Co‐optimizing compressive and heat‐insulation properties of rigid fibrous ceramics by compositing with phenolic aerogel

Abstract

AbstractLow compressive strength of rigid fibrous ceramics (RFC) greatly restricts their application as thermal protection materials. Traditional reinforcing method using ceramic aerogels shows low efficiency and impairs high‐temperature thermal‐insulation properties. Herein, a novel strategy is proposed to optimize compressive and high‐temperature thermal‐insulation performances of RFC enormously and synergistically using nanoporous phenolic aerogel as reinforcement and high‐temperature evaporative refrigerant. In‐situ X‐ray micro‐CT results reveal that phenolic aerogel can protect bonding areas and handle compressive deformation, thereby increasing compressive strength of RFC. What's more, the strengthening effect along practical application (through‐thickness) direction is more obvious than that along in‐plane direction. Ablation test results indicate that pyrolysis gas of phenolic will carry away surface heat, thus improving high‐temperature thermal‐insulation and antiablation performances. The resulting mullite RFC with 45 wt.% of phenolic aerogel exhibits a high compressive strength of 44.8 ± 1.1 MPa along through‐thickness direction, low backside temperature of 38.4°C under ablation temperature of 1500°C for 30 s. The idea and results will further advance the application of RFC in more extreme environments.