Synthesis, structure, and properties of silicon oxycarbide aerogels derived from tetraethylortosilicate /polydimethylsiloxane

Porous silicon oxycarbide (SiCO) aerogel monoliths were prepared by the sol-gel method using Tetraethylortosilicate/Polydimethylsiloxane as organic-inorganic precursors. The precursor gels were dried by supercritical ethanol fluid and pyrolyzed at 1200 °C in nitrogen atmosphere to form SiCO aerogels. The as-prepared SiCO aerogels are amorphous and present a network microstructure, surface area of 198.04 m2/g, average pore diameter of 56 nm, and pore volume of 0.648 cm3/g. The thermal conductivity of aerogel monoliths is only 0.027 W/m·K at 25 °C (Hot disk method). The atom ratios of Si, C, O elements in the SiCO aerogels are 30.77%, 14.67%, 54.56% respectively. The network microstructure of the SiCO aerogels are retained until 1100 °C, and the chemical groups and crystal phase structures are kept up until 1200 °C. There is only 1.65% of weight-loss until the same heated at 1200 °C in air, which is one of the highest thermally stable temperatures for SiCO aerogels ever reported.