Lightweight Fe3O4/Fe/C/rGO multifunctional aerogel for efficient microwave absorption, electromagnetic interference shielding, hydrophobicity and thermal insulation

[Display omitted] •Fabrication of lightweight multifunctional aerogels.•Excellent low-frequency microwave absorption with an RLmin of −65.17 dB.•Electromagnetic interference shielding effectiveness up to 81.83 dB.•The aerogel maintains excellent hydrophobicity and thermal insulation. Effective integration of multiple functions into microwave absorbing materials is a future development direction, but still remains a significant challenge. This work fabricated a lightweight, multifunctional aerogel through electrostatic self-assembly, freeze-drying and in-situ pyrolysis process, achieving an in-situ composite of magnetic/dielectric components. The regulated pyrolysis temperature achieves a good balance between abundant nanopores and heterogeneous interfaces, enriched defects, and conductivity. This balance induced a synergy of dielectric loss, magnetic loss, and conduction loss at low frequencies, improving the impedance matching. The aerogel obtains a minimum reflection loss (RLmin) of −65.17 dB in the low-frequency range and a maximum effective absorption bandwidth (EABmax) of 5.76 GHz. The radar cross section (RCS) simulation confirmed its good stealth performance. In addition, an increase in aerogel loading enhanced its electrical conductivity, resulting in a higher electromagnetic interference (EMI) shielding effectiveness (SE) of 81.83 dB, the specific shielding effectiveness (SSE) up to 359.28 dB·cm3/g and the absolute shielding effectiveness (SSEt) up to 1596.82 dB·cm2/g. Beyond microwave absorption and shielding, this aerogel also exhibited good hydrophobicity and thermal insulation. This study provides a new perspective for the development of materials with microwave absorption properties in low-frequency bands and multifunctional properties for broader applications in military, communication, aerospace, and other fields.