Lightweight magnetic metal nanochain aerogels for realizing broadband and strong absorption of electromagnetic wave

Developing lightweight and efficient magnetic metal microwave absorption materials is crucial to broaden the application of metal-based materials in the field of electromagnetic wave (EMW) absorption. In this work, monometallic aerogels with three-dimensional (3D) network structure were successfully synthesized under the synergistic effect of the reduction of NaBH₄ and the subsequent release of H₂, and the microstructure and electromagnetic parameters were regulated by changing the molar ratio of metal salts to reductant NaBH₄. Notably, Co aerogel (C-AG-0, Co²⁺∶NaBH₄ =1:3) has a density of 0.16 g/cm³ and exhibits optimum EMW absorption properties. It has an effective absorption bandwidth (EAB) of 6.24 GHz (10.88–17.12 GHz) at a thickness of 1.7 mm, even beyond reported metal-based composites. The excellent absorption performance is owed to the highly porous 3D mesh stucture, which provides good impedance matching and conduction loss, as well as the interfacial polarization caused by a large specific surface area (SSA). This work provides an alternative choice for the facile preparation of lightweight magnetic metal EMW absorbents with highly efficient absorption.