SiOC气凝胶/柔性陶瓷纤维复合材料的制备和性能

选用正硅酸乙酯(TEOS)和甲基三甲氧基硅烷(MTMS)为前驱体,用溶胶-凝胶法制备不同C/Si(原子比,下同)比的SiOC气凝胶,再用大气喷涂法将其喷涂在柔性陶瓷纤维隔热毡中制备出SiOC气凝胶/柔性陶瓷纤维复合材料。C/Si比,是影响SiOC气凝胶/柔性陶瓷纤维复合材料性能的主要因素。随着C/Si比的提高SiOC溶液的凝胶时间延长且更易浸入隔热毡,材料的密度和热导率先降低后提高。C/Si比为0.67的材料热导率最低,其室温热导率为0.026 W/m·K,1000℃时的热导率为0.174 W/m·K。与未改性的隔热毡相比,其热导率显著降低,尤其是在高温下热导率降低47%；同时,这种材料还具有优异的耐高温和抗氧化性能,在1200℃空气中静烧1 h后试样的质量损失只约为1%,静烧3 h后约为5%,随着C/Si比的提高其质量损失随之提高；同时,SiOC气凝胶复合材料还具有良好的疏水性能、柔性和回弹性。

Preparation and Properties of SiOC Aerogel/Flexible Ceramic Fiber Composite

SiOC aerogels with different C/Si ratio were prepared by sol-gel method with ethyl orthosilicate (TEOS) and methyl trimethoxysilane (MTMS) as precursor. Then the SiOC aerosol was sprayed on the flexible ceramic fiber insulation blanket by atmospheric spraying, therewith, the SiOC aerogel/flexible ceramic fiber composite material was successfully prepared. The C/Si ratio is an important factor affecting the performance of SiOC aerogel/flexible ceramic fiber composites. As the ratio of C/Si (atomic ratio) increases, the gel time of SiOC sol is prolonged, whilst it is easier to infiltrate into the insulation blanket; the density and thermal conductivity of the composite decrease first and then increase. When the ratio is 0.67 the thermal conductivity of the composite is the lowest, namely, 0.026 W/m·K at room temperature and 0.174 W/m·K at 1000℃ respectively. Compared with unmodified insulation blanket the thermal conductivity is significantly reduced, especially by 47% at high temperature environment. The composite has excellent high temperature resistance and oxidation resistance. At 1200℃ in air the mass loss percentage of the sample is about 1% after pyrolysising for 1 h, whilst about 5% after pyrolysising for 3 h. As the C/Si ratio increases the mass loss of the composite increasees; in addition, the SiOC aerogel composite material also has good hydrophobic properties, flexibility and resilience.