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Preparation of MWNTs/Al_2O_3 composites and their mechanical and electrical properties

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Science china(Technological Sciences) 2005年第6期48卷 622-631页

作者： FAN Jinpeng1,2, ZHAO Daqing1,2, XU Zening1,2 & WU Minsheng1,2 1. department of mechanical engineering, tsinghua university, beijing 100084, china 2. Key Laboratory for Advanced Manufacturing by Materials Processing Technology, tsinghua university, beijing 100084, china 1. department of mechanical engineering Tsinghua University 100084 Beijing China 2. Key Laboratory for Advanced Manufacturing by Materials Processing Technology Tsinghua University 100084 Beijing China

The mechanical and electrical properties of MWNTs/Al2O3 composite prepared fabricated by hot pressing are investigated. The relation between properties and microstructure of composites is also discussed. With 4wt% MWNTs as reinforcement, the fracture toughness of composite obtained reaches 5.55 MPa·m1/2, which is 80% higher than that of pure Al2O3 obtained in the same conditions. The main toughening mechanism is CNTs’ pinning alumina grain boundaries, and the pullout of CNTs takes effect also. Through adding 2wt% MWNTs and altering the mix method, the fracture toughness of the composite obtained is 3.97 MPa·m1/2. Furthermore, the electrical resistivity is as low as 8.4×10?3 ?·m, decreasing by 14 orders of magnitude compared with pure alumina ceramics. The function of CNTs in composite is related to the distribution state of CNTs in composite, and the distribution state of CNTs in matrix is dependent on preparation procedures.

关键词： MWNTs, alumina, composite, fracture toughness, electrical properties.

Enhancing the capacitances of electric double layer capacitors based on carbon nanotube electrodes by carbon dioxide activation and acid oxidization

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Science china(Technological Sciences) 2010年第5期53卷 1234-1239页

作者： LI ChenSha1,2,QIAO YingJie1,WU JianJun2,WANG DaZhi2 & YUAN DianBo2 1 department of Materials Science,Harbin engineering university,Harbin 150001,china 2 department of mechanical engineering,tsinghua university,beijing 100084,china 1. department of Materials Science Harbin Engineering University Harbin 150001 China2. Department of Mechanical Engineering Tsinghua University Beijing 100084 China

Polarizable electrodes of electric double layer capacitors(EDLCs) were made from carbon nanotubes(CNTs).Effect of carbon dioxide activation together with acid oxidation for the electrodes on the characteristics and performances of electrodes and EDLCs was *** dioxide activation changed the microstructure of the electrodes,increased the effective surface area of CNTs and optimized the distribution of apertures of the *** oxidization modified the surface characteristics of *** on the polarizable electrodes treated by carbon dioxide activation and acid oxidization,the performances of EDLCs were greatly *** specific capacitance of the electrodes with organic electrolyte was increased from 21.8 F/g to 60.4 F/g.

关键词： carbon nanotube electric double layer capacitor scan electron microscopy

The Influence of Preheat Temperature of Steel Plate on Steel-mushy Cu-graphite Bonding

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Journal of Wuhan university of Technology(Materials Science) 2006年第3期21卷 12-14页

作者：张鹏 department of mechanical engineering Beijing Jiaotong UniversityBeijing 100044China

The pressing bonding of steel plate to QTi3.5-3.5 graphite slurry was conducted. Under the conditions of 530 ℃ for the preheat temperature of dies, 45% for the solid fraction of QTi3.5- 3.5 graphite slurry, 50 MPa for the pressure and 2 min for the pressing time, the relationship between the preheat temperature of steel plate and interfacial mechanical property of bonding plate was studied. The results show that when the preheat temperature of steel plate is lower titan 618 ℃ , the interfacial shear strength of bonding plate increases with the increasing of the preheat temperature of steel plate. When the preheat temperature of steel plate is higher than 618 ℃ , the interfacial shear strength decreases with the increasing of the preheat temperature of steel plate. When the preheat temperature of steel plate is 618 ℃ , the highest interfacial shear strength of bonding plate of 127.8 MPa can be got.

关键词： steel-mushy QTi3.5-3.5 graphite pressing bonding interfacial shear strength preheat temperature of steel plate

Effect of Interface on mechanical Property of Steel-mushy Al-20Sn Bonding Plate

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Journal of Wuhan university of Technology(Materials Science) 2006年第1期21卷 60-62页

作者：张鹏 department of mechanical engineering Beijing Jiaotong University Beijing 100044 China

The ratio of Fe-Al compound at interace, which could determine the quarttity of Fe-Al compound at the interace of steel-mushy Al- 20 Sn bonding plate, was used to characterize the interfacial structure of steel-mushy Al-20 Sn bonding plate quantitatively. The effect of ratio of Fe-Al compound at interface on interacial shear strength was investigated perfectly. The results show that the relationship between ratio of Fe-Al compound at interace and interfacial shear strength is S = 3.3 ＋ 1.91 t - 0.0135t^2 （ where t is ratio of Fe-Al compound at in- terface and S is interfacial shear strength ）. When the ratio of Fe-Al compound at interface is 71%, the largest interfacial shear strength 70.9 MPa is got. This reasonable ratio of Fe-Al compound at interface is a quarttitative criterion of interfacial embrittlement. When the ratio of Fe-Al compound at interface is higher than 71% , interfacial embrittlement will occur.

关键词： interfacial structure ratio of Fe-Al compound at interface interfacial shear strength

Mathematical Delineation of the Thermophysical Process of Electron Beam Welding

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稀有金属材料与工程 2011年第S4期40卷 134-137页

作者： Wang Xuedong1,2,Fu Pengfei 1,Shi Qingyu 2 1National Key Laboratory of Science and Technology on Power Beam Processes,beijing Aeronautical Manufacturing Research Institute,beijing 100024,china2 department of mechanical engineering,tsinghua university,beijing 100084,china beijing Aeronaut Mfg Res Inst Natl Key Lab Sci & Technol Power Beam Proc Beijing 100024 Peoples R China tsinghua Univ Dept Mech Engn Beijing 100084 Peoples R China

Multiple factors and complicated coupling relationships exist in the weldment during EBW,in order to comprehend this process,a mathematical delineation method based on a main line was presented in this *** on the main line,the complicated coupling relationships existing in EBW were reproduced by mathematical *** calculational results were in well agreement with the experimental *** mathematical delineation was an effective method to comprehend the features and essence of EBW.

关键词： electron beam welding mass transfer identification of phase interface keyhole

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透明弹性薄膜调节可见光透射比的试验研究

太阳能学报 2003年第6期24卷 795-800页

作者：张文赵大庆华北科技学院机电系北京 101601 清华大学机械系北京100084

总结了透明弹性薄膜调节可见光的研究试验。基本原理是当光通过凸凹不平的透明薄膜时,在薄膜表面要发生散射,散射能力大致与薄膜表面粗糙度成正比。当通过外力来改变薄膜表面的粗糙度时,就可以改变薄膜的散射比,也即改变了薄膜的直射透... 详细信息

总结了透明弹性薄膜调节可见光的研究试验。基本原理是当光通过凸凹不平的透明薄膜时,在薄膜表面要发生散射,散射能力大致与薄膜表面粗糙度成正比。当通过外力来改变薄膜表面的粗糙度时,就可以改变薄膜的散射比,也即改变了薄膜的直射透射比,从而对透射光强进行一定的调节。实验表明:采用适当硬度的透明弹性薄膜,在一个大气压条件下,薄膜的直射透射比的调节范围可从最小33%达到最大86 7%,透射比的改变时间不超过1秒。这一效果比目前所报道的电致变色调光的范围要大,速度要快,视觉效果也好的多,有一定的应用前景。

关键词：粗糙度直射透射比透明弹性薄膜

Structure and property of metal melt Ⅰ:The number of residual bonds after solid-liquid phase changes

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Science china(Physics,Mechanics & Astronomy) 2010年第9期53卷 1571-1577页

作者： MI GuangBao1,2,LI PeiJie1,2 & HE LiangJu1 1 National Center of Novel Materials for International Research,tsinghua university,beijing 100084,china 2 department of mechanical engineering,tsinghua university,beijing 100084,china

Based on the mechanism of metal solid-liquid phase change and the theory of liquid metal's micro-inhomogeneity,a physical model is established between latent heats of fusion and vaporization and the numbers of residual bonds and short-range ordered atoms at the melting point inside a metal ***,the mathematical derivation and proof are also *** model produces the numbers of residual bonds and short-range ordered atoms after the solid-liquid phase change only by using basic parameters and thermophysical properties of the crystal ***,it presents a more effective way to analyze the melt's structural *** using this model,this study calculates the numbers of residual bonds and short-range ordered atoms in Al and Ni *** calculated results are consistent with the experimental ***,this study discusses the atomic number's influence on the numbers of residual bonds and short-range ordered atoms in the melts within the first(ⅠA) and second main group(ⅡA) elements.

关键词： metal melt atomic cluster number of residual bonds number of short-range ordered atoms phenomenological model melt structural information

Modifying the poly ether ester antistatic agent by carbon nanotubes, the antistatic effect on polypropylene fibers

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Progress in Natural Science:Materials International 2004年第9期 61-66页

作者： LI Chensha 1,2 *, LI Zhi 2, ZHANG Baoyou 3, LU Weizhe 2, TANG Yaping 1, FANG Gang 2, HU Xiaoqing 4 and LIANG Ji 2(1. New Material Division, Institute of Nuclear Energy Technology, tsinghua university, beijing 102201, china 2. department of mechanical engineering, tsinghua university, beijing 100084, china 3. Center for Analysis and Measurement, Harbin Institute of Technology, Harbin 150001, china 4. The State Key Laboratory of New Ceramics and Fine Processing of tsinghua university, beijing 100084, china) New Material Division，Institute of Nuclear Energy Technology，tsinghua university，beijing 102201，china department of mechanical engineering，tsinghua university，beijing 100084，china department of mechanical engineering，tsinghua university，beijing 100084，china Center for Analysis and Measurement，Harbin Institute of Technology，Harbin 150001，china New Material Division，Institute of Nuclear Energy Technology，tsinghua university，beijing 102201，china The State Key Laboratory of New Ceramics and Fine Processing of tsinghua university，beijing100084，china

A new antistatic fiber is investigated using carbon nanotubes (CNTs) to enhance the antistatic ability of polymer fibers based on the mechanism of the discharging process of polarity macromolecule. Composite antistatic agent (CAA), prepared by dispersing CNTs in an organic antistatic agent carrier containing metallic ions in their main chains, is cospun with polypropylene (PP) to prepare CAA/PP fibers. It is indicated through analyzing the measured dynamic tribo electrostatic voltages that CNTs can promote the discharging process of polarity macromolecule of antistatic agent carrier and further improve the antistatic ability of PP fibers. It is also indicated that the antistatic effect promoted by CNTs is better than that by conductive carbon black. Moreover, the antistatic effects of the CNTs treated by different methods are also compared.

关键词： carbon nanotubes polypropylene fiber antistatic agent tribo-electrostatic voltages.

Effect of Lanthanum on mechanical Properties of ZL702 Alloy at Room and High Temperature Condition

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Journal of Rare Earths 2000年第2期18卷 123-123页

作者： LI Pei jie 1,2 , ZENG Da ben 1, JIA Jun 2, LI Qing chun 2( 1. department of mechanical engineering, tsinghua university, beijing 100084, china 2. School of Materials Science and engineering, Harbin Institute of Technology, Harbin 150001, china

Effects of lanthanum on microstructure and mechanical properties of ZL702 alloy at room and high temperature conditions are studied. The experiment shows that high temperature intermetallics reticularly distributing at grain boundary are formed with La and Al, Si, Fe etc. elements of alloy, which enhances the thermal stability of the alloy. With appropriate content of La (0.10%～ 0.15%), the mechanical properties of the alloy, such as strength, at room temperature and high temperature can be improved.

关键词： rare earths lanthanum Al Si alloy room temperature mechanical properties high temperature mechanical properties