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Journal of Materials Science & Technology
Current Issue
2010, Vol.26 No.6
Online: 2010-06-22

Rapid Communication
Invited Review
Materials for Sustainable Energy
Nanomaterials and Nanotechnology
Regular Papers
 
Rapid Communication
481 M.Q. Tang H.F. Zhang Z.W. Zhu H.M. Fu A.M. Wang H. Li Z.Q. Hu
TiZr-base Bulk Metallic Glass with over 50 mm in Diameter Hot!

Low-cost TiZr-base bulk metallic glasses (BMGs) (Ti36.1Zr 33.2Ni5.8Be24.9)100-xCux (x=5, 7 and 9) with a maximum size of over 50 mm in diameter were developed by optimizing the alloy composition. The idea is initiated by selecting a particular microstructure comprising primary β-Ti dendrite and amorphous phase. Afterwards, based on this composition of amorphous phase, a class of TiZr-base bulk metallic glasses was designed step by step to reach the optimum composition range. The glass transition temperature (Tg), initial crystallization temperature (Tx) and width of supercooled region (ΔT) of (Ti36.1Zr33.2Ni5.8Be24.9)91Cu9 BMG are 611, 655 and 44 K, respectively. The (Ti36.1Zr33.2Ni5.8Be24.9)91Cu9 BMG exhibits low density of 5.541 g·cm-3 and high compressive fracture strength of 1800 MPa, which promises the potential application
as structural materials.

2010 Vol. 26 (6): 481-486 [Abstract] ( 324 ) [HTML 1KB] [PDF 812KB] ( 587 )
 
Invited Review
487 X.K. Meng S.C. Tang S. Vongehr
A Review on Diverse Silver Nanostructures Hot!

This article reviews recent advances in the utilization of various water based synthesis routes towards the shape-controlled synthesis of silver nanoparticles and microstructures in a diverse range of shapes and sizes from several nanometers to micrometers. A variety of very simple one-pot methods, at times employing commercial microwave ovens, inexpensive low power ultrasound cleaners, or two-electrode electro-chemistry, can be surprisingly effective in the controlled synthesis of a wide range of nanostructured products, if only parameters are carefully chosen. Many approaches which are adopted include synthesis of Ag nanostructures with various shapes in solution, doping of Ag nanoparticles on unmodified silica and on/inside carbon spheres, kinetically controlled growth of Ag micro-particles with novel nanostructures on flat substrates, and galvanic replacement towards bimetallic Ag-Au dendrites and carbon composites. Characterizations of shape, composition and microstructure are carried out via scanning and transmission electron microscopy, various spectroscopy methods, N2 absorption measurements and suchlike. The involved growth mechanisms are investigated in order to discover new means towards better control. Size, location and shape control, including micro- and nanostructure features, allows tuning the products properties towards desired applications. We focus on the optical properties and catalytic activities, but also the stability of compounds can be an issue of interest.

2010 Vol. 26 (6): 487-522 [Abstract] ( 915 ) [HTML 1KB] [PDF 5785KB] ( 1080 )
 
Materials for Sustainable Energy
523 Han Chen Kui Cheng Zhicheng Wang Wenjian Weng Ge Shen Piyi Du Gaorong Han
Preparation of Porous NiO-Ce0.8Sm0.2O1.9 Ceramics for Anode-supported Low-temperature Solid Oxide Fuel Cells Hot!

Porous NiO-Ce0.8Sm0.2O1.9 (NiO-SDC) ceramics with homogeneous pore distribution were prepared using polystyrene (PS) spheres as pore templates. NiO-SDC powders were synthesized by a glycine-nitrate method, ultrasonically mixed with PS spheres in ethanol, dried and then pressed into green pellets. The pellets were sintered to yield porous NiO-SDC ceramics. The effects of the sintering temperature on the microstructure and mechanical strength of the ceramics were investigated. NiO-SDC ceramics sintered at 1200 and 1350°C have interconnected pore structures and high compression strength. When single cells were fabricated using porous NiO-SDC ceramics as anode-supported layers, the peak power density of the cells at 600°C was 333 and 353 mW·cm-2 for ceramics sintered at 1200 and 1350°C, respectively. The results indicated that these porous ceramic materials are promising for anode substrates for solid oxide fuel cells.

2010 Vol. 26 (6): 523-528 [Abstract] ( 373 ) [HTML 1KB] [PDF 711KB] ( 529 )
529 Hong Su Bing Zhang Lijuan Chen
Preparation and Characterization of Platinum Supported on Carbon Nanotubes with Different Tube Diameter for Cathode Catalysts of Proton Exchange Membrane Fuel Cells

Platinum supported on carbon nanotubes (CNTs) with different tube diameters <10, 10-20, 40-60 and 60-100 nm were prepared. The catalysts were characterized by  transmission electron microscopy (TEM), X-ray diffraction (XRD). The metal particle size for 40 wt pct Pt catalysts were 2-5 nm. Self-prepared Pt/CNTs catalysts and purchased Pt/XC-72 were studied by polarization curves, and it was found that in the H2/O2 fuel cell system, Pt supported on Vulcan XC-72 (Pt/XC-72) possessed higher catalytic activity than Pt/CNTs. But in H2/air system, Pt supported on CNTs with diameter 10-20 nm (Pt/CNT1020) possessed higher activity than other Pt/C catalysts.

2010 Vol. 26 (6): 529-534 [Abstract] ( 359 ) [HTML 1KB] [PDF 939KB] ( 535 )
 
Nanomaterials and Nanotechnology
535 R. Mohammadpour A. Iraji zad N. TaghaviniaM. Rahman M.M. Ahadian
Electrochemically Assisted Photocatalytic Oxidation of Methanol on TiO2 Nanotube Arrays

In this work, the influence of an externally applied bias on photocatalytic performance of crystallized TiO2/Ti nanotubular electrode that formed by anodization in fluoride-based electrolyte were investigated and compared to the behavior of multiporous TiO2 electrode. The photoelectrocatalytic oxidation behavior of methanol over the nanotubular electrode has been studied by measuring photocurrent response, potentiodynamic polarization spectroscopy and using electrochemical impedance spectroscopy (EIS). It was found that the photoelectrocatalytic oxidation and the charge transfer rate constant of reaction on TiO2/Ti nanotubular electrode can significantly be increased by applying electrochemical bias. Moreover, based on our results we have found that the nanotubular TiO2 electrodes have considerably better performance in comparison with porous samples in photoelectrocatalytic performance

2010 Vol. 26 (6): 535-541 [Abstract] ( 419 ) [HTML 1KB] [PDF 879KB] ( 594 )
542 Yunfang Li Hui Li
Structures and Electronic, Optical Properties of Hydrogen Nanowires Encapsulated in Single-walled Boron Nitride Nanotubes

The structures of H2 nanowires were studied by a geometry optimization method. As the radii of boron nitride (BN) nanotubes increase, the structures of the H2 nanowires transform from mono-chain to helical and multishell coaxial cylinders. The density of states (DOSs) and optical properties using the density functional theory (DFT) of optimized nanowires were also obtained. From the DOSs, it can be seen the H2 nanowires are conductive in nano-scale. The DOS curve of the single atomic chain is quite different from that of the corresponding chain embedded in B-N nanotubes.

2010 Vol. 26 (6): 542-546 [Abstract] ( 501 ) [HTML 1KB] [PDF 473KB] ( 719 )
547 Wei Zhang Hongxia Wang Faling Zhang Zhengnan Qian Wenhui Su
Effect of Surface Modifications on the Magnetic Properties of Ni0.5Zn0.5Fe2O4 Nanoparticles

Two different silica sources have been used for the preparation of Ni0.5Zn0.5Fe2O4 /SiO2 nanocomposites, and their effects on the particle size, crystallinity and the magnetic properties have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and physical property measurement system (PPMS). In both cases, Ni0.5Zn0.5Fe2O4 nanoparticles of 11 nm in mean particle size were well dispersed in silica matrix. The coercivity and the blocking temperature of Ni0.5Zn0.5Fe2O4  nanoparticles modified with the silicon coupling agent show little decrease, whereas the saturation magnetization increases obviously with respect to nanoparticles dispersed directly in silica matrix. It is considered that the decrease of the surface anisotropy resulting from the change in the surface coordination is responsible for the observed behavior.

2010 Vol. 26 (6): 547-551 [Abstract] ( 451 ) [HTML 1KB] [PDF 449KB] ( 402 )
 
Regular Papers
552 B. Olofinjana G.O. Egharevba M.A. Eleruja C. Jeynes A.V. Adedeji O.O. Akinwunmi B.A. Taleatu C.U. Mordi E.O.B. Ajayi
Synthesis and Some Properties of Metal Organic Chemical Vapour Deposited Molybdenum Oxysulphide Thin Films

Molybdenum oxodithiocarbamate was prepared as a single solid source precursor for molybdenum oxysulphide thin films which were deposited on sodalime glass substrates using metal organic chemical vapour deposition (MOCVD) technique at a temperature of 420°C. Rutherford backscattering spectroscopy (RBS) was used to determine the elemental composition of the film which showed that the films contained large amounts of oxygen. The large amount of oxygen was attributed to the large abundance of oxygen in the starting material. A direct optical energy gap of 3.31 eV was obtained from the analysis of the absorption spectrum. The scanning electron microscopy (SEM) micrographs of the films showed that the films were continuous and porous. An estimated average size of the grains was below 5 μm. X-ray diffraction (XRD) showed that the deposited films were crystalline in nature.

2010 Vol. 26 (6): 552-557 [Abstract] ( 416 ) [HTML 1KB] [PDF 630KB] ( 629 )
558 Bin Tang Yi Yang Youyu Fan Long Zhang
Barium Gallogermanate Glass Ceramics for Infrared Applications

The germanate glass ceramics is a potential candidate material for infrared (IR) dome and window applications. The crystallization mechanism of 20BaO-10Ga2O3-70GeO2 glass was investigated by differential thermal analysis (DTA), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Two different types of phase evolution were found in the early stage of crystallization: (1) the further growth of the microcrystal formed during the slow cooling of glass melt and (2) the glass-in-glass phase separation. The controlled crystallization was obtained by two-step heat treatment. The middle infrared (MIR)-transparent glass ceramics were obtained, with expected thermal and mechanical improvements.

2010 Vol. 26 (6): 558-563 [Abstract] ( 446 ) [HTML 1KB] [PDF 620KB] ( 467 )
564 Zhiyong Chen Jinwei Li Jie Liu Qingjiang Wang Jianrong Liu Rui Yang
Creep Behavior of Fusion Zone and Base Metal of the Electron Beam Weldments of a Near-alpha Titanium Alloy

The high temperature creep behavior of fusion zone (FZ) and base metal (BM) of the electron beam weldments of a near-alpha titanium alloy Ti-60 has been investigated. While the BM shows a fully transformed, coarse primary βgrains with large colonies consisting of aligned α lamellar, the FZ exhibits thin martensitic α' platelets in the columnarβgrains. The creep results show that the steady state creep rates of FZ follow the power-law creep, with the stress exponents obtained in the range from 5.6 (550°C) to 5.9 (600°C), and corrected activation energies of 309-352 kJ/mol; the stress exponents of BM exhibit different values when the creep testing stress and temperature alternate. The values of 2.4-3.2 are obtained when the stresses are under 220 MPa or the temperature is 550°C, also an exponent of 6.6 is achieved at stresses above 220 MPa at 600°C. The corrected activation energies of BM corresponding to the stress exponents are 123-161 kJ/mol (n=2.4-3.2) and 344 kJ/mol (n=6.6). The creep mechanisms of FZ and BM have been discussed in light of the creep microstructures, activation energies and the stress exponents. The creep mechanisms of FZ is the diffusion controlled dislocation climb, the creep of BM is controlled by 'solute drag' creep and dislocation climb when the stress and temperature are different. Transmission electron microscopy (TEM) observations
of the dislocation structures of crept specimens are presented to give some supports for the creep behavior of FZ and BM. In addition to the creep mechanism of dislocation movement, the interface sliding has been found to play an important role during creep of FZ.

2010 Vol. 26 (6): 564-571 [Abstract] ( 430 ) [HTML 1KB] [PDF 947KB] ( 382 )
572 Yunying Wang Jiangyan Meng Qing Zhao Shuhua Qi
Accelerated Ageing Tests for Evaluations of a Durability Performance of Glass-fiber Reinforcement Polyester Composites

The paper presented accelerated ageing test results of a durability study on ortho-phthalic anhydride-type unsaturated polyester resin (191#) and its glass-fiber reinforcement polyester composites (GFRPC). The samples were exposed in an artificial xenon arc lamp ageing cell or a thermo-oxidative ageing cell. Morphology and gloss of the specimens were investigated by using a microscope and a gloss-meter, respectively. The tensile strength, bending strength and inter-laminar shear strength (ILSS) of GFRPC were tested before and after exposure, and were considered to evaluate the durability performance of this material. The polyester resin was analyzed by fourier transform infrared (FT-IR) spectroscopy. The results showed that the glossiness of the specimens got worse and some cracks appeared on their surface during the course of ageing, the
tensile strength and bending strengths of the specimens first increased and then decreased. The ILSS of the composites decreased after they were aged in the xenon arc lamp cell, but increased while they were aged in the thermo-oxidative cell. The changes of these trends become more obvious during ageing in the xenon arc lamp cell, so the main influencing factor leading to the failure of this material is UV irradiation.

2010 Vol. 26 (6): 572-576 [Abstract] ( 315 ) [HTML 1KB] [PDF 489KB] ( 648 )

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