3D针刺C/SiC-TaC复合材料的热膨胀性能

采用液相加压浸渗法将TaC渗入到三维针刺毡中, 并结合反应熔体渗透法(RMI)制得C/SiC-TaC复合材料。采用热膨胀仪测量了热处理前后复合材料从室温到1400 ℃温度范围内的热膨胀系数(CTE), 发现C/SiC-TaC的CTE数值较C/SiC的高。从材料内部热应力的变化、 制备方法及添加物和基体的性能方面定性地分析了CTE的变化机制。研究表明, C/SiC-TaC复合材料的膨胀性能在各个温度段的变化机制不同, 低温段(1100 ℃以下)CTE的不断上升主要由90°无纬布、 TaC和SiC基体贡献, 该阶段的起伏波动主要由复合材料的结构应力和孔隙分布不均及残余Si产生; 高温段(1100 ℃以上)的热膨胀性能主要由0°无纬布和界面热应力决定。热处理降低了复合材料在1100 ℃以下的CTE, 也改变了高温段的变化规律。 

Thermal expansion properties of 3D needled C/SiC-TaC composites

3D needled C/SiC-TaC composites were prepared by slurry infiltration combined with reactive melt infiltration (RMI). The coefficient of thermal expansion (CTE) of the composites was tested from room temperature to 1400 ℃ using a thermal dilatometer before and after heat treatment. The CTE value of C/SiC-TaC is higher than that of C/SiC composites. The thermal expansion behavior was qualitatively analyzed from thermal stress, preparation method and composition. The results show that the CTE of the composites increases slowly as the temperature increases at low temperature range (below 1100 ℃). The increase in CTE is contributed by the thermal expansion of 90° non-woven cloth, TaC and SiC. The fluctuations of CTE are related to the structural stress, residual silicon and asymmetrical distribution of porosities. In high temperature range (above 1100 ℃), the controlling factors of thermal expansion are 0° non-woven cloth and interfacial thermal stress. The heat-treatment resulted in the decrease in CTE values at temperatures below 1100℃ and also change the CTE behavior of the composites at temperatures higher than 1100 ℃.