Biomass-derived anisotropic silicon carbide aerogels with orientation-dependent electromagnetic absorption and high-temperature insulation performance

Silicon carbide (SiC) aerogel is a lightweight porous material, which has significant potential in electromagnetic protection due to its high porosity, excellent high-temperature resistance, and superior thermal insulation properties. However, traditional SiC aerogel typically exhibits isotropic structures, making it challenging to achieve environment-responsive orientation control. This research introduces a novel approach by using cornstalk biomass as a carbon source to prepare ultralight (density < 41.8 mg/cm 3 ) anisotropic SiC aerogels through a carbonization-thermal reduction method. The resulting material demonstrates orientation-dependent electromagnetic absorption characteristics: SiC aerogel perpendicular to the growth direction (P–SiC aerogel) achieves optimal electromagnetic wave (EMW) absorption performance with a minimum reflection loss (RL min ) of −51.72 dB and a maximum effective absorption bandwidth (EAB max ) of 6.4 GHz at a thickness of 2.0 mm. In comparison, the growth direction shows an RL min of −23.39 dB. Their multi-level pore structure also provides outstanding thermal insulation and high-temperature stability (above 900 °C). Thus, this strategy, combining biomass-derived materials with an anisotropic structure, offers an expandable, green preparation method for developing environment-adaptive EMW absorption materials. • Biomass-based SiC aerogels are light, porous, heat-stable, and insulate well. • Directional EMW absorption shows structure alignment strongly affects function. • P-SiC aerogel has an RL min of −51.72 dB and an EAB max of 6.4 GHz.