Superior High-Temperature Performances via Confined Heat and Mass Transfer in Foam-like Pores of Omnidirectionally Isotropic Ceramic Fiber Aerogels

This work breaks away from the traditional layered anisotropic structure of ceramic fiber aerogels. Instead, it employs chemical foaming and physical bonding to assemble shortcut ceramic fibers, fabricating an omnidirectionally isotropic ceramic fiber aerogel with foam-like pores (F-CFA). While maintaining structural stability up to 1300 °C, F-CFA offers superior thermal insulation performance compared to layered ceramic fiber aerogel (L-CFA) at temperatures exceeding ∼727 °C (1000 K); specifically, the order of thermal conductivity of F-CFA and L-CFA is inverted with increasing temperature. After the decoupling heat transfer mechanism, it corroborates that these elaborate pores intensify reflection and absorption of thermal radiation, leading to low thermal conductivity. Besides, the tortuous pore channel, by interconnected foam-like pores, efficiently traps 0.3-3.0 μm micronano particles but does not prevent air circulation, thereby achieving a high quality factor (QF) of 0.096 Pa^-1 for 1 μm particles at an airflow rate of 32 L min^-1 for exhaust gas filtration. The confined heat and mass transfer properties in F-CFA guarantee superior high-temperature performances, offering valuable insights for a better fibrous material.