Rigid and Lightweight CoFe2O4/Carbon Nanofibers/Polyimide Composite Aerogel with Anisotropic Structure for Efficient Microwave Absorption and Thermal Insulation

Polymer-based aerogels are the primary choice for many researchers developing multifunctional materials with excellent electromagnetic wave (EMW) attenuation capabilities. Based on the dielectric/magnetic synergistic loss mechanism, a structure-function integrated strategy was employed to construct CoFe 2 O 4 /carbon nanofibers/polyimide (CoFe 2 O 4 /CNFs/PI) composite aerogels with multidimensional heterogeneous structures. The composite aerogels were assembled from CoFe 2 O 4 nanoparticles, CNFs, and polyamic acid salt molecular chains by directional freeze-drying. The three-dimensional conductive skeleton of CNFs/PI aerogel provided conduction loss, interface polarization, dipole polarization, and multiple reflection and scattering of EMW, which synergized with the magnetic loss provided by the magnetic filler CoFe 2 O 4 to produce powerful attenuation capabilities. By adjusting the CoFe 2 O 4 content to optimize impedance matching, CoFe 2 O 4 /CNFs/PI-2 aerogel exhibited outstanding EMW absorption performance with a minimal reflection loss of -65.5 dB. At a low thickness of 2.17 mm, the maximal effective absorption bandwidth reached 6.08 GHz, successfully covering the entire Ku band and part of the X band. Furthermore, the oriented porous structure of composite aerogels endowed them with lightweight (density of 0.085 g/cm 3 ), superior anisotropic mechanical response, and excellent thermal insulation performance. These properties provide a solid foundation for electromagnetic protection in complex environments and aerospace applications.