聚硅氧烷封孔处理对C_f/SiC复合材料抗氧化性能的影响

Improvement of oxidation resistance of C_f/SiC composites by polysiloxane seal treatment

以室温粘度低的液态聚硅氧烷为原料,采用真空 加压浸渍交联工艺对Cf/SiC复合材料进行了封孔处理。研究了封孔效果及封孔处理对Cf/SiC复合材料短时间抗氧化性能的影响。结果表明,聚硅氧烷能够有效封填材料中微孔,提高Cf/SiC复合材料的致密度,同时明显提高Cf/SiC复合材料的短时间抗氧化性能。经封孔处理的Cf/SiC复合材料在1500℃空气中氧化10min后,材料强度保留率由处理前的67%提高到了95%,质量保留率由处理前的91.9%提高到99.1%。聚硅氧烷在裂解过程中会消耗氧以及裂解产物SiO2在高温下的流动能愈合孔隙,从而阻碍O2向材料内部扩散是抗氧化性能得以提高的原因。

The C_f/SiC composites fabricated by polycarbosilane pyrolysis were sealed by low viscosity polysiloxane infiltration under vacuum followed by curing under gas pressure, and the oxidation resistance of the C_f/SiC composites before and after seal treatment was investigated. It was found that the sealed C_f/SiC composites showed improved oxidation resistance at 1500℃ for a short period of time. After soaked at 1500℃ for 10min under static air, the sealed C_f/SiC composites retained 95% of original flexural strength and 99.1% of original mass while the untreated C_f/SiC composites retained only 67% and 91.9%, respectively. The improved oxidation resistance of the sealed C_f/SiC composites was attributed to (1) O_2 was consumed during the pyrolysis of polysiloxane and (2) the pores were healed by viscous SiO_2 derived from the pyrolysis, preventing O_2 from diffusing into the composites.