Lightweight and Elastic Ceramic Nanofiber Aerogels Designed by Enhancing Interfacial Compatibility for Thermal...

Ceramic aerogels are attractive candidates for thermal insulation under extreme conditions, especially at high temperatures. However, traditional ceramic aerogels often exhibit a considerable increased thermal conductivity and decreased thermomechanical performance at high temperatures. Here, lightweight and elastic ceramic nanofibrous aerogels (ECNAs) composed of an orientated fibrous network and core-shell structured opacifier nanoparticles were prepared by a directional freeze-casting combined annealing approach. These core-shell structured opacifiers can effectively reduce radiation heat transfer of the aerogel at high temperatures. On the other hand, similar components with silicon dioxide between the "shell" of opacifiers and ceramic fibrous network bring excellent interfacial compatibility, which makes excellent mechanical resilience of the aerogel after sintering. The results show that the ceramic fibrous aerogel have ultralow thermal conductivities (0.023 W m^-1 K^-1 at 25 °C; 0.06 W m^-1 K^-1 at 600 °C) and outstanding compressive resilience (compressed by up to 80% strain at a low density of 5.9 mg cm^-3) even at temperatures as high as 1100 °C. In addition, the aerogel can withstand both extremely hot and cold temperatures, showing a wide application temperature range (-196 to 1100 °C). These outstanding performances make the ceramic fibrous aerogel have great application prospects in the thermal superinsulation of aircraft and high-temperature furnaces under extreme conditions.