Started in 1985 Semimonthly
ISSN 1005-0302
CN 21-1315/TG
Impact factor:6.155

The journal has been awarded the excellent periodical in China, and its articles are covered by SCI, EI, CA, SA, JST, RJ, CSA, MA, EMA, AIA etc., PASCAL web. ISI web of Science,SCOPUS.

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      19 January 2016, Volume 32 Issue 1 Previous Issue    Next Issue
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    Orginal Article
    Physical Mechanism and Performance Factors of Metal Oxide Based Resistive Switching Memory: A Review
    Cong Ye, Jiaji Wu, Gang He, Jieqiong Zhang, Tengfei Deng, Pin He, Hao Wang
    J. Mater. Sci. Technol., 2016, 32 (1): 1-11.  DOI: 10.1016/j.jmst.2015.10.018
    Abstract   HTML   PDF
    This review summarizes the mechanism and performance of metal oxide based resistive switching memory. The origin of resistive switching (RS) behavior can be roughly classified into the conducting filament type and the interface type. Here, we adopt the filament type to study the metal oxide based resistive switching memory, which considers the migration of metallic cations and oxygen vacancies, as well as discuss two main mechanisms including the electrochemical metallization effect (ECM) and valence change memory effect (VCM). At the light of the influence of the electrode materials and switching layers on the RS characteristics, an overview has also been given on the performance parameters including the uniformity, endurance, the retention, and the multi-layer storage. Especially, we mentioned ITO (indium tin oxide) electrode and discussed the novel RS characteristics related with ITO. Finally, the challenges resistive random access memory (RRAM) device is facing, as well as the future development trend, are expressed.
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    Microstructure and Optical Properties of Yttrium-doped Zinc Oxide (YZO) Nanobolts Synthesized by Hydrothermal Method
    Sanjeev K. Sharma, Deuk Young Kim
    J. Mater. Sci. Technol., 2016, 32 (1): 12-16.  DOI: 10.1016/j.jmst.2015.11.001
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    In this work, yttrium-doped zinc oxide (YZO) nanopowder was synthesized via hydrothermal precipitation-method. The microstructure and optical properties of yttrium-doped zinc oxide nanopowder were characterized, which confirmed the well-crystalline wurtzite hexagonal phase of ZnO. The yttrium-doped zinc oxide nanopowder grains formed the nanobolts of ~400 nm in length and ~900 nm in width. High resolution-transmission electron microscopy (HR-TEM) of the nanobolts revealed uniform lattice fringes and no visible faults and/or distortions. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of yttrium in the zinc oxide lattice, proving the contribution of yttrium on the microstructural and optical properties of the material. A strong ultra violet (UV) emission peak of the YZO exhibited a red shift compared to pure zinc oxide, which was ascribed to the defects and the formation of a shallow energy level caused by the incorporation of yttrium.
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    Low-Temperature and Surfactant-Free Synthesis of Mesoporous TiO2 Sub-Micron Spheres for Efficient Dye-Sensitized Solar Cells
    Kaimo Deng, Liang Li
    J. Mater. Sci. Technol., 2016, 32 (1): 17-23.  DOI: 10.1016/j.jmst.2015.11.005
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    Dye-sensitized solar cells (DSSCs) are one of the most promising next-generation solar cells due to their advantages over other counterparts. The photoanode of DSSCs has a great effect on the photovoltaic performance. Traditional photoanode includes a bottom nanoparticle layer and an upper scattering layer for better light capture in longer wavelength. Mesoporous nanostructures with size comparable to the wavelength of visible light are considered to be excellent light scattering centers by providing extra places for dye loading. Developing a green synthetic method is of great importance. Herein we report a facile and surfactant-free synthesis of mesoporous rutile TiO2 submicrometer-sized spheres at temperature as low as 70 °C. DSSCs based on photoanodes with an upper scattering layer composed of as-obtained mesoporous spheres on nanoparticle dense layer demonstrate an 18.0% improvement of power conversion efficiency. This simple approach may offer an energy-efficient and environmentally friendly alternative for DSSCs fabrication.
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    Enhanced Electroactivity of Facet-Controlled Co3O4Nanocrystals for Enzymeless Biosensing
    Kuang-Hsu Wu, Xue Leng, Ian R. Gentle, Da-Wei Wang
    J. Mater. Sci. Technol., 2016, 32 (1): 24-27.  DOI: 10.1016/j.jmst.2015.11.014
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    In this work, we report enhanced electroactivity of Co3O4 nanocrystals (nanocubes, NCs and truncated nano-octahedra, TNO) on the exposed {111} facets as compared to the {001} facets in relation to the surface density and the activity of the octahedral CoIIIspecies. Transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy were employed to characterize the crystal facets and materials properties. The enhanced electroactivity of {111} crystal facets was evaluated by cyclic voltammetry and amperometric titration. Our results indicate that the {111} facets in TNO has a better electroactivity for enzymeless glucose sensing with a decent glucose sensitivity of 32.54 µA (mmol/L)-1 cm-2.
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    Improved Toughness and Thermal Expansion of Non-stoichiometry Gd2 - xZr2 + xO7 + x/2 Ceramics for Thermal Barrier Coating Application
    Lei Guo, Mingzhu Li, Yu Zhang, Fuxing Ye
    J. Mater. Sci. Technol., 2016, 32 (1): 28-33.  DOI: 10.1016/j.jmst.2015.11.022
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    Gd2Zr2O7 has been considered as a promising thermal barrier coating candidate, but its toughness and thermal expansion coefficient (TEC) need to be improved. In this study, Gd2 - xZr2 + xO7 + x/2 (x = 0, 0.1, 0.3, 0.5, 0.7) compounds were produced to improve the toughness and enlarge the TEC. Gd2Zr2O7 and Gd1.9Zr2.1O7.05 exhibited pyrochlore structure, while Gd2 - xZr2 + xO7 + x/2 (x = 0.3, 0.5, 0.7) consisted of pyrochlore and t'-ZrO2phases. With increasing ZrO2 content, the pyrochlore in the compounds had decreased lattice parameter, and its ordering degree decreased when x ≤ 0.3, then it almost kept unchanged with higher ZrO2 content. Among the Gd2 - xZr2 + xO7 + x/2 ceramics investigated, the toughness of the compounds increased with increasing ZrO2 content, while Gd1.7Zr2.3O7.15 exhibited the largest TEC. The related mechanisms were discussed in detail.
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    Flexural Mechanical Properties of Functional Gradient Hydroxyapatite Reinforced Polyetheretherketone Biocomposites
    Yusong Pan, Yan Chen, Qianqian Shen
    J. Mater. Sci. Technol., 2016, 32 (1): 34-40.  DOI: 10.1016/j.jmst.2015.11.011
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    Functional gradient hydroxyapatite reinforced polyetheretherketone is one of the most promising orthopedic implant biomaterials. In this study, functional gradient hydroxyapatite reinforced polyetheretherketone biocomposites were prepared by layer-by-layer method with the incorporation of hot press molding technology. Studies on the flexural mechanical properties of the functional gradient biocomposites revealed that the flexural stress-stain behavior of the biocomposites presented linear elastic characteristics. The fracture mechanism of the functional gradient biocomposites was predominated by brittle rupture. Furthermore, both flexural strength and break strain of the functional gradient HA/PEEK biocomposites obviously decreased with the rise of the total HA content. The effect of hydroxyapatite concentration difference between adjacent layers (HCDBAL) on the flexural strength obviously relied on the level of HCDBAL and total HA content in the functional gradient HA/PEEK biocomposites. The higher the total HA content in the functional gradient biocomposites is, the less the influence degree of HCDBAL on the flexural strength is. Moreover, total HA content and HCDBAL played synergistic influence on the flexural modulus of the functional gradient HA/PEEK biocomposites.

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    Concentration-dependent Morphology Control of Pt-coated-Ag Nanowires and Effects of Bimetallic Interfaces on Catalytic Activity
    Yongguang Wang, Xiangyu Wang, Bo Sun, Shaochun Tang, Xiangkang Meng
    J. Mater. Sci. Technol., 2016, 32 (1): 41-47.  DOI: 10.1016/j.jmst.2015.10.015
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    Silver nanowires (NWs) coated with platinum (Pt) nanoparticles were synthesized via a galvanic partial replacement of Ag NWs in an aqueous K2PtCl6 solution at room temperature. The products were characterized using a combination of electron microscopies, selected area electron diffraction, energy-dispersive X-ray mapping and X-ray diffraction. The surface morphology and Pt/Ag composition ratios are controlled by adjusting the K2PtCl6 concentration. Different concentrations result in various surface morphologies including rough nanoparticle coating, porous and relatively smooth surfaces. The formation mechanism was discussed based on the lattice constants' difference, concentration driven nucleation, consumption of Ag NWs, and stoichiometry of the replacement reaction. The effects of the bimetallic interface on the catalytic activity toward the reduction of 4-nitrophenol by sodium borohydride were studied. The activity of Ag-Pt NWs is highly enhanced over monometallic nanostructures, and optimized by a low Pt loading of 1.34 at.%, which indicates a catalytic role of the inter-metallic interface for the electron transfer.
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    Segregation Behavior and Evolution Mechanism of Iron-Rich Phases in Molten Magnesium Alloys
    Yaoxian Zhang, Wencheng Liu, Xiangfa Liu
    J. Mater. Sci. Technol., 2016, 32 (1): 48-53.  DOI: 10.1016/j.jmst.2015.10.013
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    A new method has been proposed to prepare Mg-Al-Si master alloys by utilizing scrap Al-Si-Fe alloys with higher Fe levels, which aims to segregate Fe from Al-Si-Fe alloys by Mg melt. The segregation behaviors, microstructure morphology and evolution mechanism of iron-rich phases in Mg-Al-Si alloy melts were studied, after Al-14Si-4Fe (wt%) alloys were added and dissolved completely. In the Mg-Al-Si alloys, iron has very little solubility and tends to combine with other elements to form intermetallic phases, which grow into a deposition layer due to the higher density. During the cooling and solidifying process of Mg-Al-Si melts, the needle-like Al5SiFe phase in Al-14Si-4Fe alloy evolved into blocky Al5Fe2 and Al0.7Fe3Si0.3 phases. Besides, the Fe levels of the Mg-Al-Si master alloys were reduced to 0.017 wt% from nominal content of 0.164 wt%. Based on the above results, this work carried out a semi-quantitative phase-compositions analysis for the deposition layer by relative intensity ratio (RIR) method, and evolution mechanism of the iron-rich phases had also been discussed. This study has paved a new way to regenerate the scrap Al-Si-Fe alloys, which has a great significance of promoting the recycling of aluminum resources.
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    Correlation between Porosity and Fracture Mechanism in High Pressure Die Casting of AM60B Alloy
    X. Li, S.M. Xiong, Z. Guo
    J. Mater. Sci. Technol., 2016, 32 (1): 54-61.  DOI: 10.1016/j.jmst.2015.10.002
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    X-ray tomography was used to characterize the porosity in high pressure die casting of AM60B alloy. In situ tensile deformation was performed to observe the change of porosities and their influences on crack initiation, propagation and subsequent fracture of specimen. Results showed that four types of porosities, including gas-shrinkage pore, gas pore, net-shrinkage and island-shrinkage, could be identified according to the formation mechanism and morphology characterization. During tensile deformation, it was shown that the gas-shrinkage pore and net-shrinkage, rather than gas pore or island-shrinkage, were the main sources for crack initiation. In addition, the crack propagated by interconnecting the porosities at the cross section with minimum efficient force bearing area. At these locations where externally solidified crystals (ESCs) were present, the crack would propagate along the ESC boundaries in an inter-granular mode, while at these locations without ESCs, the crack would propagate roughly along the direction perpendicular to the tensile stress in a combination of trans-granular and inter-granular modes.
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    Effect of Sodium Metasilicate on Structural, Optical, Dielectric and Mechanical Properties of ADP Crystal
    Mohd Anis, M.D. Shirsat, S.S. Hussaini, B. Joshi, G.G. Muley
    J. Mater. Sci. Technol., 2016, 32 (1): 62-67.  DOI: 10.1016/j.jmst.2015.09.010
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    For the first time, sodium metasilicate (SMS) doped ammonium dihydrogen phosphate (ADP) crystal was grown by slow evaporation solution technique. The unit cell parameters of grown crystal were determined by means of single crystal X-ray diffraction technique. The qualitative analysis of SMS doped ADP crystal was carried out using energy dispersive X-ray and Fourier transform infrared analysis. The increase in optical transparency of doped ADP crystal was ascertained in the range of 200-900 nm using the UV-visible spectral analysis. The vital optical constants were evaluated using the transmittance data to explore various optical device applications of crystal. The assertive influence of SMS on mechanical and dielectric behavior of ADP crystal was investigated by means of Vickers microhardness analysis and dielectric studies, respectively. The enhancement in second harmonic generation (SHG) efficiency of SMS doped ADP crystal with reference to potassium dihydrogen phosphate (KDP) and ADP was confirmed from Kurtz-Perry SHG test. The Kerr lensing nonlinearity in SMS doped ADP crystal was identified by means of Z-scan analysis and the third order nonlinear optical susceptibility (χ3) was found to be 6.19 × 10-5 esu, which vitalizes its application for laser stabilization systems.
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    Study on Dendritic Growth in Pressurized Solidification of Mg-Al Alloy Using Phase Field Simulation
    Haowei Pan, Zhiqiang Han, Baicheng Liu
    J. Mater. Sci. Technol., 2016, 32 (1): 68-75.  DOI: 10.1016/j.jmst.2015.09.005
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    A multi-grain phase field model coupled with thermodynamic calculation was adopted to describe the dendritic growth in pressurized solidification of Mg-Al alloy during squeeze casting, in which the effects of the pressure on the Gibbs free energy and chemical potential of solid and liquid phases, the solute diffusion coefficient, and the solute partition coefficient were considered. The individual effect of solute diffusion coefficient, and the Gibbs free energy on the dendritic growth was studied. With the comparison of the dendritic growth under atmospheric and elevated pressures, the effect of pressure on the microstructure evolution was discussed. The results showed that the grains are refined, the dendritic growth rate tends to increase and the secondary dendrite arms are more developed as the pressure is increased from 0.1 to 100 MPa, which showed a good agreement with the experimental results of direct squeeze casting of Mg-Al alloy. As the pressure increases, the largest dendritic growth rate can be obtained under the pressure between 200 and 250 MPa, while the growth rate decreases with a further increase of pressure.
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    Pinless Friction Stir Spot Welding of Mg?3Al?1Zn Alloy with Zn Interlayer
    R.Z. Xu, D.R. Ni, Q. Yang, C.Z. Liu, Z.Y. Ma
    J. Mater. Sci. Technol., 2016, 32 (1): 76-88.  DOI: 10.1016/j.jmst.2015.08.012
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    With the addition of a thin Zn interlayer, 2.4 mm thick Mg?3Al?1Zn alloy sheets were friction stir spot welded (FSSW) using a pinless tool with flat, convex and concave shoulder shapes. The results showed that an alloying reaction took place between the Mg substrate and Zn interlayer during FSSW, forming a discontinuous intermetallics layer composed of dispersive (α-Mg + MgZn) eutectic structure underneath the shoulder and a Mg?Zn intermetallics bonding zone at the outside of the joints. This alloying reaction increased the bonded area and eliminated the hook defects, thereby producing sound FSSW joints with a shallow keyhole without hook defects. The increase of plunge depth was beneficial to the Mg?Zn diffusion, thereby increasing the tensile-shear load of the joints. However, excessive plunge depths resulted in a decrease of the effective sheet thickness, reducing the strength of the joints. At a small plunge depth, the convex and concave shoulders were more beneficial to the interface reaction than the flat shoulder. The maximum joint load of 6.6 kN was achieved by using the concave shoulder at a plunge depth of 1.0 mm. A post-welding heat treatment promoted the dissolution of the discontinuous reaction layer in the joints; however, it led to the occurrence of void defects, influencing the bonding strength.
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    Microelectrode Array-evaluation of Neurotoxic Effects of Magnesium as an Implantable Biomaterial
    Ting Huang, Zhonghai Wang, Lina Wei, Mark Kindy, Yufeng Zheng, Tingfei Xi, Bruce Z. Gao
    J. Mater. Sci. Technol., 2016, 32 (1): 89-96.  DOI: 10.1016/j.jmst.2015.08.009
    Abstract   HTML   PDF
    Magnesium (Mg)-based biomaterials have shown great potential in clinical applications. However, the cytotoxic effects of excessive Mg2+ and the corrosion products from Mg-based biomaterials, particularly their effects on neurons, have been little studied. Although viability tests are most commonly used, a functional evaluation is critically needed. Here, both methyl thiazolyl tetrazolium (MTT) and lactate dehydrogenase (LDH) assays were used to test the effect of Mg2+ and Mg-extract solution on neuronal viability. Microelectrode arrays (MEAs), which provide long-term, real-time recording of extracellular electrophysiological signals of in vitro neuronal networks, were used to test for toxic effects. The minimum effective concentrations (ECmin) of Mg2+ from the MTT and LDH assays were 3 mmol/L and 100 mmol/L, respectively, while the ECmin obtained from the MEA assay was 0.1 mmol/L. MEA data revealed significant loss of neuronal network activity when the culture was exposed to 25% Mg-extract solution, a concentration that did not affect neuronal viability. For evaluating the biocompatibility of Mg-based biomaterials with neurons, MEA electrophysiological testing is a more precise method than basic cell-viability testing.
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ISSN: 1005-0302
CN: 21-1315/TG
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