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Sintering characteristics and microstructure of WC-Co-VC/Cr_3C_2 ultrafine cemented carbides

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Rare Metals 2009年第5期28卷 482-486页

作者： LEI Yiwen WU Enxi School of Mechanical and Electronic Engineering Tianjin Polytechnic University Tianjin 300160 China State Key Laboratory of powder metallurgy Central South University Changsha 410083 China

The sintering characteristics, microstructure, and mechanical properties of ultrafine WC-12%Co-0.2%VC/0.5%Cr3C2 cemented carbides were investigated. Dilatometric and differential thermal analyses （DTA） indicate that the compacts start to shrink at 600°C, the shrinkage rate peak is at 1190°C, and the liquid formation temperature is lower than the W-C-Co eutectic temperature （1330°C）. Microstructure analysis results show that the cemented carbides with fine and homogeneous microstructure were obtained when sintered at 1430°C. Continuous and discontinuous grain growth was suppressed due to the synergistic action of VC/Cr3C2. The transverse rupture strength （TRS） of the samples reaches 4286 MPa, with the hardness HRA 92.1. The fine and homogeneous microstructure, alloy strengthening, and different phase constitutions of binder in the cemented carbides result in high hardness and TRS. Continuous and discontinuous grain growth was observed in the cemented carbide sintered at 1450°C, which results in significant decreases of hardness and TRS. It indicates that VC/Cr3C2 additions in the cemented carbides can only suppress the grain growth at a certain temperature.

关键词： cemented carbides sintering characteristic grain growth microstructure mechanical properties

Effects of cathode materials on discharge characteristics of Li B alloy/FeS_2 thermal battery

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中国有色金属学会会刊：英文版 1999年第3期9卷 530-534页

作者： Liu Zhijian(刘志坚), Duan Wei(段伟), Li Zhiyou(李志友), Huang Yinghua(黄英华) ,Qu Xuanhui(曲选辉),Huang Baiyun(黄伯云) powder metallurgy institute, central south university of Technology, changsha 410083, P.R.China  Jinzhu powder Injection Man central south Univ of Technology Changsha China

The effects of FeS 2 on the discharge characteristics of Li B alloy/FeS 2 thermal battery had been studied. Results showed that 2.5%(mass fraction)Li 2O would be needed to rule out the voltage pulse in the first part of discharge curves for the FeS 2 powder of small particle size (2 had transformed to Fe (1- x ) S where x =0.024～0.066. The deficiency of the cathode FeS 2 would make discharge voltage decrease 0.4 V. In the discharge test at high temperature (600 ℃), the discharge voltage decreased fast with the acceleration of the thermal decomposition of FeS 2.

关键词： LiB FeS 2 thermal batteries cathode effect

Effect of Trace Sc and Zr on the Mechanical Properties and Microstructure of A1 Alloy 2618

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Journal of Materials Science & Technology 2000年第4期16卷 416-420页

作者： Kun YU, Songrui LI and Wenxian LI (Department of Materials Science and Engineering, central south university of Technology, changsha 410083, China) Department of Materials Science and Engineering Central South University of Technology Changsha 410083 China

An experimental 2618(Al-Cu-Mg-Fe-Ni) alloy added with trace Sc and Zr was prepared by ingot metallurgy (IM) method. The aging behavior of the alloy was studied by Vickers hardness measurement at 200℃ and 300℃. and the tensile properties of alloy specimens were measured at 20℃, 200℃, 250℃ and 300℃. The microstructure was observed by using optical microscope, SEM and TEM. It was found that the addition of Sc and Zr to 2618 alloy resulted in a primary Al_3(Sc,Zr) phase which could refine the grain because it acts as nuclei of heterogeneous crystallization in the melt during solidification. The secondary Al_3(Sc,Zr) particles were full coherent with matrix and had obvious precipitation hardening effect. They also made the S' phase precipitate more homogeneous. So the strength of alloy increases at both ambient and elevated temperatures without a decrease of ductility. The ductile fracture of alloy occurs by microvoid nucleation, growth and coalescence, so the microvoid coalescence is the dominant fracture mechanism.

关键词： Sc Zr Effect of Trace Sc and Zr on the Mechanical Properties and Microstructure of A1 Alloy 2618

Synthesis of Lithium-cobalt Oxides by Sol-gel Method and their Cathodical Discharge Behavior at 500 ℃

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Journal of central south university 2000年第2期12卷 57-60页

作者： LI Zhi you,HUANG Bai yun,ZHU Yong li,LIU Zhi jian,QU Xuan hui (State Key Laboratory for powder metallurgy, central south university of Technology, changsha 410083, China) State Key Laboratory for powder metallurgy Central South University of Technology Changsha China

Three kinds of lithium cobalt oxides with lithium to cobalt atomic ratios of 0.6, 0.8 and 1.0 respectively were prepared using nitrates and citric acid by sol gel process. During the baking of the dry gel powder, two exothermic peaks occur, followed by the formation of Li 2O and Co 3O 4 and then the combination of LiCoO 2, which is testified by DTA and XRD. The powder formed from an alkaline sol is finer than that from the acidic one. There are a single phase intercalation of lithium ion and an electrochemical reduction reaction for higher valence cobalt ion when simulating the discharging process of Li B/LiCl KCl/lithium cobalt oxides at 500 ℃, and the voltage and specific capacity are not sensitive to the initial ratios of lithium to cobalt.

关键词： sol gel LiCoO 2 thermal battery cathode Document code:

STRUCTURE AND FORMATION MECHANISM OF DISLOCATION NETWORKS IN TiAl^+

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Journal of central south university 1995年第1期7卷 12-15页

作者： Qu Xuanhui Huang Baiyun(powder metallurgy research institute, central south university of Technology, changsha, 410083, China)

The structure and characteristics of dislocation networks in Ti50 Al ordered alloy deformed at room temperature were studied by means of TEM diffraction contrast analysis technique. The results show that the observed... 详细信息

关键词： ordered alloy intermetallic compound dislocation networks TEM ductility/TiAl titanium aluminide

GREY　DISPLACEMENT　INPUT－OUTPUT　MODELS　OF　MINERAL　PROCESSING－metallurgy　SYSTEM

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中国有色金属学会会刊：英文版 1995年第1期5卷 11-14页

作者： Han Xuli Li Songren(Department of Mineral Engineering, central south university of Technology, changsha, 410083) CENT S UNIV TECHNOL DEPT MINERAL ENGNCHANGSHA 410083PEOPLES R CHINA

ＧＲＥＹＤＩＳＰＬＡＣＥＭＥＮＴＩＮＰＵＴ－ＯＵＴＰＵＴＭＯＤＥＬＳＯＦＭＩＮＥＲＡＬＰＲＯＣＥＳＳＩＮＧ－ＭＥＴＡＬＬＵＲＧＹＳＹＳＴＥＭＨａｎ；ＸｕｌｉＬｉ；Ｓｏｎｇｒｅｎ（ＤｅｐａｒｔｍｅｎｔｏｆＭｉｎｅｒａｌ... 详细信息

ＧＲＥＹＤＩＳＰＬＡＣＥＭＥＮＴＩＮＰＵＴ－ＯＵＴＰＵＴＭＯＤＥＬＳＯＦＭＩＮＥＲＡＬＰＲＯＣＥＳＳＩＮＧ－ＭＥＴＡＬＬＵＲＧＹＳＹＳＴＥＭＨａｎ；ＸｕｌｉＬｉ；Ｓｏｎｇｒｅｎ（ＤｅｐａｒｔｍｅｎｔｏｆＭｉｎｅｒａｌＥｎｇｉｎｅｅｒｉｎｇ，Ｃｅｎｔｒ...

关键词： mineral processing-metallurgy system input-output grey theory economic model

Activity Enhancement of Vanadium Catalysts with Ultrasonic Preparation Process for the Oxidation of Sulfur Dioxide

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Journal of Natural Gas Chemistry 2003年第2期12卷 139-144页

作者： Zhenxing Chen, Honggui Li, Lingsen WangState Key Laboratory for powder metallurgy, College of Chemistry and Chemical Engineering, central south university, changsha 410083, China State Key Laboratory for powder metallurgy College of Chemistry and Chemical EngineeringCentral South University Changsha 410083 China

The effect of ultrasonic cavitations on the activity of vanadium catalysts atlow temperatures for the oxidation of sulfur dioxide, in which refined carbonized mother liquor hadbeen added, was investigated. Twenty minutes were needed to produce obvious cavitations when thecatalyst raw material was treated in the 50 W ultrasonic generator. However, only 10 minutes wouldbe needed in a 150 W ultrasonic generator. The higher the temperature of the wet material, the lesstime was needed to produce cavitations, and the optimal temperature was 60℃. The water content inthe wet material mainly affected the quantity of cavitations. Ls-8 catalyst was prepared usingultrasonic. Its activity for conversion of SO_2 reached to 52.5% at 410℃ and 4.2% at 350℃. Thedifferential thermal analyses indicate that both endothermic peaks and exothermic peaks noticeablyshifted forward compared with Ls catalyst prepared without ultrasonic, and SEM results show auniform pore size distribution for Ls-8 catalyst.

关键词： ultrasonic dispersion vanadium catalyst low temperature activity sulfurdioxide cavitation

Modeling Study on Stress Distribution as Effects of Temperature and TGO Thickness in ScYSZ/NiCrAlY TBCs System

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稀有金属材料与工程 2011年第S4期40卷 164-168页

作者： Liu Huaifei1,2,Li Qilian2,Li Songlin1,Li Yongming1 1State Key Laboratory of powder metallurgy,central south university,changsha 410083,China 2National Key Laboratory of Science and Technology on Power Beam Process,Beijing Aeronautical Manufacturing Technology research institute,Beijing 100024,China Cent S Univ State Key Lab Powder Met Changsha 410083 Peoples R China Beijing Aeronaut Mfg Technol Res Inst Natl Key Lab Sci & Technol Power Beam Proc Beijing 100024 Peoples R China

The effects of oxidation temperature and thickness of thermally grown oxide (TGO) on thermal stress distribution in thermal barrier coatings (TBCs) system are studied in the present paper.A typical TBC system is used:air plasma sprayed (APS) Scandia,yttria-stabilized zirconia (ScYSZ) top coat (TC) and NiCrAlY bond coat (BC) deposited on the nickel super-alloy *** behavior of BC oxidation was *** the Numerical model and Finite Element (FE) method were used to analyze the stress *** objective of this study is to provide important information for understanding the failure mechanism of TBCs at least in a qualitative way.

关键词： Sc2O3-Y2O3-ZrO2 thermal barrier coating stress analysis finite element TGO

Biocompatibility evaluation in vitro. Part III: Cytotoxicity expression of human and animal osteoblasts on the biomaterials

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Journal of central south university 2001年第3期13卷 147-155页

作者： RUAN Jian-ming 1,M.H. Grant 2 (1. State Key Laboratory for powder metallurgy, central south university, Changs ha 410083, China 2. Bioengineering Unit, Strathclyde university, Glasgow, G4 0NW, UK) State Key Laboratory for powder metallurgy Central South University Changsha China Bioengineering Unit Strathclyde University Glasgow UK

Exclusion and inflammation in the clinic are observe d for various reas ons including material che- mical composition, physical properties as well a s macr o- and micro-structure of the implants, surface condition of the implants, and also patient dependent factors. Cytotoxicity expression of cells is a central issue i n current biocompatibility to screen the potential implant materials and drugs. This study was aimed at investigation reaction between the potential implant mat erials and surround tissue. Cytotoxicity of human and rat osteoblast in the mate rial extracts was determinated by testing standards such as GHS assay, MTT assay , alkaline phosphatase activity assay, LDH assay, and Lowry assay. research resu lts demonstrated that compared with the control condition polystyrene culture pl a te both human and rat osteoblast cells have normal phenotypic expression in hydr oxyapatite extract, and this expression was statistically restricted in hydroxya patite-spinel extract. How- ever, this restrict, e.g. cytotoxicity could be partially eliminated by immersion treatment of the materials in culture medium.

关键词： biomaterial cytotoxicity biological molecular technique