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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      28 May 2007, Volume 23 Issue 03 Previous Issue    Next Issue
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    Research Articles
    Directional Solidification Assisted by Liquid Metal Cooling
    Jian ZHANG, Langhong LOU
    J. Mater. Sci. Technol., 2007, 23 (03): 289-300. 
    Abstract   HTML   PDF (4465KB)
    An overview of the development and current status of the directional solidification process assisted by liquid metal cooling (LMC) has been presented in this paper. The driving force of the rapid development of the LMC process has been analyzed by considering the demands of (1) newer technologies that can provide higher thermal gradients for alleviated segregation in advanced alloy systems, and (2) better production yield of the large directionally solidified superalloy components. The brief history of the industrialization of the LMC process has been reviewed, followed by the discussion on the LMC parameters including selection of the cooling media, using of the dynamic baffle, and the influence of withdrawal rates and so on. The microstructure and mechanical properties of the traditional superalloys processed by LMC, as well as the new alloys particularly developed for LMC process were then described. Finally, future aspects concerning the LMC process have been summarized.
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    Investigation of Ge-Si Atomic Interdiffusion in Ge Nano-dots Multilayer Structure by Double Crystal X-ray Diffraction
    Wenhua SHI, Lei ZHAO, Liping LUO, Qiming WANG
    J. Mater. Sci. Technol., 2007, 23 (03): 301-303. 
    Abstract   HTML   PDF (254KB)
    The fluctuations of the strained layer in a superlattice or quantum well can broaden the width of satellite peaks in double crystal X-ray diffraction (DCXRD) pattern. It is found that the width of the 0th peak is directly proportional to the fluctuation of the strained layer if the other related facts are ignored. By this method, the Ge-Si atomic interdiffusion in Ge nano-dots and wetting layers has been investigated by DCXRD. It is found that thermal annealing can activate Ge-Si atomic interdiffusion and the interdiffusion in the nano-dots area is much stronger than that in the wetting layer area. Therefore the fluctuation of the Ge layer decreases and the distribution of Ge atoms becomes homogeneous in the horizontal Ge (GeSi actually) layer, which make the width of the 0th peak narrow after annealing.
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    A Novel Design and Fabrication of Magnetic Random Access Memory Based on Nano-ring-type Magnetic TunnelJunctions
    X.F.Han, H.X.Wei, Z.L.Peng, H.D.Yang, J.F.Feng, G.X.Du, Z.B.Sun, L.X.Jiang, Q.H.Qin, M.Ma
    J. Mater. Sci. Technol., 2007, 23 (03): 304-306. 
    Abstract   HTML   PDF (967KB)
    Nano-ring-type magnetic tunnel junctions (NR-MTJs) with the layer structure of Ta(5)/Ir22Mn78(10)/Co75Fe25(2)/Ru(0.75)/Co60Fe20B20(3)/Al(0.6)-oxide/Co60Fe20B20(2.5)/Ta(3)/Ru(5) (thickness unit: nm) were nano-fabricated on the Si(100)/SiO2 substrate using magnetron sputtering deposition combined with the optical lithography, electron beam lithography (EBL) and Ar ion-beam etching techniques. The smaller NR-MTJs with the inner- and outer-diameter of around 50 and 100 nm and also their corresponding NR-MTJ arrays were nano-patterned. The tunneling magnetoresistance (TMR & R) versus driving current (I) loops for a spin-polarized current switching were measured, and the TMR ratio of around 35% at room temperature were observed. The critical values of switching current for the free Co60Fe20B20 layer relative to the reference Co60Fe20B20 layer between parallel and anti-parallel magnetization states were between 0.50 and 0.75 mA in such NR-MTJs. It is suggested that the applicable MRAM fabrication with the density and capacity higher than 256 Mbit/inch2 even 6 Gbite/inch2 are possible using both 1 NR-MTJ+1 transistor structure and current switching mechanism based on based on our fabricated 4×4 MRAM demo devices.
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    Effect of Cu on Microstructures of Manganese Steel by EDXA and SEM
    Xinhua CHEN, Junhua DONG, Enhou HAN, Wei KE
    J. Mater. Sci. Technol., 2007, 23 (03): 307-311. 
    Abstract   HTML   PDF (1177KB)
    In order to investigate the distribution of Cu and Mg, and the effect of Cu on the microstructure of steels, manganese steels containing various Cu contents were annealed at 1260, 1100 and 1000℃, respectively, for 1 h and subsequently cooled to room temperature in the furnace to simulate the pre-rolling anneal. The results indicate that Cu is not microscopically segregated in the annealed steels. The scanning electron microscopy (SEM) observation shows that the main microstructure consist of ferrite and pearlite; the percentage of pearlite in the steels increases with increasing Cu content. The grain size reduces with the decrease of the annealing temperature. The results of energy dispersive X-ray analysis (EDXA) suggest that Cu content in pearlite is higher than that in ferrite, demonstrating that the microstructure-segregation of Cu occurred. However, the cast specimens show that Cu content in MnS and S-rich phases is high. In addition, Cu of 0.2%–0.4% could improve the distribution of MnS and S-rich inclusions. The optimal Cu content in steels and the optimal annealing temperature between 1100–1200℃ were determined.
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    Effect of Aging on Microstructure and Mechanical Property of 1900 MPa Grade Maraging Stainless Steel
    Kai LIU, Yiyin SHAN, Zhiyong YANG, Jianxiong LIANG, Lun LU, Ke YANG
    J. Mater. Sci. Technol., 2007, 23 (03): 312-318. 
    Abstract   HTML   PDF (2543KB)
    The 18%Ni alloy steels provide high strength and toughness, while age-hardenable or PH stainless steels also have good corrosion resistance. This paper focuses on an investigation of the heat treatment, mechanical properties and microstructural development of a new maraging stainless steel. It is reported that the heat treatment process should consist of solution treatment and cryogenic cooling to attain a fully martensitic structure, followed by aging at 813 K. This heat treatment resulted in an ultimate tensile strength of over 1900 MPa combined with good impact toughness. Transmission electron microscopy is used to show that, for the peak-aged condition (813 K/4 h), nano-sized precipitates, e.g. Ni3Mo and/or R-phase, and a high density of dislocations were uniformly dispersed in the lath martensite matrix. The calculated yield strength, based on a revised Orowan mechanism, is in good agreement with the test data. The steel studied has an ultimate tensile strength over 1900 MPa, excellent fracture toughness, and good resistance against over-aging and relatively good corrosion resistance as well.
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    Deformation at Room and Low Temperatures and Martensite Transformation in Resistance Spot Welding Duplex γ & α(δ) Materials of 301L Stainless Steel
    Wei LIU, Jun HE, Meng FAN, Peide LU, Li SHAO
    J. Mater. Sci. Technol., 2007, 23 (03): 319-322. 
    Abstract   HTML   PDF (1355KB)
    Transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP) effects had been widely studied in single austenite steel. But in duplex γ & α(δ) phase, such as welding materials of stainless steel, they had been less studied. Tensile shear loading experiment of resistance spot welding specimens prepared with 2 mm 301L sheets, was carried out at 15℃ and -50℃. Optical microscopy and scanning electron microscopy (SEM) as well as X-ray diffraction (XRD) were used to investigate the microstructure of weld nugget, and specimens fracture surface. The results showed that the initial weld nugget was composed of 8.4% α(δ) ferrite and 91.6% austenite. Tensile shear load bearing capacity of spot welding specimen at -50℃ was 24.8 kN, 17.7% higher than that at 15℃. About 78.5 vol. pct. martensite transformation was induced by plastic deformation at -50℃, while about 67.9 vol. pct transformation induced at 15℃. The plasticity of spot welding joint decreased with the decline of experimental temperature.
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    Effect of Sulfate-reducing Bacteria on Corrosion Behavior of Mild Steel in Sea Mud
    Xiaodong ZHAO, Jizhou DUAN, Baorong HOU, Suru WU
    J. Mater. Sci. Technol., 2007, 23 (03): 323-328. 
    Abstract   HTML   PDF (1010KB)

    Microbiologically influenced corrosion (MIC) is very severe corrosion for constructions buried under sea mud environment. Therefore it is of great importance to carry out the investigation of the corrosion behavior of marine steel in sea mud. In this paper, the effect of sulfate-reducing bacteria (SRB) on corrosion behavior of mild steel in sea mud was studied by weight loss, dual-compartment cell, electronic probe microanalysis (EPMA), transmission electron microscopy (TEM) combined with energy dispersive X-ray analysis (EDX) and electrochemical impedance spectroscopy (EIS). The results showed that corrosion rate and galvanic current were influenced by the metabolic activity of SRB. In the environment of sea mud containing SRB, the original corrosion products, ferric (oxyhydr) oxide, transformed to iron sulfide. With the excess of the dissolved H2S, the composition of the protective layer formed of FeS transformed to FeS2 or other non-stoichiometricpolysulphide, which changed the state of the former layer and accelerated the corrosion process.

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    Z-parameter Method for Damage Evaluation in HK40 Steel
    Li XING, Jie ZHAO, Fuzhong SHEN, Wei FENG
    J. Mater. Sci. Technol., 2007, 23 (03): 329-332. 
    Abstract   HTML   PDF (991KB)
    A Z-parameter method is used to evaluate the damage process of HK40 austenitic steel. By using Z-parameter based on the Larson-Miller method, the nonlinear master curve of the log stress vs Larson-Miller parameter P can be expressed as: P=27.74-3.4lgσ-0.032σ, and a family of curves parallel to the master curve can be written as: P=(27.74-Z)-3.4lgσ-0.032σ, where Z represents the magnitude of the deviation from the master curve. According to the creep rupture data both from different segments of a serviced tube and from the same segment locations with different service time, the value of parameter Z has close relationship with the deterioration of creep rupture properties. The damage state of the samples is evaluated by monitoring the changes in natural frequency f and Young0s modulus E, and the relationships between Z and the damage parameters are discussed.
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    Antibacterial Properties of an Austenitic Antibacterial Stainless Steel and Its Security for Human Body
    Ke YANG, Manqi LÜ
    J. Mater. Sci. Technol., 2007, 23 (03): 333-336. 
    Abstract   HTML   PDF (220KB)
    An austenitic antibacterial stainless steel is reported in this paper. The very fine and dispersive ε-Cu precipitations in the matrix of the antibacterial steel after the antibacterial treatment endow the steel with antibacterial function. The antibacterial function is strong, long-term and broad-spectrum, and can be maintained even after repeated wear and long time dipping in water. The steel is safe for human body and could be used widely in daily application.
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    Effect of Coiling Temperature on the Evolution of Texture in Ferritic Rolled Ti-IF Steel
    Zhaodong WANG, Yanhui GUO, Wenying XUE, Xianghua LIU, Guodong WANG
    J. Mater. Sci. Technol., 2007, 23 (03): 337-341. 
    Abstract   HTML   PDF (803KB)
    The effect of coiling temperatures on the evolution of texture in Ti-IF steel during ferritic hot rolling, cold rolling and annealing was studied. It was found that texture evolution at high temperature coiling is absolutely different from that at low temperature one. The hot band texture includes a strong α-fiber as well as a weak γ-fiber after ferritic hot rolling and low temperature coiling. Both of them intensify after cold rolling and a γ-fiber with peak at {111}<112> is the main texture of annealed samples. However, the main component of the hot band texture after high temperature coiling is γ-fiber. After cold rolling, the intensity of γ texturereduces; α fiber (except {111} <110> component) intensifies and a strong and well-proportioned γ-fiber forms in the annealed samples.
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    Energy Dissipation and Apparent Viscosity of Semi-solid Metal during Rheological Processes Part I: Energy Dissipation
    Wen LIU, Shuming XING, Peiwei BAO, Milan ZHANG, Liming XIAO
    J. Mater. Sci. Technol., 2007, 23 (03): 342-346. 
    Abstract   HTML   PDF (585KB)
    The energy dissipation caused by the viscous force has great effects on the flow property of semi-solid metal during rheological processes such as slurry preparing, delivering and cavity filling. Experimental results in this paper indicate that the viscous friction between semi-solid metal and pipe wall, the collisions among the solid particles, and the liquid flow around particles are the three main types of energy dissipation. On the basis of the hydromechanics, the energy dissipation calculation model is built. It is demonstrated that the micro-structural parameters such as effective solid fraction, particle size and shape, and flow parameters such as the mean velocity, the fluctuant velocity of particles and the relative velocity between the fluid and solid phase, affect the energy dissipation of semi-solid metal.PartⅡ:This study investigates the rheological behavior of semi-solid metal. An analytical model of apparent viscosity was built up based on analysis of energy dissipation during rheological processes such as slurry preparing, delivering and model filling. The rheological behavior of SSM slurries was described by an analytical model in terms of micro structural parameters, which consist of effective solid fraction, particle size and shape, and flow parameters such as mean velocity, fluctuation velocity and relative velocity between liquid and solid phase. The model was verified in the experiment of A356 alloys with a coaxial double-bucket rheometer. And the maximum relative error between the theoretical value and measured value is less than 10%. The results of experiment and theoretical calculation also indicate that the micro structural parameters and flow parameters are two major factors that affect the apparent viscosity of semi-solid alloys, and fluctuation velocity and relative velocity between liquid and solid phase are the key factors to distinguish between steady and transient rheological behaviors.
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    Structural Changes of α Phase in Furnace Cooled Eutectoid Zn-Al Based Alloy
    Y.H.Zhu, K.C.Chan, G.K.H.Pang, T.M.Yue, W.B.Lee
    J. Mater. Sci. Technol., 2007, 23 (03): 347-352. 
    Abstract   HTML   PDF (4070KB)
    Furnace cooling is a slow cooling process. It is of importance to study structural evolution and its effects on the properties of alloys during the furnace cooling. Decomposition of aluminium rich α phase in a furnace cooled eutectoid Zn-Al based alloy was studied by transmission electron microscopy. Two kinds of precipitates in the α phase were detected in the FCZA22 alloy during ageing at 170℃. One was the hcp transitional α′m phase which appears as directional rods and the round precipitates. The other was the fcc α′′m phase. It was found that the transitional phaseα′m grew in three preferential directions of <110>, <011> and <101>. The orientation relationship between the α phase and transitional phase α′m was determined as , . The non-equilibrium phase decomposition of the α phase is discussed in correlation with the equilibrium phase relationships. (02-2) 'm (fcc)// (02-2) (fcc) , [-111] 'm (fcc)// [-233] (fcc). The non-equilibrium phase decomposition of the phase is discussed in correlation with the equilibrium phase relationships.
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    Corrosion of Artificial Aged Magnesium Alloy AZ80 in 3.5 wt pct NaCl Solutions
    Rongchang ZENG, Enhou HAN, Wei KE
    J. Mater. Sci. Technol., 2007, 23 (03): 353-358. 
    Abstract   HTML   PDF (1943KB)
    The corrosion morphologies of aged magnesium alloy AZ80 were investigated by immersion corrosion tests, scanning electron microscopy (SEM), electrochemical measurement. The T5 heat treatment was carried out in a vacuum furnace, holding for 16 h at 177℃, and then cooling in air. The results showed intergranular corrosion (IGC) occurred as an aged AZ80 sample was immersed in 3.5 wt pct NaCl aqueous solution for 1 h and the narrow path attack progressed predominantly along the bulk β phase in the grain boundaries or took place in the eutectic areas. IGC was attributed to the network distribution of β phase along the grain boundaries, the depleted aluminium in the precipitation areas and the breakdown potential.
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    Semi-solid Thixoforming Simulation of Al-Cu-Mn-Ti Alloy Parts via AnyCasting
    Ping WANG, Jianzhong CUI, Guimin LU
    J. Mater. Sci. Technol., 2007, 23 (03): 359-362. 
    Abstract   HTML   PDF (4226KB)
    The software AnyCasting was used to simulate the thixotropic die-casting process of semi-solid Al-Cu-Mn-Ti alloy slurry to form the parts of a particular shape, especially on how the in-gate size of die and injection speed affect the process. The results showed that the die cavity can be filled well with the semi-solid slurry in form of laminar flow under conditions that the temperature of the semi-solid slurry is 640℃ and that of die 200–240℃, thickness of in-gate is 11 mm and, more important, the injection speed should be changed from 0.1 to 1.0 m/s when 60% of die cavity has been filled. The simulation result is highly proved in conformity to the actual die-casting specimens in accordance to the filling process as simulated. Moreover, the hardness of the specimens is up to 116.6 HV after the treatment of solid solution plus underaging, i.e. 45.7% higher than that in conventional ones.
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    Dilatometric Sintering of Ti-2Al and Ti-5Al Elemental Powder
    J. Mater. Sci. Technol., 2007, 23 (03): 363-366. 
    Abstract   HTML   PDF (1346KB)
    The effect of Al addition (2 and 5 at. pct) on sintering kinetics of Ti power was investigated. Al reduces the sintering rates, sinter density, increases activation energy of sintering and accelerates the grain growth. Sintering was controlled by mixed mode, i.e. transient liquid phase sintering, formation of intermetallics, and Ti grain boundary diffusion in TiAl2 and other intermetallics.
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    A new process for titanium aluminides production from TiO2
    A.R.Kamali, H.Razavizadeh, S.M.M.Hadavi
    J. Mater. Sci. Technol., 2007, 23 (03): 367-372. 
    Abstract   HTML   PDF (4024KB)
    This paper describes a new process for producing titanium aluminides, in particular TiAl, from TiO2 raw material. On the basis of obtained results, the non-completed reaction of TiO2 with Al and Ca in a special reaction vessel results in the production of granulates of titanium aluminides especially Ti3Al and other Ti-Al phases as the metallic product and Ca12Al14O33 as the non-metallic product. By adding KClO4 in the mixture, a nearly completed reaction can be carried out. The products of this reaction are titanium aluminide particularly TiAl as the metallic part and CaAl4O7 (grossite) as the non-metallic slag part. Both product and slag are produced in a separated form. This process, called KRH-method is described in this article. The scanning electron microscopic microstructure of metallic part of the product shows different phases: the matrix phase is TiAl, where the needle form precipitation is TiAl2 and the plate form precipitation includes TiAl and Ti3Al phases. The microstructure of the remelted metallic part indicates dendritic phase with a lamellar structure comprising of TiAl and Ti3Al phases. The interdendritic phase of TiAl is also seen.
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    Improvement on the Oxidation Resistance of a Ti3Al Based Alloy by Cr1-xAlxN (0≤x≤0.47) Coatings
    Ming ZHU, Meishuan LI, Shuwang DUO. Yanchun ZHOU
    J. Mater. Sci. Technol., 2007, 23 (03): 373-378. 
    Abstract   HTML   PDF (2465KB)
    Cr1-xAlxN coatings have been deposited on a Ti3Al based alloy by reactive sputtering method. The results of the isothermal oxidation test at 800–900℃ showed that Cr1-xAlxN coatings could remarkably reduce the oxidation rate of the alloy owing to the formation of Al2O3+Cr2O3 mixture oxide scale on the surface of the coatings. No spallation of the coatings or oxide scales took place during the cyclic oxidation at 800℃. Ti was observed to diffuse into the coatings, the diffusion distance of which was very short, and the diffusion ability of it was proportional to the Al content in the coatings. Compared to Ti, Nb can diffuse much more easily through the whole coatings and oxide scales.
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    Improvement on the Corrosion Resistance of AZ91D Magnesium Alloy by Aluminum Diffusion Coating
    Hongwei HUO, Ying LI, Fuhui WANG
    J. Mater. Sci. Technol., 2007, 23 (03): 379-382. 
    Abstract   HTML   PDF (1412KB)
    By combination of magnetron sputtering deposition and vacuum annealing, an aluminum diffusion coating was prepared on the substrate of AZ91D alloy to improve its corrosion resistance. The microstructure and composition of the diffusion coating was investigated by scanning electron microscopy and X-ray diffraction. The diffusion coating was mainly comprised of β phase—Al12Mg17. The continuous immersion test in 3.5 wt pct neutral NaCl solution indicated that the specimen with diffusion coating had better corrosion resistance compared with the bare AZ91D alloy specimen. The potentiodynamic polarization measurement indicated that the diffusion coating could function as an effectively protective layer to reduce the corrosion rate of AZ91D alloy when exposed to 3.5 wt pct NaCl solution.
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    Preparation and Properties of Plasma Spraying Cu-Al2O3 Gradient Coatings
    Ali LEI, Nan DONG, Lajun FENG
    J. Mater. Sci. Technol., 2007, 23 (03): 383-386. 
    Abstract   HTML   PDF (1651KB)
    In order to overcome the limitations of low adhesion strength and poor thermal-shock resistance of pure ceramic coatings, Cu-Al2O3 gradient coatings were fabricated by plasma spraying. The microstructure and distribution of Cu-Al2O3 gradient coatings were analyzed. The adhesion strength, thermal-shock resistance and porosity of the coatings were tested. The results show that the composition of the gradient coatings has a gradient distribution along the thickness of coatings. As copper has a relatively low melting point and the molten copper has good wettability on the surface of Al2O3, it can be melted sufficiently and could fill the interstices and pores among the spraying particles effectively, thus improves the adhesion strength, thermal shock resistance and reduces the porosity. The adhesion strength of the gradient coating is 15.2 MPa which is two times of that of the double-layer structure coating.
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    Preparation and Tribological Properties of Ni-P Electroless Composite Coating Containing Potassium Titanate Whisker
    Yaxu JIN, Lin HUA
    J. Mater. Sci. Technol., 2007, 23 (03): 387-391. 
    Abstract   HTML   PDF (1252KB)
    Nickel-phosphorus (Ni-P) composite coatings containing potassium titanate (K2Ti6O13) whiskers (PTWs) were prepared by electroless plating. The surface morphology and component of coatings were investigated by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), respectively before and after wear test. The tribological performance was evaluated using a pin-on-disk wear tester under dry conditions. It is found that the Ni-P-PTWs composite coatings exhibit higher wear resistance than Ni-P and Ni-P-SiC electroless coatings. The favorable effects of PTWs on the tribological properties of the composite coatings are attributed to the super-strong mechanical properties and the specific tunneling structures of PTWs. The PTWs greatly reinforce the structure of the Ni-P-based composite coatings and thereby greatly reduce the adhesive and plough wear of Ni-P-PTWs composite coatings.
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    Influence of Surface Oxide Films on Elastic Behaviors of Straight Screw Dislocations Parallel to the Surface of Pure Aluminum
    Weimin MAO, Dong LI, Yongning YU
    J. Mater. Sci. Technol., 2007, 23 (03): 392-394. 
    Abstract   HTML   PDF (496KB)
    The image stress of straight screw dislocations parallel to the medium surface covered by thin heterogeneous films was analyzed and deduced, in order to calculate the image shear stress. The relationship between image stress and distance from the screw dislocation to the interface of pure aluminum and its oxide covering was calculated based on the analysis. It was shown quantitatively that a sign conversion of the image stress appears in the case of thin oxide covering, while dislocation would pile up near the interface because of the possible slips of the screw dislocations induced by the image stress, which might break down the very thin oxide covering. Further investigation on edge dislocations or other dislocation configurations need to be done.
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    Flow instability of molten GaAs in the Czochralski configuration
    Shuxian CHEN, Mingwei LI
    J. Mater. Sci. Technol., 2007, 23 (03): 395-401. 
    Abstract   HTML   PDF (1598KB)
    The flow and heat transfer of molten GaAs under the interaction of buoyancy, Marangoni and crystal rotation in the Czochralski configuration are numerically studied by using a time-dependent and three-dimensional turbulent flow model for the first time. The transition from axisymmetric flow to non-axisymmetric flow and then returning to axisymmetric flow again with increasing centrifugal and coriolis forces by increasing the crystal rotation rate was numerically observed. The origin of the transition to non-axisymmetric flow has been proved to be baroclinic instability. Several important characteristics of baroclinic instability in the CZ GaAs melt have been predicted. These characteristics are found to be in agreement with experimental observations.
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    Effect of Heat Treatment on Silica Aerogels Prepared via Ambient Drying
    Fei SHI, Lijiu WANG, Jingxiao LIU, Miao ZENG
    J. Mater. Sci. Technol., 2007, 23 (03): 402-406. 
    Abstract   HTML   PDF (1246KB)
    Silica aerogels were prepared at ambient drying by using ethanol/trimethylchlorosilane (TMCS)/heptane solution as pore water exchange and surface modification of the wet gel before drying. The obtained silica aerogels exhibit a sponge-like structure with uniform pore size distribution. The effects of heat-treatment on the hydrophobicity, specific surface area and other properties were investigated. The results indicated that the hydrophobicity of silica aerogels could be maintained up to 350℃. With increasing heating temperature, hydrophobicity decreased, and became completely hydrophilic after heat-treatment at 500℃. Brunaueremmitt-teller (BET) surface area results indicated that the specific surface area of silica aerogels increased with increasing heating temperature in the range of 150–500℃. The effects of heat-treatment on the morphology and chemical bonding state of silica aerogels were investigated by scanning electron microscopy (SEM), differential temperature analysis (DTA) and Fourier-transform infrared spectroscopy (FT-IR).
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    A Novel Route to Prepare Nanocomposites in Larger Scale
    Wei WU, Lailong LUO, Guangwen CHU, Shengjun BAI, Haikui ZOU, Jianfeng CHEN
    J. Mater. Sci. Technol., 2007, 23 (03): 407-411. 
    Abstract   HTML   PDF (1033KB)
    A novel route to prepare nanocomposites was illustrated through preparing overbased calcium petroleum sulfonate lubricating oil detergent, where the rotating packed bed (RPB) was used as reactor in place of conventional reaction vessel. The results showed that the carbonation efficiency is improved, the raw materials consumption is reduced, and the dispersibilities, sizes and morphologies of nano-sized CaCO3 particles in overbased detergent are enhanced. It is deduced reasonably that this route can be extensively applied to nanocomposites preparation in appropriate conditions and would be a platform technology in this field.
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    Effect of Low Molecule Polyamide and Nano-SiO2 on Properties of the Poly (MMA/BA/MAA)
    Wenjun ZOU, Bo LIAO, Jin PENG, Linqi ZHANG, YunYANG, Furen XIAO
    J. Mater. Sci. Technol., 2007, 23 (03): 412-416. 
    Abstract   HTML   PDF (1482KB)
    Effects of low molecule polyamide (LMPA) and namometer SiO2 particles on the properties of the poly (MMA/BA/MAA) adhesive for wearable and nonskid PVC (polyvinyl carbazole) materials were investigated. The experimental results show that the shear strength of poly (MMA/BA/MAA)/LMPA is increased, when the LMPA is added into poly (MMA/BA/MAA). The optimum addition of LMPA is about 4 wt pct. By adding 3 wt pct nano-SiO2 into poly (MMA/BA/MAA)/LMPA adhesive, its properties such as the shear strength, thermal stability, wear resistance and sea waterproof resistance are increased too.
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    Removal Mechanism of Aqueous Lead by a Novel Eco-material: Carbonate Hydroxyapatite
    Huanyan XU, Lei YANG, Peng WANG, Yu LIU, Mingsheng PENG
    J. Mater. Sci. Technol., 2007, 23 (03): 417-722. 
    Abstract   HTML   PDF (776KB)
    Kinetics and mechanisms on the removal of aqueous lead ion by carbonate hydroxyapatite (CHap) are investigated in the present work. Experimental results show that, in the whole pH range, the lead removal percentage increases with decreasing pH values and reaches a maximum at pH=2–3. Under some conditions, the lead residual concentration is below national integrated wastewater discharge standard, even drinking water standard. The removal behavior is a complicated non-homogeneous solid/liquid reaction, which can be described by two stages from kinetic point of view. At the earlier stage, reaction rate is so fast that its kinetic course is intricate, which requires further study. At the latter stage, the rate of reaction becomes slow and the process of reaction accords with one order reaction kinetic equation. Experimental results show that the relationship between reaction rate constant k1 and temperature T accords to Arrhenius Equation, and the activation energy of sorption (Ea) is 11.93 kJ/mol and frequency factor (A) is 2.51 s-1. X-ray diffraction (XRD), scanning electron microscopy with an energy dispersive X-ray fluoresence spectrometer (SEM-EDS) and toxicity characteristic leaching procedure (TCLP) test were conducted in this work. It is indicated that the main mechanism is dissolution-precipitation, accompanying with superficial sorption.
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    Polymerization Process and Morphology of Polyurethane/Vinyl Ester Resin Interpenetrating Polymer Networks
    Dongyan TANG, Xuelian WU, Liangsheng QIANG
    J. Mater. Sci. Technol., 2007, 23 (03): 423-426. 
    Abstract   HTML   PDF (1442KB)
    A series of polyurethane (PU)/vinyl ester resin (VER) simultaneous IPNs (interpenetrating polymer networks) with different component ratios and comonomers types introduced to VER were synthesized and the polymerization processes were traced by Fourier transform infrared spectroscopy (FTIR) to study the kinetics of IPNs and hydrogen bonding action within multi-component. Furthermore, the relationship of polymerization process with morphology was investigated in detail for the first time by the morphological information given by chemical action between two networks besides physical entanglement, atomic force microscope (AFM) observation and dynamic mechanical analysis (DMA). The results indicated that the degree of hydrogen bonding (Xb, UT, %), calculated from functional group conversional rate and fine structures gained from FT-IR spectra of two networks, were affected by PU/VER weight ratios and comonomer types of VER. The relationship of formation kinetics and morphology showed that the change of Xb,UT (%) values exhibited excellent consistency with that of phase sizes observed by AFM and detected by DMA.
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    Quantificational Etching of AAO Template
    Guojun SONG, Dong CHEN, Zhi PENG, Xilin SHE, Jianjiang LI, Ping HAN
    J. Mater. Sci. Technol., 2007, 23 (03): 427-429. 
    Abstract   HTML   PDF (320KB)
    Ni nanowires were prepared by electrodeposition in porous anodized aluminum oxide (AAO) template from a composite electrolyte solution. Well-ordered Ni nanowire arrays with controllable length were then made by the partial removal of AAO using a mixture of phosphoric acid and chromic acid (6 wt pct H3PO4: 1.8 wt pct H3CrO4). The images of Ni nanowire arrays were studied by scanning electron microscopy (SEM) to determine the relationship between etching time and the length of Ni nanowire arrays. The results indicate that the length of nanowires exposed from the template can be accurately controlled by controlling etching time.
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    Surface polishing of 6H-SiC substrates
    Xiufang CHEN, Xiangang XU, Juan LI, Shouzhen JIANG, Lina NING, Yingmin WANG, Deying MA, Xiaobo HU, Minhua JIANG
    J. Mater. Sci. Technol., 2007, 23 (03): 430-432. 
    Abstract   HTML   PDF (401KB)
    The surface polishing for silicon carbide (SiC) substrates was investigated and results were presented for mechanical polishing (MP) and chemo-mechanical polishing (CMP). High quality surfaces were obtained after CMP with colloidal silica. The removal mechanism of scratches in MP and detailed physical and chemical process during CMP were analyzed. The effects of MP and CMP on the surface roughness were assessed by optical microscopy (OM), atomic force microscopy (AFM) and step profilometry. KOH etching and high resolution X-ray diffractometry (HRXRD) were applied to evaluate the subsurface damage of 6H-SiC substrates.
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CN: 21-1315/TG
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