Multifunctional Anisotropic Aerogels for Intelligent Electromagnetic Wave Absorption

The rapidly developing modern society has higher requirements for intelligent electromagnetic wave absorbing (EMA) materials than ever before. Herein, lightweight, multifunctional metal-free carbon-based aerogels (RCPs) with a longitudinal honeycomb porous framework and a transverse neatly layered structure are obtained by heat-treating graphene oxide/oxidized carbon nanotubes/hexachlorocyclotriphosphazene complex to simultaneously achieve the tunable EMA, flame retardancy, and thermal insulation. The anisotropic structure ensures the tunable properties of the carbon aerogels along with tilt angles according to environmental needs. The honeycomb porous structure effectively promotes multiple reflections and scatterings of electromagnetic waves compared with the layered structure, maximizing the penetration inside the material and thus a high EMA performance. The optimized R 10 C 2 P-4 exhibits a minimum reflection loss in the longitudinal direction of−61.5 dB, while the value is as low as −22.4 dB in the transverse direction. Furthermore, the porous structure adequately inhibits the spread of heat, accompanied by the phosphorus species induced by hexachlorocyclotriphosphazene pyrolysis, endowing a good flame retardancy and thermal insulation with a low thermal conductivity of 20.6 mW m −1 K −1 in the longitudinal direction, rather than the transverse direction. This work provides an ingenious insight into the design of multifunctional EMA materials, adapting flexibly to various application requirements.