Lightweight aerogel-like silicon oxycarbide ceramics with directionally honeycomb-like structure for high temperature environments

Abstract

Ceramic aerogels are considered promising thermal protection materials for their excellent thermal insulation performance and high-temperature stability. Lightweight aerogel-like silicon oxycarbide (SiOC) was prepared from polyhydromethylsiloxane (PHMS) as precursor and divinylbenzene (DVB) as crosslinker through solvothermal, freeze casting/drying and pyrolysis. The aerogel-like SiOC ceramic can achieve a low density of 0.087 g·cm−3 under the optimized mass ratio of DVB:PHMS of 1.5:1, with a directionally honeycomb-like structure induced by cyclohexane ice-crystals during the freeze casting. The unique porous structure endows the aerogel-like SiOC with low effective thermal conductivity (0.051–0.057 W·m−1·K−1) and good compressive strength (0.30–0.34 MPa). Moreover, the aerogel-like SiOC maintains structural and property stability after heat treatment (1400 °C in argon or 800 °C in air) for good thermal stability and oxidation resistance, which sheds light on the preparation of high-performance SiOC thermal insulation materials for high-temperature environments.