二氧化硅气凝胶隔热复合材料的高温疏水改性及失效机制

SiO₂气凝胶隔热复合材料已经广泛应用于航空航天、石油化工等隔热保温领域,通过疏水改性可大幅拓展其应用场景。为了使SiO₂气凝胶隔热复合材料在更高温度仍保持良好的疏水性能,采用聚硅氧烷改性硅酸盐涂料对SiO₂气凝胶隔热复合材料进行表面刷涂疏水改性,然后研究了涂层厚度对裂纹扩张的影响以及涂层在高温下疏水性能的失效机制和刷涂改性前后复合材料的耐磨损性能。结果表明,当涂层厚度大约为13 μm时,所制备的涂层表面无裂纹,接触角可达(113±2)°,经450 ℃高温热处理1 800 s后接触角依然可以保持在105°左右,表现出良好的热稳定性,同时涂层显著提高了复合材料的耐磨损性能。

High Temperature Hydrophobic Modification and Failure Mechanism of Silica Aerogel Thermal Insulation Composites

SiO₂ aerogel thermal insulation composites have been widely used in aerospace, petrochemical and other thermal insulation fields, and their application can be significantly expanded through hydrophobic modification. In order to maintain good hydrophobic properties of SiO₂ aerogel thermal insulation composites at high temperature, polysiloxane modified silicate coatings were used to modify the surface hydrophobicity of SiO₂ aerogel thermal insulation composites by brushing. The effect of coating thickness on crack expansion was then investigated, as well as the failure mechanism of hydrophobic properties of the coating at high temperature and the wear resistance of the composite before and after brushing coating modification. The results show that the surface of the coating is crack-free and the contact angle reaches (113±2)° when the coating thickness is about 13 μm. The contact angle still is maintained at 105° after heat treatment at 450 ℃ for 1 800 s, showing good thermal stability. Meanwhile, the coating significantly improves the wear resistance of composites.