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Nickel multilayers and their effects on bend fatigue strength of leads

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Rare Metals 2004年第2期23卷 157-160页

作者： liu Feihua WANG Zhanhua SHEN Zhuoshen school of material science and engineering, university of science and technology beijing, beijing 100083, china school of material science and engineering University of Science and Technology Beijing 北京 100083

Nickel is commonly coated on the outer leads for T8 metal package. The leadselectrodeposited by conventional dull or bright nickel over 5μm at direct current from Watt bathare hard to pass the bend fatigue test for three times. Nickel electrodeposited at multi waveformcurrent including direct current, single and double pulse from sulfamate bath can improve the bendfatigue strength of leads. Such nickel plating has a multilayer structure, its morphology ofsublayers can be clearly seen in its cross section with SEM. The electrochemical study shows thatthese sublayers have different corrosion potentials. The bend fatigue test of leads with suchplating for T8 metal package shows that the number of bend increases with the decrease of averagecurrent density of multi waveform, which can be attributed to the reduction of every sublayerthickness and the increase of layer numbers under the same condition of total thickness.

关键词： electroplating nickel multilayers multi waveform current bend fatiguestrength corrosion potential metal package

A New Process for Preparing Fine-ceramic-containing Composite Coatings──Flame Spray Synthesis

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International Journal of Minerals,Metallurgy and materials 2000年第3期14卷 214-217页

作者： Changsong liu, Jihua Huang, Sheng Yin (material science and engineering school, university of science and technology beijing, beijing 100083, china) material science and engineering school University of Science and Technology Beijing Beijing 100083 China

Flame spray synthesis (FSS), a combination of the flame spray technology and Self-propagation High-temperature Synthesis (SHS) was developed for preparing fine-ceramic-containing composite coatings. It can simplify the preparations of powder to synthesize and deposit the desired materials in one step. The preliminary results obtained from TiC-Fe cermet coatings by FSS process are reported. The peculiar microstructure of the composite coatings, which contains very fine (<1m) and round TiC and alternate TiC-rich (Hv=11€*13GPa) and TiC-poor layers (Hv=3.0 -6.0GPa), is expected to play an important role in their tribological properties.

关键词： Self-propagation High-temperature Synthesis (SHS) flame spray flame spray synthesis (FSS) TiC-Fe cermet coating

Three-Dimensional and Cross-sectional Characteristics of Normal Grain Growth Based on Monte Carlo Simulation

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International Journal of Minerals,Metallurgy and materials 1998年第3期12卷 129-133,139页

作者： Xiaoyan Song Guoquan liu(material science and engineering school, university of science and technology beijing, beijing 100083, china)(Department of materials science and engineering, Hebei university of technology, Tianjin 300130, china) material science and engineering school University of Science and Technology Beijing Beijing 100083 China Departments of materials science and engineering Hebei University of Technology Tianjin 300130 China

An appropriate Monte Carlo method was developed to simulate the three-dimensional normal grain growth more completely. Comparative investigation on the three-dimensional and the cross-sectional characteristics of normal grain growth was done. It was found that the time exponent of grain growth determined from cross-section exhibits the same rule of increasing slowly with time and approaching the theoretical value n = 0.5 of steadygrain growth as the three-dimensional (3-D) system. From change of the number of grains per unit area with timemeasured in cross-section, the state of 3-D normal grain growth may be predicted. The gtain size distribution incross-section is different from that in 3-D system and can not express the evolution characteristic of the 3-D distribution. Furthermore, there exists statistical connection between the topological parameters in cross-section and thosein three-dimensions.

关键词： Monte Carlo simulation normal grain growth three-dimension cross-section characteristics

Pb(Mg_(1/3)Nb_(2/3))O_3-PbTiO_3-BaTiO_3 Complex Perovskite Ferroelectric Ceramics with High Dielectric Constant and Low Firing Temperature

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International Journal of Minerals,Metallurgy and materials 2000年第2期14卷 115-117页

作者： Zhen Ji Zhhong Xiao Xuqing liu Zhaozeng Ma Zongsen Yu(material science and engineering school, university of science and technology Bejing, beijing 100083, china) material science and engineering school University of Science and Technology Beijing Beijing 100083 China

The effects of different firing temperatures on the stability of perovskite phase, grain size, and dielectric properties were investigated by XRD, TEM, SEM and dielectric measurements. The dielectric ceramics of Pb(Mg1/3Nb2/3)O3-PbTiO3-BaTiO3 system were obtained by chemical coprecipitation in water. The ceramics have higher dielectric constant (7003-9714), lower firing temperature(950-1150℃), quite uniform microstructure with grain size less than 2.5 mp, and lower temperature coefficients of capacitance. As a re-sult, it was confirmed that the simple and low cost chemical route used namely coprecipitation in water is a desired method for preparinghigh property dielectfic materials applicable to multilayer capacitors.

关键词： PMN-PT-BT coprecipitation dielectric property

Anisotropic characteristic in HDDR Nd_(13)Fe_(80)B_7

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Journal of university of science and technology beijing 2003年第3期10卷 26-29页

作者： Jingzhi Han, Aizhi Sun, Yaofu Xiao, Xubo liu, and Run Wangmaterials science and engineering school, university of science and technology beijing, beijing 100083, china materials science and engineering school University of Science and Technology Beijing Beijing 100083 China

The function of disproportionation and desorption stages ofhydrogenation-disproportionation-desorption-recombination (HDDR) process in the formation ofmagnetic anisotropy was studied. The results showed that degree of anisotropy (DOA) ofNd_(13)Fe_(80)B_7 induced by appropriate HDDR process is comparable with that ofNd_(13)Fe_(80-x)B_7M_x (M=Co, Zr or Ga), however, the moderate coercive force of Nd_(13)Fe_(80)B_7magnetic powder led to an undesirable (BH)_(max) of 104 kJ/m^3 in bonded magnet. Experimentsdemonstrated that a relatively short disproportionation time, combined with a high desorptiontemperature and slow desorption rate, during HDDR process is beneficial to anisotropy attainment,but HDDR Nd_(13)Fe_(80)B_7 magnetic powder becomes isotropic if the disproportionation time islonger than a certain period. This phenomenon strongly indicated that the origin of anisotropy inNdFeB-type HDDR material is contributed by disproportionation stage. XRD (X-ray Diffraction)analysis and TEM (Transmission Electron Microscope) observation told that no other phase exceptNdH_2, alpha-Fe and Fe_2B has been found in the disproportionation step. The formation of HDDRNd_(13)Fe_(80)B_7 anisotropy might be related to the early lamella disproportionation structure.

关键词： HDDR anisotropy isotropy NdFeB

Fretting corrosion of surgical 316L stainless steel in saline solutions

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International Journal of Minerals,Metallurgy and materials 1997年第3期11卷 18-21页

作者： BAI Zhijun WU Yinshun ZHANG Tiancheng liu Qiang (material science and engineering school, university of science and technology beijing, beijing 100083, china)

A new simulation system for the laboratory investigation of fretting wear is developed. It consist of a mechanism device, a electrochemical cell and a datum acqulsition and process software. Fretting of surgical 316L stainlesssteel in saline is studied. The results show that electrochemical corrosion is enhanced by fretting and anodic currentdensity under fretting is 100 times than static condition. Fretting corrosion is a mechanic -elec trochemical al Process.

关键词： fretting system 316L sninless steel saline solution

Effect of Al^(3+) on Tobermorite Crystallinity

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International Journal of Minerals,Metallurgy and materials 2000年第2期14卷 79-81页

作者： Fengmei liu Deping Chen Wen Ni Zhenyuan Cao(Resource engineering school, university of science and technology beijing, beijing 100083, china) Univ Sci & Technol beijing Resource Engn Sch Beijing 100083 Peoples R China

The difference between the systems of CaO-SiO2,-H2O and CaO-SiO2-Al(OH)3,-H2O, was studied, especially the effect of Al3+on the crystallinity of tobermorite was focussed. As a result, in the system of CaO-SiO2-H2O, tobermorite formed early, however, withreaction time forward, tobermorite was replaced by xonotlite. So far as CaO-SiO2-Al(OH)3,-H2O was concemed, hydrothermal reactionwas cdried out under the same condition as CaO-SiO2-H2O to study the morphological changes of tobermorite crystals. It was found thatAl3+ accelefated the crystal growth of tobermorite to some extent and was in faVor ofplaty crystals. Moreovef, with the Al3+ content in-creasing in the starting material, the morphology of tobermorite did not change magnificently, but platy crystals became more and moreeminent. As soon as the Al2O3 content was over 15.6%, synthetic mineral greatly changed in smicthe and haled into hibschite differentfrom 1 .1 nm tobermorite. Obviously, xonotlite was not apt to form in the presence of Al3+.

关键词： calcium silicate hydrate xonotlite 1.1 nm tobermorite hibschite

Modified HDDR Process for Producing Anisotropic NdFeB Powders

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Journal of university of science and technology beijing 2001年第2期8卷 111-114页

作者： Xubo liu, Yue Ming, Yaofu Xiao, Qi Zeng, Zhengyi Zhang, Run Wang (material science and engineering school, university of science and technology beijing, beijing 100083, china) (beijing Institute of Aeronautical materials, beijing 100095, china) Univ Sci & Technol beijing Mat Sci & Engn Sch Beijing 100083 Peoples R China Inst Aeronaut Mat Beijing 100095 Peoples R China

The effect of HDDR (hydrogenation-decomposition-desorption-recombination process) treating conditions on magnetic anisotropy of Nd13FebalCo17B7Ga1Zr0.1 powders has been studied. It is found that increasing recombination temperature is effective for magnetic anisotropy formation, but at the cost of reducing the coercive force. The microstructure analysis (TEM) indicates that the NdFeB recombination nucleation takes place markedly during the transition range from decomposition stage to recombination stage, in which both temperature and H-2 pressure change sharply. In order to create a more stable treatment condition for recombination nucleation, a modified HDDR process is established in which the conventional continuous transition range is divided into several stages. The experimental results have proved that such a process can effectively enhance the remanence of the magnet powders with high certainty, while only cause a little reduction in coercivity.

关键词： HDDR anisotropy NdFeB

Theoretical analysis of alloy multiplying factor by the empirical electron theory of solids and molecules

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science china(Technological sciences) 2007年第6期50卷 807-814页

作者： SONG YuePeng1,2, liu GuoQuan2, LI ZhiLin3, FENG ChengMing1 1 Mechanical and Electronic engineering College, Shandong Agricultural university, Tai’an 271018, china 2 College of materials science and engineering, university of science and technology, beijing 100083, china 3 College of material science and engineering, beijing university of Chemical technology, beijing 100029, china Mechanical Electronic engineering College Shandong Agricultural University Tai’an 271018 China College of materials science engineering University of Science technology Beijing 100083 China College of material science engineering Beijing University of Chemical Technology Beijing 100029 China

By introducing the distribution probability of structural units in austenite contain- ing alloying elements and considering its effects on phase transformation, this paper establishes a calculation model of distribution probability of structural units. A new valence electron structure (VES) parameter-transformation effect coefficient of alloying elements (HL), is defined and then studied both theoretically and ex- perimentally. The relationship between the parameter HL and the multiplying factor (the quenching capability factor) of alloying elements is studied. The results indi- cate that the two parameters (HL and the quenching capability factor) have the same variation characteristic and substance feature. Therefore, the multiplying factor virtually expresses the relative quantity of structural units in the alloying elements-containing austenite.

关键词： multiplying factor (the quenching capability factor), empirical electron theory of solids and molecules, transformation effect coefficient of alloying elements, structural units in austenite containing alloying elements