具有莫来石界面的C/Si-C-N复合材料热物理性能

Thermophysical properties of C/Si-C-N composite with mullite interlayer

以PIP方法制备界面层、CVI工艺制备基体,制备以Si-C-N陶瓷为基体、以莫来石为界面的碳纤维增强陶瓷基复合材料(C/mullite/Si-C-N)。采用热膨胀仪和激光导热仪分别测试C/mullite/Si-C-N的热膨胀性能和热扩散性能,采用SEM和XRD分析材料的组织和形貌,采用DSC/TG同步分析仪分析基体材料的结构变化。结果表明:在25~1200℃范围内,C/mullite/Si-C-N复合材料的平均热膨胀率为1.58×10^(-6)℃^(-1),线膨胀率为0.18%。复合材料的热扩散率与温度呈指数下降关系,这种指数关系是由基体的非晶结构造成的。热处理后的C/mullite/Si-C-N相对于未热处理的试样室温下的热扩散率显著下降,300℃以上的高温区段则略有升高,其在1000℃以下结构稳定,能满足工程应用需求。

The carbon fiber reinforced Si-C-N ceramic matrix composite with a mullite interlayer(C/mullite/Si-C-N)was fabricated with the matrix fabricated by CVI and the interphase fabricated by PIP.The thermal expansion and heat diffusion were measured by using thermal dilatometer and laser heat conductometer,respectively.SEM and XRD were used to analyze the structure and morphology of the material,and the structural changes in the matrix material were analyzed by DSC/TG simultaneous analyzer.The results indicates that the average coefficient of thermal expansion and line expansion rate of C/mullite/Si-C-N between 25-1200℃is 1.58×10^(-6)℃^(-1) and 0.18%,respectively.The thermal diffusivity decreases exponentially with temperature,which results from the amorphous structure of the matrix.As compared to the unheat-treated sample,the thermal diffusivity of the heat-treated C/mullite/Si-C-N is significantly reduced at room temperature,while slightly increased above 300℃.The structure of the composite is stable below 1000℃,which can meet the needs of engineering applications.