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Study on the thermodynamics and kinetics in the combustion reaction between titanium and boron powders

key Engineering materials 2007年 351卷 189-194页

作者： Wang, K. Fu, Z.Y. Wang, W.M. Wang, Y.C. Wang, H. Zhang, J.Y. Zhang, Q.J. State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China

Combustion synthesis of titanium diboride(TiB2) from titanium(Ti) and boron(B) powders was studied by theoretical calculation and experimental analysis. In high temperature range or in low temperature range, the calculated activation energies are 140KJ/mol or 355KJ/mol respectively, which is described by a change from dissolution-precipitation controlled process to diffusion-controlled process. With the increase of particle size of the raw materials, combustion temperature and propagating rate will both reduce. The propagating rate decreases with the addition of diluents. Further increase of diluents may result in a stop of the combustion wave halfway or even a failure of ignition.

关键词： Reaction kinetics

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Three-dimensional modeling for water transport in membrane of PEM fuel cell with serpentine flow field

Wuhan Ligong Daxue Xuebao (Jiaotong Kexue Yu Gongcheng Ban)/...

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Wuhan Ligong Daxue Xuebao (Jiaotong Kexue Yu Gongcheng Ban)/Journal of Wuhan University of technology (Transportation Science and Engineering) 2008年第5期32卷 857-860页

作者： Liu, Kun Song, Xia Xiao, Jinsheng Luo, Zhiping Pan, Mu School of Automotive Engineering WUT Wuhan 430070 China Unit 93033 PLA of China Shenyang 110141 China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing WUT Wuhan 430070 China

Water transport in membrane plays an important role in PEM fuel cell performance. Therefore research on water transport in membrane is extremely essential. This article established a 3D single fuel cell model with serpentine flow field. The influences of the operating temperature, membrane thickness, air stoichiometry, relative humidity, operating pressure and current density on the water content in membrane under low current density are studied, and then the influence of the above parameters on the performance of fuel cell is obtained. The results show that: As the temperature rises, the water content will increased and then lower. Reducing the proton exchange membrane thickness and air stoichiometry, increasing the relative humidity, pressure and current density operation, the water content in the membrane will increase, the conductivity will increase and thus will improve the performance of the fuel cell.

关键词： Fuel cell Modeling Proton exchange membrane Serpentine flow field Water transport

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Effect of alternative porosity distribution of GDL plane on PEM fuel cell performance

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Wuhan Ligong Daxue Xuebao/Journal of Wuhan University of technology 2008年第10期30卷 127-130页

作者： Liu, Kun Zhang, Yong-Sheng Liu, Yan Zhan, Zhi-Gang Xiao, Jin-Sheng School of Automotive 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 Unit 93033 PLA of China Shenyang 110141 China

In order to investigate the influence of gas diffusion layer (GDL) structure on the drainage, electric and gas conductivity of proton exchange membrane fuel cell(PEMFC), such factors as electrochemical reaction, phase change, transfer of water and oxygen, and water transfer in membrane are investigated, and GDL with spacing porosity in plane is also studied. Results show that the performance of PEMFC with GDL with spacing porosity is better than that of PEMFC with normal GDL. GDL with spacing porosity in plane can improve the transfer of liquid water and gas and then improve the performance of PEMFC.

关键词： Fuel cell Gas diffusion layer Modeling Optimization Porosity Proton exchange membrane

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Influence of MgO overlayers on the electronic states of Fe(001) thin films grown on GaAs(001)

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Physical Review B 2008年第6期77卷 064421-064421页

作者： Liu-Niu Tong Frank Matthes Martina Müller Claus M. Schneider Chan-Gyu Lee Anhui Key Laboratory of Metal Materials and Processing School of Material Science and Engineering Anhui University of Technology Ma-An-Shan 243002 Anhui China Institute of Solid State Research IFF-9 Research Centre Jülich D-52425 Jülich Germany School of Nano and Advanced Materials Engineering Changwon National University 9 Sarim-dong Changwon Gyeongnam 641-773 Korea

The valence electronic states at the model tunneling junction interface MgO∕Fe(001) system were systematically studied by comparing the spin-resolved photoemission spectroscopy of clean Fe(001) and MgO covered MgO∕Fe(001) surfaces using linearly p-polarized light. For the clean Fe(001) film on GaAs(001), five distinct features including bulk and surface-related transitions are found. The bulk and surface-state transitions are well-accounted for by the direct transition model based on the calculated energy band structure of bcc bulk Fe(001). The previously observed minority feature at a binding energy EB=−1.3eV is reinterpreted as a surface roughness associated transition. Upon the MgO adsorption on Fe(001), the surface-state transitions at EB=−0.3eV below Fermi energy EF appearing in both the majority and minority spin spectra at low photon energy (18eV to 35eV) were quenched. This is also the first direct experimental evidence of a minority spin surface state located just below the Fermi energy as predicted previously. The bulk states at the MgO∕Fe(001) interface exhibit a layer-dependent modification, i.e., the bulk states in the deeper Fe layer(s) remain unaffected, while the states of Δ5↓ band symmetry in the Fe layer(s) closest to the MgO∕Fe(001) interface are strongly modified, in contrast to the states of Δ1↑ symmetry. As a consequence of this interface effect, the “partial spin polarization” at the Fermi level changes sign from negative to positive values as seen in the spin asymmetry spectra at photon energies of 40eV and 60eV. The origin of this spin- and symmetry-dependent modification observed at MgO∕Fe(001) interfaces is discussed.

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Consolidation and properties of tungsten carbide target with low cobalt content by hot-press sintering

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key Engineering materials 2007年 351卷 98-102页

作者： Shao, G.Q. Xiong, Z. Wang, T.G. Shi, X.L. Duan, X.L. State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China

Tungsten carbide (WC) targets with low cobalt (Co) content (0.1 - 0.2 wt.%) were prepared by hot-press sintering at 1700°C for 60 minutes in argon, from element starting powders of tungsten, cobalt and carbon. Results show that the as-fabricated targets yield relatively high relative density above 99% and high HRA above 92. WC with low Co content is formed easily than pure WC The hot-press sintering process, while element starting powders are used, is an in-situ reaction technique for accelerating the WC's diffusion rate to obtain a dense sintered body.

关键词： Tungsten carbide

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Structures of ceramics/metal and ceramics/ceramics core/shell particles by hybridization

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key Engineering materials 2007年 351卷 109-113页

作者： Fu, Z.Y. Fan, Z. Tang, W.J. Zhang, J.Y. Wang, W.M. Wang, H. Wang, Y.C. Zhang, Q.J. State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China

Hybridization is a promising method for core/shell particles by a mechanical shock process involving dry blending and dry impact blending. In this paper, hybridization was used to prepare TiB2/Ni ceramics/metal and TiB2/Al2O3 ceramics/ceramics core/shell particles. The mechanism of the formation and the features of the core/shell particles were analyzed. The nano- Al203 particles can be coated on the surface of micron TiB2 particles directly by hybridization, The sub-micron Al2O3 particles can be coated on the surface of micron TiB2 particles, only with the introducing of PE-wax as transition layer. The mechanical properties of cermet sintered from TiB2/Ni core/shell ceramics/metal particles were compared with that from TiB2/Ni blended particles.

关键词： Ceramic materials

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Electronic Structures and Bonding Properties of Ti_2AlC and Ti_3AlC_2

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Journal of Wuhan University of technology(materials Science) 2007年第1期22卷 27-30页

作者：闵新民 Department of Applied Chemistry School of Science Wuhan University of Technology State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China

The relation among electronic structure, chemical bond and property of Ti2AlC, Ti3AlC2 and doping Si into Ti2AlC was studied by density function and the discrete variation （DFT-DVM） method. After adding Si into Ti2AlC, the interaction between Si and Ti is weaker than that between Al and Ti, and the strengths of ionic and covalent bonds decrease both. The ionic and covalent bonds in Ti3AlC2, especially in Ti-Al, are stronger than those in Ti2AlC. Therefore, in synthesis of Ti2AlC, the addition of Si enhances the Ti3AlC2 content instead of Ti2AlC. The density of state （DOS） shows that there is mixed conductor characteristic in Ti2AlC and Ti3AlC2. The DOS of Ti3AlC2 is much like that of Ti2AlC. Ti2SiAl1-xC has more obvious tendency to form a semiconductor than Ti2AlC, which is seen from the obvious difference of partial DOS between Si and Al 3/7.

关键词： Ti2AlC Ti3SiC2 doping electronic structure chemical bond

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Numerical simulation of two-dimensional photonic crystal with FDTD method

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Wuhan Ligong Daxue Xuebao/Journal of Wuhan University of technology 2008年第3期30卷 5-7页

作者： Zhou, Jian Jiang, Hong-Zhou Zhang, Lin Wang, Lin Zeng, Chun-Nian Chen, Ji State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China School of Information Engineering Wuhan University of Technology Wuhan 430070 China School of Automotive Engineering Wuhan University of Technology Wuhan 430070 China Department of Electrical and Computer Engineering University of Houston Houston United States

Based on the theory of photonic crystal and its characteristic, which was known as photonic band gap (PBG), the finite-difference time-domain (FDTD) method, including absorbing boundary condition and periodic boundary condition, was used to simulate transmission characteristic of two-dimensional photonic crystal, which has periodic Al2O3 cylinder array structure. Incident wave was presumed as s-polarized wave. In two incident angles which were 0° and 30°, electric field, phase and transmissivity in the range of 1-30 μm were calculated. Numerical simulation results showed that PBG of photonic crystal existed in the range 12-18 μm (infrared waveband), and it may be used to develop infrared wave-guide.

关键词： FDTD Periodic structure Photonic band gap Photonic crystal

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Microstructure and resistivity of iridium oxide thin films by pulsed laser deposition technique

Microstructure and resistivity of iridium oxide thin films b...

引用

作者： Zhang, L.M. Gong, Y.S. Wang, C.B. Shen, Q. State Key Lab. of Advanced Technology for Material Synthesis and Processing Wuhan University of Technology Wuhan 430070 China

Highly conductive IrO2 thin films were prepared on Si (100) substrates by pulsed laser deposition technique from an iridium metal target in an oxygen ambient atmosphere. The effect of substrate temperature on the structure and electrical properties of IrO2 films was investigated. The deposited films at substrate temperatures ranging from 250 to 500°C under an oxygen pressure of 20Pa were pure polycrystalline tetragonal IrO 2 and the preferential growth orientation changed with the substrate temperature. IrO2 films were well solidified with the fairly homogeneous thickness and exhibited a good adhesion with the substrate. The room-temperature resistivity of IrO2 films decreased with the increase of substrate temperature and the minimum resistivity of (42±6) μΩ·cm was deposited at 500°C.

关键词： Thin films

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Self-assembled PEMs for direct formic acid fuel cells

Self-assembled PEMs for direct formic acid fuel cells

引用

30th Fuel Cell Seminar

作者： Tang, Haolin Pan, Mu Wan, Zhaohui Yuan, Runzhang State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan China

ISBN: (纸本)9781566775496

Direct liquid fuel cells have attracted intensive research because of the promised application in portable fuel cell systems. Liquid fuel such as formic acid crossover through the proton exchange membranes (PEMs, e.g. Nafion™ membrane) is one of the major obstacles that currently prevent the widespread commercial applications of direct liquid fuel cell. In this paper, PEMs constructed by self-assembling metal nanoparticles on Nafion™ membranes were prepared to probe the direct formic crossover behaviors. The results show that the fuel crossover has a remarkable decrease comparing with the original PEMs. This satisfactory performance gives the self-assembled PEMs a promised prospect in direct liquid fuel cells. ©The Electrochemical Society.

关键词： Formic acid

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