关键词: 气凝胶;石英纤维复合材料;吸湿率;介电性能

Abstract: SiO2fiber reinforced SiO2ceramic composites filled with nano-sized SiO2were prepared by sol-gel method with vacuum impregnation, supercritical drying and surface modification.The silica sol for vacuum impregnated were prepared with tetraethyl orthosilicate(TEOS), anhydrous ethanol, water and acid catalyst as the starting materials.The water adsorption rate, apparent porosity and electrical properties of composites were investigated by means of archimedes method and waveguide method while the surface area and pore size of the aerogel samples were tested by BET, the mechanism of hydrophobicity was also discussed.The results show that the moisture absorption rate of products decreases to 1.21%from 17.36% that without filled with nano-sized SiO2, with a decreasing range of 93%.Additional coating could make the rate even as low as 0.052%.The dielectric constant has no significant change while the loss tangent decreased,with a decreasing range of 51.2%.

Key words: aerogel;SiO2fiber reinforced SiO2ceramic composite;moisture absorption rate;dielectric property