Novel SiC/C Aerogels through Pyrolysis of Polycarbosilane Precursors

Abstract

A new approach for forming aerogels with various silicon-based compositions and hybrids between ceramics and carbon has been developed by combining efficient hydrosilylation as the hybridization-crosslinking approach associated with gelation in the presence of solvent and followed by supercritical drying techniques. Highly porous carbon-enriched SiC/C aerogels with adequate mechanical durability have been synthesized, pyrolyzed, and characterized. The “wet” gels were obtained by crosslinking a commercial polycarbosilane with divinylbenzene via Pt-catalyzed hydrosilylation reaction in highly diluted condition (90 vol% of solvent). A supercritical drying was performed after exchanging the solvent (cyclohexane) with liquid CO2 forming undamaged aerogels. A subsequent pyrolysis and heat treatment (up to 1500 °C) in argon flow converted the polymeric aerogel into a SiC/C-based material with bulk density of 166 kg m−3, SSA of 444 m2 g−1, a micro-meso pore volume of 0.79 cm3 g−1, total porosity above 90 vol% and ultimate compressive strength of 1.6 MPa. The final product was compared to its cured gel and intermediates obtained during the pyrolysis process.