Characterization of SiO_2 Aerogel / SiO_2 Fiber Composites Prepared by Sol-gel Method

摘要

SiO_2 fiber reinforced SiO_2 ceramic composites filled with nano-sized SiO_2 were 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 showed that the moisture absorption rate of products was decreased to 1.21% from 17.36% that without filled with nano-sized S1O2, with a decreasing range of 93%. Additional coating could make the rate even as low as 0.052%. The dielectric constant had no significant change while the loss tangent decreased from 3.1×10~(-3) to 1.4×10~(-3), with a decreasing range of 51.2%.