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Preparation and Properties of Macroporous Silicon Nitride Ceramics by Gelcasting and Carbonthermal Reaction

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Journal of materials science & Technology 2005年第6期21卷 894-898页

作者： Wen ZHANG, Hongjie WANG+ and Zhihao JIN state key laboratory for {3. behavior of materials, school of materials science and engineering, xi’an jiaotongUniversity, xi’an 71.049, {13. state key laboratory for {3. behavior of materials School of Materials Science and Engineering Xi'an Jiaotong University Xi'an 710049 China

Macroporous silicon nitride （Si3.4） ceramics with high strength, uniform structure and relatively high porosity were obtained by gelcasting and carbonthermal reaction in a two-step sintering technique. Microstructure and composition were investigated by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD）. Open porosity, pore size distribution and basic mechanical performance were measured by Archimedes method, mercury intrusion porosimetry and three-point bending methods, respectively. SEM and TEM results revealed that pores were formed by elongated β-Si3.4. SADP measurement proved the formation of SiC particles. The SiC granules were beneficial for the formation of high ratio elongated β-Si3.4, and at proper amount, they also acted as reinforcement phase. Thermodynamic analysis indicated that the mechanisms of the reactions were mainly associated with liquid-solid reaction and gas-liquid reaction.

关键词： Ceramics Silicon nitride Silicon carbide X-ray diffraction

Ultralight X-type lattice sandwich structure (Ⅱ):Micromechanics modeling and finite element analysis

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science china(Technological sciences) 2009年第9期52卷 2670-2680页

作者： ZHANG QianCheng1,CHEN AiPing 2,CHEN ChangQing2,3.& LU TianJian2 1 state key laboratory for {3. behavior of materials,school of material science and engineering,xi’an jiaotong University,xi’an 71.049,china 2 MOE key laboratory for Strength and Vibration,{13. of Aerospace,xi’an jiaotong University,xi’an 71.049,china 3.Department of engineering Mechanics,AML,Tsinghua University,Beijing 100084,china state key laboratory for {3. behavior of materials School of Material Science and Engineering Xi’an Jiaotong University Xi’an China MOE key laboratory for Strength and Vibration School of Aerospace Xi’an Jiaotong University Xi’an China Department of engineering Mechanics AML Tsinghua University Beijing China

The methods of homogenization and finite elements are employed to predict the effective elastic constants and stress-strain responses of a new type of lattice structure,the X-structure proposed by the authors in a companion paper. It is shown that in most cases the predictions by the equivalent homogenization theory agree well with the experimental and 3.dimensional finite element calculated results. The theoretical and numerical study supports the argument that the X-structure is superior to the pyramid lattice structure in terms of mechanical strength.

关键词： sandwich panel lattice structure equivalent homogenization finite element model

Structure and electrochemical properties of low-cobalt La_(1-x)Li_xNi_(3.2)Co_(0.3.Al_(0.3. (0≤x≤0.2) hydrogen storage electrode alloys

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Rare Metals 2006年第z1期25卷 1-6页

作者： WEI Xuedong LIU Yongning ZHANG Peng state key laboratory for {3. behavior of materials School of Material Science and Engineering Xi''an Jiaotong University Xi''an 710049 China State Key Laboratory for Mechanical Behavior of Materials School of Material Science and Engineering Xi''an Jiaotong University Xi''an 710049 China State Key Laboratory for Mechanical Behavior of Materials School of Material Science and Engineering Xi''an Jiaotong University Xi''an 710049 China

The structure and electrochemical properties of a new low cobalt hydrogen storage electrode alloys La1-xLixNi3.2Co0.3.l0.3.(0≤x≤0.2) were investigated with a different additions of Li in replacement of La. With the increase of Li contents the maximum discharge capacity increases from 240 mAh·g-1(x=0) to 3.8.4 mAh·g-1(x=0.1) and the cycle stability is improved correspondingly. The capacity decay can remain 28.6% (x=0.2) after 23. charge/discharge cycles. The high rate discharge(HRD) ability of the alloys(x≤0.1) is improved and the best HRD is 3..1%(x=0.1) under the discharge current density 1200 mA·g-1. It is found that the prepared alloys are basically composed of LaNi5 as matrix phase and LaNi3.as second phase(x≤0.1). But the abundance of LaNi3.phase dramatically decreases with increasing x. When x=0.2, a new phase Al(NiCo)3.is formed.

关键词： hydrogen storage alloy microstructure high rate discharge ability cycling stability

Quasi-nano wear mechanism under repeated impact contact loading

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science china(Technological sciences) 2010年第6期53卷 1583-1589页

作者： ZHU JinHua1,REN xiangHong1,2,ZHANG JianJun1,3.XU YunHua1,3.& LU Zhengxin1,4 1 state {3. laboratory for mechanical behavior of materials,xi’an jiaotong University,xi’an 71.049,china 2 xi’an Research Institute of High-tech,xi’an 710025,china 3.school of materials science and engineering,xi’an University of Architecture and Technology,xi’an 710055,china 4 school of materials science and engineering,xi’an University of Technology,xi’an 71.049,china 1. state key laboratory for {3. behavior of materials Xi’an Jiaotong University Xi’an 710049 China2. Xi’an Research Institute of High-tech Xi’an 710025 China3. School of Materials Science and Engineering Xi’an University of Architecture and Technology Xi’an 710055 China4. School of Materials Science and Engineering Xi’an University of Technology Xi’an 710049 China

A new quasi-nano wear mechanism (QNWM) has been proposed in this paper based on the facts of wear curve turning under high energy impact contact *** characteristic is that the wear rate of QNWM is only 1/10-1/3.that of delamination mechanism at the same energy *** diameters of wear debris and pits on the worn surfaces fall into the quasi-nanometer scale (about 50-120 nm).The necessary and sufficient conditions,which bring about the QNWM,are:(i) the nano-structure (nano-crystalline + amorphous phase) in impact contact surface layer has formed by the intensive impact strain;(ii) the delamination wear cracking in sub-surface layer must be restrained;(iii) the microcracks of QNWM are produced in amorphous phase of surface nano-structure layer rather than in nano-crystalline.

关键词： impact wear quasi-nano wear mechanism delamination wear mechanism nano-structure

Microstructure and mechanical Properties of Nanocrystalline Tungsten Thin Films

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Journal of materials science & Technology 2010年第1期26卷 87-92页

作者： H.L. Sun, Z.X. Song, D.G. Guo, F. Ma and K.W. Xu state key laboratory for {3. behavior of materials, school of materials science and engineering, xi an jiaotong University, xi’an 71.049, {13. [a] state key laboratory for {3. behavior of materials school of materials science and {3. xi'an jiaotong University xi'an 71.049 china

Tungsten （W） thin films were prepared by magnetron sputtering onto Si （100） substrates. Their microstructures were characterized by X-ray diffraction （XRD）, field emission scanning electron microscopy （FE-SEM） and transmission electron microscopy （TEM）. The hardness and modulus were evaluated by nanoindentation. It is found that a 3. nm Cr sticking layer induces structure changes of deposited W film from β-W to α-W structure. In addition, remarkable hardness enhancement both for the deposited and annealed W films, were compared with that of bulk coarse-grained W, although their nanoindentation modulus is very close to that of corresponding bulk W. The intrinsic reasons that lead to structure changes and super hardness are discussed.

关键词： Tungsten film Microstructure Nanoindentation Hardness Modulus

Microstructural characterization of the Al/Cu/steel diffusion bonded joint

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Rare Metals 2009年第5期28卷 478-481页

作者： BAI Bingzhe GAO Yimin FENG Chun laboratory of Advanced materials Department of Materials Science and Engineering Tsinghua University Beijing 100084 China state key laboratory for {3. behavior of materials School of Materials Science and Engineering Xi＇an Jiaotong University Xi＇an 710049 China

A vacuum hot-pressed diffusion method was used to prepare an Al/Cu/steel composite with a gradient structure. The Al/Cu interface was investigated layer by layer by means of scanning electron microscopy, energy dispersive X-ray spectrometry, electron probe microanalysis, and Vickers microhardness. The results show that two kinds of intermetallic compounds, Cu9Al4 adjacent to the Cu side and CuAl2 adjacent to the Al side, are formed in the interface of Al/Cu. The conductivity is 0.3.9 mS/cm in the intermetallic compound with a thickness of 3.5 μm, higher than that of the intermetallic compound with a thickness of 23.μm, in which the conductivity is 0.242 mS/cm.

关键词： metal composites diffusion bonding intermetallic compounds microhardness interface

“Blocking and rebalance”mechanism-guided design strategies of bimetallic doped 2D a-phosphorus carbide as efficient catalysts for N_(2) electroreduction

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Journal of Energy Chemistry 2024年第10期97卷 68-78,I0003页

作者： Cheng He Jianglong Ma Shen xi Wenxue Zhang state key laboratory for {3. behavior of materials School of Materials Science and EngineeringXi'an Jiaotong UniversityXian 710049ShanxiChina school of materials science and {3. Chang'an UniversityXi'an 710064ShaanxiChina

Compared to single atom catalysts(SACs),the introduction of dual atom catalysts(DACs)has a significantly positive effect on improving the efficiency in the electrocatalytic nitrogen reduction reaction(NRR)which provides an environmental alternative to the Haber-Bosch ***,the research on the mechanism and strategy of designing bimetallic combinations for better performance is still in its early ***,based on"blocking and rebalance"mechanism,45 combinations of bimetallic pair dopedα-phosphorus carbide(TM_(A)TM_(B)@PC)are investigated as efficient NRR catalysts through density functional theory and machine learning *** a multi-step screening,the combinations of TiV,TiFe,MnMo,and FeW exhibit highly efficient catalytic performance with significantly lower limiting potentials(-0.17,-0.18,-0.14,and-0.3. V,respectively).Excitingly,the limiting potential for CrMo and CrW combinations is 0 V,which are considered to be extremely suitable for the NRR *** mechanism of"blocking and rebalance"is revealed by the exploration of charge transfer for phosphorus atoms in electron blocking ***,the descriptorφis proposed with machine learning,which provides design strategies and accurate prediction for finding efficient *** work not only offers promising catalysts TM_(A)TM_(B)@PC for NRR process but also provides design strategies by presenting the descriptorφ.

关键词： DACs Nitrogen reduction reaction 2D a-phosphorus carbide Inherent attributes Machine learning

Mechanism of Combustion Synthesis of TiC-Ti Cermet

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Journal of Wuhan University of Technology(materials science) 2007年第3期22卷 502-505页

作者：肖国庆 school of materials science and {3. Xi’an University of Architecture and Technology

In order to investigate the mechanism of combustion synthesis of TiC-Ti cermet, a mixture of Ti and C was used for a combustion front quenching test, and the microstructural evolution in the quenched sample was analyzed by scanning electron microscopy （SEM） and energy dispersive X-ray （EDX）. Also, a temperature-time profile of the combustion reaction was measured. Based on the experimental results, a reaction-dissolution-precipitation mechanism of the combustion synthesis of TiC-Ti was proposed.

关键词： TiC-Ti cermet combustion synthesis combustion front quenching method

Thermodynamic Analysis of the Formation of In-situ Reinforced Phases In Cast Al-4.5Cu Alloy

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Journal of Wuhan University of Technology(materials science) 2008年第3期23卷 342-345页

作者：梁艳峰 state key laboratory for {3. behavior of materials School of Materials EngineeringXi’an Jiaotong University school of materials&Chemical engineering Xi’an Technological UniversityXi'an 710032China

The thermodynamic analysis of the formation of in-situ reinforced phases in （TiB2＋Al3.i）/Al-4.5Cu composites prepared by mixed salts reaction was conducted, and heat changes of mixed salts system were analyzed by differential thermal analysis（DTA）.The results show that although TiB2 possesses the strongest formation ability in Al-Ti-B ternary system, [Ti] is relatively excessive in the in-situ reaction and it combines with Al to form AlaTi phase. The reinforced phases are TiB2 and AlaTi in the produced composites due to the reaction taking place to form reinforced phase with the addition of mixed salts into Al-4.5Cu melt between 900 ℃ and 1 03. ℃.

关键词： in-situ composites thermodynamic, TiB2 Al3.i