化学气相渗透法制备三维针刺C/SiC复合材料的烧蚀性能

ABLATION PROPERTIES OF THREE DIMENSIONAL NEEDLED C/SiC COMPOSITES BY THE CHEMICAL VAPOR INFILTRATION

用化学气相渗透法制备了三维针刺碳纤维增强碳化硅陶瓷基复合材料,复合材料的平均密度为2.15g/cm3,气孔率为16.0%。用氧乙炔焰研究了复合材料的烧蚀性能,用扫描电镜分析了烧蚀表面的形貌,用表面能谱分析了烧蚀产物的成分。复合材料的线烧蚀率和质量烧蚀率分别为0.03mm/s和0.0047g/s。在烧蚀中心区,烧蚀最严重,表层只有C纤维骨架,且C纤维呈针状,复合材料的烧蚀以升华和冲刷为主。在烧蚀过渡区,垂直于烧蚀面的C纤维表现出端部锐化、根部细化的特性,平行于烧蚀面的C纤维呈针状,复合材料的烧蚀以氧化和机械剥蚀为主。烧蚀边缘烧蚀不明显,烧蚀产物和SiC基体熔融后覆盖在烧蚀表面,阻碍了复合材料的进一步烧蚀,复合材料的烧蚀以氧化为主。

The ablation property of three dimensional needled carbon/silicon carbide composites with a density of 2.15 g/cm^3 and a porosity of 16.0% fabricated by the chemical vapor infiltration was studied using oxyacetylene ablation equipment. The linear and mass ablation rates were 0.03 mm/s and 0.004 7 g/s on average, respectively. Ablated surfaces of the samples were investigated using scanning electron microscopy and energy dispersive spectroscopy. At the ablation centre, the SiC matrix was erode out due to the combined results of the sublimation and mechanical erosion of SiC, and the C framework can be observed obviously and the C fibers is a needle-shape. The ablation of the composites was dominated by sublimation and mechanical erosion. Between the ablation center and the edge, the end of the C fibers parallel to the ablated surface is a needle-shape and the root becomes thinner. The main ablation mechanisms are thermo-oxidation and mechanical erosion. At the edge, composites were ablated slightly. There were many ablation products and SiC matrix melt on the ablated surface, preventing the ablating of the substrate material. The main ablation mechanism is thermo-oxidation ablation.