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Hybrid Nanostructures: Nanoscroll Buffered Hybrid Nanostructural VO2(B) Cathodes for High‐Rate and Long‐Life Lithium Storage (Adv. Mater. 21/2013)

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advanced materials 2013年第21期25卷

作者： Liqiang Mai Qiulong Wei Qinyou An Xiaocong Tian Yunlong Zhao Xu Xu Lin Xu Liang Chang Qingjie Zhang State Key Laboratory of Advanced Technology for Materials Synthesis and Processing WUT‐Harvard Joint Nano Key Laboratory Wuhan University of Technology Wuhan 430070 P.R. China

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The influence of Zn vacancy on thermal conductivity of β-Zn 4Sb3: A molecular dynamics study

The influence of Zn vacancy on thermal conductivity of β-Zn...

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作者： Zhai, Pengcheng Li, Guodong Wen, Pengfei Li, Yao Zhang, Qingjie Liu, Lisheng Department of Engineering Structure and Mechanics Wuhan University of Technology Wuhan 430070 China State Key Laboratory of Advanced Technology of Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China

The influence of Zn vacancy on lattice thermal conductivity of β-Zn4Sb3 is studied by non-equilibrium molecular dynamics approach. The lattice thermal conductivity of single-crystal bulk β-Zn4Sb3 decreases rapidly when there is Zn vacancy, and then when the vacancy grows, the lattice thermal conductivity decreases further but rather slowly, which suggests a scaling law of kv∼ nv-α of Zn atom vacancy (nv) to lattice thermal conductivity (kvac). This phenomenon is attributed to the fact that the existence of vacancy scattering can significantly decrease the mean free path. When the Zn atom vacant proportion reaches 10%, that is the vacancy model of β-Zn4Sb3, the lattice thermal conductivity is 1.32 W/mk along the x-axis and 1.62 W/mk along the z-axis, respectively, which drops by ∼90% that of its full occupancy model. Therefore, our calculations show that the 10% Zn atom vacancy in β-Zn 4Sb3 is the main reason for its exceptionally low thermal conductivity, and the interstitial Zn atoms have little effect on the thermal conductivity of single-crystal β-Zn4Sb3. © 2012 Elsevier Inc.

关键词： Molecular dynamics

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Leakage current and dielectric properties of integrated ferroelectric capacitor etched in non-crystalline phase

Leakage current and dielectric properties of integrated ferr...

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International Symposium on Integrated Functionalities, ISIF 2011

作者： Wang, Longhai Tian, Bin Zou, Lianying Cheng, Hao Huang, Danxia Dai, Ying Yang, Lei School of Electrical and Electronic Engineering Wuhan Institute of Technology Wuhan 430073 China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China

The leakage current, dielectric and loss properties of the integrated Pt/PbTiO3/PbZr0.3Ti0.7O3/PbTiO 3/Pt capacitors have been investigated. The capacitor has a same leakage mechanism as the film, in the low field region (less than 100 kV/cm) is Ohmic-like, and in the high field region (above 100 kV/cm) is Space-charge-limited current with deep traps. It also indicates that the process didn't affect the conduction mechanism in the capacitors, which is still determined by intrinsic character of materials. The dielectric constant of the capacitors is lower than that of the films. The loss of the capacitors is lower than thin film in the low frequency region (less than 500 kHz), and it is larger in the high frequency region (above 500 kHz). The DC voltage dependence of dielectric loss characteristic indicates that the possibility of main loss mechanism is the charge defects. The different properties between the integrated capacitors and films are ascribed to the excess Pb which volatilization is obstructed by the top electrode. The more excess Pb ion in the integrated capacitors act as charge defects, and the higher density of charged defects result in the different properties of the capacitor. Copyright © Taylor & Francis Group, LLC.

关键词： Leakage currents

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Addressable metal-ferroelectric-metal nanocapacitor arrays fabricated by focused ion beam milling

Addressable metal-ferroelectric-metal nanocapacitor arrays f...

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International Symposium on Integrated Functionalities, ISIF 2011

作者： Dai, Ying Yang, Lei Wang, Longhai Tian, Bin Zou, Lianying Cheng, Hao Huang, Danxia State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China School of Electrical and Electronic Engineering Wuhan Institute of Technology Wuhan 430073 China

Well-ordered large-area two-dimensionally (2D) periodic and individually addressable metal-ferroelectric-metal (M/F/M) nanocapacitor arrays were fabricated by focused ion beam (FIB) milling with synchronal and serial mode. Scanning electron microscopy (SEM) results indicated that the synchronal mode can fabricate more uniform arrays than serial mode, but the surface of arrays is damaged heavily. The various gray contrasts of domain images can be clearly observed in the M/F/M arrays, and its piezoresponse signal is larger than that of the F/M arrays. Piezoresponse force microscope (PFM) results also indicate that the ion damage can be reduced by top Pt electrode, but cannot be avoided. The displacement-voltage and P-E loops of the M/F/M nanocapacitor are indicative of strong ferroelectricity for the measurements. The remanent polarization is reduced by ion damage, but the coercive field is not increased comparing to the thin film. Copyright © Taylor & Francis Group, LLC.

关键词： Focused ion beams

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Mechanochemical synthesis and high-capacity performances of transition-metal borides as aqueous anode materials

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Chinese Science Bulletin 2012年第27期57卷 4225-4228页

作者： WANG YaDong GUANG XianYong PAN Mu State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan 430070China Department of Chemistry Wuhan UniversityWuhan 430072China

Transition-metal borides MB0.5(M = Co,Mo,V) were synthesized by high-speed mechanical ball-milling of the corresponding elemental metals and boron,and investigated as aqueous anode *** as-synthesized borides can achieve an excellent discharge capacity,about twice that of their parent transition *** metal boride electrodes also exhibit polarizations about 100-300 mV lower than those of their parent *** galvanostatic discharge curve of CoB0.5 shows a single discharge voltage plateau as a result of simultaneous electro-oxidation of elemental cobalt and/or amorphous cobalt *** MoB0.5 and VB0.5 show two well-defined voltage plateaus,corresponding to the electro-oxidation of the corresponding metal and *** results show that the coexisting transition metal and boride in the metal borides co-activate each other in the ball-milling process,thereby significantly enhancing their electrochemical performances.

关键词：机械化学合成过渡金属硼化物水溶液负极材料高容量表演放电电压

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Crystal structure and bonding characteristics of In-doped β-Zn 4Sb3

Crystal structure and bonding characteristics of In-doped β...

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作者： Tang, Dingguo Zhao, Wenyu Cheng, Sudan Wei, Ping Yu, Jian Zhang, Qingjie State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China Key Laboratory of Catalysis and Materials Science State Ethnic Affair Commission and Ministry of Education South-Central University for Nationalities Wuhan 430074 China

The effects of indium impurity on the crystal structure and bonding characteristics of In-doped β-Zn4Sb3 were investigated by powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XRD Rietveld refinement indicates that the indium impurity preferentially substitutes one of Sb atoms in Sb-Sb dimer at the 12c Sb(2) site and simultaneously leads to the increase of Zn occupancy. The observations of binding energy shift and a new valence state in Sb 3d core-level XPS spectra can be attributed to the charge transfer from In and Zn to Sb. As a result, more electropositive Zn atoms are needed to maintain the charge balance. The reduction of the lattice thermal conductivity is ascribed to the formation of the asymmetric Sb-In bond, resulting in much low lattice thermal conductivity of 0.49 W-1 K-1 of Zn4Sb 2.96In0.04. © 2012 Elsevier Inc.

关键词： X ray photoelectron spectroscopy

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Numerical Simulation of the Dynamic Performance of the Ceramic material Affected by Different Strain Rate and Porosity

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Journal of Physics: Conference Series 2013年第1期419卷

作者： Zhen Wang L S Liu H Mei X Lai P C Zhai D F Cao Department of Engineering Structure and Mechanics Wuhan University of Technology Wuhan 430070 China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan 430070 China

Ceramic materials are frequently used in protective armor applications for its low-density, high elastic modulus and high strength. It may be subject to different ballistic impacts in many situations, thus many studies have been carried out to explore the approach to improve the mechanical properties of the ceramic material. However, the materials manufactured in real world are full of defects, which would involve in variable fractures or damage. Therefore, the defects should be taken into account while the simulations are performed. In this paper, the dynamic properties of ceramic materials (Al2O3) affected by different strain rate (500–5000) and porosity (below 5%) are investigated. Foremost, the effect of strain rate was studied by using different load velocities. Then, compression simulations are performed by setting different porosities and random distribution of pores size and location in ceramic materials. Crack extensions and failure modes are observed to describe the dynamic mechanical behavior.

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The Application of Ti/Al2O3 Composite in W-Mo-Al System Wave Impedance Graded Flier-plate

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Journal of Physics: Conference Series 2013年第1期419卷

作者： Z Wang S Feng G P Shi Q Shen L M Zhang School of Materials Science and Engineering University of Jinan Jinan 250022 China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China

Ti/Al2O3 composite of different components were prepared by Spark Plasma Sintering technique, mechanical and acoustical properties of Ti/Al2O3 composite were analyzed, weldability of Ti/Al2O3 composite with Mo and Al was also studied. The results indicate that 38.5vol%Ti/Al2O3 composite has good mechanical performance with relative density >99.20%, bending strength 897MPa, fracture toughness 17.38 MPam1/2 and micro-hardness 17.13GPa. The wave impedance of the composite was between which of Mo and Al, and the 38.5vol% Ti/Al2O3 welded well with Mo and Ti. These demonstrate that 38.5vol%Ti/Al2O3 composite could serve as one of interlayer materials in W-Mo-Al system graded flier-plate.

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The effect of cBN additions on densification, microstructure and properties of WC - Co composites by pulse electric current sintering

The effect of cBN additions on densification, microstructure...

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作者： Wang, Bo Matsumaru, Koji Yang, Jianfeng Fu, Zhengyi Ishizaki, Kozo Department of Mechanical Engineering Nagaoka University of Technology Nagaoka 940-2188 Japan State Key Laboratory for Mechanical Behavior of Materials Xi'An Jiaotong University Xi'an 710049 China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China

Cubic boron nitride/Tungsten carbide-cobalt (cBN/WC-Co) composites were fabricated at low temperature by pulse electric current sintering (PECS) using Ni-P as sintering additives to promote low temperature densification. Effect of c-BN addition on the densification behavior, microstructure and mechanical properties of WC-Co composites was investigated. It was found that near-fully dense WC/Co with 0 ∼ 20 vol% cBN composites could be obtained at temperatures between 1100°C and 1200°C under 50 MPa, while no phase transformation of cBN into the low-hardness hexagonal hBN. The 20 vol% cBN/WC-Co sample sintered at 1100°C under a pressure of 50 MPa for 10 min has a combination of hardness 16.5 GPa and fracture toughness KIC 13.7 MP·m1/2. The homogeneously dispersed cBN particles in the WC/Co composites promoted a slight increase of hardness, but a significant improvement of fracture toughness. The cBN particle bridging or deflection and pullout contribute to the high toughness. © 2012 The American Ceramic Society.

关键词： Fracture toughness

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Adsorption of methylene blue from aqueous solution by graphene

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Colloids and Surfaces B: Biointerfaces 2012年第1期90卷 197-203页

作者： Liu, Tonghao Li, Yanhui Du, Qiuju Sun, Jiankun Jiao, Yuqin Yang, Guangming Wang, Zonghua Xia, Yanzhi Zhang, Wei Wang, Kunlin Zhu, Hongwei Wu, Dehai Laboratory of Fiber Materials and Modern Textile The Growing Base for State Key Laboratory Qingdao University 308 Ningxia Road Qingdao 266071 China College of Electromechanical Engineering Qingdao University 308 Ningxia Road Qingdao 266071 China Key Laboratory for Advanced Manufacturing Material Processing Technology Dept. of Mechanical Engineering Tsinghua University Beijing 100084 China

Graphene was prepared using a modified Hummers' method. The physico-chemical properties of graphene were characterized by TEM, BET specific surface area, FTIR, Raman and XRD measurements. The effect factors including pH, contact time, temperature and dosage on the adsorption properties of methylene blue onto graphene were investigated. The experimental data of isotherm followed the Langmuir isotherm model better than the Freundlich model. The maximum adsorption capacity obtained from Langmuir isotherm equation at 293. K was 153.85. mg/g, indicating graphene is a good adsorbent for the adsorption of MB. The kinetic study illustrated that the adsorption of methylene blue onto graphene fit the pseudo second-order model. The thermodynamic parameters indicated that the adsorption of methylene blue onto graphene was an endothermic and spontaneous process. © 2011 Elsevier B.V.

关键词： Adsorption

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