Electrospun porous Al18B4O33/h-BN composite fibers with tailored microstructures for high-temperature thermal insulation

Aluminum borate fibers are promising candidates for high-temperature thermal insulation owing to their excellent thermal stability, good chemical resistance, and relatively low density. Herein, we report a simple method for preparing porous Al 18 B 4 O 33 /h-BN composite fibers via electrospinning and stepwise heat treatment, using an aluminum isopropoxide/aluminum nitrate (AIP-AN) complex as the aluminum source and nanoscale h-BN as the boron source. The incorporation of h-BN not only promotes the in-situ formation of the Al 18 B 4 O 33 phase but also affects the fiber's pore structure. Meanwhile, the heterogeneous interface formed between h-BN and the Al 18 B 4 O 33 may introduce additional interfacial thermal resistance, thereby synergistically reducing thermal conductivity and improving thermal insulation performance. The resulting composite fibers exhibited a highly porous structure, with a high specific surface area of 53.9175 m 2  g −1 , a low density of 0.025 g cm −3 , and a low thermal conductivity of 0.0417 W m −1  K −1 . The porous Al 18 B 4 O 33 /h-BN composite fibers demonstrate significant potential for thermal insulation in extreme environments, offering a viable approach to developing high-performance ceramic fiber insulation materials.