Papers by Author: Wei Min Wang

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Authors: Zheng Yi Fu, D.H. He, Jing Ying Zhang, Wei Min Wang, Hang Wang, Qing Jie Zhang
Abstract: In this paper, we suggest PCH as a method of joining alloys. The temperature distribution in the samples during the joining process was analyzied. From the temperature distribution profiles in PCH joining, it is concluded that PCH for the joining has two advantages: (1) There is a temperature distribution peak along the sample. The contacting surfaces which need high temperature happen to obtain the highest temperature; (2) The parts to be joined at relatively lower temperatures can avoid the damage of heat attack. The optimal joining conditions were discussed. The PCH and HP techniques were compared for the joining of alloys. It was found that the high tensile strength joined structure of alloys can be fabricated by PCH method at lower joining temperature, shorter holding time, and lower pressure, compared with that by HP method. The PCH process was considered to be an eco-friendly process compared with the traditional heat diffusion joining methods.
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Authors: Jin Yong Zhang, Zheng Yi Fu, Wei Min Wang, Qing Jie Zhang
Abstract: Recently research shows that heterogeneous model is needed to explain some complex combustion behaviors in SHS. However, more heterogeneous details be considered more difficulties will be faced. A micro-heterogeneous & macro-homogeneous model is proposed in this paper based on some previous works for this problem. Combustion compact is divided into lots of little units, which are composed of a large number of small particles. Considering a well-mixed situation, properties of every unit must be almost the same, so the compact can be treated as a macro-homogeneous system on the scale of these little units. During the combustion, every unit will have a heterogeneous properties and change; it can be gotten by a micro-heterogeneous model. Therefore, the micro-heterogeneous characters are connected with the Marco-combustion behaviors. Combustion dynamics of Ti-C-Fe system was studied to certify this model. Results show well consistency with experiments results.
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Authors: Ding Peng, Hao Wang, Wei Min Wang, Yu Cheng Wang, Zheng Yi Fu
Abstract: In this paper, a carbothermal reduction and nitridation (CRN) synthesis for cubic aluminum oxynitride (γ-AlON) powders is reported. The CRN reaction was conducted via a two-step synthesis procedure at a heating rate of 100 °C/min. In the first step, the mixture of fine γ-Al2O3 and soluble starch was annealed at 1550~1580 °C for different duration. It is found that the mixture of α-Al2O3 and AlN with an appropriate ratio can be obtained by CRN reaction. The content of AlN in mixture is closely related with the reaction condition. In the second step, the as-received mixture of α-Al2O3 and AlN was heat-treated at 1700 °C for 10 min. The single phase γ-AlON powders with particle size less than 3 µm were obtained.
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Authors: Lili Zhao, Feng Gao, Wei Min Wang, Chang Sheng Tian
Abstract: The oriented 0.67Pb (Mg1/3Nb2/3)O3-0.33PbTiO3 (PMNT) polycrystals were prepared by the conventional ceramic technique and the templated grain growth method adding excess PbO in the matrix. Kinetics of the development of oriented structure was investigated systemically. In the presence of PbO liquid phase, the oriented PMNT polycrystals mainly grow by the dissolution-precipitation mechanism. The diffusion is determined by the sintering temperature and the PbO-excess content in the matrix. The thickness of oriented PMNT polycrystals displays a t1/3 dependence, which is characteristic of diffusion-controlled growth. For the thicker oriented structure, 20% excess PbO in the PMNT matrix and 1150oC for 10h are the proper experimental conditions. Moreover, the addition of PbO in the matrix hardly affects the final composition of ceramic matrix.
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Authors: Gui Min Zhang, Zheng Yi Fu, Yu Cheng Wang, Hao Wang, Wei Min Wang, Jin Yong Zhang
Abstract: Two different kinds of mullite precursors with composition 3Al2O3•2SiO2 (3:2) were prepared by conventional drying ethanol solution and spray-drying aqueous solution of aluminum nitrate nanohydrate and tetraethoxysilane, respectively. The results of scanning electron microscope (SEM) indicate that one powder consists of irregular particles with size of 1-10μm, the other powder is made of inhomogeneously sized hollow spherical particles with mean size of 0.5-5μm. The TG-DTA curves indicate the hollow spherical particles are unfavorable to eliminate the decomposed products. After the precursors were sintered by Spark Plasma Sintering at 1450°C for 10min, the microstructures of the former are made of fine equiaxed grains with sizes of around 0.5μm, the latter consist of elongated grains distributed in the matrix of fine grains with imhomogenous size of 0.5~10μm due to the liquid phase forming. The different microstructures lead to the former sintered body is transparent, while, the sample from spray-drying is opaque.
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Authors: Li Wei Huang, Zheng Yi Fu, Jin Yong Zhang, Wei Min Wang, Hao Wang, Yu Cheng Wang, Koichi Niihara, Soo Wohn Lee
Abstract: Carbon nanotubes reinforced alumina was fabricated by spark plasma sintering method. When adding 0.2wt% nanotubes, the fracture toughness of the composites prepared increases 19% compared with the pure alumina ceramics. The effect of sintering schedule on microstructure and mechanical properties is investigated systematically. Microstructure studies reveal that at high sintering temperature, the nanotubes tend to gather in the gaps surrounded by three or more grains in a flocculent state, which leads to poor mechanical properties. Raman spectrum indicates that long sintering duration may cause serious nanotubes destruction and lower the mechanical properties.
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Authors: Wei Min Wang, Xiang Chun Liu, Ming Zhao, Chang Sheng Tian
Abstract: The aim of this paper is to investigate the effects of V2O5 additive on the electrical properties of NTC thermistors based on Ni0.5Co0.5Mn2O4.The XRD analyses indicate that single spinel phase can form, and V2+ions are in the octahedral interspace. The cell can be enlarged due to the V2O5 additive. The resistivities (ρ) and the material constant (B) increase obviously, the reasons of which are mainly attributed to the outer electron configuration of V2+ and cell enlargement.
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Authors: Ming Zhao, Wei Min Wang, Xiang Chun Liu, Chang Sheng Tian
Abstract: The effects of pre-synthesized V2O5/Sb2O3 compound, SbVO4 and Sb2O3 on the microstructure and electrical properties of ZnO-V2O5 based varistor ceramics have been studied. The general homogeneous microstructure and phase composition of the ceramics have not been influenced by the antimony doping form changes, except for the gradual decrease in average grain size and the increase in spinel formation within the ceramics. The ultimate cause of micro-structural variations with the antimony doping form changes seems to have been the gradual increase in Sb3+ concentration within the ceramics. This change in micro-composition, together with the changes in microstructure, caused the electrical characteristics of the ceramics to vary. The pre-synthesized V2O5/Sb2O3 compound is the most effective antimony dopant in term of its effect on the ceramics.
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Authors: Hao Wang, Wei Min Wang, Zheng Yi Fu, Tohru Sekino, Koichi Niihara
Abstract: Mullite-based nanocomposites with embedded FeCr alloy nanoparticles were synthesized by reduction of sol-gel prepared Al5.4(Fe0.8Cr0.2)0.6Si2O13 solid solution in hydrogen. The feature of the formation of FeCr alloy is characterized by XRD analysis. Structural characterization revealed that the intragranular FeCr alloy nanoparticles along with inter-granular iron grains were obtained in as reduced sample. After acid washing, the intergranular metal grains were eliminated. The static magnetic properties of nanocomposite powders were studied using Magnetic Property Measurement System. It is found that part of the intra-granular metal nanoparticles have superparamagnetic behavior at room temperature.
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Authors: Wei Guo, Wei Min Wang, Hao Wang, Yu Cheng Wang, Zheng Yi Fu
Abstract: The Indium Tin Oxide(ITO) is known as a poorly sinterable material. The Spark Plasma Sintering(SPS) and the hot-pressing sintering(HP) were used to fabricate Indium Tin Oxide Ceramics from ITO nanoparticles. The maximum bulk density of 7.02 g/cm2(relative density; 98.2% TD)was obtained when sintered in Ar at 1000oC for 1min by SPS sintering. While the bulk density of 7.08 g/cm2(relative density; 99% TD) was obtained when sintered in Ar at 1050 oC for 4h by HP sintering.
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