Permittivity controllable CNTs/PI composite aerogels with oriented microchannels for advanced microwave absorption and thermal isolation

Polymer-based aerogels have proven to be a promising choice to obtain high-performance and lightweight materials for electromagnetic microwave (EMW) absorption. Here, directional freeze-drying was used to produce multifunctional ultralight CNTs/PI composite aerogels with oriented microchannel structures. The unique oriented pore structure causes the multiple reflections and scattering of incident EMW inside the material, which favors the attenuation of the EM energy. By changing the CNTs content in the composite aerogels, the dipole polarization and the interface polarization can be effectively regulated. With a CNTs content of 30 % and a thickness of 2.5 mm, the minimum reflection loss (RL_min) of −41 dB was achieved at 15.36 GHz. A large effective absorption bandwidth (EAB) of 6.88 GHz was achieved at a thickness of 3 mm. In addition, the CNTs/PI composite aerogels displayed excellent toughness, thermal isolation and the thermal stability. The high-temperature resistant, lightweight composite aerogels proposed in this study could provide a feasible and effective approach for the development of advanced multifunctional microwave-absorbing materials.