Started in 1985 Semimonthly
ISSN 1005-0302
CN 21-1315/TG
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Current Issue
 28 July 2005, Volume 21 Issue 04 Previous Issue    Next Issue
Research Articles
 Select Derivation of Plastic Work Rate Done per Unit Volume for Mean Yield Criterion and Its Application Dewen ZHAO, Yingjie XIE, Xiaowen WANG, Xianghua LIU J. Mater. Sci. Technol., 2005, 21 (04): 433-436.  Abstract   HTML   PDF (4049KB) In Haigh Westergaard stress space linear combination of twin shear stress and Tresca yield functions is called the mean yield (MY) criterion. The mathematical relationship of the criterion and its plastic work rate done per unit volume were derived. A generalized worked example of slab forging was analyzed by the criterion and its corresponding plastic work rate done per unit volume. Then, the precision of the solution was compared with those by Mises and Twin shear stress yield criterions, respectively. It turned out that the calculated results by MY criterion were in good agreement with those by Mises criterion.
 Select Mechanism of Bainite Nucleation in Steel, Iron and Copper Alloys Mokuang KANG, Ming ZHU, Mingxing ZHANG J. Mater. Sci. Technol., 2005, 21 (04): 437-444.  Abstract   HTML   PDF (1183KB) During the incubation period of isothermal treatment (or aging) within the bainitic transformation temperature range in a salt bath (or quenching in water) immediately after solution treatment, not only are the defects formed at high temperatures maintained, but new defects can also be generated in alloys, iron alloys and steels. Due to the segregation of the solute atoms near defects through diffusion, this leads to non-uniform distributions of solute atoms in the parent phase with distinct regions of both solute enrichment and solute depletion. It is proposed that when the Ms temperature at the solute depleted regions is equal to or higher than the isothermal (or aged) temperature, nucleation of bainite occurs within these solute depleted regions in the manner of martensitic shear. Therefore it is considered that, at least in steel, iron and copper alloy systems, bainite is formed through a shear mechanism within solute depleted regions, which is controlled and formed by the solute atoms diffusion in the parent phase.
 Select An FEGSTEM Study of Grain Boundary Segregation of Phosphorus during Quenching in a 2.25Cr-1Mo Steel Shenhua SONG, Luqian WENG J. Mater. Sci. Technol., 2005, 21 (04): 445-450.  Abstract   HTML   PDF (586KB) Quenching-induced phosphorus segregation to prior austenite grain boundaries in a 0.077 wt pct P-doped 2.25Cr-1Mo steel is examined using field emission gun scanning transmission electron microscopy (FEGSTEM). A phosphorus level of around 1.56 at. pct is observed for the water-quenched sample. In recognition of insufficiently high spatial resolution of the technique for grain boundary composition analysis, the measured results are corrected by an analytical convolution method. The corrected phosphorus segregation level may be up to about 4.7 at. pct. The quenching-induced phosphorus segregation is nonequilibrium segregation and the migration of vacancy-phosphorus complexes plays an important role in the kinetic process. For such a reason, the mechanism for migration of the complexes is discussed in some detail.
 Select High-Strength and High-Plasticity TWIP Steel for Modern Vehicle Zhenli MI, Di TANG, Ling YAN, Jin GUO J. Mater. Sci. Technol., 2005, 21 (04): 451-454.  Abstract   HTML   PDF (449KB) In this paper new high-strength and high-plasticity twinning induced plasticity (TWIP) steel for modern automobile body was investigated. Some basic experimental results were given. The results indicate the TWIP steel has excellent properties. It exhibits high ultimate tensile strength (600~1100 MPa) and extremely large elongation of 60% to 90%. In the future it would be capable of satisfying the requirements of new generation of vehicle.
 Select Primary Recrystallization of Grain Oriented Silicon Steel Strip Rolled by CSR and Annealed in Magnetic Field En LIU, Kemin QI, Xiuhua GAO, Chunlin QIU, Hezhou YE J. Mater. Sci. Technol., 2005, 21 (04): 455-458.  Abstract   HTML   PDF (812KB) The magnetic properties and textures of grain oriented silicon steel with different thickness rolled by cross shear rolling (CSR) of different mismatched speed ratio (MSR) and annealed in magnetic field under hydrogen were presented. Effects of the factors such as thickness and mismatched speed ratio on the magnetic properties and recrystallization texture were analyzed and the recrystallization principles in magnetic field annealing were discussed. The study would provide a new route for mass production of high quality ultra-thin grain oriented silicon steel strip.
 Select Localized Corrosion Behavior of 6% Mo Super Austenitic & 316L Stainless Steels in Low pH 3% NaCl Solution M.M.A.Gad, H.G.Salem, A.M.Nasreldin, H.Sabry, A.A.El-Sayed J. Mater. Sci. Technol., 2005, 21 (04): 465-469.  Abstract   HTML   PDF (633KB) Electrochemical techniques were applied to study the crevice corrosion resistance of two types of stainless steel alloys namely, conventional 316L and 6% Mo super austenitic in acidified 3% NaCl solution at room temperature. Potentiodynamic results showed that 6% Mo alloy possessed a remarkable resistance to crevice corrosion compared with 316L alloy when they are tested in the same solution. The breakdown potential at which passivity broke down for 316L alloywas 0.00 mV (SCE). The corresponding value for 6% Mo alloy couldnot reach up to the potential value of 700 mV (SCE). 316L alloy suffered extremely from crevice corrosion at room temperature (about 25℃), which indicates that the critical crevice corrosion temperature, below which crevice corrosion does not occur, was lower than the test temperature. For 6% Mo alloy, the critical crevice corrosion temperature was higher than the testing temperature. Electrochemical parameters indicated that 6% Mo alloy exhibited higher crevice corrosion resistance than 316L alloy.
 Select Effects of Mn and Cu on the Mechanical Properties of a High Strength Low Alloy NiCrMoV Steel A.Abdollah-zadeh, M.Belbasy J. Mater. Sci. Technol., 2005, 21 (04): 470-474.  Abstract   HTML   PDF (1312KB) The present study focuses on the effects of Mn and Cu on the mechanical properties, in particular, strength and toughness of a low alloy steel containing Ni, Cr, Mo and V. Specimens with different amounts of Mn (0.23%~0.85%) and Cu (0.15%~0.45%) were cast and forged, and then austenitized at 870℃ for 1 h, followed by oil quenching. All specimens were tempered at 650℃ for 1 h. The results show that as the amounts of Mn and Cu increase respectively from 0.35% to 0.85% and from 0.15% to 0.45%, the yield and tensile strength increase. The highest impact energies were observed in the specimen with 0.35% Mn and in the specimen with 0.25% Cu. The impact energy decreases with increasing the Mn and Cu from 0.35% to 0.85% and from 0.25% to 0.45%, respectively. Furthermore, the variation of Mn and Cu does not cause a considerable change in the tempered martensite microstructure. The optimum strength and toughness is observed in 0.35% Mn containing steel and in the 0.25% Cu containing steel.
 Select Microstructure and Properties of Cu-Cr-Zr Alloy after Rapidly Solidified Aging and Solid Solution Aging Ping LIU, Juanhua SU, Qiming DONG, Hejun LI J. Mater. Sci. Technol., 2005, 21 (04): 475-478.  Abstract   HTML   PDF (509KB) The structure and properties of Cu-Cr-Zr alloy were studied after rapidly solidified aging and solid solution aging. At the early stage of aging (500℃ for 15 min), the hardness and the conductivity of the alloy rapidly solidified are 143 HV and 72% IACS, respectively. Under the same aging condition, the hardness and electrical conductivity of the alloy solid solution treated can reach 86 HV and 47% IACS, respectively. The microstructure was analyzed, and the grain size after rapid solidification is much smaller than that after solid solution treatment. By rapidly solidified aging the fine precipitates distribute inside the grains and along the grain boundary, while by solid solution aging there are large Cr particles along the grain boundary.
 Select Small Angle X-ray Scattering Study of Precipitation Kinetics in Al-Zn-Mg-Cu Alloys Zhiwei DU, Tietao ZHOU, Peiying LIU, Huanxi LI, Baozhong DONG, Changqi CHEN J. Mater. Sci. Technol., 2005, 21 (04): 479-483.  Abstract   HTML   PDF (633KB) The evolution of microstructure parameters (precipitate size and volume fraction) for two types of Al-Zn-Mg-Cu alloys (7075 and 7055) during aging has been studied by synchrotron-radiation small angle X-ray scattering (SAXS). The results show that the precipitates are only a few nanometers for both alloys ageing even at higher temperature of 160℃ for 72 h (4.44 and 5.82 nm, respectively). The maximum of the precipitate volume fraction increases with in creasing Zn content and is about 0.023~0.028 and 0.052~0.054, respectively. The coarsening of precipitate is consistent with LSW (Lifshitz-Slyozov-Wagner) model even at the initial stage where volume fraction is still varying. The activation energy of coarsening regime has been determined to be about 1.22±0.02 eV and 1.25±0.02 eV for alloys 7075 and 7055, respectively.
 Select Ingredient Losses during Melting Binary Ni-Ti Shape Memory Alloys S.K.Sadrnezhaad, S.Badakhshan Raz J. Mater. Sci. Technol., 2005, 21 (04): 484-488.  Abstract   HTML   PDF (868KB) Losses of the alloying elements during vacuum induction melting of the binary NiTi alloys were evaluated by visual observation and chemical analysis of the NiTi melted specimens and the scalp formed on the internal surface of the crucible. The results indicated that the major sources of the losses were (a) evaporation of the metals, (b) formation of the NiTi scalp and (c) the sprinkling drops splashed out of the melt due to the exothermic reactions occurring between Ni and Ti to form the NiTi parent phase. Quantitative evaluations were made for the metallic losses by holding the molten alloy for 0.5, 3, 5, 10 and 15 min at around 100℃ above the melting point inside the crucible. Chemical analysis showed that there existed an optimum holding time of 3 min during which the alloying elements were only dropped to a predictable limit. Microstructure, chemical composition, shape memory and mechanical properties of the cast metal ingots were determined to indicate the appropriate achievements with the specified 3 min optimum holding time.
 Select Oxidation of NiAl-Ag Alloys at 1000℃ in 0.1 MPa O2 Xuejun ZHANG, Yan NIU J. Mater. Sci. Technol., 2005, 21 (04): 489-492.  Abstract   HTML   PDF (773KB) Small amounts of silver have been added to the intermetallic compound NiAl with the purpose of improving its mechanical properties. Four ternary NiAl-Ag alloys containing 0.5, 1, 5 and 10 at. pct Ag, denoted as NiAl-0.5Ag, NiAl-1Ag, NiAl-5Ag and NiAl-10Ag, and the Ag-free NiAl have been oxidized at 1000℃ for 24 h in 0.1 MPa O2 to study the effect of the presence of silver on the oxidation behavior of NiAl. All the NiAl-Ag alloys are composed of a matrix of β-NiAl containing a dispersion of isolated particles of a second silver-rich phase. A continuous external layer of Al2O3 formed on all the alloys. In addition, the scales formed on NiAl-5Ag contained a thin and discontinuous layer of pure silver located at the alloy/Al2O3 interface, while those formed on NiAl-10Ag contained isolated particles as well as discontinuous layers of silver at various locations in the scale extending up to the gas/scale interface. The kinetic curves of all the alloys were generally composed of two main parabolic stages with smaller parabolic rate constants for the final stage. The addition of silver does not significantly affect the oxidation behavior of the NiAl intermetallic compound in all cases, as expected because silver is essentially present only as a second phase due to its very small solubility in β-NiAl.
 Select Microstructure and Strength of Brazed Joints of Ti3Al Base Alloy with Cu-P Filler Metal Peng HE, Jicai FENG, Heng ZHOU J. Mater. Sci. Technol., 2005, 21 (04): 493-498.  Abstract   HTML   PDF (770KB) Brazing of Ti3Al alloys with the filler metal Cu-P was carried out at 1173~1273 K for 60~1800 s. When products are brazed, the optimum brazing parameters are as follows: brazing temperature is 1215~1225 K; brazing time is 250~300 s. Four kinds of reaction products were observed during the brazing of Ti3Al alloys with the filler metal Cu-P, i.e., Ti3Al phase with a small quantity of Cu (Ti3Al(Cu)) formed close to the Ti3Al alloy; the TiCu intermetallic compounds layer and the Cu3P intermetallic compounds layer formed between Ti3Al(Cu) and the filler metal, and a Cu-base solid solution formed with the dispersed Cu3P in the middle of the joint. The interfacial structure of brazed Ti3Al alloys joints with the filler metal Cu-P is Ti3Al/Ti3Al(Cu)/TiCu/Cu3P/Cu solid solution (Cu3P)/Cu3P/TiCu/Ti3Al(Cu)/Ti3Al, and this structure will not change with brazing time once it forms. The thickness of TiCu+Cu3P intermetallic compounds increases with brazing time according to a parabolic law. The activation energy Q and the growth velocity K0 of reaction layer TiCu+Cu3P in the brazed joints of Ti3Al alloys with the filler metal Cu-P are 286 kJ/mol and 0.0821 m2/s, respectively, and growth formula was y2=0.0821exp(-34421.59/T)t. Careful control of the growth for the reaction layer TiCu+Cu3P can influence the final joint strength. The formation of the intermetallic compounds TiCu+Cu3P results in embrittlement of the joint and poor joint properties. The Cu-P filler metal is not fit for obtaining a high-quality joint of Ti3Al brazed.
 Select Effect of Temperature and Ram Speed on Isothermal Extrusion for Large-size Tube with Piece-wing He YANG, Jun ZHANG, Yangmin HE, Bingtao HAN J. Mater. Sci. Technol., 2005, 21 (04): 499-504.  Abstract   HTML   PDF (1381KB) Heat energy change during the extrusion of 7075 aluminium alloy large-size tube with piece-wing in a container was analyzed. Extrusion load vs ram displacement diagrams and exit temperature vs ram displacement diagrams at various speeds were obtained by 3D FEM simulation. Results show that the exit temperature becomes higher as the ram speed and displacement increase. For large-size tube with piece-wing, there is certainly a curve of ram speed decreasing with increasing ram displacement, which enables isothermal extrusion to be achieved. Therefore, an attempt was made to divide the working stroke into five different zones. Each of them has a preset speed that decreases from the ram displacement beginning to the ending. And then, new exit temperature vs ram displacement diagram was obtained by 3D FEM simulation for the five different speeds. It is shown that the variation of exit temperature is very small. Through the above research, a basic method for realizing isothermal extrusion of 7075 large-size tube with piece-wing was obtained, that is, the working stroke was divided into several different zones with a decreasing speed during extrusion, each zones' speed was real-time adjusted on the feedback signal of exit temperature by proportional hydraulic valve through closed-loop control. The engineering experiment verification was carried out on 100 MN aluminium extrusion press with oil-driven double action. The experimental results of the exit temperature agrees with the simulation ones. The achievements of this study may serve as a significant guide to the practice of the relevant processes, particularly for isothermal extrusion. The verified method has been used in the design and manufacture of 125 MN aluminium extrusion press with oil-driven double action.
 Select Compressive Deformation of Semi-Solid AZ91D Magnesium Alloy Weimin MAO, Aimei YIN, Xueyou ZHONG J. Mater. Sci. Technol., 2005, 21 (04): 505-509.  Abstract   HTML   PDF (521KB) The compression tests of semi-solid AZ91D Mg alloy have been conducted on a parallel-plate viscometer. The results are as follows. With increasing the compression temperature, the deformation rate or the strain rate of the specimens rises, but the compressive stress continuously decreases; the deformation strain is obviously linear with the compressive stress and independent on compression temperature under a given compression load. In the wake of the compression load being added, the compressive strain increases but the compressive stress decreases clearly; the deformation strain is obviously linear with the compressive stress under different compression load. The mathematical apparent viscosity model about the semi-solid compressed AZ91D Mg alloy has been established, i.e. ηapp=2004.2exp(15.61fs)ý1.317fs-1.3511.
 Select Cavitation Behavior during Superplastic Deformation of AZ31 Magnesium Alloy Kaifeng ZHANG, Deliang YIN, Guofeng WANG, Wenbo HAN J. Mater. Sci. Technol., 2005, 21 (04): 510-514.  Abstract   HTML   PDF (913KB) Superplasticity of AZ31 Mg alloy at the temperature range of 250~450℃ and stain rate range of 0.7×10-3~1.4×10-1 s-1 was examined through uniaxial tensile test. Optical microscopy (OM) and scanning electron microscopy (SEM) were employed to investigate the morphology of cavities and surface relief near fracture surface, respectively. It is shown that AZ31 Mg alloy starts to exhibit superplasticity from 300℃. The maximum elongation of 362.5% was obtained at 400℃ and strain rate of 0.7×10-3 s-1. There exist many O-shaped cavities and filaments at the boundaries near fracture surface. The fracture of filaments results in intergranular cavity and the model for the formation of intergranular cavities is proposed. The growth of cavities is plasticity-controlled and the serrated boundaries of intergranular cavities agree with the results of surface relieves.
 Select Neural Network Modeling and System Simulating for the Dynamic Process of Varied Gap Pulsed GTAW with Wire Filler Guangjun ZHANG, Shanben CHEN, Lin WU J. Mater. Sci. Technol., 2005, 21 (04): 515-520.  Abstract   HTML   PDF (3224KB) As the base of the research work on the weld shape control during pulsed gas tungsten arc welding (GTAW) with wire filler, this paper addressed the modeling of the dynamic welding process. Topside length Lt, maximum width Wt and half-length ratio Rhl were selected to depict topside weld pool shape, and were measured on-line by vision sensing. A dynamic neural network model was constructed to predict the usually unmeasured backside width and topside height of the weld through topside shape parameters and welding parameters. The inputs of the model were the welding parameters (peak current, pulse duty ratio, welding speed, filler rate), the joint gap, the topside pool shape parameters (Lt, Wt, and Rhl), and their history values at two former pulse, a total of 24 numbers. The validating experiment results proved that the artificial neural network (ANN) model had high precision and could be used in process control. At last, with the developed dynamic model, steady and dynamic behavior was analyzed by simulation experiments, which discovered the variation rules of weld pool shape parameters under different welding parameters, and further knew well the characteristic of the welding process.
 Select A New Curve Fitting Method for Forming Limit Experimental Data Jieshi CHEN, Xianbin ZHOU J. Mater. Sci. Technol., 2005, 21 (04): 521-525.  Abstract   HTML   PDF (741KB) The forming limit curve (FLC) can be obtained by means of curve fitting the limit strain points of different strain paths. The theory of percent regression analysis is applied to the curve fitting of forming limit experimental data. Forecast intervals of FLC percentiles can be calculated. Thus reliability and confidence level can be considered. The theoretical method to get the limits of limit strain points distributing region is presented, and the FLC position can be adjusted according to practical requirement. Method for establishing FLC with high reliability using small samples is presented at the same time. This method can make full use of the current experimental data and the previous data. Compared with the traditional method that can only use current experimental data, fewer specimens are required in the present method to obtain the same precision and the result is more accurate with the same number of specimens.
 Select Numerical Simulation of Two Types of Electromagnetic Edge Dam Used in Twin Roll Strip Cast Peiwei BAO, Peijie LI, Hongshuang DI, Xianghua LIU, Guodong WANG J. Mater. Sci. Technol., 2005, 21 (04): 526-530.  Abstract   HTML   PDF (1343KB) Two types of electromagnetic edge dams were analyzed by using finite element method in present paper. The magnetic vector potential method and edge element method were used. The distributions of the magnetic field, the eddy current intensity and the magnetic force were obtained from the computing. The differences in these fields were explained according to the two types of electromagnetic dam, and characters of their application in twin roll casting were also discussed.
 Select Effect of Friction on the Drawing Process of Hot-Galvanized Sheet Steel Hongying GONG, Wei ZHU, Zhiliang ZHANG, Zhenliang LOU J. Mater. Sci. Technol., 2005, 21 (04): 531-535.  Abstract   HTML   PDF (534KB) A probe test method was employed to detect the friction condition of the interfaces between tools and blank. At the same time a self-developed measurement apparatus to realize the probe test method was also presented. Based on the analysis of force, a correlative friction model was also given. With the self-developed measurement apparatus, the effects of three kinds of lubricating oils which were in common use during the process of sheet steel drawing were studied. By probing the friction coefficient values of different lubricating oils during the drawing process of the hot-galvanized sheet steel (steel brand: ST07Zn), we can see that the friction caused by PK oil was the lowest, so the effect of PK oil was the best. Then PK oil was used as the base lubricating oil and some solid additive powers was added into it to make a new type lubrication (named as L oil).The result of test proved that the new lubricating oil had remarkable effect on the drawing process of hot-galvanized sheet steel.
 Select Heteroepitaxial Growth and Characterization of 3C-SiC Films on Si Substrates Using LPVCVD Haiwu ZHENG, Junjie ZHU, Zhuxi FU, Bixia LIN, Xiaoguang LI J. Mater. Sci. Technol., 2005, 21 (04): 536-540.  Abstract   HTML   PDF (537KB) 3C-SiC films have been deposited on Si (111) substrates by the low-pressure vertical chemical vapor deposition (LPVCVD) with gas mixtures of SiH4, C3H8 and H2. The growth mechanism of SiC films can be obtained through the observations using field emission scanning electron microscope (FESEM). It is found that the growth process varies from surface control to diffusion control when the deposition temperature increases from 1270 to 1350℃. The X-ray diffraction (XRD) patterns show that the SiC films have good crystallinity and strong preferred orientation. The results of the high resolution transmission electron microscopy (HRTEM) image and the transmission electron diffraction (TED) pattern indicate a peculiar superlattice structure of the film. The values of the binding energy in the high resolution X-ray photoelectron spectra (XPS) further confirm the formation of SiC.
 Select X-ray Photoelectron Spectroscopy Studies of TixAl1-xN Thin Films Prepared by RF Reactive Magnetron Sputtering Rui XIONG, Jing SHI J. Mater. Sci. Technol., 2005, 21 (04): 541-544.  Abstract   HTML   PDF (332KB) TixAl1-xN films have been prepared by RF reactive magnetron sputtering. X-ray diffraction results showed that TixAl1-xN thin films in this study were hexagonal wurtzite structure with the Ti content up to 0.18. X-ray photoelectron spectrocopy studies provided that the N1s core-electron spectrum of TixAl1-xN thin film brodend with increasing Ti content, and the difference of the chemical shifts for Ti2p3/2 line between TiN and TixAl1-xN thin film was 0.7 eV.
 Select Plasma Enhanced Chemical Vapor Deposition Nanocrystalline Tungsten Carbide Thin Film and Its Electro-catalytic Activity Huajun ZHENG, Chunan MA, Jianguo HUANG, Guohua LI J. Mater. Sci. Technol., 2005, 21 (04): 545-548.  Abstract   HTML   PDF (1025KB) Nanocrystalline tungsten carbide thin films were fabricated on graphite substrates by plasma enhanced chemical vapor deposition (PECVD) at H2 and Ar atmosphere, using WF6 and CH4 as precursors. The crystal phase, structure and chemical components of the films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS), respectively. The results show that the film prepared at CH4/WF6 concentration ratio of 20 and at 800℃ is composed of spherical particles with a diameter of 20 TixAl1-xN 35 nm. Electrochemical investigations show that the electrochemical real surface area of electrode of the film is large, and the electrode of the film exhibits higher electro-catalytic activity in the reaction of methanol oxidation. The designated constant current of the film catalyst is 123.6 mA/cm2 in the mixture solution of H2SO4 and CH3OH at the concentration of 0.5 and 2.0 mol/L at 70℃, and the designated constant potential is only 0.306 V (vs SCE).
 Select Structural, Morphological and Optical Properties of ZnO Thin Films Grown on γ-LiAlO2 Substrate by Pulsed Laser Deposition Jun ZOU, Shengming ZHOU, Xia ZHANG, Fenglian SU, Xiaomin LI, Jun XU J. Mater. Sci. Technol., 2005, 21 (04): 549-551.  Abstract   HTML   PDF (332KB) ZnO thin films were deposited on the substrates of (100) γ-LiAlO2 at 400, 550 and 700℃ using pulsed laser deposition (PLD) with the fixed oxygen pressure of 20 Pa, respectively. When the substrate temperature is 400℃, the grain size of the film is less than 1~$\mu$m observed by Leitz microscope and measured by X-ray diffraction (XRD). As the substrate temperature increases to 550℃, highly-preferred c-orientation and high-quality ZnO film can be attained. While the substratetemperature rises to 700℃, more defects appears on the surface of film and the ZnO films become polycrystalline again possibly because more Li of the substrate diffused into the ZnO film at high substrate temperature. The photoluminescence (PL) spectra of ZnO films at room temperature show the blue emission peaks centered at 430~nm. We suggest that the blue emission corresponds to the electron transition from the level of interstitial Zn to the valence band. Meanwhile, the films grown on γ-LiAlO2 (LAO) exhibit green emission centered at 540 nm, which seemed to be ascribed to excess zinc and/or oxygen vacancy in the ZnO films caused by diffusion of Li from the substrates into the films during the deposition.
 Select Hydrothermal Synthesis and Electrochemical Behavior of Nanosized Orthorhombic LiMnO2 Xiaoyan TU, Guanglie LU, Yuewu ZENG, Zhiqing YUAN, Xiurong HU J. Mater. Sci. Technol., 2005, 21 (04): 552-554.  Abstract   HTML   PDF (434KB) Nanosized orthorhombic LiMnO2 was successfully synthesized using Mn2O3 and LiOH•H2O as starting materials. Not only the reaction temperature was lower, but the reaction time for synthesizing was notably shortened to 1 h. In this hydrothermal process, the cations of the starting materials were capable of mixing and interacting in ionic scale, which resulted in the rapid formation of o-LiMnO2 powders at relatively low temperature. The particle size conformed by transmission electron microscopy is around 50~150 nm. Benefiting from its small particle size and good uniformity, the obtained o-LiMnO2 can reach the maximum discharge capacity of 163 mA•h•g-1 at 0.1 C rate after several cycles. X-ray diffraction data and electrochemical properties suggested the phase transformation from orthorhombic LiMnO2 to defect-type spinel LiMn2O4 with minor Li2MnO3, which resulted in the capacity fading during cycling.
 Select Preparation of Rare Earth Hydroxide and Oxide Nanoparticles by Precipitation Method Xiangting DONG, Guangyan HONG J. Mater. Sci. Technol., 2005, 21 (04): 555-558.  Abstract   HTML   PDF (622KB) A series of rare earth hydroxide and oxide nanoparticles have been prepared by precipitation method with alcohol as the dispersive and protective reagent. Transmission electron microscope (TEM) images indicate that the particles are spherical in shape and smaller than 100 nm in size. The crystallite sizes of cubic Ln2O3 have lanthanide shrinking effect, while average crystal lattice distortion rates possess lanthanide swelling effect. The diffraction peak intensity of heavy rare earth oxide nanometer powders is remarkably stronger than that of light rare earth oxide nanometer powders. The variation of diffraction intensity with atomic number presents an inverted W type, forming a double peak structure. Fourier transform infrared (FTIR) spectrums reveal that Ln2O3 nanopowders have higher surface activity than that of ordinary Ln2O3 powders. The UV-vis spectra show that Ln-O bond of these particles is slightly blue-shifted, and its absorption intensity decreases.
 Select Explanation of Unusual Photoluminescence Behavior from InAs Quantum Dots with InAlAs Capping Zhongyuan YU, Yongqiang WEI J. Mater. Sci. Technol., 2005, 21 (04): 559-562.  Abstract   HTML   PDF (611KB) The effect of different kinds of cap layers on optical property of InAs quantum dots (QDs) on GaAs (100) substrate was studied. Temperature dependent photoluminescence (PL) indicates that the PL integrated intensity from the ground state of InAs QDs capped with an intermediate InAlAs layer drops very little as compared to QDs capped with a thin InGaAs or GaAs cap layer from 15~K up to room temperature. PL integrated intensity ratio of the first excited to ground states for InAs QDs capped with an intermediate InAlAs layer is unexpectedly decreased with increasing temperature, which are attributed to phonon bottleneck effect. A virtual barrier is proposed to describe this physics process and shows good agreement with experimental results when fitting the curve with the value of the virtual barrier 30 meV.
 Select Particle Size Distribution and Characterization of High Siliceous and Microporous Materials S.K.Durrani, J.Akhtar, M.Ahmad, M.J.Moughal J. Mater. Sci. Technol., 2005, 21 (04): 563-570.  Abstract   HTML   PDF (1812KB) Particle size, textural and surface characteristics influence some major technological properties of high siliceous aluminosilicate zeolite and sillicoaluminophosphate (SAPO) microporous materials. A comparative study was furnished for measuring surface characteristics, particle size and particle size distribution using particle size analyzer (PSA) and scanning electron microscope (SEM). The PSA is capable of measuring particle diameter in micron range. The results of these techniques for estimation of particle size were compared and correlated statistically. Student t-test and variance ratio test (F-test) methods were performed for the significance of results by the analysis of variance (ANONA) and multiple-range tests. Textural and surface characteristics were evaluated by Brunauer, Emmett & Teller (BET) volumetric technique and v-αs plotting method. The textural results shows that the external surface area and micropore volume of microporous materials were higher than those of the high siliceous zeolites and its zeotype materials.
 Select Arg-Gly-Asp (RGD) Modified Biomimetic Polymeric Materials Xufeng NIU, Yuanliang WANG, Yanfeng LUO, Juan XIN, Yonggang LI J. Mater. Sci. Technol., 2005, 21 (04): 571-576.  Abstract   HTML   PDF (168KB) The new generation of biomaterials focuses on the design of biomimetic polymeric materials that are capable of eliciting specific cellular responses and directing new tissue formation. Since Arg-Gly-Asp (RGD) sequences have been found to promote cell adhesion in 1984, numerous polymers have been functionalized with RGD peptides for tissue engineering applications. This review gave the advance in RGD modified biomimetic polymeric materials, focusing on the mechanism of RGD, the surface and bulk modification of polymer with RGD peptides and the evaluation in vitro and in vivo of the modified biomimetic materials.
 Select Experimental Investigation of Folding Damage for the Rigidizable Carbon-Epoxy Composites Youshan WANG, Zhimin XIE, Zhimin WAN, Xingwen DU J. Mater. Sci. Technol., 2005, 21 (04): 577-580.  Abstract   HTML   PDF (352KB) This paper focused on the folding damage behavior of the space rigidizable materials in terms of 3-layer composite membranes. An experimental scheme was presented. The composite membranes were folded between the two plates for a short time, and then the unfolded composite membranes were compressively cured in an oven. By adjusting the displacement of one plate, the folding radius was changed. As expected, the strength and effective modulus of the cured composite membranes drop with decreasing the folding radius. When the strain controlled failure rule is applied to the composite membranes, a minimal folding radius can be reached, beyond which the membranes will keep intact. Furthermore, folding damage due to folding and unfolding processes was evaluated by a simplified model. Compared with the measured residual strength and effective modulus, calculated results have the same trend. A discrepancy is attributed to neglecting the effects of the transverse fibers and the matrix.
 Select DSC Study on the Polyacrylonitrile Precursors for Carbon Fibers Wangxi ZHANG, Musen LI J. Mater. Sci. Technol., 2005, 21 (04): 581-584.  Abstract   HTML   PDF (362KB) Different polyacrylonitrile (PAN) precursor fibers that displayed various thermal properties were studied by using differential scanning calorimetry (DSC). Results showed that some commercial PAN precursor fibers displayed double separated peaks and these fibers were of high quality because of their process stability during their conversion to carbon fibers of high performance. Some fabrication processes, such as spinning, drawing, could not apparently change the DSC features of a PAN precursor fiber. It was concluded that the thermal properties of a PAN precursor fiber was mainly determined from its comonomer content type and compositions.
 Select Preparation, Morphology and Damping Property of PU/UP Interpenetrating Polymer Networks Dongyan TANG, Liangsheng QIANG, Zheng JIN, Liancheng ZHAO J. Mater. Sci. Technol., 2005, 21 (04): 585-588.  Abstract   HTML   PDF (1057KB) Interpenetrating polymer networks (IPNs) composed of acrylate-modified polyurethane (PU)/unsaturated polyester (UP) resin $via$ simultaneous polymerization with various component ratios of PU/UP were prepared. The polymerization processes of IPNs were traced through infrared spectrum (IR) techniques, by which the phase separation in systems could be controlled effectively. Results for the morphology and miscibility among multiple phases of IPNs, obtained by transmission electron microscope (TEM) indicated that the domains between two phases were constricted in nanometer scales. The dynamic mechanical thermal analyzer (DMTA) detection results revealed that the loss factor (tanδ) and loss modulus (E'') increased with the polyurethane amounts in system, and the peak value in curves of tanδ and E'' appeared toward low temperature ranges. Maximum tanδ values of all samples were above 0.3 in the nearly 50℃ ranges. Also, the mechanical properties of PU/UP IPNs were studied in detail.
 Select Effect of Relative Reduction on Property of Steel-Mushy Cu-Graphite Composite Peng ZHANG, Yunhui DU, Hanwu LIU, Daben ZENG, Jianzhong CUI, Limin BA J. Mater. Sci. Technol., 2005, 21 (04): 589-592.  Abstract   HTML   PDF (737KB) The rolling treatment of steel-mushy QTi3.5-3.5 graphite composite was conducted under different relative reduction at room temperature. The effect of room-temperature rolling on interfacial mechanical property of steel-mushy QTi3.5-3.5 graphite composite was studied and the relationship between interfacial shear strength and relative reduction was established. The results show that, for steel-mushy QTi3.5-3.5 graphite composite, which consists of 1.2 mm-thick 08Al steel plate and 2.8 mm-thick QTi3.5-3.5 graphite layer, there is a nonlinear relationship between interfacial shear strength and relative reduction in graphite layer. When relative reduction is smaller than 1.1%, interfacial shear strength increases with increasing the relative reduction. When relative reduction is larger than 1.1%, interfacial shear strength decreases with increasing the relative reduction. When relative reduction is 1.1%, the largest interfacial shear strength of 145.2 MPa can be obtained.
 Select Effect of Co Ion Implantation on GMR of [NiFeCo(10 nm)/Ag(10 nm)]×20 Multilayer Film Yuding HE, Shejun HU, Jian LI, Guangrong XIE J. Mater. Sci. Technol., 2005, 21 (04): 593-598.  Abstract   HTML   PDF (1224KB) The composition, phase structure and microstructure of the discontinuous multilayer film [NiFeCo(10 nm)/ Ag(10 nm)]×20 were investigated after Co ion implantation and annealing at 280, 320, 360 and 400℃, respectively. GMR (giant magnetoresistance) ratio of the film with/without Co ion implantation was measured. The results showed that Co ion implantation decreased the granule size of the annealed multilayer film, and increased Hc value and GMR ratio of the multilayer film. After annealing at 360℃, the multilayer film [NiFeCo(10 nm)/Ag(10 nm)]×20 with/without Co ion implantation both exhibited the highest GMR ratio of 12.4%/11% under 79.6 kA/m of applied saturation magnetic field.
 Select Thermal Residual Stresses in Multilayered Coatings Xiancheng ZHANG, Binshi XU, Haidou WANG, Yixiong WU J. Mater. Sci. Technol., 2005, 21 (04): 599-605.  Abstract   HTML   PDF (541KB) The mechanical integrity and reliability of coated devices are strongly affected by the residual stresses in thin films and coatings. However, due to the metallurgical complexity of materials, it is rather difficult to obtain a closed-form solution of residual stresses within multilayered coatings (e.g. functionally graded coatings, FGCs). In this paper, an analytical model is developed to predict the distribution of residual stresses within multilayered coatings. The advantage of this model is that the solution of residual stresses is independent of the number of layers. Specific results are obtained by calculating elastic thermal stresses in ZrO2/NiCoCrAlY FGCs, which consist of different material layers. Furthermore, the residual stress distribution near the edges and the stress-induced failure modes of coating are also analyzed. The topics discussed provide some insights into the development of a methodology for designing fail-safe coating systems.
 Select Synthesis of Ultrafine Fe3O4 Powder via a Novel Ageing Process Yongrui LI, Nanlin SHI J. Mater. Sci. Technol., 2005, 21 (04): 606-608.  Abstract   HTML   PDF (487KB) Ultrafine Fe3O4 powder was successfully synthesized via a novel ageing process from a precursor FeO(OH), which was the hydrolysate of FeCl3 in the urea solution. The structure of as-synthesized powder was characterized by X-ray diffraction (XRD), and the morphology of these nanoparticles was investigated using a transmission electron microscope (TEM). Pure phase Fe3O4 was obtained and the mean diameter of these nanoparticles was about 21nm. Furthermore, the study indicated that the precursor FeO(OH) played an important role in the formation of Fe3O4 nanoparticles. The mechanism was also discussed.
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CN: 21-1315/TG
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