAs) material system is indispensable as the active layer of diode lasers emitting at 1310 or 1550 nm, which are used in optical fiber communications. However, the course of the high-temperature instability of a quantum well structure, which [...] Read more.

An aluminum gallium indium arsenic (AlGaInAs) material system is indispensable as the active layer of diode lasers emitting at 1310 or 1550 nm, which are used in optical fiber communications. However, the course of the high-temperature instability of a quantum well structure, which is closely related to the diffusion of indium atoms, is still not clear due to the system’s complexity. The diffusion process of indium atoms was simulated by thermal treatment, and the changes in the optical and structural properties of an AlGaInAs quantum well are investigated in this paper. Compressive strained Al_0.07Ga_0.22In_0.71As quantum wells were treated at 170 °C with different heat durations. A significant decrement of photoluminescence decay time was observed on the quantum well of a sample that was annealed after 4 h. The microscopic cathodoluminescent (CL) spectra of these quantum wells were measured by scanning electron microscope-cathodoluminescence (SEM-CL). The thermal treatment effect on quantum wells was characterized via CL emission peak wavelength and energy density distribution, which were obtained by spatially resolved cathodoluminescence. The defect area was clearly observed in the Al_0.07Ga_0.22In_0.71As quantum wells layer after thermal treatment. CL emissions from the defect core have higher emission energy than those from the defect-free regions. The defect core distribution, which was associated with indium segregation gradient distribution, showed asymmetric character. Full article

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13 pages, 10550 KiB

Open AccessArticle

Percent Reduction in Transverse Rupture Strength of Metal Matrix Diamond Segments Analysed via Discrete-Element Simulations

by Xiuyu Chen^1,2, Guoqin Huang^1,2,3,*

, Yuanqiang Tan^1,2,3, Yiqing Yu^1,2, Hua Guo^1,2,3 and Xipeng Xu^1,2,3

¹ Institute of Manufacturing Engineering, Huaqiao University, Xiamen 361021, China

² MOE Engineering Research Center for Machining of Brittle Materials, Huaqiao University, Xiamen 361021, China

³ Fujian Engineering Research Center of Intelligent Manufacturing for Brittle Materials, Fujian 361021, China

Materials 2018, 11(6), 1048; https://doi.org/10.3390/ma11061048 - 20 Jun 2018

Cited by 3 | Viewed by 3741

Abstract

The percent TRS reduction, D_TRS, which is the percent reduction of the transverse rupture strength of metal matrix diamond segments with or without diamonds, is a key metric for evaluating the bonding condition of diamonds in a matrix. In this work, [...] Read more.

The percent TRS reduction, D_TRS, which is the percent reduction of the transverse rupture strength of metal matrix diamond segments with or without diamonds, is a key metric for evaluating the bonding condition of diamonds in a matrix. In this work, we build, calibrate, and verify a discrete-element simulation of a metal matrix diamond segment to obtain D_TRS for diamond segments with various diamond-grain sizes, concentrations, and distributions. The results indicate that D_TRS increases with increasing diamond-grain concentration and decreases with increasing diamond-grain size. Both factors can be explained by the total diamond contact length, the increase of which causes the increase in D_TRS. The distribution of diamond grains in segments also strongly influences the increase of D_TRS. The use of D_TRS as a metric to assess the bonding condition of diamonds in matrixes is not valid unless the diamond-grain size, concentration, and distribution and total diamond contact length are the same for all diamond segments under consideration. Full article

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10 pages, 1829 KiB

Open AccessArticle

Study on the Preparation of Plasma-Modified Fly Ash Catalyst and Its De–NO_X Mechanism

by Lei Zhang^1,*, Xin Wen¹, Lei Zhang², Xiangling Sha³, Yusu Wang¹, Jihao Chen¹, Min Luo¹ and Yonghui Li²

¹ School of Geology and Environment, Xi’an University of Science and Technology, Xi’an 710054, China

² China National Heavy Machinery Research Institute Co., Ltd., Xi’an 710032, China

³ Shandong Baichuan Tongchuang Energy Co., Ltd., Jinan 250101, China

Materials 2018, 11(6), 1047; https://doi.org/10.3390/ma11061047 - 20 Jun 2018

Cited by 12 | Viewed by 3762

Abstract

Fly ash and bentonite were mixed in a certain proportion as raw materials to prepare a denitration catalyst. In previous studies, it has been concluded that fly ash-type catalysts can provide significant catalytic activity for denitrification after being modified with oxygen. In this [...] Read more.

Fly ash and bentonite were mixed in a certain proportion as raw materials to prepare a denitration catalyst. In previous studies, it has been concluded that fly ash-type catalysts can provide significant catalytic activity for denitrification after being modified with oxygen. In this study, the effect of plasma conditions on the denitration performance of the catalyst was investigated from the aspects of plasma modification power, modification time, and the flow rate of the gas. Boehm titration and infrared analysis systems were used to characterize the performance of the catalyst. The experimental results show that the optimal modification power is 60 W, the optimal modification time is 20 min, and the optimal gas flow rate is 40 mL/min. Full article

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15 pages, 5295 KiB

Open AccessArticle

Quadratic Solid–Shell Finite Elements for Geometrically Nonlinear Analysis of Functionally Graded Material Plates

by Hocine Chalal and Farid Abed-Meraim^*

Laboratory LEM3, Université de Lorraine, CNRS, Arts et Métiers ParisTech, F-57000 Metz, France

Materials 2018, 11(6), 1046; https://doi.org/10.3390/ma11061046 - 20 Jun 2018

Cited by 9 | Viewed by 4975

Abstract

In the current contribution, prismatic and hexahedral quadratic solid–shell (SHB) finite elements are proposed for the geometrically nonlinear analysis of thin structures made of functionally graded material (FGM). The proposed SHB finite elements are developed within a purely 3D framework, with displacements as [...] Read more.

In the current contribution, prismatic and hexahedral quadratic solid–shell (SHB) finite elements are proposed for the geometrically nonlinear analysis of thin structures made of functionally graded material (FGM). The proposed SHB finite elements are developed within a purely 3D framework, with displacements as the only degrees of freedom. Also, the in-plane reduced-integration technique is combined with the assumed-strain method to alleviate various locking phenomena. Furthermore, an arbitrary number of integration points are placed along a special direction, which represents the thickness. The developed elements are coupled with functionally graded behavior for the modeling of thin FGM plates. To this end, the Young modulus of the FGM plate is assumed to vary gradually in the thickness direction, according to a volume fraction distribution. The resulting formulations are implemented into the quasi-static ABAQUS/Standard finite element software in the framework of large displacements and rotations. Popular nonlinear benchmark problems are considered to assess the performance and accuracy of the proposed SHB elements. Comparisons with reference solutions from the literature demonstrate the good capabilities of the developed SHB elements for the 3D simulation of thin FGM plates. Full article

(This article belongs to the Special Issue Advances in Mechanical Problems of Functionally Graded Materials and Structures)

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16 pages, 4770 KiB

Open AccessArticle

A Novel Multiscale Mathematical Model for Building Bone Substitute Materials for Children

by Abdennasser Chekroun^1,†, Laurent Pujo-Menjouet^2,†

and Jean-Philippe Berteau^3,4,5,*

¹ Laboratoire d’Analyse Non Linéaire et Mathématiques Appliquées, University of Tlemcen, Chetouane 13000, Algeria

² Université de Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5208, Institut Camille Jordan, F-69622 Villeurbanne CEDEX, France; Inria Team Dracula, Inria Grenoble Rhône-Alpes Center, 69100 Villeurbanne CEDEX, France

³ Department of Physical Therapy, College of Staten Island, City University of New York, New York, NY 10314, USA

⁴ New York Center for Biomedical Engineering, City College of New York, City University of New York, New York, NY 10031, USA

⁵ Nanoscience Initiative, Advance Science Research Center, City University of New York, New York, NY 10031, USA

^† These authors contributed equally to this work.

Materials 2018, 11(6), 1045; https://doi.org/10.3390/ma11061045 - 20 Jun 2018

Cited by 2 | Viewed by 3970

Abstract

Bone is an engineering marvel that achieves a unique combination of stiffness and toughness exceeding that of synthesized materials. In orthopedics, we are currently challenged for the child population that needs a less stiff but a tougher bone substitute than adults. Recent evidence [...] Read more.

Bone is an engineering marvel that achieves a unique combination of stiffness and toughness exceeding that of synthesized materials. In orthopedics, we are currently challenged for the child population that needs a less stiff but a tougher bone substitute than adults. Recent evidence suggests that the relationship between inter-molecular connections that involve the two main bone building blocks, TropoCollagen molecules (TC) and carbonated Hydroxyapatite (cAp), and bone macroscopic mechanical properties, stiffness and toughness, are key to building bone substitute materials for children. The goal of our study is to establish how inter-molecular connections that occur during bone mineralization are related to macroscopic mechanical properties in child bones. Our aim is to link the biological alterations of the TC-cAp self assembly process happening during bone mineralization to the bone macroscopic mechanical properties’ alterations during aging. To do so, we have developed a multiscale mathematical model that includes collagen cross links (TC–TC interface) from experimental studies of bone samples to forecast bone macroscopic mechanical properties. Our results support that the Young’s modulus cannot be a linear parameter if we want to solve our system. In relation to bone substitute material with innovative properties for children, our results propose values of several biological parameters, such as the number of crystals and their size, and collagen crosslink maturity for the desired bone mechanical competence. Our novel mathematical model combines mineralization and macroscopic mechanical behavior of bone and is a step forward in building mechanically customized biomimetic bone grafts that would fit children’s orthopedic needs. Full article

(This article belongs to the Special Issue Bone Substitute Materials)

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18 pages, 42031 KiB

Open AccessArticle

Hot Deformation Behavior and Microstructure Evolution of 14Cr ODS Steel

by Qian Zhao, Liming Yu, Zongqing Ma, Huijun Li, Zumin Wang and Yongchang Liu^*

State Key Lab of Hydraulic Engineering Simulation and Safety, School of Materials Science & Engineering, Tianjin University, Tianjin 300354, China

Materials 2018, 11(6), 1044; https://doi.org/10.3390/ma11061044 - 20 Jun 2018

Cited by 17 | Viewed by 4722

Abstract

Hot deformation tests of 14Cr oxide dispersion strengthened (ODS) steel fabricated by mechanical alloying and hot isostatic pressing (HIP) were performed on a Gleeble-1500D simulator at temperatures ranging from 1050 to 1200 °C with the strain rate range of 0.001⁻¹ s⁻¹ [...] Read more.

Hot deformation tests of 14Cr oxide dispersion strengthened (ODS) steel fabricated by mechanical alloying and hot isostatic pressing (HIP) were performed on a Gleeble-1500D simulator at temperatures ranging from 1050 to 1200 °C with the strain rate range of 0.001⁻¹ s⁻¹. The relationship between the rheological stress and the deformation condition was studied, and a processing map at the true strain of 0.5 was proposed. Microstructure evolution during the deformation process and the effects of deformation conditions on microstructures were also investigated, as well as the stability of nanoparticles. Results show that the 14Cr ODS steel possesses positive strain rate sensitivity. The flow stress increases with the decrease of deformation temperature and the increase of strain rate. The recrystallization process is promoted by the increase of deformation temperature and the reduction of strain rate. Nanoparticles possess excellent stability during the deformation process and are coherent with the matrix. Full article

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10 pages, 2735 KiB

Open AccessArticle

Wear Resistance of 3D Printing Resin Material Opposing Zirconia and Metal Antagonists

by Ji-Man Park¹

, Jin-Soo Ahn², Hyun-Suk Cha³ and Joo-Hee Lee^3,*

¹ Department of Prosthodontics, College of Dentistry, Yonsei University, 250 Seongsanno, Seodaemun-gu, Seoul 03722, Korea

² Department of Dental Biomaterials Science and Dental Research Institute, School of Dentistry, Seoul National University, 101 Daehak-ro, Jongno-gu, Seoul 03080, Korea

³ Division of Prosthodontics, Department of Dentistry, Asan Medical Center, College of Medicine, University of Ulsan, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Korea

Materials 2018, 11(6), 1043; https://doi.org/10.3390/ma11061043 - 20 Jun 2018

Cited by 51 | Viewed by 7820

Abstract

3D printing offers many advantages in dental prosthesis manufacturing. This study evaluated the wear resistance of 3D printing resin material compared with milling and conventional resin materials. Sixty substrate specimens were prepared with three types of resin materials: 3D printed resin, milled resin, [...] Read more.

3D printing offers many advantages in dental prosthesis manufacturing. This study evaluated the wear resistance of 3D printing resin material compared with milling and conventional resin materials. Sixty substrate specimens were prepared with three types of resin materials: 3D printed resin, milled resin, and self-cured resin. The 3D printed specimens were printed at a build angle of 0° and 100 μm layer thickness by digital light processing 3D printing. Two kinds of abraders were made of zirconia and CoCr alloy. The specimens were loaded at 5 kg for 30,000 chewing cycles with vertical and horizontal movements under thermocycling condition. The 3D printed resin did not show significant difference in the maximal depth loss or the volume loss of wear compared to the milled and the self-cured resins. No significant difference was revealed depending on the abraders in the maximal depth loss or the volume loss of wear. In SEM views, the 3D printed resin showed cracks and separation of inter-layer bonds when opposing the metal abrader. The results suggest that the 3D printing using resin materials provides adequate wear resistance for dental use. Full article

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

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17 pages, 7653 KiB

Open AccessArticle

Experimental and Theoretical Investigation of Thiazolyl Blue as a Corrosion Inhibitor for Copper in Neutral Sodium Chloride Solution

by Li Feng¹, Shengtao Zhang^1,2,*, Yujie Qiang¹, Yue Xu¹, Lei Guo^3,*

, Loutfy H. Madkour⁴

and Shijin Chen⁵

¹ School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044, China

² Material Corrosion and Protection Key Laboratory of Sichuan province, Zigong 643000, China

³ School of Material and Chemical Engineering, Tongren University, Tongren 554300, China

⁴ Chemistry Department, Faculty of Science and Arts, Al Baha University, Baljarashi 65635, Saudi Arabia

⁵ Bomin Electronics Ltd., Meizhou 514021, China

Materials 2018, 11(6), 1042; https://doi.org/10.3390/ma11061042 - 19 Jun 2018

Cited by 59 | Viewed by 7133

Abstract

The anticorrosion effect of thiazolyl blue (MTT) for copper in 3% NaCl at 298 K was researched by electrochemical methods, scanning electron-microscopy (SEM), and atomic force microscopy (AFM). The results reveal that MTT can protect copper efficiently, with a maximum efficiency of 95.7%. [...] Read more.

The anticorrosion effect of thiazolyl blue (MTT) for copper in 3% NaCl at 298 K was researched by electrochemical methods, scanning electron-microscopy (SEM), and atomic force microscopy (AFM). The results reveal that MTT can protect copper efficiently, with a maximum efficiency of 95.7%. The corrosion inhibition mechanism was investigated by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectral (FT-IR), and theoretical calculation. The results suggest that the MTT molecules are adsorbed on metal surface forming a hydrophobic protective film to prevent copper corrosion. It also indicates that the MTT and copper form covalent bonds. The molecular dynamic simulation further gives the evidence for adsorption. The adsorption isotherm studies demonstrate that a spontaneous, mixed physical and chemical adsorption occurs, which obeys Langmuir adsorption isotherm. The present research can help us better understand the corrosion inhibition process and improve it. Full article

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19 pages, 6501 KiB

Open AccessArticle

Elucidating the Photocatalytic Behavior of TiO₂-SnS₂ Composites Based on Their Energy Band Structure

by Marin Kovacic

, Jozefina Katic

, Hrvoje Kusic^*, Ana Loncaric Bozic and Mirjana Metikos Hukovic^*

Faculty of Chemical Engineering and Technology, University of Zagreb, Marulicev trg 19, Zagreb 10000, Croatia

Materials 2018, 11(6), 1041; https://doi.org/10.3390/ma11061041 - 19 Jun 2018

Cited by 21 | Viewed by 5637

Abstract

TiO₂-SnS₂ composite semiconducting photocatalysts with different building component ratios were prepared by hydrothermal synthesis (TiO₂-SnS₂-HT) and by immobilization of commercial TiO₂ and SnS₂ particles (TiO₂-SnS₂-COMM). The band gap values, which [...] Read more.

TiO₂-SnS₂ composite semiconducting photocatalysts with different building component ratios were prepared by hydrothermal synthesis (TiO₂-SnS₂-HT) and by immobilization of commercial TiO₂ and SnS₂ particles (TiO₂-SnS₂-COMM). The band gap values, which determine the catalysts’ photoactivity, were examined by diffuse reflectance spectroscopy and Kubelka–Munk transformations. The catalysts’ surface properties: specific surface area, charge and adsorption capacitance at the solid–solution interface were characterized using BET analysis, potentiometric titration and electrochemical impedance spectroscopy, respectively. The electronic band structure of TiO₂-SnS₂ photocatalyst, as the key property for the solar-driven photocatalysis, was deduced from the thermodynamic data and the semiconducting parameters (type of semiconductivity, concentration of the charge carriers, flat band potential) obtained by Mott–Schottky analysis. The photoactivity of both composites was studied in photocatalytic treatment of diclofenac (DCF) under simulated solar irradiation and was compared to the benchmark photocatalyst (TiO₂ P25) activity. The influence of process parameters, such as pH, H₂O₂, and composite formulation on the effectiveness of DCF removal and conversion was investigated and discussed by employing response surface modeling (RSM) approach. The photocatalytic efficiency of both composite materials was discussed on the basis of the hetereojunction formation that facilitated the photoelectron transfer, promoting more efficient photocatalytic degradation of DCF. Full article

(This article belongs to the Special Issue Photocatalysis for Wastewater Treatment)

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22 pages, 5859 KiB

Open AccessReview

Magnetic Particle Filled Elastomeric Hybrid Composites and Their Magnetorheological Response

by Seung Hyuk Kwon¹, Jin Hyun Lee^2,*

and Hyoung Jin Choi^1,*

¹ Department of Polymer Science and Engineering, Inha University, Incheon 22212, Korea

² Polymer Technology Institute, Sungkyunkwan University, Suwon 16419, Korea

Materials 2018, 11(6), 1040; https://doi.org/10.3390/ma11061040 - 19 Jun 2018

Cited by 49 | Viewed by 8290

Abstract

The magnetorheological (MR) elastomer as a hard and soft hybrid functional material, a composite material consisting of magnetic hard particles embedded in elastomeric soft matrix, is a branch of MR materials that are functional smart materials rapidly responding to external magnetic fields. These [...] Read more.

The magnetorheological (MR) elastomer as a hard and soft hybrid functional material, a composite material consisting of magnetic hard particles embedded in elastomeric soft matrix, is a branch of MR materials that are functional smart materials rapidly responding to external magnetic fields. These tunable properties of MR elastomers facilitate a variety of applications. In this brief review paper, in addition to general information on the MR elastomers, recent research not only on a wide variety of MR elastomeric systems focusing on various magnetic particles, elastomeric matrices, additives and particle modification methods, but also on their characteristics including MR properties from dynamic oscillation tests is covered along with their mechanical properties such as the Payne effect, tensile strength and engineering applications. Full article

(This article belongs to the Special Issue Hard and Soft Hybrid Functional Materials)

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11 pages, 4546 KiB

Open AccessArticle

Giant Enhancement of Magnetostrictive Response in Directionally-Solidified Fe₈₃Ga₁₇Er_x Compounds

by Radhika Barua^1,*, Parisa Taheri¹, Yajie Chen¹, Anjela Koblischka-Veneva²

, Michael R. Koblischka²

, Liping Jiang³ and Vincent G. Harris^1,*

¹ College of Engineering, Northeastern University, Boston, MA 02115, USA

² Institute of Experimental Physics, Saarland University, 66123 Saarbrucken, Germany

³ Baotou Research Institute of Rare Earths, Baotou 014010 China

Materials 2018, 11(6), 1039; https://doi.org/10.3390/ma11061039 - 19 Jun 2018

Cited by 27 | Viewed by 4466

Abstract

We report, for the first time, correlations between crystal structure, microstructure and magnetofunctional response in directionally solidified [110]-textured Fe₈₃Ga₁₇Er_x (0 < x < 1.2) alloys. The morphology of the doped samples consists of columnar grains, mainly composed of [...] Read more.

We report, for the first time, correlations between crystal structure, microstructure and magnetofunctional response in directionally solidified [110]-textured Fe₈₃Ga₁₇Er_x (0 < x < 1.2) alloys. The morphology of the doped samples consists of columnar grains, mainly composed of a matrix phase and precipitates of a secondary phase deposited along the grain boundary region. An enhancement of more than ~275% from ~45 to 170 ppm is observed in the saturation magnetostriction value (λ_s) of Fe₈₃Ga₁₇Er_x alloys with the introduction of small amounts of Er. Moreover, it was noted that the low field derivative of magnetostriction with respect to an applied magnetic field (

i . e ., d λ_{s} / d H_{a p p}

for H_app up to 1000 Oe) increases by ~230% with Er doping (

d λ_{s} / d H_{a p p, FeGa} =

0.045 ppm/Oe;

d λ_{s} / d H_{a p p, FeGaEr} =

0.15 ppm/Oe). The enhanced magnetostrictive response of the Fe₈₃Ga₁₇Er_x alloys is ascribed to an amalgamation of microstructural and electronic factors, namely: (i) improved grain orientation and local strain effects due to deposition of Er in the intergranular region; and (ii) strong local magnetocrystalline anisotropy, due to the highly anisotropic localized nature of the 4f electronic charge distribution of the Er atom. Overall, this work provides guidelines for further improving galfenol-based materials systems for diverse applications in the power and energy sector. Full article

(This article belongs to the Special Issue Magnetostrictive Composite Materials)

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21 pages, 3458 KiB

Open AccessArticle

Influence of Microstructure and Shot Peening Treatment on Corrosion Resistance of AISI F55-UNS S32760 Super Duplex Stainless Steel

by Andrea Francesco Ciuffini^1,*

, Silvia Barella¹

, Luis Borja Peral Martínez², Carlo Mapelli¹ and Inés Fernández Pariente²

¹ Dipartimento di Meccanica, Politecnico di Milano, via La Masa 34, 20156 Milano, Italy

² Escuela Politécnica de Ingeniería de Gijón, Universidad de Oviedo, Campus de Viesques, Gijón 33203, Spain

Materials 2018, 11(6), 1038; https://doi.org/10.3390/ma11061038 - 19 Jun 2018

Cited by 13 | Viewed by 5016

Abstract

Shot peening is a surface process commonly used in the aeronautic and automotive industries to improve fatigue resistance. Shot peening is proven to be beneficial in the fatigue behavior of components, but rarely has its influence on wear and pitting corrosion resistance been [...] Read more.

Shot peening is a surface process commonly used in the aeronautic and automotive industries to improve fatigue resistance. Shot peening is proven to be beneficial in the fatigue behavior of components, but rarely has its influence on wear and pitting corrosion resistance been evaluated. In this work, shot peening was performed on AISI F55-UNS S32760 super-duplex stainless steel samples previously submitted to various thermal treatments, to obtain different initial microstructures and properties. Samples have been characterized in terms of microstructure morphology, local chemical composition, microhardness of each constituent phase, and energy dissipation modes. The enhanced properties provided by shot peening has been evaluated through residual stress depth profiles and Full Width at Half Maximum (FWHM) using X-ray diffraction (XRD), surface hardness, surface roughness, and corrosion resistance through salt spray fog tests. The 1400 °C solution thermal treatment was identified as the optimum initial condition, which maximizes the advantages of the shot peening treatment, even pitting corrosion resistance. These results are related to the uniformity of austenite and ferrite in terms of microstructure morphology, micromechanical properties, and alloying elements distribution. Full article

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

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10 pages, 3274 KiB

Open AccessArticle

High-Temperature Tolerance in Multi-Scale Cermet Solar-Selective Absorbing Coatings Prepared by Laser Cladding

by Xuming Pang^*

, Qian Wei, Jianxin Zhou and Huiyang Ma

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

Materials 2018, 11(6), 1037; https://doi.org/10.3390/ma11061037 - 19 Jun 2018

Cited by 11 | Viewed by 3930

Abstract

In order to achieve cermet-based solar absorber coatings with long-term thermal stability at high temperatures, a novel single-layer, multi-scale TiC-Ni/Mo cermet coating was first prepared using laser cladding technology in atmosphere. The results show that the optical properties of the cermet coatings using [...] Read more.

In order to achieve cermet-based solar absorber coatings with long-term thermal stability at high temperatures, a novel single-layer, multi-scale TiC-Ni/Mo cermet coating was first prepared using laser cladding technology in atmosphere. The results show that the optical properties of the cermet coatings using laser cladding were much better than the preplaced coating. In addition, the thermal stability of the optical properties for the laser cladding coating were excellent after annealing at 650 °C for 200 h. The solar absorptance and thermal emittance of multi-scale cermet coating were 85% and 4.7% at 650 °C. The results show that multi-scale cermet materials are more suitable for solar-selective absorbing coating. In addition, laser cladding is a new technology that can be used for the preparation of spectrally-selective coatings. Full article

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16 pages, 4921 KiB

Open AccessFeature PaperArticle

Single Step Laser Transfer and Laser Curing of Ag NanoWires: A Digital Process for the Fabrication of Flexible and Transparent Microelectrodes

by Filimon Zacharatos^1,*

, Panagiotis Karvounis², Ioannis Theodorakos¹

, Antonios Hatziapostolou² and Ioanna Zergioti¹

¹ Physics Department, Zografou Campus, National Technical University of Athens, Athens 15780, Greece

² Campus 1, School of Engineering, University of West Attica, Aigaleo 12243, Greece

Materials 2018, 11(6), 1036; https://doi.org/10.3390/ma11061036 - 19 Jun 2018

Cited by 19 | Viewed by 4163

Abstract

Ag nanowire (NW) networks have exquisite optical and electrical properties which make them ideal candidate materials for flexible transparent conductive electrodes. Despite the compatibility of Ag NW networks with laser processing, few demonstrations of laser fabricated Ag NW based components currently exist. In [...] Read more.

Ag nanowire (NW) networks have exquisite optical and electrical properties which make them ideal candidate materials for flexible transparent conductive electrodes. Despite the compatibility of Ag NW networks with laser processing, few demonstrations of laser fabricated Ag NW based components currently exist. In this work, we report on a novel single step laser transferring and laser curing process of micrometer sized pixels of Ag NW networks on flexible substrates. This process relies on the selective laser heating of the Ag NWs induced by the laser pulse energy and the subsequent localized melting of the polymeric substrate. We demonstrate that a single laser pulse can induce both transfer and curing of the Ag NW network. The feasibility of the process is confirmed experimentally and validated by Finite Element Analysis simulations, which indicate that selective heating is carried out within a submicron-sized heat affected zone. The resulting structures can be utilized as fully functional flexible transparent electrodes with figures of merit even higher than 100. Low sheet resistance (<50 Ohm/sq) and high visible light transparency (>90%) make the reported process highly desirable for a variety of applications, including selective heating or annealing of nanocomposite materials and laser processing of nanostructured materials on a large variety of optically transparent substrates, such as Polydimethylsiloxane (PDMS). Full article

(This article belongs to the Special Issue Selective Laser Sintering (SLS) of Materials)

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23 pages, 5691 KiB

Open AccessArticle

Pore Structure Characterization of Sodium Hydroxide Activated Slag Using Mercury Intrusion Porosimetry, Nitrogen Adsorption, and Image Analysis

by Yibing Zuo^*

and Guang Ye

Microlab, Faculty of Civil Engineering and Geosciences, Delft University of Technology, Stevinweg 1, 2628 CN Delft, The Netherlands

Materials 2018, 11(6), 1035; https://doi.org/10.3390/ma11061035 - 19 Jun 2018

Cited by 37 | Viewed by 6688

Abstract

The pore structure of alkali-activated slag has a significant influence on its performance. However, the literature shows insufficient studies regarding the suitability of different techniques for characterizing the pore structure and the influences of Na₂O and curing age on pore structure [...] Read more.

The pore structure of alkali-activated slag has a significant influence on its performance. However, the literature shows insufficient studies regarding the suitability of different techniques for characterizing the pore structure and the influences of Na₂O and curing age on pore structure development. In pursuit of a better understanding, the pore structure of sodium hydroxide activated slag paste was characterized by multiple techniques, e.g., mercury intrusion porosimetry (MIP), nitrogen (N₂) adsorption, and scanning electron microscopy (SEM) image analysis. The sodium hydroxide activated slag pastes were prepared with three different contents of Na₂O (Na₂O/slag = 4, 6, and 8%) and cured for different times up to 360 days. The microstructure observation reveals that outer C–(N–)A–S–H and inner C–(N–)A–S–H grow successively around the reacting slag grains, along with crystalline reaction products which are formed in the empty coarse pore space. The increase of Na₂O content and curing age lead to a finer pore structure. The MIP measurements show that the total porosity drops about 70% within the first day, and that one peak at most, corresponding to gel pores, was identified in the differential curves of all the investigated samples from 1 to 360 days. On the contrary, only one peak, corresponding to capillary pores, was identified by SEM-image analysis. The differential curves derived from N₂ adsorption generally reveal two peaks, and the trend that the pore diameters of those two peaks vary with curing age depends on the content of Na₂O. Compared to Portland cement, sodium hydroxide activated slag has a higher pore space filling capacity (χ, V_products/V_slag-reacted), while the capacity decreases with increasing Na₂O content and curing age. Full article

(This article belongs to the Section Porous Materials)

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9 pages, 4064 KiB

Open AccessArticle

Noninvasive Mechanochemical Imaging in Unconstrained Caenorhabditis elegans

by Takuma Sugi^1,2,*, Ryuji Igarashi^2,3,4,* and Masaki Nishimura¹

¹ Molecular Neuroscience Research Center, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan

² PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan

³ QST Future Laboratory, National Institute for Quantum and Radiological Science and Technology, Anagawa 4-9-1, Inage-ku, Chiba 263-8555, Japan

⁴ Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan

Materials 2018, 11(6), 1034; https://doi.org/10.3390/ma11061034 - 19 Jun 2018

Cited by 6 | Viewed by 3934

Abstract

Physical forces are transduced into chemical reactions, thereby ultimately making a large impact on the whole-animal level phenotypes such as homeostasis, development and behavior. To understand mechano-chemical transduction, mechanical input should be quantitatively delivered with controllable vibration properties–frequency, amplitude and duration, and its [...] Read more.

Physical forces are transduced into chemical reactions, thereby ultimately making a large impact on the whole-animal level phenotypes such as homeostasis, development and behavior. To understand mechano-chemical transduction, mechanical input should be quantitatively delivered with controllable vibration properties–frequency, amplitude and duration, and its chemical output should be noninvasively quantified in an unconstrained animal. However, such an experimental system has not been established so far. Here, we develop a noninvasive and unconstrained mechanochemical imaging microscopy. This microscopy enables us to evoke nano-scale nonlocalized vibrations with controllable vibration properties using a piezoelectric acoustic transducer system and quantify calcium response of a freely moving C. elegans at a single cell resolution. Using this microscopy, we clearly detected the calcium response of a single interneuron during C. elegans escape response to nano-scale vibration. Thus, this microscopy will facilitate understanding of in vivo mechanochemical physiology in the future. Full article

(This article belongs to the Special Issue Smart Materials for Soft Sensors and Actuators)

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12 pages, 3383 KiB

Open AccessArticle

Characterization and Microstructure of Linear Electrode-Electrospun Graphene-Filled Polyvinyl Alcohol Nanofiber Films

by Ting-Ting Li^1,2, Mengxue Yan¹, Qian Jiang¹, Hao-Kai Peng¹, Jia-Horng Lin^1,3,4,5,6,7 and Ching-Wen Lou^2,4,7,8,*

¹ Innovation Platform of Intelligent and Energy-Saving Textiles, Tianjin Polytechnic University, Tianjin 300387, China

² Fujian Key Laboratory of Novel Functional Fibers and Materials, Minjiang University, Fuzhou 350108, China

³ Laboratory of Fiber Application and Manufacturing, Department of Fiber and Composite Materials, Feng Chia University, Taichung 40724, Taiwan

⁴ Department of Chemical Engineering and Materials, Ocean College, Minjiang University, Fuzhou 350108, China

⁵ Department of Fashion Design, Asia University, Taichung 41354, Taiwan

⁶ School of Chinese Medicine, China Medical University, Taichung 40402, Taiwan

⁷ College of Textile and Clothing, Qingdao University, Shandong 266071, China

⁸ Department of Bioinformatics and Medical Engineering, Asia University, Taichung 41354, Taiwan

Materials 2018, 11(6), 1033; https://doi.org/10.3390/ma11061033 - 19 Jun 2018

Cited by 10 | Viewed by 3525

Abstract

With the aim of achieving controllable mass production of electrospun nanofiber films, this study proposes and investigates the feasibility of using a custom-made linear electrode- electrospun device to produce conductive graphene (GR)-filled polyvinyl alcohol (PVA) nanofibers. The film morphology and diameter of nanofibers [...] Read more.

With the aim of achieving controllable mass production of electrospun nanofiber films, this study proposes and investigates the feasibility of using a custom-made linear electrode- electrospun device to produce conductive graphene (GR)-filled polyvinyl alcohol (PVA) nanofibers. The film morphology and diameter of nanofibers are observed and measured to examine the effects of viscosity and conductivity of the PVA/GR mixtures. Likewise, the influence of the content of graphene on the hydrophilicity, electrical conductivity, electromagnetic interference shielding effectiveness (EMSE), and thermal stability of the PVA/GR nanofiber films is investigated. The test results show that the PVA/GR mixture has greater viscosity and electric conductivity than pure PVA solution and can be electrospun into PVA/GR nanofiber films that have good morphology and diameter distribution. The diameter of the nanofibers is 100 nm and the yield is 2.24 g/h, suggesting that the process qualifies for use in large-scale production. Increasing the content of graphene yields finer nanofibers, a smaller surface contact angle, and higher hydrophilicity of the nanofiber films. The presence of graphene is proven to improve the thermal stability and strengthens the EMSE by 20 dB at 150–1500 MHz. Mass production is proven to be feasible by the test results showing that PVA/GR nanofiber films can be used in the medical hygiene field. Full article

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11 pages, 1087 KiB

Open AccessFeature PaperArticle

Copolymerization of UF Resins with Dimethylurea for Improving Storage Stability without Impairing Adhesive Performance

by Pedro Pereira¹, João Pereira², Nádia. T. Paiva¹, João. M. Ferra¹, Jorge M. Martins^3,4, Luísa. H. Carvalho^3,4

and Fernão. D. Magalhães^4,*

¹ EuroResinas-Indústrias Químicas, 7520 Sines, Portugal

² ARCP—Associação Rede de Competência em Polímeros, 4200 Porto, Portugal

³ DEMad—Instituto Politécnico de Viseu, 3504 Viseu, Portugal

⁴ LEPABE—Faculdade de Engenharia da Universidade do Porto, 4200 Porto, Portugal

Materials 2018, 11(6), 1032; https://doi.org/10.3390/ma11061032 - 19 Jun 2018

Cited by 7 | Viewed by 4079

Abstract

Urea-formaldehyde (UF) resins are the most used resins in the wood industry due to high reactivity and low price. However, their reduced stability during storage is a drawback, imposing strict limits in terms of allowable shipping distances and storage times. This instability, manifested [...] Read more.

Urea-formaldehyde (UF) resins are the most used resins in the wood industry due to high reactivity and low price. However, their reduced stability during storage is a drawback, imposing strict limits in terms of allowable shipping distances and storage times. This instability, manifested by viscosity increase that renders the resin unusable, occurs due to the progress of condensation reactions between the polymeric species present in the liquid medium. In order to achieve a stable resin formulation, dimethylurea (DMeU) was selected for being less reactive than urea. Dimethylurea is shown to co-polymerize with the UF polymer during the acidic synthesis condensation step. However, during storage it behaves like an end group blocker, due to its lower reactivity at basic pH. By adding 1.25% DMeU, it was possible to obtain a formulation that remained with stable viscosity during two-month storage at 40 °C. The reference UF resin remained stable only for eight days in these conditions. Wood particleboards produced with modified resins showed internal bond strengths of about 0.5 N·mm⁻², similar to the fresh reference UF resin, even when the resins were used after the two-month storage period. Formaldehyde content values were below the limit for E1 class, ≤8 mg/100 g oven dry board (EN 13986). Full article

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27 pages, 4460 KiB

Open AccessArticle

Properties of Experimental Dental Composites Containing Antibacterial Silver-Releasing Filler

by Robert Stencel¹, Jacek Kasperski², Wojciech Pakieła³, Anna Mertas⁴

, Elżbieta Bobela⁴, Izabela Barszczewska-Rybarek⁵

and Grzegorz Chladek^3,*

¹ Private Practice, Center of Dentistry and Implantology, ul. Karpińskiego 3, 41-500 Chorzów, Poland

² Department of Prosthetic Dentistry, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia, pl. Akademicki 17, 41-902 Bytom, Poland

³ Faculty of Mechanical Engineering, Institute of Engineering Materials and Biomaterials, Silesian University of Technology, ul. Konarskiego 18a, 44-100 Gliwice, Poland

⁴ Chair and Department of Microbiology and Immunology, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia in Katowice, ul. Jordana 19, 41-808 Zabrze, Poland

⁵ Department of Physical Chemistry and Technology of Polymers, Silesian University of Technology, 44-100 Gliwice, Poland

Materials 2018, 11(6), 1031; https://doi.org/10.3390/ma11061031 - 18 Jun 2018

Cited by 49 | Viewed by 6952 | Correction

Abstract

Secondary caries is one of the important issues related to using dental composite restorations. Effective prevention of cariogenic bacteria survival may reduce this problem. The aim of this study was to evaluate the antibacterial activity and physical properties of composite materials with silver [...] Read more.

Secondary caries is one of the important issues related to using dental composite restorations. Effective prevention of cariogenic bacteria survival may reduce this problem. The aim of this study was to evaluate the antibacterial activity and physical properties of composite materials with silver sodium hydrogen zirconium phosphate (SSHZP). The antibacterial filler was introduced at concentrations of 1%, 4%, 7%, 10%, 13%, and 16% (w/w) into model composite material consisting of methacrylate monomers and silanized glass and silica fillers. The in vitro reduction in the number of viable cariogenic bacteria Streptococcus mutans ATCC 33535 colonies, Vickers microhardness, compressive strength, diametral tensile strength, flexural strength, flexural modulus, sorption, solubility, degree of conversion, and color stability were investigated. An increase in antimicrobial filler concentration resulted in a statistically significant reduction in bacteria. There were no statistically significant differences caused by the introduction of the filler in compressive strength, diametral tensile strength, flexural modulus, and solubility. Statistically significant changes in degree of conversion, flexural strength, hardness (decrease), solubility (increase), and in color were registered. A favorable combination of antibacterial properties and other properties was achieved at SSHZP concentrations from 4% to 13%. These composites exhibited properties similar to the control material and enhanced in vitro antimicrobial efficiency. Full article

(This article belongs to the Special Issue Bioactive and Therapeutic Dental Materials)

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17 pages, 5788 KiB

Open AccessArticle

Degradation of Methylene Blue Dye in the Presence of Visible Light Using SiO₂@α-Fe₂O₃ Nanocomposites Deposited on SnS₂ Flowers

by Sridharan Balu¹

, Kasimayan Uma^2,*, Guan-Ting Pan¹

, Thomas C.-K. Yang^1,2,*

and Sayee Kannan Ramaraj³

¹ Department of Chemical Engineering and biotechnology, National Taipei University of Technology, Taipei 106, Taiwan, bsridharanbsc.12@gmail.com (S.B.)

² Precision Analysis and Research Center, National Taipei University of Technology, Taipei 106, Taiwan

³ PG & Research Department of Chemistry, Thiagarajar College, Madurai 625009, Tamilnadu, India

Materials 2018, 11(6), 1030; https://doi.org/10.3390/ma11061030 - 17 Jun 2018

Cited by 132 | Viewed by 7152

Abstract

Semiconductor materials have been shown to have good photocatalytic behavior and can be utilized for the photodegradation of organic pollutants. In this work, three-dimensional flower-like SnS₂ (tin sulfide) was synthesized by a facile hydrothermal method. Core-shell structured SiO₂@α-Fe₂O [...] Read more.

Semiconductor materials have been shown to have good photocatalytic behavior and can be utilized for the photodegradation of organic pollutants. In this work, three-dimensional flower-like SnS₂ (tin sulfide) was synthesized by a facile hydrothermal method. Core-shell structured SiO₂@α-Fe₂O₃ nanocomposites were then deposited on the top of the SnS₂ flowers. The as-synthesized nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–Vis Spectroscopy, Brunauer–Emmett–Teller (BET) surface area analysis, and photoluminescence (PL) spectroscopy. The photocatalytic behavior of the SnS₂-SiO₂@α-Fe₂O₃ nanocomposites was investigated by observing the degradation of methylene blue (MB). The results show an effective enhancement of photocatalytic activity for the degradation of MB especially for the 15 wt % SiO₂@α-Fe₂O₃ nanocomposites on SnS₂ flowers. Full article

(This article belongs to the Section Catalytic Materials)

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13 pages, 2750 KiB

Open AccessArticle

Concrete Properties Comparison When Substituting a 25% Cement with Slag from Different Provenances

by María Eugenia Parron-Rubio¹

, Francisca Perez-García^2,*, Antonio Gonzalez-Herrera² and María Dolores Rubio-Cintas¹

¹ Departamento de Ingeniería Industrial y Civil, Universidad de Cádiz, 11205 Algeciras, Spain

² Departamento de Ingeniería Civil, Materiales y Fabricación, Universidad de Málaga, 29071 Málaga, Spain

Materials 2018, 11(6), 1029; https://doi.org/10.3390/ma11061029 - 17 Jun 2018

Cited by 42 | Viewed by 5572

Abstract

Concrete consumption greatly exceeds the use of any other material in engineering. This is due to its good properties as a construction material and the availability of its components. Nevertheless, the present worldwide construction increases and the high-energy consumption for cement production means [...] Read more.

Concrete consumption greatly exceeds the use of any other material in engineering. This is due to its good properties as a construction material and the availability of its components. Nevertheless, the present worldwide construction increases and the high-energy consumption for cement production means a high environmental impact. On the other hand, one of the main problems in the iron and steel industry is waste generation and byproducts that must be properly processed or reused to promote environmental sustainability. One of these byproducts is steel slag. The cement substitution with slag strategy achieves two goals: raw materials consumption reduction and waste management. In the present work, four different concrete mixtures are evaluated. The 25% cement substitution is carried out with different types of slag. Tests were made to evaluate the advantages and drawbacks of each mixture. Depending on the origin, characteristics, and treatment of the slag, the concrete properties changed. Certain mixtures provided proper concrete properties. Stainless steel slag produced a fluent mortar that reduced water consumption with a slight mechanical strength loss. Mixtures with ground granulated blast furnace slag properties are better than the reference concrete (without slag). Full article

(This article belongs to the Collection Additive Manufacturing: Alloy Design and Process Innovations)

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16 pages, 4173 KiB

Open AccessArticle

Fatigue Behavior of Glass Fiber-Reinforced Polymer Bars after Elevated Temperatures Exposure

by Guanghui Li¹, Jun Zhao^2,*

and Zike Wang²

¹ School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China

² School of Mechanics and Engineering Science, Zhengzhou University, Zhengzhou 450001, China

Materials 2018, 11(6), 1028; https://doi.org/10.3390/ma11061028 - 16 Jun 2018

Cited by 25 | Viewed by 5252

Abstract

Fiber-reinforced polymer (FRP) bars have been widely applied in civil engineering. This paper presents the results of an experimental study to investigate the tensile fatigue mechanical properties of glass fiber-reinforced polymer (GFRP) bars after elevated temperatures exposure. For this purpose, a total of [...] Read more.

Fiber-reinforced polymer (FRP) bars have been widely applied in civil engineering. This paper presents the results of an experimental study to investigate the tensile fatigue mechanical properties of glass fiber-reinforced polymer (GFRP) bars after elevated temperatures exposure. For this purpose, a total of 105 GFRP bars were conducted for testing. The specimens were exposed to heating regimes of 100, 150, 200, 250, 300 and 350 °C for a period of 0, 1 or 2 h. The GFRP bars were tested with different times of cyclic load after elevated temperatures exposure. The results show that the tensile strength and elastic modulus of GFRP bars decrease with the increase of elevated temperature and holding time, and the tensile strength of GFRP bars decreases obviously by 19.5% when the temperature reaches 250 °C. Within the test temperature range, the tensile strength of GFRP bars decreases at most by 28.0%. The cyclic load accelerates the degradation of GFRP bars after elevated temperature exposure. The coupling of elevated temperature and holding time enhance the degradation effect of cyclic load on GFRP bars. The tensile strength of GFRP bars after elevated temperatures exposure at 350 °C under cyclic load is reduced by 50.5% compared with that at room temperature and by 36.3% compared with that after exposing at 350 °C without cyclic load. In addition, the elastic modulus of GFRP bars after elevated temperatures exposure at 350 °C under cyclic load is reduced by 17.6% compared with that at room temperature and by 6.0% compared with that after exposing at 350 °C without cyclic load. Full article

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10 pages, 2988 KiB

Open AccessArticle

An Investigation of the Wear on Silicon Surface at High Humidity

by Xiaodong Wang^1,2, Jian Guo^2,3, Lin Xu¹, Guanggui Cheng¹ and Linmao Qian^2,*

¹ Center of Micro/Nano Science and Technology, Jiangsu University, Zhenjiang 212013, China

² Tribology Research Institute, State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031, China

³ School of Mechanical Engineering, University of South China, Hengyang 421000, China

Materials 2018, 11(6), 1027; https://doi.org/10.3390/ma11061027 - 16 Jun 2018

Cited by 3 | Viewed by 3762

Abstract

Using an atomic force microscope (AFM), the wear of monocrystalline silicon (covered by a native oxide layer) at high humidity was investigated. The experimental results indicated that tribochemistry played an important role in the wear of the silicon at different relative humidity levels [...] Read more.

Using an atomic force microscope (AFM), the wear of monocrystalline silicon (covered by a native oxide layer) at high humidity was investigated. The experimental results indicated that tribochemistry played an important role in the wear of the silicon at different relative humidity levels (RH = 60%, 90%). Since the tribochemical reactions were facilitated at 60% RH, the wear of silicon was serious and the friction force was around 1.58 μN under the given conditions. However, the tribochemical reactions were restrained when the wear pair was conducted at high humidity. As a result, the wear of silicon was very slight and the friction force decreased to 0.85 μN at 90% RH. The slight wear of silicon at high humidity was characterized by etching tests. It was demonstrated that the silicon sample surface was partly damaged and the native oxide layer on silicon sample surface had not been totally removed during the wear process. These results may help us optimize the tribological design of dynamic microelectromechanical systems working in humid conditions. Full article

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8 pages, 3691 KiB

Open AccessArticle

Grain Size Effect on the Hot Ductility of High-Nitrogen Austenitic Stainless Steel in the Presence of Precipitates

by Zhenhua Wang^1,2,3,*

, Yong Wang¹ and Chengming Wang³

¹ School of Mechanical Engineering, Yanshan University, Qinhuangdao 066004, China

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

³ HBIS Group Technology Research Institute, Shijiazhuang 050023, China

Materials 2018, 11(6), 1026; https://doi.org/10.3390/ma11061026 - 15 Jun 2018

Cited by 10 | Viewed by 3641

Abstract

Precipitation occurs easily during the hot forming of high-nitrogen austenitic stainless steels, which reduces their hot ductility significantly. The effect of grain size on the hot ductility of high-nitrogen austenitic stainless steel in the presence of precipitates was investigated. Different grain sizes of [...] Read more.

Precipitation occurs easily during the hot forming of high-nitrogen austenitic stainless steels, which reduces their hot ductility significantly. The effect of grain size on the hot ductility of high-nitrogen austenitic stainless steel in the presence of precipitates was investigated. Different grain sizes of 18Mn18Cr0.5N steel specimens, with and without precipitates, were hot-tension tested. The precipitate morphology, fracture surface, and cracks were studied by scanning electron microscopy, transmission electron microscopy, and electron backscatter diffraction analysis. For the 18Mn18Cr0.5N steel, damage-formation strains of all grain-size specimens were reduced by the precipitates during the hot-tension test. Crack-formation sites were located at grain boundaries and were independent of the Taylor factor. A larger grain size resulted in an increased sensitivity of the fracture strain to precipitates. When the grain size was smaller than 51 μm, the fracture strain became insensitive to the precipitates. A method was suggested to mitigate surface cracking for metal materials with a high precipitation tendency. Full article

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12 pages, 4151 KiB

Open AccessArticle

Effects of Annealing on the Residual Stress in γ-TiAl Alloy by Molecular Dynamics Simulation

by Ruicheng Feng^1,2

, Wenyuan Song¹, Haiyan Li^1,2,*, Yongnian Qi¹, Haiyang Qiao¹ and Longlong Li¹

¹ School of Mechanical and Electronical Engineering, Lanzhou University of Technology, Lanzhou 730050, China

² Key Laboratory of Digital Manufacturing Technology and Application, Ministry of Education, Lanzhou University of Technology, Lanzhou 730050, China

Materials 2018, 11(6), 1025; https://doi.org/10.3390/ma11061025 - 15 Jun 2018

Cited by 23 | Viewed by 4531

Abstract

In this paper, molecular dynamics simulations are performed to study the annealing process of γ-TiAl alloy with different parameters after introducing residual stress into prepressing. By mainly focusing on the dynamic evolution process of microdefects during annealing and the distribution of residual stress, [...] Read more.

In this paper, molecular dynamics simulations are performed to study the annealing process of γ-TiAl alloy with different parameters after introducing residual stress into prepressing. By mainly focusing on the dynamic evolution process of microdefects during annealing and the distribution of residual stress, the relationship between microstructure and residual stress is investigated. The results show that there is no phase transition during annealing, but atom distortion occurs with the change of temperature, and the average grain size slightly increases after annealing. There are some atom clusters in the grains, with a few point defects, and the point defect concentration increases with the rise in temperature, and vice versa; the higher the annealing temperature, the fewer the point defects in the grain after annealing. Due to the grain boundary volume shrinkage and and an increase in the plastic deformation of the grain boundaries during cooling, stress is released, and the average residual stress along Y and Z directions after annealing is less than the average residual stress after prepressing. Full article

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10 pages, 5486 KiB

Open AccessArticle

Effects of Different Hot Working Techniques on Inclusions in GH4738 Superalloy Produced by VIM and VAR

by Zhengyang Chen^1,2, Shufeng Yang^1,2,*, Jingshe Li^1,2, Hao Guo^1,2 and Hongbo Zheng^1,2

¹ School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China

² Beijing Key Laboratory of Special Melting and Preparation of High-End Metal Materials, Beijing 100083, China

Materials 2018, 11(6), 1024; https://doi.org/10.3390/ma11061024 - 15 Jun 2018

Cited by 14 | Viewed by 3714

Abstract

Hot working is a key process in the production of superalloys; however, it may result in the formation of inclusions that affect the superalloy performance. Therefore, the effects of hot working on inclusions in a superalloy must be studied. GH4738 superalloy was manufactured, [...] Read more.

Hot working is a key process in the production of superalloys; however, it may result in the formation of inclusions that affect the superalloy performance. Therefore, the effects of hot working on inclusions in a superalloy must be studied. GH4738 superalloy was manufactured, herein, by vacuum induction melting and vacuum arc remelting. Hot working was performed by unidirectional drawing, upsetting and drawing, and upsetting/drawing with radial forging. The types and distributions of inclusions after these three hot working processes and those in an original ingot were analyzed using scanning electron microscopy, energy dispersive spectroscopy, and Image-Pro Plus software. The results showed that the melting technology essentially determined the inclusion types in GH4738. Four types of inclusions were found in the experiments: TiC–TiN–Mo–S composite, TiC–TiN composite, Ce–Mo–S composite, and SiC inclusions. In the case of hot working by unidirectional drawing, the average inclusion size first decreased, and then increased from the center to the edge. In the case of upsetting and drawing, and upsetting/drawing with radial forging, the average inclusion size decreased from the center to the edge. Full article

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11 pages, 2600 KiB

Open AccessArticle

Compressive Behavior and Constitutive Model of Austenitic Stainless Steel S30403 in High Strain Range

by Yang Peng, Jiang Chu and Jun Dong^*

College of Civil Engineering, Nanjing Tech University, Nanjing 211816, China

Materials 2018, 11(6), 1023; https://doi.org/10.3390/ma11061023 - 15 Jun 2018

Cited by 9 | Viewed by 4123

Abstract

Material anisotropy for tension and compression is a significant characteristic of austenitic stainless steel compared to carbon steel. Due to limitations during the testing of the restrained jig, the maximum strain value of compressive experiments of austenitic stainless steel is around 2%. This [...] Read more.

Material anisotropy for tension and compression is a significant characteristic of austenitic stainless steel compared to carbon steel. Due to limitations during the testing of the restrained jig, the maximum strain value of compressive experiments of austenitic stainless steel is around 2%. This value cannot satisfy the requirements of accurate finite simulation on austenitic stainless steel columns and beams in the high compressive strain range. In this study, a new type of compressive specimen that satisfies the high compressive strain test was designed. The stress-strain response of austenitic stainless steel S30403 (JISCO, Gansu, China) was investigated in the high compressive strain range up to 10%, and constitutive models were compared with the experimental data. It was found that the new type specimen with length-to-diameter ratio of 1:1 can reliably obtain the stress-strain response of austenitic stainless steel S30403 in the high compressive strain range. It was found that the material anisotropy of austenitic stainless steel S30403 is remarkable in the high compressive strain range up to 10%. The strain-hardening curve of the austenitic stainless steel S30403 can be represented by a straight line in the high compressive strain range. Our study also found that the Quach constitutive model accurately describes the two-stage strain-hardening phenomenon in the high compressive strain range up to 10%. Full article

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13 pages, 3684 KiB

Open AccessArticle

Synthesis of TiO_2NWS@Au_NPS Composite Catalyst for Methylene Blue Removal

by Fan Fu¹, Feifei Wang¹, Ting Li¹, Chenlu Jiao¹, Yan Zhang^1,2,* and Yuyue Chen^1,*

¹ National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou 215123, China

² Nantong Textile & Silk Industrial Technology Research Institute, Nantong 226314, China

Materials 2018, 11(6), 1022; https://doi.org/10.3390/ma11061022 - 15 Jun 2018

Cited by 13 | Viewed by 3875

Abstract

In this article, HBP-NH₂-modified titania nanowire (TiO_2NWS)-decorated Au nanoparticles (TiO_2NWS@Au_NPS) were synthesized by one-step method. The role of HBP-NH₂ concentration in the formation of TiO_2NWS was investigated. The fineness and uniformity of pure [...] Read more.

In this article, HBP-NH₂-modified titania nanowire (TiO_2NWS)-decorated Au nanoparticles (TiO_2NWS@Au_NPS) were synthesized by one-step method. The role of HBP-NH₂ concentration in the formation of TiO_2NWS was investigated. The fineness and uniformity of pure TiO_2NWS were enhanced by absorbed amino groups from amino-terminated hyperbranched polymer (HBP-NH₂). The morphology and crystal structure of TiO_2NWS and TiO_2NWS@Au_NPS were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fournier transform infrared (FTIR) spectroscopy. The chemical states of gold, titanium and oxygen were analyzed by X-ray photoelectron spectroscopy (XPS). The results showed that at the concentration of HBP-NH₂ 100 g/L, the mean diameter of TiO_2NWS was nearly 72 nm and Au nanoparticles were uniformly distributed on the surface of TiO_2NWS. The presence of Au_NPS improved the photocatalytic properties of TiO_2NWS under UV light irradiation. The Au load was believed to improve the utilization rate of the photoelectron and activated the adsorbed oxygen. The obtained TiO_2NWS@Au_NPS decomposed 99.6% methylene blue (MB) after 300 min when subjected to UV light irradiation. After five cycles of the catalyzing process, the TiO_2NWS@Au_NPS still retained over 90% of its catalytic ability for MB. The Au deposition was found responsible for the high catalytic activity of TiO_2NWS@Au_NPS. Full article

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8 pages, 2506 KiB

Open AccessFeature PaperCommunication

Redox Activity of Sodium Vanadium Oxides towards Oxidation in Na Ion Batteries

by Evan Adamczyk

, Muthaiyan Gnanavel and Valerie Pralong^*

Normandie Univ, ENSICAEN, UNICAEN, CNRS, CRISMAT, 14000 Caen, France

Materials 2018, 11(6), 1021; https://doi.org/10.3390/ma11061021 - 15 Jun 2018

Cited by 10 | Viewed by 4231

Abstract

The search for new materials that could be used as electrode material for Na-ion batteries is one of the most challenging issues of today. Many transition metal oxide families as well as transition metal polyanionic frameworks have been proposed over the last five [...] Read more.

The search for new materials that could be used as electrode material for Na-ion batteries is one of the most challenging issues of today. Many transition metal oxide families as well as transition metal polyanionic frameworks have been proposed over the last five years. In this work, we report the sodium extraction from Na₂V₃O₇, which is a tunnel type structure built of [V₃O₇]²⁻_∞ nanotubes held by sodium ions. We report a reversible charge capacity of 80 mAh/g at 2.8 V vs. Na⁺/Na due to the V⁵⁺/V⁴⁺ redox activity. No oxygen redox activity has been observed for this material nor for the vanadium (5+) oxide Na₄V₂O₇. Full article

(This article belongs to the Special Issue Electrode Materials for High Performance Sodium-ion Batteries)

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11 pages, 6657 KiB

Open AccessArticle

Using Spin-Coated Silver Nanoparticles/Zinc Oxide Thin Films to Improve the Efficiency of GaInP/(In)GaAs/Ge Solar Cells

by Po-Hsun Lei^*, I-Jen Chen, Jia-Jan Chen, Po-Chun Yang and Yan-Hua Gong

Institute of Electro-Optical and Materials Science, National Formosa University, 64 Wen-Hwa Rd, Hu-Wei, Yun-Lin 623, Taiwan

Materials 2018, 11(6), 1020; https://doi.org/10.3390/ma11061020 - 15 Jun 2018

Cited by 3 | Viewed by 5079

Abstract

We synthesized a silver nanoparticle/zinc oxide (Ag NP/ZnO) thin film by using spin-coating technology. The treatment solution for Ag NP/ZnO thin film deposition contained zinc acetate (Zn(CH₃COO)₂), sodium hydroxide (NaOH), and silver nitrate (AgNO₃) aqueous solutions. The [...] Read more.

We synthesized a silver nanoparticle/zinc oxide (Ag NP/ZnO) thin film by using spin-coating technology. The treatment solution for Ag NP/ZnO thin film deposition contained zinc acetate (Zn(CH₃COO)₂), sodium hydroxide (NaOH), and silver nitrate (AgNO₃) aqueous solutions. The crystalline characteristics, surface morphology, content of elements, and reflectivity of the Ag NPs/ZnO thin film at various concentrations of the AgNO₃ aqueous solution were investigated using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, and ultraviolet–visible–near infrared spectrophotometry. The results indicated that the crystalline structure, Ag content, and reflectance of Ag NP/ZnO thin films depended on the AgNO₃ concentration. Hybrid antireflection coatings (ARCs) composed of SiN_x and Ag NPs/ZnO thin films with various AgNO₃ concentrations were deposited on GaInP/(In)GaAs/Ge solar cells. We propose that the optimal ARC consists of SiN_x and Ag NP/ZnO thin films prepared using a treatment solution of 0.0008 M AgNO₃, 0.007 M Zn(CH₃COO)₂, and 1 M NaOH, followed by post-annealing at 200 °C. GaInP/(Al)GaAs/Ge solar cells with the optimal hybrid ARC and SiN_x ARC exhibit a conversion efficiency of 34.1% and 30.2% with V_oc = 2.39 and 2.4 V, J_sc = 16.63 and 15.37 mA/cm², and fill factor = 86.1% and 78.8%. Full article

(This article belongs to the Special Issue Selected Papers from IEEE ICASI 2018)

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Materials, Volume 11, Issue 6 (June 2018) – 182 articles

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