超高温陶瓷改性C/SiC复合材料的制备及其性能

Preparation and Properties of Ultra High Temperature Ceramic Modified C/SiC Composites

以碳纤维为增强体,聚碳硅烷和聚烷基铪为前驱体,采用前驱体浸渍裂解(PIP)工艺制备C/SiC-HfC复合材料,将其与同种工艺所得C/SiC复合材料进行对比评价分析。发现C/SiC-HfC复合材料具有较低密度和较好的高温力学性能,且在1650℃静态氧化实验中,含有HfC的基体对纤维具有更佳保护效果。C/SiC-HfC密度约为1.92 g/cm^(3),常温弯曲强度为345 MPa,1800℃高温无氧环境弯曲强度可达424 MPa。C/SiC-HfC复合材料表现出更加优异高温力学性能是由于HfC组分的添加抑制了SiC晶粒的生长,降低了基体内部较大裂纹产生的概率。在1650℃空气环境下,含有HfC的基体对纤维具有更佳保护作用,主要是由于HfC组分的添加使材料表面的SiC及时氧化成SiO2,SiO2在纤维和基体表面形成包覆层,防止了材料内部的进一步氧化。

C/SiC-HfC composites were prepared by PIP process with carbon fiber as reinforcement and polycarbosilane and polyalkyl hafnium as precursors.It was found that the C/SiC-HfC composites had lower density,and much better mechanical properties at high temperatures compared with C/SiC composites,and matrix with HfC had a better protection to the carbon fiber in the static oxidation test under 1650℃.The density of C/SiC-HfC composites is about 1.92 g/cm^(3),the bending strength at room temperature is 245 MPa,and the high temperature bending strength is 424 MPa at 1800℃.The better mechanical properties of C/SiC-HfC composites at high temperatures are due to the fact that the addition of HfC can inhibit the growth of silicon carbide and reduce the probability of large cracks in the matrix.The addition of HfC on the surface made the SiC oxidized to SiO2 in time under 1650℃in air,SiO2 coating was formed on the surface of the fiber and the matrix,which prevented the further oxidation inside the material.