SiC对C/C-ZrC-SiC复合材料的微观形貌、烧蚀及热物理性能的影响

Effects of SiC addition on the microstructure,ablative and thermophysical properties of C/C-ZrC-SiC composites

为了研究SiC及其前驱体聚碳硅烷对聚合物浸渍裂解法(PIP)制备的C/C-ZrC-SiC复合材料的影响,本文以聚碳硅烷和有机锆分别为SiC和ZrC的前驱体,利用PIP法制备了C/C-ZrC和C/C-ZrC-SiC两组复合材料,采用扫描电子显微镜(SEM)和X射线衍射仪(XRD)对材料的微观结构进行分析,在氧乙炔环境下考核了复合材料的抗烧蚀性能,并选用热分析仪对两组材料的热物理性能进行对比分析。结果表明,聚碳硅烷因其较高的SiC产率可以提高C/C-ZrC-SiC复合材料中陶瓷基体的致密程度,其产物SiC改善了陶瓷基体与碳基体的界面结合状态。氧乙炔烧蚀120 s后,与C/C-ZrC相比,SiC的加入使C/C-ZrC-SiC表现出更优异的抗烧蚀性能,主要归功于烧蚀中心表面熔融ZrO2保护层和烧蚀边缘致密SiO2层的形成。此外,SiC有利于提高材料的导热性能,同时降低其热膨胀系数。

In order to investigate the effects of SiC and its precursor-polycarbosilane on C/C-ZrC-SiC composites prepared byprecursor infiltration and pyrolysis process(PIP), C/C-ZrC and C/C-ZrC-SiC composites were prepared by PIP process by usingpolycarbosilane and organic zirconium as precursor of SiC and ZrC,respectively.The microstructure of the composites were investiga-ted by scanning electron microscopy(SEM) and X-ray diffraction.The effects of SiC on the ablative and thermophysical properties ofthe composites were studied. Ablation properties and thermal physical properties of the composites were determined by means of oxy-acetylene flame tests and thermal analyzer,respectively.The results show that polycarbosilane improve the density and compactnessof ceramic matrix of the composites,and its product SiC could enhance the interface bonding between pyrolytic carbon and ceramicmatrix greatly.Compared with C/C-ZrC composites,C/C-ZrC-SiC composites exhibit a better ablation resistance after ablation for 120 s,which is mainly attributed to the formation of molten ZrO2 protective layer and SiO2 layer on the surface of ablation center andablation brim region,respectively.In addition,SiC could improve the thermal conductivity of the composites and reduce their coeffi-cient of thermal expansion.