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Effects on synthesis of Ti2AlC/Ti3AlC2 doped with Si from elemental powders by hot pressing and theoretical analysis

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Gongneng Cailiao/Journal of Functional materials 2007年第6期38卷 1037-1040页

作者： Wang, Ping Mei, Bing-Chu Min, Xin-Min Hong, Xiao-Lin Zhou, Wei-Bing School of Science Wuhan University of Technology Wuhan 430070 China State Key Lab. of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China

Ti2AlC/Ti3AlC2 bulk material were synthesized by hot pressing using elemental powder mixture of Ti, Al, Si and active carbon whose molar ratios were 2.0Ti/1.1Al/1.0C, 0.1mol Al replaced by Si and 0.2mol Al replaced by Si. Through calculating according to models of Ti2AlC, Ti3AlC2 and Si-doped, even net charge of the atoms and even covalent bond orders were calculated respectively. Results show that Ti2AlC material with little Ti3AlC2 could be synthesized by hot pressing elemental powder mixture of 2.0Ti/1.1Al/1.0C at 1450°C for 60min. On the other hand, the effect of Si was very obvious when 0.2mol Al replaced by Si and it did not improve the synthesis of Ti2AlC but Ti3AlC2 at the same temperature. Moreover, experimental results were explained by the effect of Si doped on net charge of the atoms and covalent bond orders.

关键词： Ceramic materials

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Preparation and property of self-dispersed nanometer γ-AlOOH

Preparation and property of self-dispersed nanometer γ-AlOO...

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作者： Liao, Haida Wu, Bolin Zhang, Lianmeng Liao, Donghua Wang, Huixian State Key Lab. of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China Manning China Guilin China College of Chemistry and Ecological Engineering Guangxi University for Nationalities Nanning 530006 China Department of Materials and Chemical Engineering Guilin University of Technology Guilin China

A peptizing-hydrothermal method to prepare nanometer γ-AlOOH crystal powder with industrial Al(OH)3 as raw materials has been proposed in the present paper. The XRD and TEM results show the product is a pure γ type nanometer A100H crystal powder with average grain diameter of 70nm. Laser grading analysis indicates the average grain diameters of the product in the solution are 66.52nm in water and 84.33nm in N,N-dimethylformamide, respectively without surface modification and dispersant. The experimental result indicated that polymer/inorganic nano-composite with high content of nanometer AlOOH presents inorganic characteristic of polymer. The wear rate of the alumina ceramic ball sintered at 1465°C from ceramic, which contains 98% alumina (wt), can be reduced up to 40% with addition of 3.5% nanometer AlOOH.

关键词： Hydrothermal synthesis

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Research on the curing reaction heat resistance of ATPU/epoxy resin system

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Wuhan Ligong Daxue Xuebao/Journal of Wuhan University of technology 2007年第1期29卷 37-39页

作者： Chen, Wen-Yi Guan, Jian-Guo Center for Material Research and Analysis Wuhan University of Technology Wuhan 430070 China State Key Lab of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China

Thermogravimetry (TG-DTA) was used to study the heat resistance characteristics and curing heat decomposition kinetics of ATPU/epoxy resin system. Results showed that the decomposition temperature of the cured ATPU-2/E-44 was higher than that of ATPU-1.5/E-44. The calculation results of decomposition reaction showed that the cured system of ATPU-2/E-44 had better heat resistance, the reaction decomposition active energy of ATPU-2/E-44 system was higher than that of ATPU-1.5/E-44.

关键词： Active energy Amine-terminated polyurethane (ATPU) Epoxy resin Heat decomposition kinetics Heat resistance

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Research on the heat treatment of cubic boron nitride powder

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Wuhan Ligong Daxue Xuebao/Journal of Wuhan University of technology 2007年第10期29卷 121-123+127页

作者： Duan, Xing-Long Shao, Gang-Qin Wang, Jing Shi, Xiao-Liang Yan, Li Jiao, Lin State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China Henan Union Abrasives Corp Zhengzhou 450003 China

Cubic Boron Nitride powder was heat treated in N2 or in vacuum at different temperatures and dwell time. Its phase composition and morphology were investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. Results showed that the cubic Boron Nitride was transformed into hexagonal phase after heat treatment in N2 at 1350°C for 10 h, or in vacuum (pressure = 1-5 Pa) at 1550°C for 5 h, while no changes occurred in particle size and morphology.

关键词： cBN hBN Heat treatment Nitrogen Vaccum

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Thermal shock experiment and simulation of ceramic/metal gradient thermal barrier coating

Thermal shock experiment and simulation of ceramic/metal gra...

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作者： Xiao, Jinsheng Liu, Kun Zhao, Wenhua Fu, Weibiao School of Automotive Engineering Wuhan University of Technology Hubei 430070 China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Hubei 430070 China Department of Engineering Mechanics Tsinghua University Beijing 100084 China

A thermal shock experiment is designed to explore the thermal shock properties of ceramic/metal gradient thermal barrier coating. The specimens are heated up by oxygen-acetylene flame and cooled by water spray. The experiment procedure includes two stages, heating the specimen from the initial temperature 30°C for 40s, and then cooling for 20s. The heat transfer and the associated thermal stresses produced during the thermal shock procedure are simulated by finite element method. Experimental results indicated that the specimen of gradient coating behaves better in thermal shock experiments, which agree with the results of simulation.

关键词： Thermal barrier coatings

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The preparation and thermal transport property of nanostructured Yb-filled CoSb3 induced by melt spinning technique

The preparation and thermal transport property of nanostruct...

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International Conference on Thermoelectrics (ICT)

作者： H. Li X.F. Tang X.L. Su W.Q. Cao Q.J. Zhang State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan China

The Yb-filled Yb x Co 4 Sb 12 (times=0.2-0.5) bulk materials with special nanostructure were prepared by combining melt spinning method with spark plasma sintering (SPS). The microstructure and thermal transport property of Yb x Co 4 Sb 12 were investigated. The microstructure observations were performed by using high-resolution transmission electron microscopy and field emitted scanning electron microscopy (HRTEM and FESEM). The results show that ribbon-shaped samples after melt spinning are composed of nanocrystals and amorphous-like phases, and possess preferable crystal granularity and evengranular distribution with roller linear speed of 30 m/s and nozzle pressure of 0.02 MPa; the bulk materials after SPS are composed of minicrystals with 200 nm average diameter which is formed by nanocrystals with 5-20 nm diameter. This special microstructure increases grain boundary scattering notably, and has great effect on phonon behavior. As a result, the thermal conductivity of the material is decreased remarkably. Compared with the sample prepared by melting-quench-diffusion annealing method with the same filling fraction (times=0.5), thermal conductivity of the sample prepared by melt spinning method decreased 50% from 4.0 Wm -1 K -1 to 2.0 Wm -1 K -1 at 600 K, and the sample still possesses relatively high power factor.

关键词： Thermal conductivity Spinning Microstructure Nanostructured materials Electron emission Scanning electron microscopy Transmission electron microscopy Nanocrystals Grain boundaries Conducting materials

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Nanostructure and thermoelectric properties of p-type Bi0.5Sb1.5Te3 compound prepared by melt spinning technique

Nanostructure and thermoelectric properties of p-type Bi0.5S...

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International Conference on Thermoelectrics (ICT)

作者： W.J. Xie X.F. Tang G. Chen Q. Jin Q.J. Zhang State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan China

P-type Bi 0.5 Sb 1.5 Te 3 bulk material with fine nanostructure has been prepared by combining melt spinning technique with spark plasma sintering (SPS), and the effects of microstructure on the thermoelectric transport properties are investigated. Bi 0.5 Sb 1.5 Te 3 ribbons with fine nanostructure are obtained during the melt spinning process and the grain sizes of Bi 0.5 Sb 1.5 Te 3 are about 5-15 nm observed by High-resolution transmission electron microscopy. Such structure has great influence on thermoelectric transport properties of Bi 0.5 Sb 1.5 Te 3 compound. Compared with zone melting and directing SPS samples, the lattice thermal conductivity of the sample processed by melt spinning decreases significantly due to the intensive phonon scattering induced by the fine nanostructure. The greatest thermoelectric figure of merit (ZT) of 1.20 is obtained at 300K for the sample which is prepared by melt spinning with roller linear speed of 10 m/s.

关键词： Thermoelectricity Bismuth Tellurium Spinning Nanostructured materials Plasma properties Thermal conductivity Sparks Plasma materials processing Plasma transport processes

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synthesis and electrical transport properties of p-type Ba8Ga16CdxGe30−x type-I clathrates

Synthesis and electrical transport properties of p-type Ba8G...

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International Conference on Thermoelectrics (ICT)

作者： Shukang Deng Xinfeng Tang Han Li Yonggao Yan QingJie Zhang State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan China

P-type Ba 8 Ga 16 Cd x Ge 30-x (x=0.95, 1.00, 1.05, 1.10) type-I clathrates with different Cd contents were synthesized by combining melt method with spark plasma sintering (SPS). The effects of Cd content on electrical transport properties have been investigated. The results show that all samples exhibit p-type conduction. The Seebeck coefficient alpha and room temperature carrier mobility mu H decrease with the increasing Cd content. The electrical conductivity sigma and the room temperature carrier concentration N p increase with the increase of Cd content. In the low temperature range (T<150 K), the carrier scattering mechanism is mainly ionized impurity mechanism, and gradually changes to an acoustical mechanism with the rising temperature. The maximum power factor value of 0.35times10 -3 Wm -1 K -2 is obtained at 550 K for Ba 8 Ga 16 Cd 1.00 Ge 29.00 .

关键词： Plasma temperature Thermal conductivity Temperature distribution Thermoelectricity X-ray scattering Plasma properties Sparks Reactive power Conducting materials Inorganic materials

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Low temperature depositing diamond films in microwave plasma CVD method and its characterization

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Wuhan Ligong Daxue Xuebao/Journal of Wuhan University of technology 2007年第4期29卷 49-51+78页

作者： Wang, Lin Wang, Yong-Ming Liu, Gui-Zhen Zhou, Jian School of Information Engineering Wuhan University of Technology Wuhan 430070 China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China

Diamond films were deposited by using CH4/A1-/H2 gas system and silicon (111) wafers as substrate in microwave plasma CVD (MPCVD) at low temperature about 350°C . The effects of the gas system and proportion, different microwave power, and different pretreatment methods of substrate on the microstructure of diamond films were respectively discussed. The diamond film samples were investigated by X-ray-diffraction (XRD) and scanning electron microscopy (SEM). The results showed that diamond (111) peak of XRD patterns was very low because of non-diamond phase and defects. The SEM images showed that diamond films were stacked with regular ranged and about 200 nm ball-like diamond secondary nucleation particles. The diamond films are consisted of no well-faceted particles.

关键词： Argon Diamond films Low temperature MPCVD

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High temperature thermoelectric property of Sr-filled skutterudite Sr yCo4Sb12

High temperature thermoelectric property of Sr-filled skutte...

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作者： Zhao, Xueying Shi, Xun Chen, Lidong Bai, Shengqiang Zhang, Wenbing Tang, Xinfeng State Key Laboratory of High Performance Ceramics and Superfine Microstructure Shanghai Institute of Ceramics CAS Shanghai 200050 China Graduate School Chinese Academy of Sciences Beijing China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China

Sr-filled skutterudite compounds SryCo4Sb 12 (y=0-0.20) were synthesized by melting method. XRD and EPMA results revealed that the obtained samples are single skutterudite phase with homogeneous chemical composition. The lattice parameters increase linearly with increasing Sr content in the range of y=0-0.20. The thermal conductivity, electrical conductivity and Seebeck coefficient were measured in the temperature range of 300-850K. The measurement of Hall effect was performed by Van de Pauw method at room temperature. The obtained Sr-filled skutterudite exhibits n-type conduction. The absolute value of the Seebeck coefficient of Sr yCo4Sb12 decreases with the increase of Sr content. The electrical conductivity increases with the increase of Sr content. The lattice thermal conductivity of SryCo4Sb12 is significantly depressed as compared with unfilled CoSb3. The maximum dimensionless thermoelectric figure of merit is 0.7 for Sr 0.20Co4Sb12 at 850K. Further optimization of chemical composition would improve the thermoelectric performance.

关键词： Strontium compounds

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