SiOC气凝胶/柔性陶瓷纤维复合材料的制备和性能

Preparation and Properties of SiOC Aerogel/Flexible Ceramic Fiber Composite

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。

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.