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PREPARING NANO-CRYSTALLINE La DOPED WC/Co POWDER BY HIGH ENERGY BALL MILLING

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Acta Metallurgica Sinica(English Letters) 2002年第5期15卷 448-452页

作者： S. Liu, D.Q. Yi, Y.X. Li and D.ZouSchool of materials science & engineering, central south university, changsha 410083, chinaHunan Yin Zhou Nonferrous Metals Hi.-Tech. Limited Company, changsha 410083, china School of materials science engineering Central South University Hunan Yin Zhou Nonferrous Metals Hi.-Tech. Limited Company

The La doped WC/Co powder was prepared by high energy ball milling. The changes of crystal structure, micrograph and defect of the powder were investigated by means of XRD (X-ray diffraction), SEM (scanning electron microscope) and DTA (differential thermal analysis). The results show that adding trace La element into carbides is effective to minish the grain size of WC/Co powder. The La doped carbides powder with grain size of 30nm can be obtained after 10h ball milling. The XRD peak of Co phase disappeared after 20h ball milling, which indicated solid solution (or secondary solid solution) of Co phase in WC phase. The La doped powder with grain size of 10nm is obtained after 30h ball milling. A peak of heat release at the temperature of 470℃ was emerged in DTA curve within the range of heating temperature, which showed that the crystal structure relaxation of the powder appeared in the process of high energy ball milling. After consolidated the La doped WC/Co alloy by high energy ball milling exhibits ultra-fine grain sizes and better mechanical properties.

关键词： cemented carbide nano-crystalline powder rare earth high en-ergy ball milling

A Novel Method for Preparation of TaC Coating on C/C Composite Material

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Journal of materials science & Technology 2005年第3期21卷 381-385页

作者： Hanwei HE, Kechao ZHOU and Xiang XIONG State Key Lab of Powder Metallurgy, central south university, changsha 410083, china Lab. of Powder Metallurgy Central South University Changsha 410083 China

A new method for preparation of TaC coating on C/C composite material is reported. The amorphous ethylate tantalum jellied as the precursor is prepared and spread densely on the surface of the C/C composite material so as to form a multilayer film. In a graphitization furnace the multilayer film is transformed into TaC coating at various temperatures. Ethylate tantalum film is characterized by FT-IR (Fourier transform infrared) spectra, XRD (X-ray diffraction) and SEM (scanning electron microscopy) and TaC coating is characterized by XRD and SEM. At 1200℃ the coating contained TaC and Ta2O5, and at above 1400℃ only TaC is formed. The coating formed at 1600℃ is a continuous stratum structure, and that formed at 1600℃ is a porous net structure. Analysis on thermodynamics and formation mechanism of TaC indicates that, after ethylate tantalum is decomposed, Ta2O5 is first produced and then transformed into Ta2C, and newly formed Ta2C is transformed into TaC by the sufficient C at last.

关键词： C/C composite TaC coating Ethylate tantalum

Study on H atoms diffusion and adsorption properties of MgH_2-V systems

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science china(Technological sciences) 2008年第7期51卷 979-988页

作者： ZHOU DianWu1,2, LIU JinShui3 & PENG Ping3 1 State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan university, changsha 410082, china 2 college of Mechanical and Automatic engineering, Hunan university, changsha 410082, china 3 college of materials science and engineering, Hunan university, changsha 410082, china 1. State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan University Changsha 410082 China 2. college of Mechanical and Automatic engineering Hunan University Changsha 410082 China 3. college of materials science and engineering Hunan University Changsha 410082 China

Based on experimental results that VH0.81/MgH2 interface was found during the process of mechanically milling MgH2+5at.%V nanocomposite, H atoms diffusion and adsorption properties of MgH2-V systems have been investigated by using a first-principles plane-wave pseudopotential method based on the density functional theory. The results are as follows. When VH/MgH2 interface is formed due to V alloying MgH2 phase, the vacancy formed by H atoms near VH phase region is more stable than that without V alloying, while vacancy near MgH2 phase region is less stable than that without V alloying. During the process of H atoms diffusion after V alloying, the max migration barrier energy of H atoms in MgH2-V systems is reduced compared with that of MgH2 phase, which means that H atoms diffuse easily. When H diffuses into VH from MgH2 across VH/MgH2 interface, among three substitutions such as the replacement of H for V vacancy, or interstitial site or V atoms, the replacement of H for V vacancy has the strongest diffusion ability, next interstitial site, and finally V atoms site. As far as H adsorbed on different surfaces of VH phase is concerned, physical adsorption is carried out more easily than chemical adsorption, and the behavior of H atoms adsorbed on the surface near VH phase region can be found more easily than that near MgH2 phase region.

关键词： plane-wave pseudopotential theory magnesium hydride diffusion adsorption

Influence of Mg5Ga2 compound on microstructures and electrochemical properties of Mg-5%Hg-22%Ga alloy

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Progress in Natural science:materials International 2011年第1期21卷 73-79页

作者： Yan FENG~1,Ri-chu WANG~1,Chao-qun PENG~1,Hui-ping TANG~2,Hai-yan LIU~2 1.School of materials science and engineering,central south university,changsha 410083,china 2.Northwest Institute for Non-ferrous Metals Research,Xi'an 710016,china [a] School of materials science and engineering Central South University Changsha 410083 China [b] Northwest Institute for Non-ferrous Metals Research Xi'an 710016 China

The Mg-5%Hg-22%Ga（mole fraction） alloy was *** at 573-673 K for different times was carried out to ensure the fine dispersion of the *** electron microscopy（SEM）,X-ray diffractometry（XRD） and energy spectrum analysis（ESA） were employed to characterize the microstructures and phases of the Mg-5%Hg-22%Ga *** electrochemical and corrosion behaviors of the above alloy were studied by potentiodynamic,galvanostatic and electrochemical impedance spectroscopy（EIS） *** relationship between the Mg5Ga2compound and the electrochemical properties of the Mg-5%Hg-22%Ga alloy was *** results demonstrate that the heat treatment at 573-673 K for 24 h accelerates the growth of the intergranular eutectic Mg-Mg5Ga2and the heat treatment for 200 h prompts the transition of eutectic to dispersed linear Mg phase and *** transition enhances the electrochemical activity and corrosion resistance of the Mg-5%Hg-22%Ga *** the galvanostatic tests with current density of 100 mA/cm2,the most negative potential,-1.991 V, occurs in the sample aged for 200 *** largest corrosion current density of 44.36 mA/cm2occurs in the sample aged for 24 h.

关键词： Mg-Hg-Ga alloys anodic behavior Mg5Ga2 phase intergranular corrosion

Chemical synthesis of nanocrystalline ZrO_2-SnO_2 composite powders

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Rare Metals 2004年第2期23卷 182-184页

作者： YANG Huaming ZHANG Xiangchao YANG Wuguo HUANG Chenghuan QIU Guanzhou Department of Inorganic materials, School of Resources Processing and Bioengineering, central south university, changsha 410083, china Department of Inorganic materials School of Resources Processing and Bioengineering Central South University Changsha 410083

ZrO_2-SnO_2 composite nanoparticles were prepared by heating the hydrateprecursors synthesized by the chemical co-precipitation reaction of ZrOCl_2 and SnCl_4. Theprecursors were examined by differential thermal analysis (DTA) and thermogravimetric analysis(TGA). The composite powder was characterized using X-ray diffraction (XRD), transmission electronmicroscopy (TEM) and desorption isotherm (Barrett-Joyner-Halenda method). The average crystal sizeof the nanoparticle ranges from 15 to 30 nm for the sample containing 5%-25% ZrO_2 (mass fraction).Most of the pores in the ZrO_2-SnO_2 nanoparticles are about 10-20 nm in diameter. The compositepowder is promising for chemical sensors.

关键词： inorganic materials ZrO_2-SnO_2 nanocomposites chemical synthesis doping pore structure

Effects of Trace Silver and Magnesium on the Microstructure and Mechanical Properties of Al-Cu-Li Alloys

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Journal of Wuhan university of Technology(materials science) 2005年第1期20卷 9-12页

作者：陈志国 School of materials science and engineering Central South Univer sityChangsha 410083China

The effects of trace silver and magnesium additions on the microstructure and me chanical properties of the Al-Cu-Li alloys were investigated. The experimental results indicate that the effect of combined additions of Ag and Mg is the most obvious,the next is that of individual addition of Mg, and that of individual a ddition of Ag is the least. The addition of Ag and Mg in Al-Cu-Li alloy accele rates the precipitation of T1 and results in increasing the ageing hardness and strength. Prior cold work significantly improves the tensile strength by enhanci ng T1 precipitation in all the alloys investigated.

关键词： aluminium-lithium alloy ageing microstructure silver

Dynamic scheduling model of computing resource based on MAS cooperation mechanism

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science in china(Series F) 2009年第8期52卷 1302-1320页

作者： JIANG WeiJin1,2, ZHANG LianMei3 & WANG Pu4 1 School of Computer and Electronic engineering, Hunan university of Commerce, changsha 410205, china 2 School of Information engineering, Xiangtan university, Xiangtan 411000, china 3 Electrical engineering college, Wuhan university, Wuhan 430072, china 4 School of Commerce, central south university, changsha 410083, china 1. School of Computer and Electronic engineering Hunan University of Commerce Changsha 410205 China 2. School of Information engineering Xiangtan University Xiangtan 411000 China 3. Electrical engineering college Wuhan University Wuhan 430072 China 4. School of Commerce Central South University Changsha 410083 China

Allocation of grid resources aims at improving resource utility and grid application performance. Currently, the algorithms proposed for this purpose do not fit well the autonomic, dynamic, distributive and heterogeneous features of the grid environment. According to MAS （multi-agent system） cooperation mechanism and market bidding game rules, a model of allocating allocation of grid resources based on market economy is introduced to reveal the relationship between supply and demand. This model can make good use of the studying and negotiating ability of consumers＇ agent and takes full consideration of the consumer＇s behavior, thus rendering the application and allocation of resource of the consumers rational and valid. In the meantime, the utility function of consumer is given; the existence and the uniqueness of Nash equilibrium point in the resource allocation game and the Nash equilibrium solution are discussed. A dynamic game algorithm of allocating grid resources is designed. Experimental results demonstrate that this algorithm diminishes effectively the unnecessary latency, improves significantly the smoothness of response time, the ratio of throughput and resource utility, thus rendering the supply and demand of the whole grid resource reasonable and the overall grid load balanceable.

关键词： multi-agent system (MAS) resource scheduling model evolutionary game cooperation mechanism utility function

A Prediction of the Excess Partial Molar Free Energies of MgCl_2 in the KCI-MgCl_2-LiCl Molten Salt System Containing MgCl_2 below 0.5 from Thermodynamic Properties of Binary Systems

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Journal of materials science & Technology 2000年第1期16卷 85-87页

作者： Quanru ZHANG, Yuangao LI and Zheng FANG (Department of Chemistry, central south university of Technology, changsha 410083, china) Department of Chemistry Central South University of Technology Changsha 410083 China

The thermodynamical properties of MgCl_2 in KCI-MgCl_2-LiCl molten electrolytes containing MgCl_2 below 0.5 (mole fraction, the same below) have been determined from the interchange energies of two binary systems KCI-MgCl_2 and LiCI-MgCl_2, by means of a model on the assumptions that the electrolytes in the solution are treated as independent particles instead of their ion forms and the interchange energy between the component pair KCI-LiCl is ignored when compared with those of component pairs KCl-MgCl_2 and MgCl_2-LiCl. The interchange energies, wKCl-MgCl_2 and wMgcCl_2-Licl, are obtained as-70000 and -13800 ***-1, from the corresponding binary solutions, respectively.

关键词： KCI Free A Prediction of the Excess Partial Molar Free Energies of MgCl2 in the KCI-MgCl2-LiCl Molten Salt System Containing MgCl2 below 0.5 from Thermodynamic Properties of Binary Systems LiCl

SUPERPLASTIC BEHAVIOUR OF A FINE GRAINED TiAl BASED ALLOY TREATED BY MULTI-STEP THERMO-MECHANICAL TREATMENT

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中国有色金属学会会刊：英文版 1998年第1期8卷 108-109页

作者： Huang Baiyun, Deng Zhongyong and He YuehuiPowder Metallurgy Research Institute,central south university of Technology, changsha 410083, P. R. chinaSun Jian and Liu QinDepartment of materials science and engineeringShanghai Jiao Tong university Powder Metallurgy Research Institute Central South University of Technology Changsha 410083 China Department of materials science and engineering Shanghai Jiao Tong University Shanghai 200030 China

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关键词： TiAl forging superplasticity