Flexible Si3n4 Nanoribbon Aerogels with Amorphous Coating for Ultra-High-Temperature Thermal Protection and Exceptional Thermal Insulation

Abstract

Ultra-high-temperature ceramic aerogels exhibit low density, exceptional thermal stability, and superior thermal insulation capabilities, making them ideal candidates for thermal protection in next-generation high-end aerospace applications. However, the development of ceramic aerogels with enhanced structural and thermal stability in extreme environments remains a significant challenge. Although fibrous ceramic aerogels demonstrate improved flexibility compared to granular counterparts, they struggle to recover after large deformations due to the absence of inter-fiber constraints. Furthermore, existing elastic aerogels fail to provide reliable thermal protection in extreme harsh environments (ultra-high temperature aerobic) due to detrimental crystallization and oxidation at high temperatures. Here, we propose a strategy combining single-crystal ceramic nanoribbons and amorphous glassy coating to synthesize Si3N4/amorphous coating (Si3N4/AC) aerogels. The three-dimensional porous crosslinked network is formed by a combination of single-crystal Si3N4 nanoribbons and the amorphous coating that encapsulates and welds nanoribbons together. The inherent flexibility and thermal stability of Si3N4 nanoribbons, coupled with the displacement restriction and antioxidant effect of the amorphous coating, confer excellent compression recovery and thermal stability to the aerogels. Additionally, these aerogels exhibit ultralow thermal conductivity (~29.7 mW m−1 K−1), attributable to the minimal solid heat transfer within the porous network and the rapid dissipation of thermal energy by the high interfacial thermal resistance at crystalline-amorphous phase boundaries. This robust thermal protection system material is compatible with lightweight (~20 mg cm−3), large strain (60%) recoverable compressibility, fatigue resistance, refractory performance, and excellent thermal stability over wide temperature range (−196–1600 °C), offering new options and possibilities for future deep-space exploration.

Keywords: Ceramic aerogels, resilience, thermal insulation, fire resistance, high-temperature stability