Materials

15 pages, 3407 KiB

Open AccessArticle

Fe-Doped Sol-Gel Glasses and Glass-Ceramics for Magnetic Hyperthermia

by Francesco Baino, Elisa Fiume, Marta Miola, Federica Leone, Barbara Onida, Francesco Laviano, Roberto Gerbaldo and Enrica Verné

Materials 2018, 11(1), 173; https://doi.org/10.3390/ma11010173 - 22 Jan 2018

Cited by 52 | Viewed by 7290

Abstract

This work deals with the synthesis and characterization of novel Fe-containing sol-gel materials obtained by modifying the composition of a binary SiO₂-CaO parent glass with the addition of Fe₂O₃. The effect of different processing conditions (calcination in [...] Read more.

This work deals with the synthesis and characterization of novel Fe-containing sol-gel materials obtained by modifying the composition of a binary SiO₂-CaO parent glass with the addition of Fe₂O₃. The effect of different processing conditions (calcination in air vs. argon flowing) on the formation of magnetic crystalline phases was investigated. The produced materials were analyzed from thermal (hot-stage microscopy, differential thermal analysis, and differential thermal calorimetry) and microstructural (X-ray diffraction) viewpoints to assess both the behavior upon heating and the development of crystalline phases. N₂ adsorption–desorption measurements allowed determining that these materials have high surface area (40–120 m²/g) and mesoporous texture with mesopore size in the range of 18 to 30 nm. It was assessed that the magnetic properties can actually be tailored by controlling the Fe content and the environmental conditions (oxidant vs. inert atmosphere) during calcination. The glasses and glass-ceramics developed in this work show promise for applications in bone tissue healing which require the use of biocompatible magnetic implants able to elicit therapeutic actions, such as hyperthermia for bone cancer treatment. Full article

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

► Show Figures

Figure 1

10 pages, 4027 KiB

Open AccessArticle

The Enhanced Catalytic Performance and Stability of Rh/γ-Al₂O₃ Catalyst Synthesized by Atomic Layer Deposition (ALD) for Methane Dry Reforming

by Yunlin Li, Jing Jiang, Chaosheng Zhu, Lili Li, Quanliang Li, Yongjie Ding and Weijie Yang

Materials 2018, 11(1), 172; https://doi.org/10.3390/ma11010172 - 22 Jan 2018

Cited by 16 | Viewed by 5808

Abstract

Rh/γ-Al₂O₃ catalysts were synthesized by both incipient wetness impregnation (IWI) and atomic layer deposition (ALD). The TEM images of the two catalysts showed that the catalyst from ALD had smaller particle size, and narrower size distribution. The surface chemical states [...] Read more.

Rh/γ-Al₂O₃ catalysts were synthesized by both incipient wetness impregnation (IWI) and atomic layer deposition (ALD). The TEM images of the two catalysts showed that the catalyst from ALD had smaller particle size, and narrower size distribution. The surface chemical states of both catalysts were investigated by both XPS and X-ray Absorption Near Edge Structure (XANES), and the catalyst from IWI had higher concentration of Rh³⁺ than that from ALD. The catalytic performance of both catalysts was tested in the dry reforming of methane reaction. The catalyst from ALD showed a higher conversion and selectivity than that from IWI. The stability testing results indicated that the catalyst from ALD showed similar stability to that from IWI at 500 °C, but higher stability at 800 °C. Full article

(This article belongs to the Section Advanced Nanomaterials and Nanotechnology)

► Show Figures

Figure 1

19 pages, 3077 KiB

Open AccessArticle

Electrochemical Behaviour and Galvanic Effects of Titanium Implants Coupled to Metallic Suprastructures in Artificial Saliva

by Ana Mellado-Valero, Anna Igual Muñoz, Virginia Guiñón Pina and Ma Fernanda Sola-Ruiz

Materials 2018, 11(1), 171; https://doi.org/10.3390/ma11010171 - 22 Jan 2018

Cited by 32 | Viewed by 6729

Abstract

The aim of the present study is to analyze the electrochemical behavior of five different dental alloys: two cobalt-chromium alloys (CoCr and CoCr-c), one nickel-chromium-titanium alloy (NiCrTi), one gold-palladium alloy (Au), and one titanium alloy (Ti6Al4V), and the galvanic effect when they are [...] Read more.

The aim of the present study is to analyze the electrochemical behavior of five different dental alloys: two cobalt-chromium alloys (CoCr and CoCr-c), one nickel-chromium-titanium alloy (NiCrTi), one gold-palladium alloy (Au), and one titanium alloy (Ti6Al4V), and the galvanic effect when they are coupled to titanium implants (TiG2). It was carried out by electrochemical techniques (open circuit measurements, potentiodynamic curves and Zero-Resistance Ammetry) in artificial saliva (AS), with and without fluorides in different acidic conditions. The studied alloys are spontaneously passivated, but NiCrTi alloy has a very narrow passive domain and losses its passivity in presence of fluorides, so is not considered as a good option for implant superstructures. Variations of pH from 6.5 to 3 in artificial saliva do not change the electrochemical behavior of Ti, Ti6Al4V, and CoCr alloys, and couples, but when the pH of the artificial saliva is below 3.5 and the fluoride content is 1000 ppm Ti and Ti6Al4V starts actively dissolving, and CoCr-c superstructures coupled to Ti show acceleration of corrosion due to galvanic effects. Thus, NiCrTi is not recommended for implant superstructures because of risk of Ni ion release to the body, and fluorides should be avoided in acidic media because Ti, Ti6Al4V, and CoCr-c superstructures show galvanic corrosion. The best combinations are Ti/Ti6Al4V and Ti/CoCr as alternative of noble gold alloys. Full article

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

► Show Figures

Figure 1

12 pages, 5796 KiB

Open AccessArticle

Orientation of Steel Fibers in Magnetically Driven Concrete and Mortar

by Wen Xue, Ju Chen, Fang Xie and Bing Feng

Materials 2018, 11(1), 170; https://doi.org/10.3390/ma11010170 - 22 Jan 2018

Cited by 22 | Viewed by 5284

Abstract

The orientation of steel fibers in magnetically driven concrete and magnetically driven mortar was experimentally studied in this paper using a magnetic method. In the magnetically driven concrete, a steel slag was used to replace the coarse aggregate. In the magnetically driven mortar, [...] Read more.

The orientation of steel fibers in magnetically driven concrete and magnetically driven mortar was experimentally studied in this paper using a magnetic method. In the magnetically driven concrete, a steel slag was used to replace the coarse aggregate. In the magnetically driven mortar, steel slag and iron sand were used to replace the fine aggregate. A device was established to provide the magnetic force. The magnetic force was used to rotate the steel fibers. In addition, the magnetic force was also used to vibrate the concrete and mortar. The effect of magnetic force on the orientation of steel fibers was examined by comparing the direction of fibers before and after vibration. The effect of magnetically driven concrete and mortar on the orientation of steel fibers was also examined by comparing specimens to normal concrete and mortar. It is shown that the fibers could rotate about 90° in magnetically driven concrete. It is also shown that the number of fibers rotated in magnetically driven mortar was much more than in mortar vibrated using a shaking table. A splitting test was performed on concrete specimens to investigate the effect of fiber orientation. In addition, a flexural test was also performed on mortar test specimens. It is shown that the orientation of the steel fibers in magnetically driven concrete and mortar affects the strength of the concrete and mortar specimens. Full article

► Show Figures

Figure 1

13 pages, 3083 KiB

Open AccessArticle

Effect of Aspect Ratio on the Permittivity of Graphite Fiber in Microwave Heating

by Jun Fukushima, Shuntaro Tsubaki, Tomoki Matsuzawa, Keiichiro Kashimura, Tomohiko Mitani, Tomoaki Namioka, Satoshi Fujii, Naoki Shinohara, Hirotsugu Takizawa and Yuji Wada

Materials 2018, 11(1), 169; https://doi.org/10.3390/ma11010169 - 22 Jan 2018

Cited by 7 | Viewed by 5829

Abstract

Microwave (MW) heating has received attention as a new heating source for various industrial processes. Some materials are expected to be a more effective absorber of MW, and graphite is observed as a possible candidate for high-temperature application. We investigated the dependence of [...] Read more.

Microwave (MW) heating has received attention as a new heating source for various industrial processes. Some materials are expected to be a more effective absorber of MW, and graphite is observed as a possible candidate for high-temperature application. We investigated the dependence of the aspect ratio of graphite fibers on both their heating behavior and permittivity under a 2.45 GHz MW electric field. In these experiments, both loss tangent and MW heating behavior indicated that the MW absorption of conductive fibers increases with their aspect ratio. The MW absorption was found to be well accounted for by the application of a spheroidal model for a single fiber. The absorption of graphite fibers decreases with increasing aspect ratio when the long axis of the ellipsoid is perpendicular to the electric field, whereas it increases with the aspect ratio when the long axis is parallel to the electric field. The analytical model indicated that MW heating of the conductive fibers is expected to depend on both the shape and arrangement of the fibers in the electric field. Full article

(This article belongs to the Special Issue Electromagnetic Wave Absorbing Structures)

► Show Figures

Figure 1

11 pages, 5000 KiB

Open AccessFeature PaperArticle

One-Step Preparation of Large Area Films of Oriented MoS₂ Nanoparticles on Multilayer Graphene and Its Electrocatalytic Activity for Hydrogen Evolution

by Jinbao He, Cristina Fernández, Ana Primo and Hermenegildo Garcia

Materials 2018, 11(1), 168; https://doi.org/10.3390/ma11010168 - 22 Jan 2018

Cited by 6 | Viewed by 5288

Abstract

MoS₂ is a promising material to replace Pt-based catalysts for the hydrogen evolution reaction (HER), due to its excellent stability and high activity. In this work, MoS₂ nanoparticles supported on graphitic carbon (about 20 nm) with a preferential 002 facet orientation [...] Read more.

MoS₂ is a promising material to replace Pt-based catalysts for the hydrogen evolution reaction (HER), due to its excellent stability and high activity. In this work, MoS₂ nanoparticles supported on graphitic carbon (about 20 nm) with a preferential 002 facet orientation have been prepared by pyrolysis of alginic acid films on quartz containing adsorbed (NH₄)₂MoS₄ at 900 °C under Ar atmosphere. Although some variation of the electrocatalytic activity has been observed from batch to batch, the MoS₂ sample exhibited activity for HER (a potential onset between 0.2 and 0.3 V vs. SCE), depending on the concentrations of (NH₄)₂MoS₄ precursor used in the preparation process. The loading and particle size of MoS₂, which correlate with the amount of exposed active sites in the sample, are the main factors influencing the electrocatalytic activity. Full article

(This article belongs to the Special Issue Graphene/Carbon Nanotubes Application in Solar Cells)

► Show Figures

Figure 1

17 pages, 10537 KiB

Open AccessArticle

Microstructure Evolution and Mechanical Properties of Underwater Dry and Local Dry Cavity Welded Joints of 690 MPa Grade High Strength Steel

by Yonghua Shi, Kun Sun, Shuwan Cui, Min Zeng, Jianglong Yi, Xiaoqin Shen and Yaoyong Yi

Materials 2018, 11(1), 167; https://doi.org/10.3390/ma11010167 - 22 Jan 2018

Cited by 24 | Viewed by 6107

Abstract

Q690E high strength low alloy (HSLA) steel plays an important role in offshore structures. In addition, underwater local cavity welding (ULCW) technique was widely used to repair important offshore constructions. However, the high cooling rate of ULCW joints results in bad welding quality [...] Read more.

Q690E high strength low alloy (HSLA) steel plays an important role in offshore structures. In addition, underwater local cavity welding (ULCW) technique was widely used to repair important offshore constructions. However, the high cooling rate of ULCW joints results in bad welding quality compared with underwater dry welding (UDW) joints. Q690E high strength low alloy steels were welded by multi-pass UDW and ULCW techniques, to study the microstructural evolution and mechanical properties of underwater welded joints. The microstructure and fracture morphology of welded joints were observed by scanning electron microscope and optical microscope. The elemental distribution in the microstructure was determined with an Electron Probe Microanalyzer. The results indicated that the microstructure of both two welded joints was similar. However, martensite and martensite-austenite components were significantly different with different underwater welding methods such that the micro-hardness of the HAZ and FZ in the ULCW specimen was higher than that of the corresponding regions in UDW joint. The yield strength and ultimate tensile strength of the ULCW specimen are 109 MPa lower and 77 MPa lower, respectively, than those of the UDW joint. The impact toughness of the UDW joint was superior to those of the ULCW joint. Full article

► Show Figures

Figure 1

19 pages, 3625 KiB

Open AccessFeature PaperReview

Advanced Material Strategies for Next-Generation Additive Manufacturing

by Jinke Chang, Jiankang He, Mao Mao, Wenxing Zhou, Qi Lei, Xiao Li, Dichen Li, Chee-Kai Chua and Xin Zhao

Materials 2018, 11(1), 166; https://doi.org/10.3390/ma11010166 - 22 Jan 2018

Cited by 86 | Viewed by 14801

Abstract

Additive manufacturing (AM) has drawn tremendous attention in various fields. In recent years, great efforts have been made to develop novel additive manufacturing processes such as micro-/nano-scale 3D printing, bioprinting, and 4D printing for the fabrication of complex 3D structures with high resolution, [...] Read more.

Additive manufacturing (AM) has drawn tremendous attention in various fields. In recent years, great efforts have been made to develop novel additive manufacturing processes such as micro-/nano-scale 3D printing, bioprinting, and 4D printing for the fabrication of complex 3D structures with high resolution, living components, and multimaterials. The development of advanced functional materials is important for the implementation of these novel additive manufacturing processes. Here, a state-of-the-art review on advanced material strategies for novel additive manufacturing processes is provided, mainly including conductive materials, biomaterials, and smart materials. The advantages, limitations, and future perspectives of these materials for additive manufacturing are discussed. It is believed that the innovations of material strategies in parallel with the evolution of additive manufacturing processes will provide numerous possibilities for the fabrication of complex smart constructs with multiple functions, which will significantly widen the application fields of next-generation additive manufacturing. Full article

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

► Show Figures

Figure 1

26 pages, 7053 KiB

Open AccessArticle

Poly(hydroxyalkanoate)s-Based Hydrophobic Coatings for the Protection of Stone in Cultural Heritage

by Serena Andreotti, Elisa Franzoni, Micaela Degli Esposti and Paola Fabbri

Materials 2018, 11(1), 165; https://doi.org/10.3390/ma11010165 - 20 Jan 2018

Cited by 48 | Viewed by 7011

Abstract

Reversibility is a mandatory requirement for materials used in heritage conservation, including hydrophobic protectives. Nevertheless, current protectives for stone are not actually reversible as they remain on the surfaces for a long time after their hydrophobicity is lost and can hardly be removed. [...] Read more.

Reversibility is a mandatory requirement for materials used in heritage conservation, including hydrophobic protectives. Nevertheless, current protectives for stone are not actually reversible as they remain on the surfaces for a long time after their hydrophobicity is lost and can hardly be removed. Ineffective and aged coatings may jeopardise the stone re-treatability and further conservation interventions. This paper aims at investigating the performance of PHAs-based coatings for stone protection, their main potential being the ‘reversibility by biodegradation’ once water repellency ended. The biopolymer coatings were applied to three different kinds of stone, representative of lithotypes used in historic architecture: sandstone, limestone and marble. Spray, poultice and dip-coating were tested as coating techniques. The effectiveness and compatibility of the protectives were evaluated in terms of capillary water absorption, static and dynamic contact angles, water vapour diffusion, colour alteration and surface morphology. The stones’ wettability after application of two commercial protectives was investigated too, for comparison. Finally, samples were subjected to artificial ageing to investigate their solar light stability. Promising results in terms of efficacy and compatibility were obtained, although the PHAs-based formulations developed here still need improvement for increased durability and on-site applicability. Full article

(This article belongs to the Special Issue Recent Advances in Smart Materials for the Built Environment)

► Show Figures

Figure 1

12 pages, 4042 KiB

Open AccessArticle

Preparation of 1D Hierarchical Material Mesosilica/Pal Composite and Its Performance in the Adsorption of Methyl Orange

by Mei Wu, Haifeng Han, Lingli Ni, Daiyun Song, Shuang Li, Tao Hu, Jinlong Jiang and Jing Chen

Materials 2018, 11(1), 164; https://doi.org/10.3390/ma11010164 - 20 Jan 2018

Cited by 9 | Viewed by 4312

Abstract

This paper highlights the synthesis of a one-dimensional (1D) hierarchical material mesosilica/palygorskite (Pal) composite and evaluates its adsorption performance for anionic dye methyl orange (MO) in comparison with Pal and Mobile crystalline material-41 (MCM-41). The Mesosilica/Pal composite is consisted of mesosilica coated Pal [...] Read more.

This paper highlights the synthesis of a one-dimensional (1D) hierarchical material mesosilica/palygorskite (Pal) composite and evaluates its adsorption performance for anionic dye methyl orange (MO) in comparison with Pal and Mobile crystalline material-41 (MCM-41). The Mesosilica/Pal composite is consisted of mesosilica coated Pal nanorods and prepared through a dual template approach using cetyltrimethyl ammonium bromide (CTAB) and Pal as soft and hard templates, respectively. The composition and structure of the resultant material was characterized by a scanning electron microscope (SEM), transmissionelectron microscopy (TEM), N₂ adsorption-desorption analysis, small-angle X-Ray powder diffraction (XRD), and zeta potential measurement. Adsorption experiments were carried out with different absorbents at different contact times and pH levels. Compared with Pal and MCM-41, the mesosilica/Pal composite exhibited the best efficiency for MO adsorption. Its adsorption ratio is as high as 70.4%. Its adsorption equilibrium time is as short as 30 min. Results testify that the MO retention is promoted for the micro-mesoporous hierarchical structure and positive surface charge electrostatic interactions of the mesosilica/Pal composite. The regenerability of the mesosilica/Pal composite absorbent was also assessed. 1D morphology makes it facile to separate from aqueous solutions. It can be effortlessly recovered and reused for up to nine cycles. Full article

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

► Show Figures

Graphical abstract

9 pages, 3800 KiB

Open AccessArticle

Glass Polarization Induced Drift of a Closed-Loop Micro-Accelerometer

by Wu Zhou, Jiangbo He, Huijun Yu, Bei Peng and Xiaoping He

Materials 2018, 11(1), 163; https://doi.org/10.3390/ma11010163 - 20 Jan 2018

Cited by 3 | Viewed by 4041

Abstract

The glass polarization effects were introduced in this paper to study the main cause of turn-on drift phenomenon of closed-loop micro-accelerometers. The glass substrate underneath the sensitive silicon structure underwent a polarizing process when the DC bias voltage was applied. The slow polarizing [...] Read more.

The glass polarization effects were introduced in this paper to study the main cause of turn-on drift phenomenon of closed-loop micro-accelerometers. The glass substrate underneath the sensitive silicon structure underwent a polarizing process when the DC bias voltage was applied. The slow polarizing process induced an additional electrostatic field to continually drag the movable mass block from one position to another so that the sensing capacitance was changed, which led to an output drift of micro-accelerometers. This drift was indirectly tested by experiments and could be sharply reduced by a shielding layer deposited on the glass substrate because the extra electrical filed was prohibited from generating extra electrostatic forces on the movable fingers of the mass block. The experimental results indicate the average magnitude of drift decreased about 73%, from 3.69 to 0.99 mV. The conclusions proposed in this paper showed a meaningful guideline to improve the stability of micro-devices based on silicon-on-glass structures. Full article

► Show Figures

Figure 1

18 pages, 7608 KiB

Open AccessArticle

Influence of Magnesium Ions in the Seawater Environment on the Improvement of the Corrosion Resistance of Low-Chromium-Alloy Steel

by Sol-Ji Song and Jung-Gu Kim

Materials 2018, 11(1), 162; https://doi.org/10.3390/ma11010162 - 20 Jan 2018

Cited by 11 | Viewed by 5761

Abstract

This study examined the synergic effect of alloying the element Cr and the environmental element Mg²⁺ ions on the corrosion property of a low-alloy steel in seawater at 60 °C, by means of electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) tests [...] Read more.

This study examined the synergic effect of alloying the element Cr and the environmental element Mg²⁺ ions on the corrosion property of a low-alloy steel in seawater at 60 °C, by means of electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) tests and weight-loss tests. The Mg²⁺ ions in seawater played an important role in lowering the electron transfer of the rust layer in the Cr-containing steel. The corrosion resistance of the Cr-containing steel is superior to that of blank steel in Mg²⁺ ions containing seawater. XPS and XRD results indicated that the formation of MgFe₂O₄ and a mixed layer (Cr oxide + FeCr₂O₄ + MgCr₂O₄) improved the corrosion resistance of the low-alloy steel in the seawater. Full article

► Show Figures

Graphical abstract

16 pages, 2946 KiB

Open AccessArticle

Blood Vessel Formation and Bone Regeneration Potential of the Stromal Vascular Fraction Seeded on a Calcium Phosphate Scaffold in the Human Maxillary Sinus Floor Elevation Model

by Elisabet Farré-Guasch, Nathalie Bravenboer, Marco N. Helder, Engelbert A. J. M. Schulten, Christiaan M. Ten Bruggenkate and Jenneke Klein-Nulend

Materials 2018, 11(1), 161; https://doi.org/10.3390/ma11010161 - 20 Jan 2018

Cited by 46 | Viewed by 6732

Abstract

Bone substitutes are used as alternatives for autologous bone grafts in patients undergoing maxillary sinus floor elevation (MSFE) for dental implant placement. However, bone substitutes lack osteoinductive and angiogenic potential. Addition of adipose stem cells (ASCs) may stimulate osteogenesis and osteoinduction, as well [...] Read more.

Bone substitutes are used as alternatives for autologous bone grafts in patients undergoing maxillary sinus floor elevation (MSFE) for dental implant placement. However, bone substitutes lack osteoinductive and angiogenic potential. Addition of adipose stem cells (ASCs) may stimulate osteogenesis and osteoinduction, as well as angiogenesis. We aimed to evaluate the vascularization in relation to bone formation potential of the ASC-containing stromal vascular fraction (SVF) of adipose tissue, seeded on two types of calcium phosphate carriers, within the human MSFE model, in a phase I study. Autologous SVF was obtained from ten patients and seeded on β-tricalcium phosphate (n = 5) or biphasic calcium phosphate carriers (n = 5), and used for MSFE in a one-step surgical procedure. After six months, biopsies were obtained during dental implant placement, and the quantification of the number of blood vessels was performed using histomorphometric analysis and immunohistochemical stainings for blood vessel markers, i.e., CD34 and alpha-smooth muscle actin. Bone percentages seemed to correlate with blood vessel formation and were higher in study versus control biopsies in the cranial area, in particular in β-tricalcium phosphate-treated patients. This study shows the safety, feasibility, and efficiency of the use of ASCs in the human MSFE, and indicates a pro-angiogenic effect of SVF. Full article

(This article belongs to the Special Issue Novel Advances and Approaches in Biomedical Materials Based on Calcium Phosphates)

► Show Figures

Graphical abstract

13 pages, 13463 KiB

Open AccessArticle

Quadrilateral Micro-Hole Array Machining on Invar Thin Film: Wet Etching and Electrochemical Fusion Machining

by Woong-Kirl Choi, Seong-Hyun Kim, Seung-Geon Choi and Eun-Sang Lee

Materials 2018, 11(1), 160; https://doi.org/10.3390/ma11010160 - 19 Jan 2018

Cited by 6 | Viewed by 7261

Abstract

Ultra-precision products which contain a micro-hole array have recently shown remarkable demand growth in many fields, especially in the semiconductor and display industries. Photoresist etching and electrochemical machining are widely known as precision methods for machining micro-holes with no residual stress and lower [...] Read more.

Ultra-precision products which contain a micro-hole array have recently shown remarkable demand growth in many fields, especially in the semiconductor and display industries. Photoresist etching and electrochemical machining are widely known as precision methods for machining micro-holes with no residual stress and lower surface roughness on the fabricated products. The Invar shadow masks used for organic light-emitting diodes (OLEDs) contain numerous micro-holes and are currently machined by a photoresist etching method. However, this method has several problems, such as uncontrollable hole machining accuracy, non-etched areas, and overcutting. To solve these problems, a machining method that combines photoresist etching and electrochemical machining can be applied. In this study, negative photoresist with a quadrilateral hole array pattern was dry coated onto 30-µm-thick Invar thin film, and then exposure and development were carried out. After that, photoresist single-side wet etching and a fusion method of wet etching-electrochemical machining were used to machine micro-holes on the Invar. The hole machining geometry, surface quality, and overcutting characteristics of the methods were studied. Wet etching and electrochemical fusion machining can improve the accuracy and surface quality. The overcutting phenomenon can also be controlled by the fusion machining. Experimental results show that the proposed method is promising for the fabrication of Invar film shadow masks. Full article

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

► Show Figures

Graphical abstract

15 pages, 3675 KiB

Open AccessArticle

Nitrogen-Containing Functional Groups-Facilitated Acetone Adsorption by ZIF-8-Derived Porous Carbon

by Liqing Li, Xiancheng Ma, Ruofei Chen, Chunhao Wang and Mingming Lu

Materials 2018, 11(1), 159; https://doi.org/10.3390/ma11010159 - 19 Jan 2018

Cited by 44 | Viewed by 8576

Abstract

Nitrogen-doped porous carbon (ZC) is prepared by modification with ammonia for increasing the specific surface area and surface polarity after carbonization of zeolite imidazole framework-8 (ZIF-8). The structure and properties of these ZCs were characterized by Transmission electron microscopy, X-ray diffraction, N₂ [...] Read more.

Nitrogen-doped porous carbon (ZC) is prepared by modification with ammonia for increasing the specific surface area and surface polarity after carbonization of zeolite imidazole framework-8 (ZIF-8). The structure and properties of these ZCs were characterized by Transmission electron microscopy, X-ray diffraction, N₂ sorption, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Through static adsorption tests of these carbons, the sample obtained at 600 °C was selected as an excellent adsorbent, which exhibited an excellent acetone capacity of 417.2 mg g⁻¹ (25 °C) with a very large surface area and high-level nitrogen doping (13.55%). The microporosity, surface area and N-containing groups of the materials, pyrrolic-N, pyridinic-N, and oxidized-N groups in particular, were found to be the determining factors for acetone adsorption by means of molecular simulation with density functional theory. These findings indicate that N-doped microporous carbon materials are potential promising adsorbents for acetone. Full article

► Show Figures

Graphical abstract

13 pages, 9372 KiB

Open AccessArticle

A Composite Photocatalyst Based on Hydrothermally-Synthesized Cu₂ZnSnS₄ Powders

by Shih-Jen Lin, Jyh-Ming Ting, Kuo-Chin Hsu and Yaw-Shyan Fu

Materials 2018, 11(1), 158; https://doi.org/10.3390/ma11010158 - 19 Jan 2018

Cited by 13 | Viewed by 5617

Abstract

A novel composite photocatalyst based on Cu₂ZnSnS₄ (CZTS) powders was synthesized and investigated for use as a photocatalyst. CZTS powders were first made using a conventional hydrothermal method and were then used to grow silver nanoparticles hybridized onto the CZTS [...] Read more.

A novel composite photocatalyst based on Cu₂ZnSnS₄ (CZTS) powders was synthesized and investigated for use as a photocatalyst. CZTS powders were first made using a conventional hydrothermal method and were then used to grow silver nanoparticles hybridized onto the CZTS under various conditions through a microwave-assisted hydrothermal process. After the obtained samples were subsequently mixed with 1T-2H MoS₂, the three synthesized component samples were characterized using X-ray diffractometry (XRD), scanning electron microscopy, transmission electron microscopy (FE-SEM, FE-TEM), UV-visible spectroscopy (UV-Vis), Brunauer-Emmet-Teller (BET), photoluminescence spectroscopy (PL), and X-ray photoelectron spectroscopy (XPS). The resulting samples were also used as photocatalysts for the degradation of methylene blue (MB) under a 300 W halogen lamp simulating sunlight with ~5% UV light. The photodegradation ability was greatly enhanced by the addition of Ag and 1T-2H MoS₂. Excellent photodegradation of MB was obtained under visible light. The effects of material characteristics on the photodegradation were investigated and discussed. Full article

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

► Show Figures

Figure 1

14 pages, 2695 KiB

Open AccessArticle

Effect of Novel Quercetin Titanium Dioxide-Decorated Multi-Walled Carbon Nanotubes Nanocomposite on Bacillus subtilis Biofilm Development

by Diana S. Raie, Eisha Mhatre, Doaa S. El-Desouki, Ahmed Labena, Gamal El-Ghannam, Laila A. Farahat, Tareq Youssef, Wolfgang Fritzsche and Ákos T. Kovács

Materials 2018, 11(1), 157; https://doi.org/10.3390/ma11010157 - 18 Jan 2018

Cited by 11 | Viewed by 6621

Abstract

The present work was targeted to design a surface against cell seeding and adhering of bacteria, Bacillus subtilis. A multi-walled carbon nanotube/titanium dioxide nano-power was produced via simple mixing of carbon nanotube and titanium dioxide nanoparticles during the sol-gel process followed by [...] Read more.

The present work was targeted to design a surface against cell seeding and adhering of bacteria, Bacillus subtilis. A multi-walled carbon nanotube/titanium dioxide nano-power was produced via simple mixing of carbon nanotube and titanium dioxide nanoparticles during the sol-gel process followed by heat treatment. Successfully, quercetin was immobilized on the nanocomposite via physical adsorption to form a quercetin/multi-walled carbon nanotube/titanium dioxide nanocomposite. The adhesion of bacteria on the coated-slides was verified after 24 h using confocal laser-scanning microscopy. Results indicated that the quercetin/multi-walled carbon nanotube/titanium dioxide nanocomposite had more negativity and higher recovery by glass surfaces than its counterpart. Moreover, coating surfaces with the quercetin-modified nanocomposite lowered both hydrophilicity and surface-attached bacteria compared to surfaces coated with the multi-walled carbon nanotubes/titanium dioxide nanocomposite. Full article

► Show Figures

Figure 1

12 pages, 4647 KiB

Open AccessArticle

Fabrication, Structural Characterization and Uniaxial Tensile Properties of Novel Sintered Multi-Layer Wire Mesh Porous Plates

by Liuyang Duan, Zhaoyao Zhou and Bibo Yao

Materials 2018, 11(1), 156; https://doi.org/10.3390/ma11010156 - 17 Jan 2018

Cited by 12 | Viewed by 5049

Abstract

There is an increasing interest in developing porous metals or metallic foams for functional and structural applications. The study of the physical and mechanical properties of porous metals is very important and helpful for their application. In this paper, a novel sintered multilayer [...] Read more.

There is an increasing interest in developing porous metals or metallic foams for functional and structural applications. The study of the physical and mechanical properties of porous metals is very important and helpful for their application. In this paper, a novel sintered multilayer wire mesh porous plate material (WMPPs) with a thickness of 0.5 mm–3 mm and a porosity of 10–35% was prepared by winding, pressing, rolling, and subsequently vacuum sintering them. The pore size and total size distribution in the as-prepared samples were investigated using the bubble point method. The uniaxial tensile behavior of the WMPPs was investigated in terms of the sintering temperature, porosity, wire diameter, and manufacturing technology. The deformation process and the failure mechanism under the tensile press was also discussed based on the appearance of the fractures (SEM figures). The results indicated that the pore size and total size distribution were closely related to the raw material used and the sintering temperature. For the WMPPs prepared by the wire mesh, the pore structures were inerratic and the vast majority of pore size was less than 10 μm. On the other hand, for the WMPPs that were prepared by wire mesh and powder, the pore structures were irregular and the pore size ranged from 0 μm–50 μm. The experimental data showed that the tensile strength of WMPPs is much higher than any other porous metals or metallic foams. Higher sintering temperatures led to coarser joints between wires and resulted in higher tensile strength. The sintering temperature decreased from 1330 °C to 1130 °C and the tensile strength decreased from 296 MPa to 164 MPa. Lower porosity means that there are more metallurgical joints and metallic frameworks resisting deformation per unit volume. Therefore, lower porosities exhibit higher tensile strength. An increase of porosity from 17.14% to 32.5% led to the decrease of the tensile strength by 90 MPa. The coarser wires led to a bigger contact area between the interconnecting wires, resulting in a stronger sintering neck that exhibited higher tensile strength. The wire diameter increased from 81 μm to 122 μm and the tensile strength increased from 296 MPa to 362 MPa. The fracture morphology showed that the wires experience necking deformation and ductile fracture. Full article

(This article belongs to the Section Porous Materials)

► Show Figures

Figure 1

13 pages, 5980 KiB

Open AccessArticle

Synthesis and Characterization of a Heterometallic Extended Architecture Based on a Manganese(II)-Substituted Sandwich-Type Polyoxotungstate

by Masooma Ibrahim, Eufemio Moreno-Pineda, Thomas Bergfeldt, Christopher E. Anson and Annie K. Powell

Materials 2018, 11(1), 155; https://doi.org/10.3390/ma11010155 - 17 Jan 2018

Cited by 7 | Viewed by 5538

Abstract

The reaction of [α-P₂W₁₅O₅₆]¹²⁻ with Mn^II and Dy^III in an aqueous basic solution led to the isolation of an all inorganic heterometallic aggregate Na₁₀(OH₂)₄₂[{Dy(H₂O) [...] Read more.

The reaction of [α-P₂W₁₅O₅₆]¹²⁻ with Mn^II and Dy^III in an aqueous basic solution led to the isolation of an all inorganic heterometallic aggregate Na₁₀(OH₂)₄₂[{Dy(H₂O)₆}₂Mn₄P₄W₃₀O₁₁₂(H₂O)₂]·17H₂O (Dy₂Mn₄-P₂W₁₅). Single-crystal X-ray diffraction revealed that Dy₂Mn₄-P₂W₁₅ crystallizes in the triclinic system with space group P

\bar{1}

, and consists of a tetranuclear manganese(II)-substituted sandwich-type phosphotungstate [Mn₄(H₂O)₂(P₂W₁₅O₅₆)₂]¹⁶⁻ (Mn₄-P₂W₁₅), Na, and Dy^III cations. Compound Dy₂Mn₄-P₂W₁₅ exhibits a 1D ladder-like chain structure based on sandwich-type segments and dysprosium cations as linkers, which are further connected into a three-dimensional open framework by sodium cations. The title compound was structurally and compositionally characterized in solid state by single-crystal XRD, powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric (TGA), and elemental analyses. Further, the absorption and emission electronic spectra in aqueous solutions of Dy₂Mn₄-P₂W₁₅ and Mn₄-P₂W₁₅ were studied. Also, magnetic properties were studied and compared with the magnetic behavior of [Mn₄(H₂O)₂(P₂W₁₅O₅₆)₂]¹⁶⁻. Full article

(This article belongs to the Special Issue Polyoxometalate and Nanohybrid Materials)

► Show Figures

Graphical abstract

12 pages, 4184 KiB

Open AccessFeature PaperArticle

Tailoring Cu Nanoparticle Catalyst for Methanol Synthesis Using the Spinning Disk Reactor

by Christian Ahoba-Sam, Kamelia V. K. Boodhoo, Unni Olsbye and Klaus-Joachim Jens

Materials 2018, 11(1), 154; https://doi.org/10.3390/ma11010154 - 17 Jan 2018

Cited by 16 | Viewed by 6959

Abstract

Cu nanoparticles are known to be very active for methanol (MeOH) synthesis at relatively low temperatures, such that smaller particle sizes yield better MeOH productivity. We aimed to control Cu nanoparticle (NP) size and size distribution for catalysing MeOH synthesis, by using the [...] Read more.

Cu nanoparticles are known to be very active for methanol (MeOH) synthesis at relatively low temperatures, such that smaller particle sizes yield better MeOH productivity. We aimed to control Cu nanoparticle (NP) size and size distribution for catalysing MeOH synthesis, by using the spinning disk reactor. The spinning disk reactor (SDR), which operates based on shear effect and plug flow in thin films, can be used to rapidly micro-mix reactants in order to control nucleation and particle growth for uniform particle size distribution. This could be achieved by varying both physical and chemical operation conditions in a precipitation reaction on the SDR. We have used the SDR for a Cu borohydride reduction to vary Cu NP size from 3 nm to about 55 nm. XRD and TEM characterization confirmed the presence of Cu₂O and Cu crystallites when the samples were dried. This technique is readily scalable for Cu NP production by processing continuously over a longer duration than the small-scale tests. However, separation of the nanoparticles from solution posed a challenge as the suspension hardly settled. The Cu NPs produced were tested to be active catalyst for MeOH synthesis at low temperature and MeOH productivity increased with decreasing particle size. Full article

(This article belongs to the Special Issue Latest Nanotechnology Research Output 2017—Select papers from Applied Nanotechnology and Nanoscience International Conference—ANNIC 2017)

► Show Figures

Figure 1

13 pages, 3813 KiB

Open AccessFeature PaperArticle

GaN-Based Laser Wireless Power Transfer System

by Carlo De Santi, Matteo Meneghini, Alessandro Caria, Ezgi Dogmus, Malek Zegaoui, Farid Medjdoub, Boris Kalinic, Tiziana Cesca, Gaudenzio Meneghesso and Enrico Zanoni

Materials 2018, 11(1), 153; https://doi.org/10.3390/ma11010153 - 17 Jan 2018

Cited by 30 | Viewed by 6322

Abstract

The aim of this work is to present a potential application of gallium nitride-based optoelectronic devices. By using a laser diode and a photodetector, we designed and demonstrated a free-space compact and lightweight wireless power transfer system, whose efficiency is limited by the [...] Read more.

The aim of this work is to present a potential application of gallium nitride-based optoelectronic devices. By using a laser diode and a photodetector, we designed and demonstrated a free-space compact and lightweight wireless power transfer system, whose efficiency is limited by the efficiency of the receiver. We analyzed the effect of the electrical load, temperature, partial absorption and optical excitation distribution on the efficiency, by identifying heating and band-filling as the most impactful processes. By comparing the final demonstrator with a commercial RF-based Qi system, we conclude that the efficiency is still low at close range, but is promising in medium to long range applications. Efficiency may not be a limiting factor, since this concept can enable entirely new possibilities and designs, especially relevant for space applications. Full article

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

► Show Figures

Figure 1

8 pages, 729 KiB

Open AccessArticle

Hydroxyl Ion Diffusion through Radicular Dentine When Calcium Hydroxide Is Used under Different Conditions

by Michael Cai, Paul Abbott and Jacqueline Castro Salgado

Materials 2018, 11(1), 152; https://doi.org/10.3390/ma11010152 - 17 Jan 2018

Cited by 10 | Viewed by 5090

Abstract

Calcium hydroxide’s anti-bacterial action relies on high pH. The aim here was to investigate hydroxyl ion diffusion through dentine under different conditions. Teeth were divided into control (n = 4) and four experimental groups (n = 10): Group 1—no medicament; Group [...] Read more.

Calcium hydroxide’s anti-bacterial action relies on high pH. The aim here was to investigate hydroxyl ion diffusion through dentine under different conditions. Teeth were divided into control (n = 4) and four experimental groups (n = 10): Group 1—no medicament; Group 2—Calmix; Group 3—Calmix/Ledermix; Group 4—Calasept Plus/Ledermix; Group 5—Pulpdent/smear layer. Deep (inner dentine) and shallow (outer dentine) cavities were cut into each root. pH was measured in these cavities for 12 weeks. The inner and outer dentine pH in Group 2 was significantly higher than all groups. Inner dentine pH in Group 3 was slightly higher than that in Group 4 initially but subsequently comparable. After Day 2, Group 5 had significantly lower pH than Groups 3 and 4. The outer dentine pH in Group 3 started higher than that in Groups 4 and 5, but by Day 28 the difference was insignificant. The time for the inner dentine to reach maximum pH was one week for Group 2 and four weeks for Groups 3 and 4. The time for the outer dentine to reach maximum pH was eight weeks for all experimental groups. Mixing different Ca(OH)₂ formulations with Ledermix gave similar hydroxyl ion release but pH and total diffusion was lower than Ca(OH)₂ alone. The smear layer inhibited diffusion. Full article

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

► Show Figures

Figure 1

13 pages, 3546 KiB

Open AccessArticle

Comparisons of Different Models on Dynamic Recrystallization of Plate during Asymmetrical Shear Rolling

by Tao Zhang, Lei Li, Shi-Hong Lu, Hai Gong and Yun-Xin Wu

Materials 2018, 11(1), 151; https://doi.org/10.3390/ma11010151 - 17 Jan 2018

Cited by 11 | Viewed by 4718

Abstract

Asymmetrical shear rolling with velocity asymmetry and geometry asymmetry is beneficial to enlarge deformation and refine grain size at the center of the thick plate compared to conventional symmetrical rolling. Dynamic recrystallization (DRX) plays a vital role in grain refinement during hot deformation. [...] Read more.

Asymmetrical shear rolling with velocity asymmetry and geometry asymmetry is beneficial to enlarge deformation and refine grain size at the center of the thick plate compared to conventional symmetrical rolling. Dynamic recrystallization (DRX) plays a vital role in grain refinement during hot deformation. Finite element models (FEM) coupled with microstructure evolution models and cellular automata models (CA) are established to study the microstructure evolution of plate during asymmetrical shear rolling. The results show that a larger DRX fraction and a smaller average grain size can be obtained at the lower layer of the plate. The DRX fraction at the lower part increases with the ascending speed ratio, while that at upper part decreases. With the increase of the offset distance, the DRX fraction slightly decreases for the whole thickness of the plate. The differences in the DRX fraction and average grain size between the upper and lower surfaces increase with the ascending speed ratio; however, it varies little with the change of the speed ratio. Experiments are conducted and the CA models have a higher accuracy than FEM models as the grain morphology, DRX nuclei, and grain growth are taken into consideration in CA models, which are more similar to the actual DRX process during hot deformation. Full article

(This article belongs to the Special Issue Dynamic Recrystallization and Microstructural Evolution in Alloys)

► Show Figures

Figure 1

8 pages, 826 KiB

Open AccessFeature PaperArticle

Spin Absorption Effect at Ferromagnet/Ge Schottky-Tunnel Contacts

by Michihiro Yamada, Yuichi Fujita, Shinya Yamada, Kentarou Sawano and Kohei Hamaya

Materials 2018, 11(1), 150; https://doi.org/10.3390/ma11010150 - 17 Jan 2018

Cited by 2 | Viewed by 5089

Abstract

We study the influence of the junction size in ferromagnet (FM)/semiconductor (SC) contacts on four-terminal nonlocal spin signals in SC-based lateral spin-valve (LSV) structures. When we use FM/Ge Schottky-tunnel junctions with relatively low resistance-area products, the magnitude of the nonlocal spin signal depends [...] Read more.

We study the influence of the junction size in ferromagnet (FM)/semiconductor (SC) contacts on four-terminal nonlocal spin signals in SC-based lateral spin-valve (LSV) structures. When we use FM/Ge Schottky-tunnel junctions with relatively low resistance-area products, the magnitude of the nonlocal spin signal depends clearly on the junction size, indicating the presence of the spin absorption effect at the spin-injector contact. The temperature-dependent spin signal can also be affected by the spin absorption effect. For SC spintronic applications with a low parasitic resistance, we should consider the influence of the spin absorption on the spin-transport signals in SC-based device structures. Full article

(This article belongs to the Special Issue Magnetoresistance Effects and Their Application to Spintronic Devices)

► Show Figures

Figure 1

9 pages, 4873 KiB

Open AccessArticle

Characterization of an Additive Manufactured TiAl Alloy—Steel Joint Produced by Electron Beam Welding

by Gloria Basile, Giorgio Baudana, Giulio Marchese, Massimo Lorusso, Mariangela Lombardi, Daniele Ugues, Paolo Fino and Sara Biamino

Materials 2018, 11(1), 149; https://doi.org/10.3390/ma11010149 - 17 Jan 2018

Cited by 18 | Viewed by 5237

Abstract

In this work, the characterization of the assembly of a steel shaft into a γ-TiAl part for turbocharger application, obtained using Electron Beam Welding (EBW) technology with a Ni-based filler, was carried out. The Ti-48Al-2Nb-0.7Cr-0.3Si (at %) alloy part was produced by Electron [...] Read more.

In this work, the characterization of the assembly of a steel shaft into a γ-TiAl part for turbocharger application, obtained using Electron Beam Welding (EBW) technology with a Ni-based filler, was carried out. The Ti-48Al-2Nb-0.7Cr-0.3Si (at %) alloy part was produced by Electron Beam Melting (EBM). This additive manufacturing technology allows the production of a lightweight part with complex shapes. The replacement of Nickel-based superalloys with TiAl alloys in turbocharger automotive applications will lead to an improvement of the engine performance and a substantial reduction in fuel consumption and emission. The welding process allows a promising joint to be obtained, not affecting the TiAl microstructure. Nevertheless, it causes the formation of diffusive layers between the Ni-based filler and both steel and TiAl, with the latter side being characterized by a very complex microstructure, which was fully characterized in this paper by means of Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, and nanoindentation. The diffusive interface has a thickness of about 6 µm, and it is composed of several layers. Specifically, from the TiAl alloy side, we find a layer of Ti₃Al followed by Al₃NiTi₂ and AlNi₂Ti. Subsequently Ni becomes more predominant, with a first layer characterized by abundant carbide/boride precipitation, and a second layer characterized by Si-enrichment. Then, the chemical composition of the Ni-based filler is gradually reached. Full article

(This article belongs to the Special Issue Intermetallic Alloys: Fabrication, Properties and Applications 2017)

► Show Figures

Figure 1

15 pages, 6423 KiB

Open AccessArticle

Poly(lactic acid) (PLA) Based Tear Resistant and Biodegradable Flexible Films by Blown Film Extrusion

by Norma Mallegni, Thanh Vu Phuong, Maria-Beatrice Coltelli, Patrizia Cinelli and Andrea Lazzeri

Materials 2018, 11(1), 148; https://doi.org/10.3390/ma11010148 - 17 Jan 2018

Cited by 92 | Viewed by 11609

Abstract

Poly(lactic acid) (PLA) was melt mixed in a laboratory extruder with poly(butylene adipate-co-terephthalate) (PBAT) and poly(butylene succinate) (PBS) in the presence of polypropylene glycol di glycidyl ether (EJ400) that acted as both plasticizer and compatibilizer. The process was then scaled up [...] Read more.

Poly(lactic acid) (PLA) was melt mixed in a laboratory extruder with poly(butylene adipate-co-terephthalate) (PBAT) and poly(butylene succinate) (PBS) in the presence of polypropylene glycol di glycidyl ether (EJ400) that acted as both plasticizer and compatibilizer. The process was then scaled up in a semi-industrial extruder preparing pellets having different content of a nucleating agent (LAK). All of the formulations could be processed by blowing extrusion and the obtained films showed mechanical properties dependent on the LAK content. In particular the tearing strength showed a maximum like trend in the investigated composition range. The films prepared with both kinds of blends showed a tensile strength in the range 12–24 MPa, an elongation at break in the range 150–260% and a significant crystallinity. Full article

(This article belongs to the Section Biomaterials)

► Show Figures

Graphical abstract

16 pages, 6736 KiB

Open AccessArticle

Synthesis and Characterization of WO₃/Graphene Nanocomposites for Enhanced Photocatalytic Activities by One-Step In-Situ Hydrothermal Reaction

by Xiaoxiao Hu, Peiquan Xu, Hongying Gong and Guotao Yin

Materials 2018, 11(1), 147; https://doi.org/10.3390/ma11010147 - 17 Jan 2018

Cited by 63 | Viewed by 7882

Abstract

Tungsten trioxide (WO₃) nanorods are synthesized on the surface of graphene (GR) sheets by using a one-step in-situ hydrothermal method employing sodium tungstate (Na₂WO₄·2H₂O) and graphene oxide (GO) as precursors. The resulting WO₃/GR [...] Read more.

Tungsten trioxide (WO₃) nanorods are synthesized on the surface of graphene (GR) sheets by using a one-step in-situ hydrothermal method employing sodium tungstate (Na₂WO₄·2H₂O) and graphene oxide (GO) as precursors. The resulting WO₃/GR nanocomposites are characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The results confirm that the interface between WO₃ nanorod and graphene contains chemical bonds. The enhanced optical absorption properties are measured by UV-vis diffuse reflectance spectra. The photocatalytic activity of the WO₃/GR nanocomposites under visible light is evaluated by the photodegradation of methylene blue, where the degradation rate of WO₃/GR nanocomposites is shown to be double that of pure WO₃. This is attributed to the synergistic effect of graphene and the WO₃ nanorod, which greatly enhances the photocatalytic performance of the prepared sample, reduces the recombination of the photogenerated electron-hole pairs and increases the visible light absorption efficiency. Finally, the photocatalytic mechanism of the WO₃/GR nanocomposites is presented. The synthesis of the prepared sample is convenient, direct and environmentally friendly. The study reports a highly efficient composite photocatalyst for the degradation of contaminants that can be applied to cleaning up the environment. Full article

► Show Figures

Graphical abstract

15 pages, 12895 KiB

Open AccessArticle

Selective Laser Melting Produced Ti-6Al-4V: Post-Process Heat Treatments to Achieve Superior Tensile Properties

by Gerrit M. Ter Haar and Thorsten H. Becker

Materials 2018, 11(1), 146; https://doi.org/10.3390/ma11010146 - 17 Jan 2018

Cited by 175 | Viewed by 10408

Abstract

Current post-process heat treatments applied to selective laser melting produced Ti-6Al-4V do not achieve the same microstructure and therefore superior tensile behaviour of thermomechanical processed wrought Ti-6Al-4V. Due to the growing demand for selective laser melting produced parts in industry, research and development [...] Read more.

Current post-process heat treatments applied to selective laser melting produced Ti-6Al-4V do not achieve the same microstructure and therefore superior tensile behaviour of thermomechanical processed wrought Ti-6Al-4V. Due to the growing demand for selective laser melting produced parts in industry, research and development towards improved mechanical properties is ongoing. This study is aimed at developing post-process annealing strategies to improve tensile behaviour of selective laser melting produced Ti-6Al-4V parts. Optical and electron microscopy was used to study α grain morphology as a function of annealing temperature, hold time and cooling rate. Quasi-static uniaxial tensile tests were used to measure tensile behaviour of different annealed parts. It was found that elongated α’/α grains can be fragmented into equiaxial grains through applying a high temperature annealing strategy. It is shown that bi-modal microstructures achieve a superior tensile ductility to current heat treated selective laser melting produced Ti-6Al-4V samples. Full article

► Show Figures

Graphical abstract

33 pages, 7839 KiB

Open AccessArticle

Real Time Spectroscopic Ellipsometry Analysis of First Stage CuIn_1−xGa_xSe₂ Growth: Indium-Gallium Selenide Co-Evaporation

by Puja Pradhan, Puruswottam Aryal, Dinesh Attygalle, Abdel-Rahman Ibdah, Prakash Koirala, Jian Li, Khagendra P. Bhandari, Geethika K. Liyanage, Randy J. Ellingson, Michael J. Heben, Sylvain Marsillac, Robert W. Collins and Nikolas J. Podraza

Materials 2018, 11(1), 145; https://doi.org/10.3390/ma11010145 - 16 Jan 2018

Cited by 4 | Viewed by 4923

Abstract

Real time spectroscopic ellipsometry (RTSE) has been applied for in-situ monitoring of the first stage of copper indium-gallium diselenide (CIGS) thin film deposition by the three-stage co-evaporation process used for fabrication of high efficiency thin film photovoltaic (PV) devices. The first stage entails [...] Read more.

Real time spectroscopic ellipsometry (RTSE) has been applied for in-situ monitoring of the first stage of copper indium-gallium diselenide (CIGS) thin film deposition by the three-stage co-evaporation process used for fabrication of high efficiency thin film photovoltaic (PV) devices. The first stage entails the growth of indium-gallium selenide (In_1−xGa_x)₂Se₃ (IGS) on a substrate of Mo-coated soda lime glass maintained at a temperature of 400 °C. This is a critical stage of CIGS deposition because a large fraction of the final film thickness is deposited, and as a result precise compositional control is desired in order to achieve the optimum performance of the resulting CIGS solar cell. RTSE is sensitive to monolayer level film growth processes and can provide accurate measurements of bulk and surface roughness layer thicknesses. These in turn enable accurate measurements of the bulk layer optical response in the form of the complex dielectric function ε = ε₁ − iε₂, spectra. Here, RTSE has been used to obtain the (ε₁, ε₂) spectra at the measurement temperature of 400 °C for IGS thin films of different Ga contents (x) deduced from different ranges of accumulated bulk layer thickness during the deposition process. Applying an analytical expression in common for each of the (ε₁, ε₂) spectra of these IGS films, oscillator parameters have been obtained in the best fits and these parameters in turn have been fitted with polynomials in x. From the resulting database of polynomial coefficients, the (ε₁, ε₂) spectra can be generated for any composition of IGS from the single parameter, x. The results have served as an RTSE fingerprint for IGS composition and have provided further structural information beyond simply thicknesses, for example information related to film density and grain size. The deduced IGS structural evolution and the (ε₁, ε₂) spectra have been interpreted as well in relation to observations from scanning electron microscopy, X-ray diffractometry and energy-dispersive X-ray spectroscopy profiling analyses. Overall the structural, optical and compositional analysis possible by RTSE has assisted in understanding the growth and properties of three stage CIGS absorbers for solar cells and shows future promise for enhancing cell performance through monitoring and control. Full article

(This article belongs to the Section Thin Films and Interfaces)

► Show Figures

Figure 1

17 pages, 9638 KiB

Open AccessArticle

Effects of Polypropylene Orientation on Mechanical and Heat Seal Properties of Polymer-Aluminum-Polymer Composite Films for Pouch Lithium-Ion Batteries

by Fangxinyu Zeng, Jinyao Chen, Feng Yang, Jian Kang, Ya Cao and Ming Xiang

Materials 2018, 11(1), 144; https://doi.org/10.3390/ma11010144 - 16 Jan 2018

Cited by 33 | Viewed by 8986

Abstract

In this study, polyamide-aluminum foil-polypropylene (PA-Al-PP) composite films with different orientation status of the PP layer were prepared, and their morphology, tensile, peeling and heat seal behavior were studied. The comparative study of tensile and fracture behaviors of single-layer film of PA, Al [...] Read more.

In this study, polyamide-aluminum foil-polypropylene (PA-Al-PP) composite films with different orientation status of the PP layer were prepared, and their morphology, tensile, peeling and heat seal behavior were studied. The comparative study of tensile and fracture behaviors of single-layer film of PA, Al and PP, as well as the composite films of PA-Al, PP-Al and PA-Al-PP revealed that in PA-Al-PP composite film, the PA layer with the highest tensile strength can share the tensile stress from the Al layer during stretching, while the PP layer with the lowest tensile strength can prevent further development of the small cracks on boundary of the Al layer during stretching. Moreover, the study of heat seal behavior suggested that both the orientation status and the heat seal conditions were important factors in determining the heat seal strength (HSS) and failure behavior of the sample. Four failure types were observed, and a clear correspondence between HSS and failure types was found. The results also elucidated that for the composite film, only in the cases where the tensile stress was efficiently released by each layer during HSS measurement could the composite film exhibit desired high HSS that was even higher than its tensile strength. Full article

► Show Figures

Figure 1

Journal Menu

Journal Browser

Materials, Volume 11, Issue 1 (January 2018) – 173 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI