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ISSN 1005-0302
CN 21-1315/TG
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      28 September 2008, Volume 24 Issue 05 Previous Issue    Next Issue
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    Research Articles
    Doped-TiO2 Photocatalysts and Synthesis Methods to Prepare TiO2 Films
    Ying CUI, Hao DU, Lishi WEN
    J. Mater. Sci. Technol., 2008, 24 (05): 675-689. 
    Abstract   HTML   PDF (6912KB)
    TiO2 is a promising photocatalyst. However, the low photocatalytic efficiency calls for the modification of TiO2. Metal- and nonmetal-doping of TiO2 have been proved to be effective ways to enhance photocatalytic properties. This review provides a deep insight into the understanding of the metal- and nonmetal-doped TiO2 photocatalysts. This article begins with the introduction of the crystal structures of TiO2 and applications of TiO2 materials. We then reviewed the doped-TiO2 system in two categories: (1) metal-doped TiO2 photocatalysts system, and (2) nonmetal-doped TiO2 photocatalysts system. Both experimental results and theoretical analyses are elaborated in this section. In the following part, for the advantages of TiO2 thin films over particles, various preparation methods to obtain TiO2 thin films are briefly discussed. Finally, this review ends with a concise conclusion and outlook of new trends in the development of TiO2-based photocatalysts.
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    Effect of Ar on Polycrystalline Si Films Deposited by ECR-PECVD using SiH4
    Hua CHENG, Aimin WU, Nanlin SHI, Lishi WEN
    J. Mater. Sci. Technol., 2008, 24 (05): 690-692. 
    Abstract   HTML   PDF (1649KB)
    In this paper, polycrystalline silicon films were deposited by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) using SiH4/Ar and SiH4/H2 gaseous mixture. Effects of argon flow rate on the deposition efficiency and the film property were investigated by comparing with H2. The results indicated that the deposition rate of using Ar as discharge gas was 1.5–2 times higher than that of using H2, while the preferred orientations and the grain sizes of the films were analogous. Film crystallinity increased with the increase of Ar flow rate. Optimized flow ratio of SiH4 to Ar was obtained as F(SiH4): F(Ar)=10:70 for the highest deposition rate.
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    Morphologies and Superhydrophobicity of Hybrid Film Surfaces Based on Silica and Fluoropolymer
    Ailan QU, Xiufang WEN, Pihui PI, Jiang CHENG, Zhuoru YANG
    J. Mater. Sci. Technol., 2008, 24 (05): 693-699. 
    Abstract   HTML   PDF (3470KB)
    Fluoropolymer and different kinds of silica particles were used for controlling surface chemistry and morphology, respectively. A superhydrophobic surface originated from strawberry-like or quincunx-shaped composite silica particles was obtained. The dual size particles are obtained by utilizing the graft of different modified silica particles with epoxy functional group and amine functional group. This makes the surface of film form a composite interface to have irregular binary structure which plays an essential role in trapping air between the substrate surface and the liquid droplets to be necessary for high contact angle and low contact angle hysteresis. The maximum contact angle for water on the hybrid film is about 174±2° and the contact angle hysteresis is less than 2°. The surface morphologies, roughness and the wettability on the surface of films containing different structural silica particles were compared. It was shown that the hierarchical irregularly structure with a low roughness factor and high air-trapped ratio is indispensable for superhydrophobic surface. Although this structural surfaces based on composite silica particles play a vital role in governing the surface wettability, it is necessary to combine with a low surface energy to make the surface superhydrophobic.
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    Biological Properties of Chitosan Films with Different Degree of Deacetylation
    Jing CHANG, Wanshun LIU, Baoqin HAN, Bing LIU
    J. Mater. Sci. Technol., 2008, 24 (05): 700-708. 
    Abstract   HTML   PDF (6912KB)
    Chitin and chitosan films were prepared by solution casting method. Chitosan specimens used in this study were deacetylated by 56.4%, 69.2%, 85.5% and 96.3%. Their water content, protein adhesion ability, cyto-compatibility, cell adhesion ability, in vitro and vivo degradability and biocompatibility were evaluated. Results indicated that with the degree of deacetylation (DD) between 50% and 70%, the chitosan showed higher water content. The higher the DD, the stronger protein adhesion ability the chitosan had. All the films have good cytocompatibility and the films with higher DD have better cell adhesion ability. Chitin films degraded more rapidly than others, which disappeared in 2 to 4 weeks after they were implanted in subcutaneous tissue and musculature. Their inflammatory reaction became weaker as the films degraded. As the DD got higher, the films degraded slower. The films of DD 85.5% and DD 96.3% even didn0t disappeared in 12 weeks after they were implanted. Their inflammatory reaction was mild at the beginning of degradation, and became severe in 4 to 8 weeks, then weaken at last. This basic result can be very helpful for tissue engineering.
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    Lattice Effect on Magnetic and Electrical Properties of Ln2/3Pb1/3MnO3 (Ln=La, Pr, Nd) Films
    Li'an HAN, Huaping YANG, Yongjun HE
    J. Mater. Sci. Technol., 2008, 24 (05): 709-711. 
    Abstract   HTML   PDF (189KB)
    Lattice effect on magnetic and electrical transport properties of Ln2/3Pb1/3MnO3 (Ln=La, Pr, Nd) films prepared by RF magnetron sputtering technique were investigated. With the decrease of the average ions radius , the structure of Ln2/3Pb1/3MnO3 (Ln=La, Pr, Nd) targets transit from the rhombohedral phase to the orthorhombic phase, and the Curie temperature reduces rapidly with the decrease of . The electrical properties show that films are the metallic state which can be fitted to the formula: ρ(T)= ρ0+ρ1T2+ρ2T4.5 at low temperatures. The temperature range of the ferromagnetic metallic state becomes narrow with the decrease of . The phenomenon can be explained by the lattice effect.
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    Effect of Bath pH on the Squareness of Electroless CoNiWP Magnetic Films
    Haibin CHENG, Shuai XU, Wenyu ZHAO, Suling ZHAO, Pengcheng ZHAI, Zhigang SUN, Qingjie ZHANG
    J. Mater. Sci. Technol., 2008, 24 (05): 712-714. 
    Abstract   HTML   PDF (827KB)
    Electroless CoNiWP magnetic films were prepared by varying the bath pH and then characterized by energy dispersive X-ray analysis, X-ray diffraction and magnetic force microscopy. It has been found that the microstructure and the magnetic properties of films were influenced greatly by the bath pH. At the bath pH 8.06, the grain size and coercivity of the films reach maximum, while the squareness (Mr=Ms) of MH curves reaches minimum. The Henkel plots indicates that the exchange-coupling interaction is very weak at this pH, which may be caused by phase-separation and large grain size, and then results in the lowest squareness. At pH above 8.5, obvious exchange-coupling interaction is observed because of the inexistence of phase-separation and the refinement of grain size.
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    Effect of Temperature on Pitting Corrosion Resistance of 316 Stainless Steel Coated by Cerium Oxide Film in 3.5% NaCl Solution
    H.Hasannejad, T.Shahrabi, A.Sabour Rouhaghdam, M.Aliofkhazraei
    J. Mater. Sci. Technol., 2008, 24 (05): 715-717. 
    Abstract   HTML   PDF (1537KB)
    One of the main problems of stainless steel is its poor pitting corrosion resistance in the aggressive environment containing Cl-, such as seawater. In this paper we investigated the corrosion behavior of the 316 stainless steel coated by cerium oxide nanocoating prepared by sol-gel process. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to study the corrosion behavior of cerium oxide nanocoatings in 3.5% NaCl solution. The microstructure of the cerium oxide was examined by scanning electron microscopy (SEM) and the formed phases was identified by X-ray diffraction (XRD). The pitting corrosion resistance of the cerium oxide nanocoating was found to be improved after heat treatment of the cerium oxide nanocoating at 300°C for 30 min.
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    Effect of Trace Sn on Pitting Behaviors of High Voltage Anode Aluminum Foil
    Jingbo SONG, Weimin MAO, Hong YANG, Huiping FENG
    J. Mater. Sci. Technol., 2008, 24 (05): 718-722. 
    Abstract   HTML   PDF (3934KB)
    The effect of trace Sn on the pitting morphology of high voltage anode aluminum foils was investigated. The distributions of microelement Sn, Fe, Si, Cu and Mg in the surface layer of aluminum foils with different Sn content were determined by using a secondary ion mass spectrometer. It was found that the micro-alloyed Sn is enriched at the external surface. The mechanism of pitting behavior of trace Sn on aluminum surface is similar with that of lead. Enrichment of Sn in the surface layer provides large numbers of sites for initiation of pitting corrosion, while pitting sites appeared relatively inhomogenously in the foils without Sn. Sn, as an eco-friendly microelement, can be applied to replace Pb in improving the homogenous pitting behaviors of high voltage aluminum foils, in which the volume fraction of cube texture is not reduced.
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    Effects of Nickel Distribution on the Strengthening and Toughening of Alumina Ceramics
    Mohamed. M. EL-Sayed Seleman
    J. Mater. Sci. Technol., 2008, 24 (05): 723-728. 
    Abstract   HTML   PDF (3930KB)
    Three types of composite materials were designed and fabricated by hot pressing powder blends of alumina with 20 vol. pct nickel particles. The composites differ in the shape, size and distribution of the nickel particles. Composite microstructures are described and measurements of density, hardness, flexure strength, and fracture toughness are reported. The results showed that the fracture strength of the composite with dispersed nickel particles is higher than the other two composites (network microstructure and mixed microstructure) and the alumina matrix. For all the composites studied, tougher materials than the monolithic alumina were produced. The fracture toughness of the composite with a network microstructure is much higher than that of the other composites. The toughening mechanisms were described based on the observation of the fracture surfaces and the crack-particle interactions. Moreover, the parameters for microstructural tailoring of these materials have been deduced. The toughening of the produced composites was explained in light of the interfacial bond strength.
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    One-dimensional Incremental Constitutive Relation of SMA Wire Reinforced Smart Composites with Damages
    Zili HU, Wanlin ZHOU
    J. Mater. Sci. Technol., 2008, 24 (05): 729-732. 
    Abstract   HTML   PDF (236KB)
    A new Martensitic transformation kinetic model for shape memory alloy (SMA) is proposed based on the phenomenological description of the Martensitic transformation heat flow-temperature curve and on the linear relationship between the partial derivatives of Martensite fraction and of Gbbis free energy with respect to the temperature. A meso-mechanical model is developed to describe the longitudinal stiffness reduction and thermo-dilatation variation of the composites caused by fiber breaking or fiber peeling off the base material. One-dimensional incremental constitutive relation is then established for SMA wire reinforced smart composites with damages by introducing three parameters to describe respectively the extent of fiber breaking, fiber peeling off the base material and interface weakening. The results presented herein may provide a theoretical basis for further studying on SMA smart composites with damages.
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    Microstructures and Properties of FeAl-Fe3AlC0.5 Composites Prepared by SHS Casting
    Jun DING, Jun YANG, Qinling BI, Jiqiang MA, Weimin LIU, Qunji XUE
    J. Mater. Sci. Technol., 2008, 24 (05): 733-736. 
    Abstract   HTML   PDF (1608KB)
    FeAl composites with 21, 37 and 50 wt pct Fe3AlC0.5 were fabricated by a self-propagating high temperature synthesis (SHS) casting. Phases and microstructures were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Microhardness and bending strength of the composites were measured. The composites with 21 and 50 wt pct Fe3AlC0.5 mainly consisted of FeAl and Fe3AlC0.5 phases, whereas the composite with 37 wt pct Fe3AlC0.5 was composed of FeAl, Fe3AlC0.5 and graphite phases. The bonding of the reinforcement and the matrix was good. Hardness and bending strength of the composite with 37 wt pct Fe3AlC0.55 was lower than those of the 21 and 50 wt pct composites owing to the presence of the soft graphite phase.
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    Facile Solid-State Synthesis Route to Metal Nitride Nanoparticles
    Yinxiao DU, Ming LEI, Hui YANG
    J. Mater. Sci. Technol., 2008, 24 (05): 737-741. 
    Abstract   HTML   PDF (3494KB)
    By a facile and efficient solid-state reaction route using an organic reagent cyanamide (CN2H2) as a precursor with another one being metal oxides, we successfully synthesized seven technologically important metal nitrides including cubic VN, CrN, NbN, hexagonal GaN, AlN, BN, and WN at moderate temperatures. The experimental results show that cyanamide (CN2H2) is a powerfully reducing and nitridizing reagent and the metal oxides are completely converted into the corresponding nitride nanoparticles at lower temperatures than that reported in the conventional methods. It is found that CN2H2 can exhibit some interesting condensation processes, and the final products, highly active carbon nitride species, play a crucial role in the reducing and nitridizing processes.
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    Effects on the Phase Transformation Temperature of Nanofluids by the Nanoparticles
    Huaqing XIE, Jifen WAN, Lifei CHEN
    J. Mater. Sci. Technol., 2008, 24 (05): 742-744. 
    Abstract   HTML   PDF (2288KB)
    Nanofluids have been demonstrated to have intriguing thermodynamic properties. In this work, we described the investigation of the phase transformation behaviors of nanofluids containing alumina (Al2O3) or titania (TiO2) nanoparticles with different weight fractions. The experimental results indicate that the melting temperatures of nanofluids (in freezing states) are reduced with the increase of the weight fraction of nanoparticles. The reduction is related to nanoparticle species as well as nanoparticle size.
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    Nanoscale Morphology in Tensile Fracture of a Brittle Amorphous Ribbon
    Xifeng LI, Kaifeng ZHANG, Guofeng WANG
    J. Mater. Sci. Technol., 2008, 24 (05): 745-749. 
    Abstract   HTML   PDF (2938KB)
    The paper reports on the observation of nanoscale morphology on the tensile fracture surface of a brittle amorphous Fe-based ribbon. The formation of nanoscale damage cavity structure is a main characteristic morphology on the fracture surfaces. Approaching the ribbon boundary, these damage cavities assemble and form the nanoscale periodic corrugations, which are neither Wallner lines nor crack front waves. The periodic corrugations result from the interactions between the reflected elastic waves by the boundaries of amorphous ribbon and the stress fields of the crack tip.
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    A Study on Nanoscale Infrared Absorbent Working in Waveband Range of 1300–400 cm-1
    Yongmao HU, Jinzhong XIANG, Xueqing ZHANG, Ruheng LI, Xinghui WU
    J. Mater. Sci. Technol., 2008, 24 (05): 750-752. 
    Abstract   HTML   PDF (1124KB)
    Samples of nanoscale powder of SiO2/Al2O3/TiO2 composite were prepared by sol-gel method. The microstructure and morphology of the obtained samples were characterized with IR, XRD spectra and TEM images. It is proved that infrared absorbing peaks of the samples are in waveband range of 1300-400 cm-1, and then peak shape changes with their component. Mechanism of the infrared peak's positions and shapes which changes with the size and morphology of the prepared nano-particles has been tentatively discussed.
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    Organic Electrofluorescent Materials Using Pyridine-Containing Macrocyclic Compounds
    Tingxi LI, Long FU, Wenwen YU, Renhe HUANG
    J. Mater. Sci. Technol., 2008, 24 (05): 753-756. 
    Abstract   HTML   PDF (1086KB)
    Novel pyridine-containing macrocyclic compounds, such as 6,12,19,25-tetramethyl-7,11,20,24-dinitrilo-dibenzo[b,m]1,4,12,15-tetra-azacyclodoc osine (TMCD), were synthesized and used as electron transport layer in organic electroluminescent devices. Devices with a structure of glass/indium-tin oxide/arylamine derivative/tris(quinolinolato)aluminum(III) (Alq)/TMCD/LiF/Al exhibited green emission from the Alq layer with external quantum efficiency of 0.84% and luminous efficiency of 1.3 lm/W. The derivatives of TMCD were synthesized and characterized as well. These compounds were also found to be useful as the electron-transporting materials in organic electroluminescent devices.
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    Transport Properties of Bi2S3 Single Crystals
    H.T.Shaban, M.M.Nassary, M.S.El-Sadek
    J. Mater. Sci. Technol., 2008, 24 (05): 757-760. 
    Abstract   HTML   PDF (273KB)
    Bi2S3 single crystals were grown by using a modification of Bridgman method. Measurements of the electrical conductivity, Hall effect and thermoelectric power (TEP) were preformed in two crystallographic directions (parallel and perpendicular to the c-axis). The measurements showed that the electrical conductivity, Hall mobility, and Seebeck coefficient have anisotropic nature. From these measurements some physical parameters were estimated and the crystals showed n-type of conduction mechanism. Also, values of the energy gap were found to be different in the two directions.
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    Synthesis and Characterization of Fine Grained High Density La2Mo2O9-based Oxide-ion Conductors
    Jianxin WANG, Qin WANG, Xianping WANG, Chun LI, Qianfeng FANG
    J. Mater. Sci. Technol., 2008, 24 (05): 761-765. 
    Abstract   HTML   PDF (2167KB)
    A cost-effective technique, including nanocrystalline powder preparation using a modified Pechini method and a two-step low-temperature sintering route, was developed for the synthesis of high performance La2Mo2O9-based oxide-ion conductors. The optimum parameters of the compaction pressure, the first step and the second step sintering temperatures for the synthesis of fine grained, high density and uniform La2Mo2O9-based oxide-ion conductors were determined by a series of sintering experiments. High density and uniform sintered La2Mo2O9 samples with average grain size from 0.8 to 5 μm and La1.96K0.04Mo2O8.96 sample with average grain size as small as 500 nm were synthesized by using this cost-effective method. The impedance measurement results show that the as-fabricated La2Mo2O9-based ceramics possess much higher ionic conductivity than that obtained by solid state reaction method. It is found that in the range of 0.8{5 μm the grain size of dense La2Mo2O9 samples prepared from the nanocrystalline powders has little influence on their conductivities.
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    Corrosion Behaviors of Steel A3 Exposed to Thiobacillus Ferrooxidans
    Jianhua LIU, Xin LIANG, Songmei LI
    J. Mater. Sci. Technol., 2008, 24 (05): 766-770. 
    Abstract   HTML   PDF (1923KB)
    The corrosion behaviors of steel A3 in synergistic action of Thiobacillus ferrooxidans (T.f) and electrochemically accelerated corrosion were studied by electrochemical, microbiology and surface analysis methods. The open circuit potential (Eocp) and electrochemical impedance spectroscopy (EIS) of the steel A3 electrodes were measured in leathen culture medium without and with T.f (simply called T.f solution in the following paper) in immersion electrode way at the time of the 2nd, 5th, 10th, 20th and 30th days, respectively. It was found that Eocp of the electrode for immersion in leathen culture medium shifted negatively with the immersion time while that for immersion in T.f solutions shifted negatively, then positively and finally negatively. On the 20th day, the corrosion of steel A3 for immersion in culture medium was in pitting initiation stage while that for immersion in T.f solutions was in pitting growth stage. It was found that the corrosion of steel A3 was accelerated by T.f. The morphology of corrosion product of steel A3 immersion in T.f solutions observed through scanning electron microscopy (SEM) transformed from solid globules to tabular plates and to spongy globules and plates.
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    Thermodynamic Assessment and Experimental Investigation of Fe-Al-C System
    Weiyan LÜ, Lin LI, Li WANG, Yanlin HE, Shuigen HUANG
    J. Mater. Sci. Technol., 2008, 24 (05): 771-774. 
    Abstract   HTML   PDF (2077KB)
    Phase diagram information of the Fe-C, Fe-Al and Al-C systems are reviewed and the Fe-Al-C system is assessed. A FeAlC database is created by combining a set of thermodynamic parameters established by Kumar and SSOL database in Thermo-Calc software package. Ternary phase diagrams are calculated with FeAlC and the newly developed Thermo-Calc databases SSOL2 and SSOL4. The FeAlC database is the best one to describe the Fe-Al-C system. A1 and A3 values on the vertical section containing 1.5 wt pct Al are calculated with the FeAlC database in this work. To validate the thermodynamic calculation, critical temperatures Ac1 and Ac3 are determined by using dilatometer analysis. There exist some errors between the calculated values and the experimental results. So further optimization of the Fe-Al-C system regarding bcc and fcc phases is necessary. The experimental data in this work could be of some value in further optimization.
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    Precipitation of Epsilon Copper in Ferrite Antibacterial Stainless Steel
    Zhixia ZHANG, Gang LIN, Zhou XU
    J. Mater. Sci. Technol., 2008, 24 (05): 775-780. 
    Abstract   HTML   PDF (6163KB)
    The precipitation of epsilon copper at 1023 K ageing in ferrite antibacterial stainless steel was investigated by a combination of electron microscopy and micro-Vickers hardness measurement. The results show that epsilon copper precipitation occurs within 90 s. Complex multilayer structure confirmed as twins and stacking faults on {111}ε-Cu planes was observed in the precipitates. The precipitates grow by the lengthwise enlargement of a set of parallel layers, having [111] ε-Cu and ε-Cu preferred growth orientations. The volume fraction of precipitates f formed within 120 min can be predicted by a modified Avrami equation ( ). Simultaneously, substituent atom clusters with a size of 5–10 nm was found to occur in the solution and cause matrix strain. The precipitate morphology and distribution on the surface of ferrite antibacterial stainless steel are associated with surface crystallographic orientation of the matrix. The precipitates are predominantly located within the ferrite grains of <110> orientation. The precipitates located on {111}α-Fe surface planes have sphere or ellipse shape.Key words: Stainless steel; Copper precipitation; Complex multilayer structure; Electron microscopy; Surface crystallographic orientation
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    Effects of Nitrogen Concentration on Microstructure and Antibacterial Property of Copper-Bearing Austenite Stainless Steels
    Zhixia ZHANG, Laizhu JIANG, Gang LIN, Zhou XU
    J. Mater. Sci. Technol., 2008, 24 (05): 781-786. 
    Abstract   HTML   PDF (1146KB)
    Austenite antibacterial stainless steels have been found to have wide applications in hospitals and food industries. In recent years epsilon copper precipitation in antibacterial stainless steels has obtained much research interest due to its antibacterial action. The objective of this study was to determine the effects of nitrogen concentration on the precipitation of epsilon copper and antibacterial property. Two kinds of austenite antibacterial stainless steels containing copper and different nitrogen concentration (0.02 and 0.08 wt pct, respectively) were prepared and the microstructures were characterized by a combination of electron microscopy and thermodynamic analysis. A mathematical expression was deduced to predict the effect of nitrogen concentration on the activity coefficient of copper, ln(fCu/fCu0)=0.53524+4.11xN-0:48xN2. Higher nitrogen was found to increase the free energy difference of copper concentration distribution between precipitation phase and austenite matrix, stimulate the aggregation of copper atoms from austenite, increase the precipitation amount and consequently enhance the antibacterial property of steel.
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    High-cycle Fatigue Fracture Behavior of Ultrahigh Strength Steels
    Weijun HUI, Yihong NIE, Han DONG, Yuqing WENG, Chunxu WANG
    J. Mater. Sci. Technol., 2008, 24 (05): 787-792. 
    Abstract   HTML   PDF (2832KB)
    The fatigue fracture behavior of four ultrahigh strength steels with different melting processes and therefore different inclusion sizes were studied by using a rotating bar two-point bending fatigue machine in the high-cycle regime up to 107 cycles of loading. The fracture surfaces were observed by field emission scanning electron microscopy (FESEM). It was found that the size of inclusion has significant effect on the fatigue behavior. For AISI 4340 steel in which the inclusion size is smaller than 5.5 μm, all the fatigue cracks except one didnot initiated from inclusion but from specimen surface and conventional S-N curve exists. For 65Si2MnWE and Aermet 100 steels in which the average inclusion sizes are 12.2 and 14.9 μm, respectively, fatigue cracks initiated from inclusions at lower stress amplitudes and stepwise S-N curves were observed. The S-N curve displays a continuous decline and fatigue failures originated from large oxide inclusion for 60Si2CrVA steel in which the average inclusion size is 44.4 μm. In the case of internal inclusion-induced fractures at cycles beyond about 1×106 for 65Si2MnWE and 60Si2CrVA steels, inclusion was always found inside the fish-eye and a granular bright facet (GBF) was observed in the vicinity around the inclusion. The GBF sizes increase with increasing the number of cycles to failure Nf in the long-life regime. The values of stress intensity factor range at crack initiation site for the GBF are almost constant with Nf , and are almost equal to that for the surface inclusion and the internal inclusion at cycles lower than about 1×106. Neither fish-eye nor GBF was observed for Aermet 100 steel in the present study.
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    Evaluation of Mechanical Properties According to Nb Content of High Strength Steel Manufactured in VIM
    Byung-Hui Choi, Byung-Ki Choi
    J. Mater. Sci. Technol., 2008, 24 (05): 793-796. 
    Abstract   HTML   PDF (6190KB)
    As the aircraft and aerospace industry and the automobile industry are developed, the demand of reliable materials with high strength and high toughness is steadily increased. The grain miniature method which improves the ductility and the toughness simultaneously under high strength is the miniature of the casting microstructure. In this paper, the Nb which affects the austenite grain miniature is added by 0.00%, 0.03% and 0.06% in this steel and the ingot is manufactured in a vacuum induction melting furnace (VIM). The casting microstructure and the mechanical property of the maraging steel according to Nb contents are analyzed by conducting the solution annealing and the age hardening after hot rolling. In this result, a specimen containing 0.03% Nb is most miniature. When it does the long time age hardening, the precipitation estimated as the carbide is appeared. The mechanical properties are excellent if a specimen containing 0.06% Nb does the age hardening during 8 h in 482°C.
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    Predication of Component Activities in the Molten Aluminosilicate Slag CaO-Al2O3-SiO2 by Molecular Interaction Volume Model
    Dongping TAO
    J. Mater. Sci. Technol., 2008, 24 (05): 797-802. 
    Abstract   HTML   PDF (247KB)
    A novel thermodynamic model-the molecular interaction volume model (MIVM) which can be reduced to the Flory-Huggins equation of polymer solution was employed for the prediction of component activities in the ternary molten aluminosilicate slag CaO-Al2O3-SiO2 at different temperatures. The results show that the predicted values of activity of CaO, Al2O3 and SiO2 are in reasonably agreement with experimental data in some ranges of their concentrations which are about x1<0.25 for CaO, x2=0.05–0.55 for Al2O3 and x3=0.03–0.85 for SiO2. This further shows that MIVM requires only two binary parameters for each sub-binary system to predict activities of all components in a multicomponent solution and is the superior alternative in a molten slag.
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    Microstructural Features and Mechanical Properties Induced by the Spray Forming and Cold Rolling of the Cu-13.5 wt pct Sn Alloy
    Xiaofeng WANG, Jiuzhou ZHAO, Jie HE, Jiangtao WANG
    J. Mater. Sci. Technol., 2008, 24 (05): 803-808. 
    Abstract   HTML   PDF (7123KB)
    Copper alloys with high strength and high conductivity are an important functional material with full of potential applications. In the present investigation, a bronze with higher tin content (Cu-13.5 wt pct Sn) was prepared successfully by spray forming, the feasibility of cold rolling this alloy was investigated, and the cold rolling characteristics of this alloy have also been discussed. The results indicate that the spray-formed Cu-13.5 wt pct Sn alloy, compared with the as-cast ingot, shows a quite fine and homogeneous single-phase structure, and, therefore shows an excellent workability. It can be cold-rolled with nearly 15% reduction in the thickness per pass and the total reduction can reach 80%. The classical border between the wrought and cast alloys is shifted to considerably higher tin contents by spray forming. After proper thermo-mechanical treatment, spray-formed Cu-13.5 wt pct Sn alloy exhibits excellent comprehensive mechanical properties. Particularly, it shows a low elastic modulus (~88 GPa) and a high flow stress (over 800 MPa) after cold forming. This combination of properties is unique in the domain of metallic materials and could open new possibilities in spring technology field.
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    Analysis of the Phenomena of Diamond Synthesis by Seeding with Diamond
    Meiguang ZHANG, Haiyan YAN, Fang PENG
    J. Mater. Sci. Technol., 2008, 24 (05): 809-812. 
    Abstract   HTML   PDF (4345KB)
    Synthesizing diamond single crystal by diamond seed particles which were electroplated with nickel film as catalyst under high pressure and high temperature (HPHT) was described. The microstructure of nickel film after synthesis and morphology of grown diamond were investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The phase structure in nickel film were graphite, NiC, Ni, and diamond structure hadn0t been found. A lot of recrystallized graphite pits appear in interface between the inner surface of nickel film and the surface diamond. It is shown that the new-grown diamond was developed epitaxially on the crystal planes of seeds. Also, the new-grown diamond grew by two-dimensional nucleation and by a layer growth mechanism. The growth process of crystal was microaggregate→step→expansion→new crystal layers, and the flat growth interface transformed into a cellular interface at the same time.
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    A Banding Structure in a Ni-Cu-Si Cast Alloy
    Qi ZHENG, Yufeng ZHENG, Hongyu ZHANG, Xiaofeng SUN, Hengrong GUAN, Zhuangqi HU
    J. Mater. Sci. Technol., 2008, 24 (05): 813-815. 
    Abstract   HTML   PDF (4291KB)
    The solidified microstructure of a Ni-Cu-Si cast alloy has been investigated, and a kind of banding structure was observed. The results showed that, the banding structure was composed of coarser particles which were Ni3Si type of precipitates and similar to the fine particles precipitate uniformly distributed within matrix of Ni solid solution, in both crystal structure and composition. The formation of bandings was resulted from cast thermal stress and dislocation walls. It was found that the cracks propagated along these bandings in tensile test. The banding structure can be depressed by reducing the cast thermal stress, which can improve the tensile ductility.
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    Preparation of Ultrafine Tungsten Powder by Sol-Gel Method
    Yuxian HAN, Tai QIU, Tao SONG
    J. Mater. Sci. Technol., 2008, 24 (05): 816-818. 
    Abstract   HTML   PDF (1993KB)
    Sol-gel method was employed for the preparation of nanoscale tungsten powder. The effects of different preparation conditions on particle size were discussed and the optimum preparation condition was found. The products were characterized by X-ray diffraction, scan electron microscopy and so on. The results show that the intermediate is monoclinic WO3, its particle shape is approximately spherical, and the particle size distribution is narrow. The average particle size is about 60 nm. After deoxidization, WO3 turns into cubic tungsten powder with small particle size (average particle size about 120 nm) and narrow size distribution.
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ISSN: 1005-0302
CN: 21-1315/TG
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