Thermally insulating, fiber-reinforced alumina-silica aerogel composites with ultra-low shrinkage up to 1500 °C

Highly porous, heat resisting and thermal insulating alumina-based aerogel materials are considered as promising high-temperature thermal insulations. The major obstacles for their applications are poor mechanical strengths, transparency to infrared radiation and complex preparation processes. In this study, a direct solimmersion-gel (SIG) and supercritical fluid drying (SCFD) strategy for synthesizing mullite fiber reinforced alumina-silica aerogel composites (MFASs) was developed to overcome these problems. No tedious operation such as solvent exchange or gel modification was needed. The MFASs, with bulk density less than 0.4 g/cm(3), experienced no deformation and ultra-low dimensional shrinkage even under 1500 degrees C exposure at air atmosphere, also exhibit good compressive strength and toughness. Thanks to cooperation of mullite fibers and the alumina-silica aerogel (ASA), the MFASs show quite low thermal conductivity (0.082 W/(m.K) at 1200 degrees C) and proved to be extremely thermal insulating during the quartz lamp heating test at 1500 degrees C. The light-weight, strong MFASs with superior heat resistance and thermal insulating performances can satisfy the urgent need for high-temperature thermal insulations such as thermal protection system (TPS) for space vehicles.

Automated summary

A new method was developed to synthesize alumina-silica aerogel composites with mullite fiber reinforcement, which exhibit excellent thermal insulation performance and strong mechanical strength. These materials have low thermal conductivity and are ideal for high-temperature insulation applications.