Papers by Author: Yan Yan Wang

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Authors: Chang Ling Zhou, Yan Yan Wang, Zhi Qiang Cheng, Chong Hai Wang, Jie Fan, Cheng Gong Sun, Bao Lin Feng
Abstract: ZrB2-SiC and ZrB2-SiC-C ultra-high temperature ceramics (UHTCs) were fabricated by pressureless sintering under an argon atmosphere. The mass and linear ablation rates were tested in an oxyacetylene flame with high velocity. The microstructure and phase transformation of the ZrB2-based UHTCs were characterized by scanning electron microscopy along with energy dispersive spectrometry. Results show that the UHTCs have excellent properties of ablation resistance at ultra-high temperature. The values of mass and linear ablation rates were lower in the ZrB2-SiC UHTCs than those measured for ZrB2-SiC-C. The effect of C addition on the ablation resistant was not obvious but it influenced the microstructure of the ZrB2-SiC UHTCs. And the ablation resistant mechanisms of ZrB2-based UHTCs were discussed according to microstructure analysis.
Authors: Kai Jiang, Yan Yan Wang, Chang Ling Zhou, Han Li, Fang Hong Yang
Abstract: In this paper, using PCS and ZrB2 precursor as raw materials, we prepared Cf/SiC-ZrB2 composites by precursor infiltration and pyrolysis (PIP) process. We studied the solution of different solid content on the influence of porosity and weight gain,and also studied the effect of pressure and other conditions in the process of infiltration. The viscosity of the solution is tested with NDJ-8S digital rotational viscometer. We observed the microstructure of materials through the scanning electron microscope (SEM). The optimum technological parameter was determined by the experiment. The results showed that: a reasonable solution group in relation to the viscosity of the mixed solution,that is the main factor affecting on the performance of the impregnation; The method of vacuum and pressure impregnation can reduce the preparation period and improve material density rapidly. Under the experimental conditions, the best viscosity of the mixed solution is 54.8 mpa•s, the time of vacuum impregnation is 1.5h, and the optimum value of pressure impregnation is 7 MPa.
Authors: Cheng Gong Sun, Jin Ye Niu, Chong Hai Wang, Chang Ling Zhou, Bao Lin Feng, Jie Fan, Yan Yan Wang, Jian Shan Hao
Abstract: With AlN, Al2O3 and Al powders as starting materials, ALON powders were prepared by high temperature solid state reaction at 1650°C, 1750°C and 1850°C respectively. Nitrogen gas at 1atm was selected as reaction atmosphere. X-ray diffraction analysis and scanning electron microscope analysis were carried out for the as-prepared ALON powders. In this paper, single-component γ-ALON porous materials were obtained at temperatures below 1800 degree with void ratio more than 75%, which is prone to be grinded to powders less than 1μm and applicable for the preparation of transparent ceramics. Aluminum oxynitride spinel γ-ALON transparent ceramics were successfully obtained with the as-prepared ALON powders. The volume density of the transparent ceramics was 3.67g/cm2, which is 99.3 percent of the theoretical density of γ-ALON materials. The bending strength of the transparent ceramics was 296MPa and the transmittance was about 75% in the wavelength range of 1.2 to 5.3μm.
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