Started in 1985 Semimonthly
ISSN 1005-0302
CN 21-1315/TG
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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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      15 May 2014, Volume 30 Issue 5 Previous Issue    Next Issue
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    Nanoarchitectured LiMn2O4/Graphene/ZnO Composites as Electrodes for Lithium Ion Batteries
    Saad Aziz1, Jianqing Zhao1, Carrington Cain, Ying Wang
    J. Mater. Sci. Technol., 2014, 30 (5): 427-433.  DOI: 10.1016/j.jmst.2014.03.007
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    LiMn2O4 nanoparticles are facilely synthesized using a sol–gel processing method. Graphene is added to LiMn2O4 electrode aiming at increasing specific capacity and improving rate capability. In order to further improve cycling stability of LiMn2O4/graphene electrode, atomic layer deposition (ALD) is used to deposit ultrathin ZnO coating composed of six ZnO ALD layers and modify the surface of either LiMn2O4/graphene electrode or individual LiMn2O4 particles to form nanoarchitectured LiMn2O4/graphene/ZnO electrodes. Both ZnO-ALD-modified LiMn2O4/graphene electrodes demonstrate enhanced cycling performance at 1C, retaining the final discharge capacity above 122 mA h g−1 after 100 electrochemical cycles, which is higher than 115 mA h g−1 of pristine LiMn2O4/graphene electrode and 109 mA h g−1 of bare LiMn2O4 electrode. The improved electrochemical performance of nanoarchitectured LiMn2O4/graphene/ZnO electrodes can be attributed to the cooperative effects from high electronic conductivity of graphene sheets to facilitate electron transportation and effective protection of ZnO ALD coating to restrict Mn dissolution and electrolyte decomposition.

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    Hydrochlorination of Acetylene Using SiC Foam Supported Structured C/Au Catalysts
    Xiaodan Yang, Chunhai Jiang, Zhenming Yang, Jinsong Zhang*
    J. Mater. Sci. Technol., 2014, 30 (5): 434-440.  DOI: 10.1016/j.jmst.2014.01.013
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    AuCl3 loaded structured catalysts were prepared on SiC foam supported with pre-coated activated carbon layers. The catalytic properties of the structured catalysts towards hydrochlorination of acetylene were tested in a fixed-bed reactor with the AuCl3 loaded on activated carbon pellets as a reference. For isopyknic catalysts, the structured catalyst with only one fifth of the Au amount as that was used on the reference catalyst exhibited even a little higher acetylene conversion and much better stability than the latter no matter what the gas hourly space velocities of acetylene were used. The results indicated that the more homogeneous distribution of AuCl3 particles and better heat transfer along the fixed-bed reactor originated from the low pressure drop and high thermal conductivity of the SiC foam supported structured catalysts might be able to account for their improved efficiency and stability. It is believed that these novel structured C/Au catalysts can be potentially applied in VCM industrialization in view of their greatly reduced cost and much prolonged life.

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    Enhanced Stability of Anisotropic Gold Nanoparticles by Poly(N-isopropylacrylamide)
    Jiayun Hu, Chase A. Brackemyer, Hongsik Byun, Jun-Hyun Kim
    J. Mater. Sci. Technol., 2014, 30 (5): 441-448.  DOI: 10.1016/j.jmst.2014.03.012
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    A simple synthetic method has been described to prepare anisotropic gold nanoparticles (AuNPs) possessing unique optical and structural properties at room temperature, and subsequently the nanoparticles have been stabilized by temperature-sensitive poly(N-isopropylacrylamide), or poly(NIPAM). Although poly(NIPAM) does not exhibit a strong binding affinity to gold, simply introducing poly(NIPAM) to these unstable anisotropic AuNPs can maintain the original structures and absorption properties for several weeks. This increased stability is presumably caused by the adsorbed polymer layer around the anisotropic AuNPs. The existence of adsorbed linear poly(NIPAM) around the AuNPs is confirmed through the reversible absorption properties of the nanoparticles upon heating and cooling. To verify the presence of weak attractive forces (e.g., van der Waals, dipole–dipole, and possible hydrogen bonding) between the polymer and the AuNPs, various concentrations of linear poly(NIPAM) are introduced during the formation of the AuNPs resulting in the systematical control of the size and roughness of the nanoparticles. In addition, the preferential attachment of pre-formed anisotropic AuNPs on cross-linked poly(NIPAM) nanoparticles indicates the presence of weak attractive forces between AuNPs and poly(NIPAM). As such, poly(NIPAM) and its derivatives can serve as a useful stabilizing and capping agent to preserve the properties of the anisotropic AuNPs.

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    New Nanocomposite Materials by Incorporation of Nanocrystalline TiO2 Particles into Polyaniline Conductive Films
    F.J. Feliciano, O.C. Monteiro
    J. Mater. Sci. Technol., 2014, 30 (5): 449-454.  DOI: 10.1016/j.jmst.2014.03.001
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    This work is focused on the combination of two building-blocks, nanocrystalline TiO2 particles and polyaniline conductive films (PAni). The preparation of new nanostructured composite materials, displaying electron- and proton-conductive properties, to be used for the fabrication of new and superior energy storage devices was envisaged. The semiconducting TiO2 nanoparticles were obtained by means of a hydrothermal route. The PAni films were prepared on glassy carbon electrodes by electrochemical polymerization, under potential dynamic conditions. After characterization by X-ray diffraction, transmission electron microscopy or scanning electron microscopy and electrochemical techniques, the nanocrystalline particles were immobilized in the polymer matrix. The incorporation of the TiO2 was achieved using two distinct approaches: during the polymer growth or by deposition over previously prepared PAni films. The results demonstrate that the PAni morphology depends on the experimental conditions used during the polymer growth. After TiO2 immobilization, the best electrochemical response was obtained for the nanocomposite structure produced through the TiO2 incorporation after the PAni film synthesis. The modified electrodes were structurally and morphologically characterized and their electro-catalytic activity towards the hydrogen evolution reaction was analyzed. A new electrochemical performance related with the oxidation of molecular hydrogen entrapped in the PAni-TiO2 matrix was observed for the modified electrode after TiO2 incorporation. This behavior can be directly associated with the synergetic combination of the TiO2 and PAni, and is dependent on the amount of the semiconductor.

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    Effects of Pressure during Preparation on the Grain Orientation of Ruddlesden–Popper Structured BaLa2Ti3O10 Ceramic
    Xizhong Wang, Lei Guo, Hongbo Guo, Guohui Ma1, Shengkai Gong
    J. Mater. Sci. Technol., 2014, 30 (5): 455-458.  DOI: 10.1016/j.jmst.2013.12.003
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    As potential thermal barrier coating (TBC) materials, Ruddlesden–Popper structured BaLn2Ti3O10 (Ln = rare earth) compounds possess excellent phase stability and desirable thermo-physical properties as well as interesting anisotropic structure. In this paper, the effects of pressure during BaLa2Ti3O10 (BLT) bulk preparation on the grain orientation were investigated. BLT grains exhibited lamellar structure, but the grain orientation depended strongly on the existence of pressure during bulk preparation. When pressure was applied, BLT grains preferentially grew along pressing direction, leading to formation of the texture parallel to pressing direction, but BLT grain orientation became relatively random when pressure was absent. However, in the small scale area, BLT grains grew preferentially along c-axis with independence on pressure during preparation. Pressure affected BLT grain orientation at the rapid growth stage according to the grain growth model of BLT.

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    Mo6+ Modified (K0.5Na0.5)NbO3 Lead Free Ceramics: Structural, Electrical and Optical Properties
    Jyoti Rani, Piyush Kumar Patel, Nidhi Adhlakha, Hemant Singh, K.L. Yadav, Satya Prakash
    J. Mater. Sci. Technol., 2014, 30 (5): 459-465.  DOI: 10.1016/j.jmst.2013.10.022
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    Lead free polycrystalline ceramics (K0.5Na0.5)Nb(1−x)MoxO3 (x = 0, 0.02, 0.04, 0.06 and 0.08) have been synthesized via solid state reaction method. The formation of single phase perovskite structure up to 6 mol% of Mo6+ has been confirmed by X-ray diffraction pattern. Impedance spectroscopy reveals that bulk resistance decreases with increasing temperature, which indicates negative temperature coefficient of resistance (NTCR) behaviour of the compounds. The diffuse reflectance spectroscopy results indicate a red shift of the band gap energy of K0.5Na0.5NbO3 (KNN, from 4.28 to 3.61 eV) with increasing Mo6+ concentration due to structural modification. The photoluminescence spectra of doped samples are composed of two emission bands at room temperature. One emission band is near band edge ultraviolet (UV) emission (∼354 nm) and other is visible emission band (∼397 nm) which may explore the possibility of these ceramics to be used in optical device applications.

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    Crystallined Hybrid Carbon Synthesized by Catalytic Carbonization of Biomass and in-situ Growth of Carbon Nanofibers
    Shuhe Liu, Shuchun Zhao, Yaochun Yao, Peng Dong, Chao Yang
    J. Mater. Sci. Technol., 2014, 30 (5): 466-472.  DOI: 10.1016/j.jmst.2013.11.004
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    Crystallined hybrid carbon was synthesized by the catalytic carbonization of biomass (Pinus kesiya sawdust) at 1100 °C and in-situ growth of carbon nanofibers (CNFs) at 750 °C from acetylene. The microstructure of the composite was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). It was found that highly crystallined carbon composed of well-aligned graphene layers with interlayer spacing of 0.34 nm can be formed by catalytic carbonization of biomass. However, the structure of the in-situ growing CNFs is less-aligned. Based on the results of the investigation, the formation mechanism of the crystallined hybrid carbon was discussed. Owning to synergistic effect of the highly crystallined carbon and the conductive network formed by CNFs, the crystallined hybrid carbon shows 32.6% lower electrical resistivity than biocarbon. When being used as anode material of lithium-ion batteries (LIBs), the crystallined hybrid carbon and the biocarbon have nearly the same first coulombic efficiencies (CEs), however, the former has a discharge capacity of 67% higher than the latter since the second cycle.

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    Effects of the Thickness Ratio of CrN vs Cr2O3 Layer on the Properties of Double-layered CrN/Cr2O3 Coatings Deposited by Arc Ion Plating
    Chang-Ming Shi, Tie-Gang Wang, Zhi-Liang Pei, Jun Gong, Chao Sun
    J. Mater. Sci. Technol., 2014, 30 (5): 473-479.  DOI: 10.1016/j.jmst.2014.01.007
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    In this study, CrN/Cr2O3 double-layered coatings with various thickness ratios of CrN vs Cr2O3 layer were prepared by arc ion plating technology. The influences of the thickness ratio of CrN vs Cr2O3 layer on the microstructural characteristics as well as the mechanical and tribological properties of the CrN/Cr2O3 double-layered coatings were investigated. The corresponding mechanisms were also discussed. The results indicated that the insertion of CrN layer between the Cr2O3 layer and substrate can effectively decrease the internal stress level of the coating. With increasing the thickness ratio of CrN vs Cr2O3 layer, the surface roughness of double-layered coatings decreased gradually, which had a certain influence on the friction coefficient. In addition, the microhardness also declined gradually, the adhesive strength almost increased linearly, whereas the wear rate declined firstly and then increased slightly. As the thickness ratio was 2:1, the double-layered coating exhibited the best wear resistance.

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    Microstructural Evolution of a Ni-base Alloy DZ468 Joint Bonded with a New Co-base Filler
    Yanhong Jing, Zhi Zheng, Enze Liu, Yi Guo
    J. Mater. Sci. Technol., 2014, 30 (5): 480-486.  DOI: 10.1016/j.jmst.2013.12.010
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    Ni-base alloy DZ468 has been joined by transient liquid phase bonding technique with a newly developed Co-based filler. The microstructures of the Co-base filler and the joint, the effects of heat treatment on microstructure and hardness of the joint have been investigated by various experimental methods. Results show that the Co-base filler consists of γ, M2B, M5B3 and M23B6 phases. Because of the interdiffusion between the base metal and the filler, γ, MC, M5B3 and M23B6 phases are formed in the bonding zone. And localized liquidation of substrate occurs in the diffusion affected zone, with MC and M3B2 precipitating in this area. During heat treatment, the volume of the intermetallic phases in the bonding zone resulting from incomplete isothermal solidification decreases obviously. On the contrary, the width of the diffusion affected zone increases at the solution stage and subsequently decreases at the aging stages.

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    Cytotoxic Effects of Biodegradation of Pure Mg and MAO-Mg on Tumor Cells of MG63 and KB
    Qiang Wang, Shi Jin, Xiao Lin, Yang Zhang, Ling Ren, Ke Yang
    J. Mater. Sci. Technol., 2014, 30 (5): 487-492.  DOI: 10.1016/j.jmst.2014.03.004
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    Magnesium (Mg) based metals possess unique features of biodegradation that can be used for different purposes. In this study, two tumor cells, MG63 and KB, were cultured directly on a pure Mg with and without MAO coating to evaluate their cytotoxic effects on the tumor cells. It was found that both MG63 cells and KB cells adhered better on the surface of the coated Mg samples than those on the pure Mg samples. However, the survivals of two kinds of tumor cells were obviously inhibited on both Mg samples with and without coating, compared with that on the pure titanium. In addition, the survival of MG63 cells was more susceptive to the Mg degradation compared with the KB cells. Thus, the application of such effect should take account of that the degradation of Mg based metal may result in different cytotoxic effect on different cells.

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    Microstructure and Mechanical Properties of Electron Beam Welded Alloy J75
    Shenghu Chen, Mingjiu Zhao, Hao Liang, Lijian Rong
    J. Mater. Sci. Technol., 2014, 30 (5): 493-498.  DOI: 10.1016/j.jmst.2013.11.011
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    Microstructure and mechanical properties of electron beam welded alloy J75 were studied under as-welded and post-weld aging treatment (PWAT) conditions. The results showed that high-quality welds were produced by electron beam welding. Under as-welded condition, a fine dendritic structure consisting of gamma dendrite matrix and Laves phase was observed in the welds. Better mechanical properties were obtained in the weld zone than that of base metal because of the fine size of the dendritic structure. After PWAT, a discontinuous distribution of γ′ particles existed in the dendritic structure. The presence of a γ′ depletion zone in the dendrite core resulted in a significant degradation of mechanical properties of the weld.

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    Mechanism of Gravity Effect on Solidification Microstructure of Eutectic Alloy
    Nannan Zhang, Xinghong Luo*, Shaobo Feng, Yuhu Ren
    J. Mater. Sci. Technol., 2014, 30 (5): 499-503.  DOI: 10.1016/j.jmst.2013.11.009
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    The influence of gravity on the solidification microstructure of Al–Al3Ni eutectic alloy was investigated by using a 50-m-long drop tube. It was found that at different growth rates the average inter-rod spacing was always larger under microgravity (μg) than those under normal gravity (1g). Moreover, with increasing growth rate, the spacing difference between 1g samples and μg samples reduced progressively. Based on the experimental results and analysis, a physical model was proposed to describe the effect of gravity on the solidification process of eutectic alloy.

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    Corrosion Behavior of X52 Anti-H2S Pipeline Steel Exposed to High H2S Concentration Solutions at 90 °C
    Meng Liu,Jianqiu Wang,Wei Ke, En-Hou Han
    J. Mater. Sci. Technol., 2014, 30 (5): 504-510.  DOI: 10.1016/j.jmst.2013.10.018
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    Initial corrosion kinetics of X52 anti-H2S pipeline steel exposed to 90 °C/1.61 MPa H2S solutions was investigated through high temperature and high pressure immersion tests. Corrosion rates were obtained based on weight loss calculation. The corrosion products were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and electron probe micro-analysis (EPMA). The initial corrosion kinetics was found to obey the exponential law. With increasing immersion time, the main corrosion products changed from iron-rich mackinawite to sulfur-rich pyrrhotite. The corrosion films had two layers: an inner fine-grained layer rich in iron and an outer columnar-grained layer rich in sulfur. The corrosion film formed through the combination of outward diffusion of Fe2+ ions and inward diffusion of HS ions. The variation of the corrosion products and compaction of the corrosion layer resulted in a decrease in the diffusion coefficient with increasing immersion time. The double-layered corrosion film formed after long time immersion acted as an effective barrier against diffusion.

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    Phase Transformation under Continuous Cooling Conditions in Medium Carbon Microalloyed Steels
    Manuel Gomez, Lucía Rancel, Esther Escudero, Sebastian F. Medina
    J. Mater. Sci. Technol., 2014, 30 (5): 511-516.  DOI: 10.1016/j.jmst.2014.03.015
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    Several 35CrMo4 and 38MnV7 steels with different additions of Ti and V were manufactured by electroslag remelting. The influence of the alloying and microalloying elements on phase transformation at different cooling rates was studied and the continuous cooling transformation diagrams were plotted. In order to optimize the heat treatment and improve the mechanical properties, the range of cooling rates leading to a fully bainitic microstructure (without ferrite, pearlite and especially without martensite) was determined. Bainite and martensite transformation start temperatures (Bs, Ms) were also established and compared with the values predicted by empirical equations. The important role of precipitates (especially V carbonitride particles) on final microstructure and mechanical properties was assessed.

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    The First-principles Study on the Occupation Behavior and the Ductility Mechanism of Zr in Ni–Ni3Al System with Lattice Misfit
    Yuxi Wu, Wanglin Zhang, Jia Guo, Jieshan Hou, Xiuyan Li, Renzhong Huang, Xiufang Ma, Qianfeng Zhang
    J. Mater. Sci. Technol., 2014, 30 (5): 517-522.  DOI: 10.1016/j.jmst.2014.03.018
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    The influence of lattice misfit on the occupation behavior and the ductility effect of Zr in Ni–Ni3Al alloys were explored. It is found in energy analysis that the preferable site of Zr between Ni sublattice and Al sublattice will change under different lattice misfit, however, the Zr prefers to segregate Ni phase rather than Ni3Al phase in all lattice misfit range, which makes it impossible for Zr to go into Ni3Al phase to occupy Al sublattice in Ni–Ni3Al system. Bond order (BO) analysis shows that the localized ductility effect of Zr differs in different region, and the comparison between Zr-free and Zr-doped BO analysis successfully explain the mechanism of the embrittlement of Ni–Ni3Al alloys and the ductility effect of Zr.

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ISSN: 1005-0302
CN: 21-1315/TG
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