Flexible and resilient mullite fiber felts modified by SiBCN ceramic aerogel with enhanced thermal insulation performance

Mullite fiber felts with excellent thermal insulation performance are commonly used in thermal protection systems (TPSs) for high-speed vehicles. However, the large pore structure formed by overlapping fibers results in inadequate obstruction of thermal convection and insufficient resilience force, thereby limiting their suitability as thermal sealing materials for the gaps in aircraft moving parts. In this work, a SiBCN aerogel/mullite fiber composite was fabricated via vacuum impregnation and a typical PDC aerogel method to improve the thermal insulation performance and strength of flexible mullite fiber felts. This approach enhances the strength while maintaining the flexibility of the fiber felts. The impact of impregnation times on the evolution of the microstructure, rebound resilience, and thermal insulation performance of the composite was investigated. The nano-pore structured SiBCN aerogels can pad the large pores of mullite fiber felts, resulting in a decrease in the thermal conductivity of the composite from 0.047 W m −1  K −1 to 0.038 W m −1  K −1 . Owing to the integration of adequate resilience and excellent thermal insulation properties, the SiBCN aerogel/mullite fiber composite provides the foundation for thermal sealing materials for aerospace applications.