Aerogels are ultralight solids with a 3D interconnected porous network, high porosity, and large specific surface area, exhibiting outstanding performance in applications such as thermal/acoustic /electrical insulation, as catalyst supports, drug carriers, cosmic dust collectors, energy conversion, storage materials, sensors, etc. However, due to mechanical brittleness and weak elasticity, most aerogels suffer from a structural collapse and performance damping when external shocks (e.g., compression, bending, twisting, or stretching), their use in many practical applications was hindered.
Herein, professor Xuetong Zhang and Alexander Eychmüller reported on a temperature-invariant super-flexibility of BN aerogels constructed by intertwined BN nanoribbons derived from high temperature amination of the hydrogen-bond directed assemblies of melamine and boric acid. These BN nanoribbon aerogels can bear compressing, bending, twisting, or cutting forces over a wide temperature range from liquid nitrogen temperature (−196 °C) to more than 1000 °C.
BN nanoribbons intertwine/interweave and contact with each other to form an isotropic porous open cell network, and the individual BN nanoribbons exhibit different states in the porous network, such as flat, bended, twisted, etc., indicating the flexibility of the individual BN nanoribbons. The BN aerogel yielded the ultralight (with the density of ≈15.5 mg cm−3), thermal-insulating (with the conductivity of 0.0346 ± 0.0015 W m−1 K−1), high specific surface area (920 m2 g−1). The BN aerogel also exhibited excellent resistance to bending, cutting, and twisting. Placing a BN aerogel in a flame or in a tube furnace with a temperature of 1018–1020 °C, it can recover its original shape without combustion or fracture after the external shocks removed. When in liquid N2, the BN aerogel could adsorb liquid N2, but it did not become hardened. It could be compressed about 80% strain without fracture.
Authors believed that are expected to be applied in thermal insulation and wave-transparent of aerospace, or in Nuclear protection of nuclear reactor.
Boron Nitride Aerogels with Super-Flexibility Ranging from Liquid Nitrogen Temperature to 1000 °C, Advanced Functional Materials, 2019, 29, 1900188
Placing a BN aerogel in a flame or in a tube furnace with a temperature of 1018–1020 °C, it can recover its original shape without combustion or fracture after the external shocks removed.
