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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      30 May 2013, Volume 29 Issue 5 Previous Issue    Next Issue
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    ZnO Nanoparticles as Ethanol Gas Sensors and the Effective Parameters on Their Performance
    Asieh Sadat Kazemi, Reza Afzalzadeh, Mohamadreza Abadyan
    J. Mater. Sci. Technol., 2013, 29 (5): 393-400.  DOI: 10.1016/j.jmst.2013.03.009
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    ZnO nanoparticles are synthesized and applied as ethanol gas sensors. In some cases, the sensitivity and response time of these particles are shown to be higher than that has been reported in the literature. It has been investigated that the most possible reason for this higher gas sensing performance can be attributed to the quantity of the activity coefficient of its initial components. However, other effects such as pH and thermal decomposition are of importance as well. Specific ion interaction (SIT) model is applied to derive the mean activity coefficient values of the additives used in synthesis of ZnO nanoparticles.

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    Thin Film Assembly of Gold Nanoparticles for Vapor Sensing via Droplet Interfacial Reaction
    Kun Luo, Tao Huang, Yujia Luo, Haiming Wang, Chao Sang, Xiaogang Li
    J. Mater. Sci. Technol., 2013, 29 (5): 401-405.  DOI: 10.1016/j.jmst.2013.03.021
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    A facile approach to prepare a thin film vapor sensor is demonstrated through droplet interfacial reaction on an IDA microelectrode. Scanning electron microscopy, atomic force microscopy and transmission electron microscopy analyses show that the film of the vapor sensor is composed of self-assembled gold nanocrystals in an average diameter of about 4.3 nm. The as-prepared sensor was examined by potential step method and impedance measurement, which exhibited significant ΔR/Ri responses and excellent cycle performance to the volatile organic compound (VOC) vapors of acetone, methanol, styrene, benzene, toluene and ethanol. The selectivity to the VOCs with benzene ring or organic solvents suggests that the sensor is probably in line with the swelling and dielectric sensing mechanisms.

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    Quantitative Analysis of Graphene Sheet Content in Wood Char Powders during Catalytic Pyrolysis
    Yan-Jia Liou, Wu-Jang Huang
    J. Mater. Sci. Technol., 2013, 29 (5): 406-410.  DOI: 10.1016/j.jmst.2013.03.008
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    The quantitative characterization of the graphene sheet content in carbon-containing materials is arguable and has not yet been developed. The authors report on a feasible method to characterize graphene sheet content quantitatively in pyrolized carbon materials using an X-ray diffraction (XRD) spectrometer. A direct carbonation at 300 °C followed by catalytic pyrolysis (heat-treatment temperature was set at 700–1400 °C) under a vacuum condition was used for turning wood waste into pyrolized wood char powders. The graphene content in the samples was calculated through an analysis of full width at half maximum (FWHM) of the carbon (100) crystal plane at around 42°–43° in XRD. Results showed that the FWHM and the calculated graphene sheet content of pyrolized wood char powders depended on the heat-treatment temperature, and the FWHM of wood char powder with well-developed graphene sheets (100%) was determined to be 5.0. In addition, the trend to 100% graphene sheet-contained pyrolized carbon powder was obtained at a heat-treatment temperature of 2700 °C. The resistivity of the wood char powder with 100% graphene sheets was predicted to be 0.01 Ω cm, close to our experimental data of 0.012 and 0.006 Ω cm for commercial graphite and graphene products, respectively.

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    Comparative Analysis of Ti, Ni, and Au Electrodes on Characteristics of TiO2 Nanofibers for Humidity Sensor Application
    S.S. Batool, Z. Imran, M. Israr Qadir, M. Usman, H. Jamil, M.A. Rafiq, M.M. Hassan,M. Willander
    J. Mater. Sci. Technol., 2013, 29 (5): 411-414.  DOI: 10.1016/j.jmst.2013.02.017
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    The effect of metal (Ti, Ni, and Au) electrodes on humidity sensing properties of electrospun TiO2 nanofibers was investigated in this work. The devices were fabricated by evaporating metal contacts on SiO2 layer thermally grown on silicon substrate. The separation between the electrodes was 90 μm for all sensors. The sensors were tested from 40% to 90% relative humidity (RH) by AC electrical characterization at room temperature. When sensors are switched between 40% and 90% RH, the corresponding response and recovery time are 3 s and 5 s for Ti-electrode sensor, 4 s and 7 s for Ni-electrode sensor, and 7 s and 13 s for Au-electrode sensor. The hysteresis was 3%, 5% and 15% for Ti-, Ni-, and Au-electrode sensor, respectively. The sensitivity of Ti, Ni, and Au-electrode sensors are 7.53 MΩ/%RH, 5.29 MΩ/%RH and 4.01 MΩ/%RH respectively at 100 Hz. Therefore Ti-electrode sensor is found to have linear response, fast response and recovery time and higher sensitivity as compared with those of Ni- and Au-electrode sensors. Comparison of humidity sensing properties of sensors with different electrode material may propose a compelling route for designing and optimizing humidity sensors.

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    Submicrometer-scale ZnO Composite Aggregate Arrays Photoanodes for Dye-sensitized Solar Cells
    Wei Jia, Suihu Dang, Hairui Liu, Zhuxia Zhang, Tianbao Li, Xuguang Liu, Bingshe Xu
    J. Mater. Sci. Technol., 2013, 29 (5): 415-418.  DOI: 10.1016/j.jmst.2013.02.004
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    Submicrometer-scale ZnO composite aggregate arrays of nanorods and nanoparticles were prepared by simple wet-chemical route and studied as dye-sensitized solar cells (DSSCs) photoanodes. The ZnO composite aggregate arrays significantly improved the efficiency of DSSCs due to their relatively high surface area, fast electron transport, and enhanced light-scattering capability. A short current density (Jsc) of 11.7 mA/cm2 and an overall solar-to-electric energy conversion efficiency (η) of 3.17% were achieved for the ZnO composite aggregate DSSCs, which were much higher than those obtained for the monodisperse aggregate DSSCs (Jsc = 6.9 mA/cm2, η = 1.51%) and ZnO nanorod array DSSCs (Jsc = 4.2 mA/cm2, η = 0.61%).

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    Structural and Physical Property Analysis of ZnO-SnO2-In2O3-Ga2O3 Quaternary Transparent Conducting Oxide System
    P. Jayaram, T.P. Jaya, Smagul Zh. Karazhanov, P.P. Pradyumnan
    J. Mater. Sci. Technol., 2013, 29 (5): 419-422.  DOI: 10.1016/j.jmst.2013.02.011
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    The increasing demand in the diverse device applications of transparent conducting oxides (TCOs) requires synthesis of new TCOs of n- or p-type conductivity. This article is about materials engineering of ZnO–SnO2–In2O3–Ga2O3 to synthesize powders of the quaternary compound Zn2xSn1xInxGaxO4δ in the stoichiometry of x = 0.2, 0.3, and 0.4 by solid state reaction at 1275 °C. Lattice parameters were determined by X-ray diffraction (XRD) technique and solubility of In3+ and Ga3+ in spinel Zn2SnO4 was found at 1275 °C. The solubility limit of In3+ and Ga3+ in Zn2SnO4 is found at below x = 0.4. The optical transmittance approximated by the UV–Vis reflectance spectra showed excellent characteristics while optical band gap was consistent across 3.2 eV with slight decrease along increasing x value. Carrier mobility of the species was considerably higher than the older versions of zinc stannate spinel co-substitutions whereas the carrier concentrations were moderate.

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    Application of the Extrusion to Increase the Binding between the Ceramic Particles and the Metal Matrix: Enhancement of Mechanical and Tribological Properties
    Ali Mazahery, Mohsen Ostad Shabani
    J. Mater. Sci. Technol., 2013, 29 (5): 423-428.  DOI: 10.1016/j.jmst.2013.03.016
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    Aluminum alloyed with magnesium and silicon has been used as the matrix material owing to its excellent mechanical properties coupled with good formability and its wide applications in industrial sector. An extrusion process was developed to consolidate Al 6061–SiCp composites from mixed powders. The results show that the composites were fully densified, with no sign of pores or oxide layers observable in the optical microscope. The SiC particles were distributed uniformly in the matrix. As compared with 6061 alloys, the composites demonstrated a smaller elongation, but exhibited a higher Young's modulus and a larger work hardening capacity. These composites possessed much higher elongation at the same strength level. The present study also addressed the dry wear behavior of the composites at different sliding speeds and applied loads. Values of the friction coefficient of the matrix alloy and composite materials were in expected range for light metals in dry sliding conditions. All of these improvements were attributed to the merits, including full densification of the bulk, uniform dispersion of the SiC particles in the matrix, and strong binding between the SiC particles and the matrix resulting from the extrusion.

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    Effect of Microstructure of Composite Powders on Microstructure and Properties of Microwave Sintered Alumina Matrix Ceramics
    Hanmin Bian, Yong Yang, You Wang, Wei Tian, Haifu Jiang, Zhijuan Hu, Weimin Yu
    J. Mater. Sci. Technol., 2013, 29 (5): 429-433.  DOI: 10.1016/j.jmst.2013.03.024
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    Two kinds of different structured alumina–titania composite powders were used to prepare alumina matrix ceramics by microwave sintering. One was powder mixture of alumina and titania at a micron–submicron level, in which fused-and-crushed alumina particles (micrometers) was clad with submicron-sized titania. The other was powder mixture of alumina and titania at nanometer–nanometer level, in which nano-sized alumina and nano-sized titania particles were homogeneously mixed by ball-milling and spray dried to prepare spherical alumina–titania composite powders. The effect of the microstructure of composite powders on microstructure and properties of microwave sintered alumina matrix ceramics were investigated. Nano-sized composite (NC) powder showed enhanced sintering behavior compared with micro-sized composite (MC) powders. The as-prepared NC ceramic had much denser, finer and more homogenous microstructure than MC ceramic. The mechanical properties of NC ceramic were significantly higher than that of MC ceramic, e.g. the flexural strength, Vickers hardness and fracture toughness of NC ceramic were 85.3%, 130.3% and 25.7% higher than that of MC ceramic, respectively. The improved mechanical properties of NC ceramic compared with that of MC ceramic were attributed to the enhanced densification and the finer and more homogeneous microstructure through the use of the nanostructured composite powders.

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    Preparation, Characterization and Hot Storage Stability of Asphalt Modified by Waste Polyethylene Packaging
    Changqing Fang, Ying Zhang, Qian Yu, Xing Zhou, Dagang Guo, Ruien Yu, Min Zhang
    J. Mater. Sci. Technol., 2013, 29 (5): 434-438.  DOI: 10.1016/j.jmst.2013.02.016
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    Waste polyethylene packaging (WPE) was used to modify asphalt, and hot storage stability of the modified asphalt was studied in this paper. The morphological change and component loss of WPE modified asphalt were characterized by fluorescence microscopy, Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetry (TG) and isolation testing. In addition, the mechanism of the hot storage stability of WPE modified asphalt was discussed. The results showed that the modification of asphalt with WPE was a physical process. It was found that the filament or partly network-like structure formed in the modified asphalt system was beneficial to improving the hot storage stability. Moreover, the addition of WPE resulted in a decrease in both the light components volatilization and the macromolecules decomposition of asphalt. It was demonstrated that when the content of WPE in matrix asphalt was less than 10 wt%, the service performances of modified asphalt could be better.

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    Effect of Pressure on Microstructure and Mechanical Properties of AM60B Alloy Used for Motorcycle Wheels Formed by Double Control Forming
    Jufu Jiang, Yuansheng Cheng, Zhiming Du, Jun Liu, Yuanfa Li, Shoujing Luo
    J. Mater. Sci. Technol., 2013, 29 (5): 439-445.  DOI: 10.1016/j.jmst.2013.02.009
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    A set of novel forming die combining the advantages of dies casting and forging was designed, by which double control forming idea was firstly proposed. The motorcycle wheel made of AM60B alloy was used as the typical component to demonstrate advantages of the double control forming. The effect of pressure on the mechanical properties and microstructure of the parts formed by double control forming was investigated. The results showed that high mechanical properties and complex shape were achieved in the parts formed by double control forming. Compared to die casting, the mechanical properties of the formed part significantly increased and the microstructure changed from the coarse dendrites to fine equiaxed grains. The shrinkage voids and microcracks in the formed parts were obviously reduced or even completely eliminated with the increase of pressure. When a pressure of 4000 kN was applied, the optimal mechanical properties such as ultimate tensile strength of 265.6 MPa and elongation of 21% were achieved and the microstructure was characterized by fine and uniform equiaxed grains due to the large undercooling degree caused by the high pressure.

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    Continuous Cooling Bainite Transformation Characteristics of a Low Carbon Microalloyed Steel under the Simulated Welding Thermal Cycle Process
    Xiangwei Kong, Chunlin Qiu
    J. Mater. Sci. Technol., 2013, 29 (5): 446-450.  DOI: 10.1016/j.jmst.2013.03.022
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    Continuous cooling transformation of a low carbon microalloyed steel was investigated after it was subjected to the simulation welding thermal cycle process and the interrupted cooling test. Microstructure observation was performed by optical microscopy and transmission electron microscopy. On the basis of the dilatometric data and microstructure observation, the continuous cooling transformation (CCT) diagram was determined, which showed that the main microstructure changes from a mixture of lath martensite and bainitic ferrite to full granular bainite with the increase in the cooling time t8/5 from 10 to 600 s, accompanied with a decrease in the microhardness. The interrupted cooling test confirmed that the bainitic ferrite can form attached to grain boundaries at the beginning of transformation even if the final microstructure contains a mixture of granular bainite and bainitic ferrite.

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    Deformation Temperature Dependence of Mechanical Properties and Microstructures for a Novel Quenching-Partitioning-Tempering Steel
    Ying Wang, Zhenghong Guo, Nailu Chen, Yonghua Rong
    J. Mater. Sci. Technol., 2013, 29 (5): 451-457.  DOI: 10.1016/j.jmst.2013.01.003
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    The present investigation on a designed high strength Fe–0.25C–1.48Mn–1.20Si–1.51Ni–0.05Nb (wt%) steel treated by a novel quenching–partitioning–tempering (Q–P–T) process was focused on deformation temperature dependence of mechanical properties and microstructures. The results indicate that the Q–P–T steel deformed at various deformation temperatures from −70 to 300 °C exhibits superior mechanical properties due to excellent thermal stability of retained austenite. The microstructural characterization by transmission electron microscopy (TEM) reveals that the high strength of the Q–P–T steel results from dislocation-type martensite laths and fcc NbC carbides or/and hcp ?-carbides precipitated dispersively in martensite matrix, while excellent ductility is attributed to the significant transformation induced plasticity (TRIP) effect produced by considerable amount of retained austenite. The relationship between mechanical properties and microstructures at different deformation temperatures was clarified.

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    Effects of Filler Metal Composition on Inclusions and Inclusion Defects for ER NiCrFe-7 Weldments
    Wenlin Mo, Shanping Lu, Dianzhong Li, Yiyi Li
    J. Mater. Sci. Technol., 2013, 29 (5): 458-466.  DOI: 10.1016/j.jmst.2013.03.015
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    The effects of filler metal (FM) composition on inclusions and inclusion defects for ER NiCrFe-7 weldments have been investigated and analyzed. Results show that as Al, Ti content in FM increases from 0.14 wt% Al, 0.30 wt% Ti to 0.42 wt% Al, 0.92 wt% Ti, the Al, Ti reduction will increase during welding. Inclusion defects (point-like defects named by welding workers) are prone to form in the high Al, Ti content weldments. Inclusion defects with Mg, Ca, Al, and Ti as major metallic elements have been found on the surface and interior of the weldments, as Al, Ti content in FM is over 0.29 wt% Al, 0.62 wt% Ti. Less Ti content in FM cannot prevent ductility-dip-cracking (DDC) through producing enough intragranular precipitates and lessening intergranular M23C6 precipitates. Nb can be used to replace Ti to reduce the sensitivity of the DDC in the NiCrFe-7 alloy weldments.

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    In-situ Observation of Point Defect and Precipitate Evolvement of CLAM Steel under Electron Irradiation
    Yong Xin, Tongda Ma, Xin Ju, Jie Qiu
    J. Mater. Sci. Technol., 2013, 29 (5): 467-470.  DOI: 10.1016/j.jmst.2013.02.015
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    The point defect and precipitate evolution of China low activation martensitic steel (CLAM) under electron beam irradiation were characterized by high voltage electron microscopy. The process was recorded in-situ on electron-sensitive films. The irradiation dose rate was 1.78 × 10−3 dpa/s and the highest dose was 2.12 dpa/s. Irradiation introduced dislocation loops into the sub-grain, which increased density when the irradiation dose was increased from 0.53 dpa to 1.59 dpa at 723 K. The precipitate, found to be an M6C type, was irradiated at 773 K at the [011] plane direction. The precipitate morphology and structure were unchanged when the irradiation dose was increased to 2.12 dpa. Compared with the irradiation at 723 K in the sub-grain, no other defects were generated at the nearby grain boundary at 773 K.

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    Shear Deformation Behaviors of Sn3.5Ag Lead-free Solder Samples
    Jing Han, Hongtao Chen, Mingyu Li, Chunqing Wang
    J. Mater. Sci. Technol., 2013, 29 (5): 471-479.  DOI: 10.1016/j.jmst.2013.01.012
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    In this study, shear tests have been performed on the as-reflowed Sn3.5Ag solder bumps and joints to investigate the deformation behavior of Sn3.5Ag lead-free solder samples. Scanning electron microscopy (SEM) was employed to characterize the microstructures of the samples and orientation imaging microscopy (OIM) with electron backscattered diffraction (EBSD) in SEM was used to obtain crystallographic orientation of grains to provide a detailed characterization of the deformation behavior in Sn3.5Ag solder samples after shear tests. The deformation behavior in solder samples under shear stress was discussed. The experimental results suggest that the dynamic recrystallization could occur under shear stress at room temperature and recrystallized grains should evolve from subgrains by rotation. Compared with that of non-recrystallized and as-reflowed microstructures, the microhardness of the recrystallized microstructure decreased after shear tests.

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    Microstructural Evolution and Mechanical Properties of Inconel 625 Alloy during Pulsed Plasma Arc Deposition Process
    Fujia Xu, Yaohui Lv, Yuxin Liu, Fengyuan Shu, Peng He, Binshi Xu
    J. Mater. Sci. Technol., 2013, 29 (5): 480-488.  DOI: 10.1016/j.jmst.2013.02.010
    Abstract   HTML   PDF

    Pulsed plasma arc deposition (PPAD), which combines pulsed plasma cladding with rapid prototyping, is a promising technology for manufacturing near net shape components due to its superiority in cost and convenience of processing. In the present research, PPAD was successfully used to fabricate the Ni-based superalloy Inconel 625 components. The microstructures and mechanical properties of deposits were investigated by scanning electron microscopy (SEM), optical microscopy (OM), transmission electron microscopy (TEM) with energy dispersive spectrometer (EDS), microhardness and tensile testers. It was found that the as-deposited structure exhibited homogenous columnar dendrite structure, which grew epitaxially along the deposition direction. Moreover, some intermetallic phases such as Laves phase, minor MC (NbC, TiC) carbides and needle-like δ-Ni3Nb were observed in γ-Ni matrix. Precipitation mechanism and distribution characteristics of these intermetallic phases in the as-deposited 625 alloy sample were analyzed. In order to evaluate the mechanical properties of the deposits, microhardness was measured at various location (including transverse plane and longitudinal plane). The results revealed hardness was in the range of 260–285 HV0.2. In particular, microhardness at the interface region between two adjacent deposited layers was slightly higher than that at other regions due to highly refined structure and the disperse distribution of Laves particles. Finally, the influence of precipitation phases and fabrication strategies on the tensile properties of the as-deposited samples was investigated. The failure modes of the tensile specimens were analyzed with fractography.

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