High-strength and superior thermal insulating SiOC ceramic aerogels derived from thermostable silicone aerogels

Ceramic aerogels are promising porous materials with high thermal and chemical stability, but their notably low mechanical strength severely restricts their applications. Herein, high-strength SiOC ceramic aerogels (SiOCA S ) were prepared by pyrolyzing thermostable silicone aerogels derived from the polymerization of polysiloxane. The effects of side groups in siloxane and pyrolysis temperature on the structure of SiOCA S were investigated. Methyl side groups induce significant mass loss and volume shrinkage in the aerogels during pyrolysis, attributed to the release of oligomers; in contrast, vinyl and phenyl side groups can promote the high-yield transformation of the SiOC structure and the intact preservation of the 3D aerogel network. At 800 °C, vinyl-functionalized silicones are converted into amorphous SiOC and SiO 4 structures; between 800 and 1400 °C, the SiOC structure decomposes into SiO x and free carbon; and at 1400 °C, it further transforms into β-SiC. The as-prepared SiOCA S exhibit porosities of 65 %–75 %, pore sizes of 56–68 nm, compressive strengths of 25–62 MPa, and excellent electromagnetic wave absorption performance. Furthermore, carbon fiber-reinforced SiOCA S composites exhibit an ultrahigh compressive strength of 155 MPa and a low thermal conductivity of 0.2 W m −1 K −1 at 500 °C, highlighting their significant potential for high-temperature insulation applications.