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Effect of powder mixing process on the microstructure and thermal conductivity of Al/diamond composites fabricated by spark plasma sintering

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Rare Metals 2010年第1期29卷 86-91页

作者： CHU Ke, JIA Chengchang, LIANG Xuebing, and CHEN Hui school of Materials science and engineering, {3. of science and Technology beijing, beijing 100083. china school of Materials science and engineering University of Science and Technology Beijing

Two powder mixing processes, mechanical mixing （MM） and mechanical alloying （MA）, were used to prepare mixed Al/diamond powders, which were subsequently consolidated using spark plasma sintering （SPS） to produce bulk Al/diamond composites. The effects of the powder mixing process on the morphologies of the mixed powders, the microstructure and the thermal conductivity of the composites were investigated. The results show that the powder mixing process can significantly affect the microstructure and the thermal conductivity of the composites. Agglomerations of the particles occurred in mixed powders using MM for 3. min, which led to high pore content and weak interfacial bonding in the composites and resulted in low relative density and low thermal conductivity for the composites. Mixed powders of homogeneous distribution of diamond particles could be obtained using MA for 10 min and MM for 2 h. The composite prepared through MA indicated a high relative density but low thermal conductivity due to its defects, such as damaged particles, Fe impurity, and local interfacial debonding, which were mainly introduced in the MA process. In contrast, the composite made by MM for 2 h demonstrated high relative density and an excellent thermal conductivity of 3.5 W.m^-1.K^-1, owing to its having few defects and strong inter-facial bonding.

关键词： metal matrix composites thermal properties sintering powder mixing

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, {3. 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

Secure communication by generalized chaotic synchronization

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Journal of university of science and Technology beijing 2003年第2期10卷 75-78页

作者： Lequan Min, Xianhua zhang, and Miao YangApplied science school, {3. of science and Technology beijing, beijing 100083. china Applied science school University of Science and Technology Beijing Beijing 100083 China

Chaotic communication is a rather new and active field of research. Althoughit is expected to have promising advantages, some investigators provide evidences that chaoticcommunication is not safety. This letter provides a new chaotic secure communication scheme based ona generalized synchronization theory of coupled system. The secret message hidden in the chaoticsource signal generated via the scheme is very difficult to be unmasked by so-called nonlineardynamic forecasting technique. One example for Internet communications was presented to illustratethe security of our scheme.

关键词： secure communication generalized chaotic synchronization Internet

Bonded Terfenol-D composites with low eddy current loss and high magnetostriction

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Rare Metals 2010年第6期29卷 579-582页

作者： TIAN Jianjun,ZUO Zhijun,PAN De’an,and zhang Shengen school of Materials science and {3.,university of science and Technology beijing,beijing 100083.china school of Materials science and engineering University of Science and Technology Beijing Beijing China

Bonded Terfenol-D composites,with high electrical resistivity and low eddy current loss,can be used in an alternating magnetic field with high ***,the nonmagnetic binder impairs the magnetostriction of the *** achieve high magnetostriction and low eddy current loss,the mixture of the alloy powder and binder was compressed at low pressure in an oriented magnetic *** this,the aligned samples were recompressed by cold isostatic pressing（CIP）.Besides,the effect of particle size on the magnetostriction of the bonded Terfenol-D composites was also *** results showed that the bonded Terfenol-D composites had excellent magnetostriction when the particle size was 50-80 μ*** oriented magnetic field and CIP could improve the magnetostriction of the bonded composites,which reaches 1020×*** bonded Terfenol-D composites had good compact structure and high density（7.24 g/cm3..The magnetic loss of the bonded Terfenol-D composites was 192 mW/cm3.at a frequency of 100 kHz in a magnetic field of 960 A/m,which was about one third of that of casting Terfenol-D alloys.

关键词： composites Terfenol-D magnetostriction eddy current losses density

TEM Study on Hydrogen-Induced Cracking of Fe_3.l Alloy

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Journal of university of science and Technology beijing 2001年第1期8卷 35-38页

作者： Biao Gu, Lijie Qiao, Wuyang Chu Material science and engineering school, {3. of science and Technology beijing, beijing 100083. china Univ Sci & Technol beijing Sch Mat Sci & Engn Beijing 100083 Peoples R China

Hydrogen-induced cracking (HIC) of Fe3.l alloy was studied by in situ transmission electron microscope (TEM). Electron transparent specimens were mounted onto a constant displacement device. Stress was applied to the specimen by using a bolt through the device. The results showed that hydrogen enhanced the dislocation emission and motion in Fe3.l alloy. A dislocation free zone (DFZ) was formed following the dislocation emission. Microcrack initiated in the DFZ or at the main crack tip when the emission reached a critical extension. Hydrogen played an important role in the process of brittle fracture of Fe3.l alloy.

关键词： TEM Fe3.l intermetallics hydrogen induced cracking dislocation emission dislocation free zone

Predicting Equation for Adjusting Glass Temperature of Binder Used for P/M Warm Compaction Processing

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International Journal of Minerals,Metallurgy and Materials 1998年第1期12卷 39-40页

作者： Shiju Guo Tao Lin Mingyi Li (Materials science and engineering school, {3. of science and Technology beijing, beijing 100083. china) Materials science and engineering school University of Science and Technology Beijing Beijing 100083 China

Based on considering both negative effect of compacting pressure on glass temperature (Tg) and positiveeffect of plasticizer added into organic binder, a mathematical equation for adjusting Tg of binder used for warmcompaction processing is given. The equation shows that mass fraction of plasticizer need for lowering Tg is function of compacting plessure. The rationality of the equation for warm compaction processing is also discussed.

关键词： warm compaction binder glass temperature

Calculating Model of Mass Action Concentrations for Fe-Cr-P Melts and Optimization of Thermodynamic Parameters

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International Journal of Minerals,Metallurgy and Materials 1999年第1期13卷 11-14页

作者： Jian zhang (Metallurgy school, university of {3. and Technology Beliing, beijing 100083. china) Metallurgy school University of Science and Technology Beijing Beijing 100083 China

According to the results of research on the thermodynamic propelles of Fe-Cr, Fe-P and Cr-P melts, the measured achvihes of Fe-Cr-P melts from reference sources as well as the coexistence theory of metallic melts structure involving compound formation, a calculating model of the mass action concentrations for Fe-Cr-P melts has been formulated and some of its thermodynamic parameters have been optimized. The calculated mass action concentrations agree with the measured achvities, which shows that this model can reflect the structural reality of Fe-Cr-P melts.

关键词： activity dephosphorization of stainless steel, coexistence theory mass action concentration

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, {3. 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 (3.Pa) 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

Cleaning of Chromate Manufacture Process

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International Journal of Minerals,Metallurgy and Materials 2000年第2期14卷 132-134页

作者： Xing Zou Yi zhang(Applied science school, {3. of science and Technology beijing, beijing 100083. china)(Institute of engineering Chemistry and Metallurgy, Chinese Academy of sciences, beijing 100080, china) Applied science school University of Science and Technology Beijing Beijing 100083 China Institute of engineering Chemistry and Metallurgy Chinese Academy of Sciences Beijing 100080 China

Sodium chromate solubility is determined in the range of NaOH concentrations from 450 to 810 g/L andsolution temperatUres from 3. to 110℃. The optimized conditions to separate sodium chromate from NaOH inleached solution are resolved. It is first found the method to efficiently separate sbdium chromate from NaOH andsodium altuninate in crude sodium chromate. Bench-scale studies on the separating are performed. Finally, goodseparation results are achieved.

关键词： chromate separation clean process