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Massive Si Phase and Its Growth Mechanism in Al-Si Casting Alloy

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Journal of mat.rials sci.nce & Technology 2004年第5期20卷 589-591页

作者： Heng.heng.LIAO and Guoxiong SUNDepaxtment of mat.rials sci.nce and eng.neering, Southeast University, Nanjing 210018, China dept. of mat. sci. and eng. Southeast Univ. Nanjing 210018 China

Optical microscope and scanning electron microscope were used to observe the microstructure of the AI-11.6%Si and AI-11.6%Si-0.4%Mg alloys and the morphology of the massive silicon particles. It is found that the massive silicon phase, observed in the unfully modified alloys with 0.010%Sr, disappears completely in the alloys fully modified with 0.020%Sr. The serrations and reentrant edges shown in the massive silicon particles with the conventional casting indicate that the TPRE mechanism plays an important role in the growth of the massive silicon phase. The ripples and steps suggest that the "lateral microscopic growth" may be another operating mechanism.

关键词： Al-Si alloy Massive silicon Microstructure Growth mechanism

Structure and Magnetic Properties of Y(Fe_(1-x)Co_x)_ (11.3) Nb_(0.7)

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Journal of Rare Earths 2001年第1期19卷 25-28页

作者：罗广圣李劲松 dept. of mat. sci. and eng. Nanchang Univ. Nanchang 330047 China

The structure and magnetic properties of the intermetallic compounds Y(Fe 1- x Co x ) 11.3 Nb 0.7 ( x =0, 0 05, 0 1, 0 2) were studied by X ray diffraction and magnetic property measurements. X ray diffraction patterns and thermomagnetic curves show that all compounds almost exhibit single phase. All Y(Fe 1- x Co x ) 11.3 Nb 0.7 compounds ( x =0, 0 05, 0 1, 0 2) crystallize in ThMn 12 type structure. Substitution of Co for Fe leads to a clear increasing of Curie temperature and a monotonic decreasing of lattice constants. At room temperature the composition dependence of saturation magnetization exhibits a maximum at about x =0 1～0 2. The magnetocrystalline anisotropy field at room temperature at first increases and then decreases with the increasing of Co content.

关键词： rare earths ThMn 12 type structure Curie temperature saturation magnetization anisotropy field

Influence of Electric Field on Mechanical Properties of Al-Li Alloy Containing Cerium and Electronic Mechanism

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Journal of Rare Earths 2001年第2期19卷 97-102页

作者：刘兵陈铮王永欣王西宁 dept. of mat. sci. and eng. Northwest Polytechnical Univ. Xi'an 710072 China

The effect of electric field on the mechanical properties and microstructure of AI-Li alloy containing Ce was investigated, and mechanism was discussed. The experimental results show that the ductility of the alloy is enhanced by the electric field. The fracture features are changed and the precipitates are dispersed under the effect of the electric field. The mechanism discussion reveals that the effects of the electric field on the alloy are due to the change of the electron density in the alloy.

关键词： rare earths electric field mechanical property fracture feature precipitates electron density

Hydrogen Storage Properties of Ti_(1.2)Fe+xCa Hydrogen Storage Alloys

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Rare Metals 2001年第4期20卷 265-269页

作者： Wei Wang, Changpin Chen, Haiou Xu, Hon gbo Li, Qidong Wang Department mat.riak sci.nce and eng.neering, Zhejiang University, Hangvhou 310027. China dept. of mat. sci. and eng. Zhejiang Univ. Hangzhou 310027 China

The hydrogen storage properties of Ti1.2Fe+xCa (x=1%, 3% and 5% in mass fraction) alloys was investigated. Results stow that the modified alloys can be activated without any thermal treatment at room temperature due to the addition of Ca and excess Ti in (lie alloys. Hydrogen storage properties of these modified alloys vary with Ca amount and reaction temperature. In addition, the influence mechanism of the addition of Ca and excessive Ti on the activation behavior and hydrogen storage capacity of the alloys was discussed.

关键词： TiFe Ca hydrogen storage alloy hydrogen storage property

Properties of Hot-Pressed Al_2O_3-Fe Composites

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Journal of mat.rials sci.nce & Technology 2001年第5期17卷 538-542页

作者： M.M.El-Sayed Seleman, Xudong SUN and Liang ZUO Department of mat.rials sci.nce and eng.neering, Northeastern University, Shenyang 110006, China K.A.Khalil Powder Metallurgy Institute, Central South University, Changsha 410083, China dept. of mat. sci. and eng. Northeastern Univ. Shenyang 110006 China

Alumina-(0-20 vol. pct) iron composites were fabricated by hot-pressing of well-mixed alumina and iron powders at 1400℃ and 30 MPa for 30 mm. Hot-pressed bodies with nearly theoretical density were obtained for addition up to 10 vol. pct Fe, but relative density decreased gradually with further increase in Fe addition. The mat.rials exhibit a homogeneous dispersion of Fe. Fracture streng.h of the composites exhibits a maximum value of 604 MPa at 15 vol. pct Fe, which is 1.5 times that of alumina alone. Fracture toughness increases with the increase in Fe content, reaching 7.5 MPa.m1/2 at 20 vol. pct Fe. The theoretical values of fracture toughness was calculated and compared with the experimental one. Toughening mechanisms of the composites are also discussed.

关键词： Fe Properties of Hot-Pressed Al2O3-Fe Composites Al

Dopant Behaviours of Sm_2O_3 on Microstructure and Properties of Barium Zirconium Titanate Ceramics

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Journal of Rare Earths 2001年第4期19卷 266-270页

作者：王永力李龙土齐建全桂治轮 dept. of mat. sci. and eng. Tsinghua Univ. Beijing 100084 China

The effect of Sm 2O 3 dopant on the sintering characteristics and dielectric properties of barium zirconium titanate ceramics (BaZr x Ti 1- x O 3) was investigated. It is shown that trace amount of Sm 2O 3 can greatly affect the grain growth and densification of barium zirconium titanate ceramics during sintering. At the same time, the dielectric peak at high temperature shifts to lower temperature and that at low temperature shifts to higher temperature. The two dielectric peaks overlap with each other when the Sm 2O 3 dopant content varies from 0 25% to 1%, and the maximum relative dielectric constant is greatly enhanced. These effects may be attributed to the substitution actions of the rare earth element in perovskite lattice. At the doping content of 0 75%, the dielectric constant maximum of 23570 can be obtained. By adopting some proper additives, an excellent Y5V dielective mat.rial is obtained, and the room temperature properties are as follows: relative dielectric constant ε RT ≥23,000, dielectric loss tgδ≤0 0075 and the breakdown streng.h under alternating field E b≥5 kV·mm -1 .

关键词： rare earths barium zirconium titanate high voltage ceramic capacitors dielectric properties

Effect of Transition Metal on the Electrochemical Performances of Some Intermetallic Anodes for Lithium Ion Batteries

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Journal of mat.rials sci.nce & Technology 2004年第3期20卷 344-346页

作者： Jian XIE Xinbing ZHAO Gaoshao CAO Mingjian ZHAO Yaodong ZHONG Department of mat.rials sci.nce and eng.neering, Zhejiang University Hangzhou 310027,China dept. of mat. sci. and eng. Zhejiang Univ. Hangzhou 310027 China

Some transition metal antimonides were prepared by levitation melting and subsequent ball-milling. The electrochem-ical behaviors of these mat.rials as new candidate negative electrode mat.rials in lithium ion secondary batteries wereinvestigated. It was found that they exhibited significantly larger volumetric capacity than carbon-based mat.ri-als. The format.on and composition of solid electrolyte interface (SEI) film were characterized by electrochemicalimpedance spectroscopy (EIS) and Fourier transform infra-red (FTIR) spectroscopy.

关键词： Antimonide Lithium ion batteries Anode mat.rials Levitation melting

mat.rials Design of Microstructure in Grain Boundary and Second Phase Particles

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Journal of mat.rials sci.nce & Technology 2003年第2期19卷 97-101页

作者： Yaping ZONG and Liang ZUODepartment of mat.rials sci.nce and eng.neering, Northeastern University, Shenyang 110004, China dept. of mat. sci. and eng. Northeastern Univ. Shenyang 110004 China

A concept of microstructure design for mat.rials or mat.rials microstructure eng.neering is proposed. The argument was suggested based on literature review and. some our new research work on second phase streng.hening mechanisms and mechanical property modeling of a particulate reinforced metal mat.ix composite. Due to development of computer technology, it is possible now for us to establish the relationship between microstructures and properties systemat.cally and quantitatively by analytical and numerical modeling in the research scope of computerization mat.rials. Discussions and examples on intellectual optimization of microstructure are presented on two aspects: grain boundary eng.neering and optimal geometry of particulate reinforcements in two-phase mat.rials.

关键词： Microstructure design Particulate reinforcement Grain boundary eng.neering Streng.hening mechanism Eshelby approach Numerical modelling

Preparation and Electromechanical Properties of PVDF mat.ix Piezoelectric Composites Containing Highly Oriented BaTiO_3 Whiskers

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Journal of mat.rials sci.nce & Technology 2004年第4期20卷 441-444页

作者： Xuetao LUO, Lifu CHEN, Xiaojun CHEN and Qianjun HUANGDepartment of mat.rials sci.nce and eng.neering, Xiamen University, Xiamen 361005, China dept. of mat. sci. and eng. Xiamen Univ. Xiamen 361005 China

The piezoelectric composites containing highly oriented BaTiO3 whiskers as active phase and PVDF as mat.ix have been prepared by micro-hole extrusion and orientation in carried fibers. The morphology of oriented BaTiO3 whiskers and microstructure of the composites were observed by SEM. As for its electromechanical properties, it is found that the dielectric constant, piezoelectric constant and remnant of polarization in the BaTiO3 whisker-PVDF composite are considerably higher than that in the BaTiO3 powders-PVDF composite, while the loss factors follow the opposite trend. For the BaTiO3 whisker-PVDF composite, the values of ε, d33 and Pr parallel to the whisker orientation (normal specimen) are much higher than that perpendicular to the whisker orientation (parallel specimen). The significant effects of the connective passages of active phase on electromechanical properties of the piezoelectric composites has also been investigated.

关键词： Piezoelectric composite BaTiO3 whiskers Electromechanical properties Polarization Connective passages