Lightweight carbon nanotube/aramid nanofiber aerogel with superior electromagnetic wave absorption, thermal insulation, and flame resistance

Carbon nanotubes, presenting distinguished electromagnetic wave (EMW) loss capacity and light-weight advantage, are promising candidates for EMW absorption materials. However, poor dispersibility, inadequate processibility, and excessive permittivity leading to impedance mismatch limit the application of carbon nanotubes. Herein, branched aramid nanofiber (ANF) acting as a surfactant, gelling agent, and electromagnetic parameter regulator is utilized to ameliorate the performances of carboxylic multi-walled carbon nanotube (c-MWCNT). The c-MWCNT/ANF aerogels with anisotropic structures are assembled through electrostatic-repulsion-assisted dispersion, hydrogen-bond-induced gelation, unidirectional freezing, and freeze-drying. By adjusting the proportion of c-MWCNT and ANF to optimize the impedance matching and electromagnetic parameters, the composite aerogel with ultralow density (∼26.2 mg cm−3) shows an extraordinary minimum reflection loss of −60.43 dB and a maximum effective absorption bandwidth of 5.34 GHz along the vertical direction of oriented channels. Moreover, benefiting from high porosity and remarkable thermal stability, the aerogels possess prominent thermal insulation and flame resistance. This work provides a strategy for the advanced EMW absorption materials, which have great potential value for aerospace applications under harsh environments.