Abstract: Most reported electromagnetic wave absorption (EWA) materials show significant effective absorption in a certain frequency range, but their performances deteriorate dramatically as the frequency changes. As the range of working frequencies for electronic devices is gradually widening, it is of great interest to explore frequency-insensitive EWA materials that can achieve efficient absorption in every waveband by simply changing the absorption thickness. To this end, a multi-scale absorber (Fe/Fe₃C@NC) is rationally synthesized by chemical foaming and in-situ growth strategy. By controlling the growth of carbon nanotubes, the Fe/Fe₃C@NC-2 exhibits a well-constructed 3D multi-scale architecture. Thanks to dipole polarization, interface polarization and magnetic-dielectric energy conversion, the Fe/Fe₃C@NC-2 overcomes the frequency dispersion behavior and keeps a stable dielectric attenuation capability across the entire frequency range. Consequently, it delivers a superb full-band absorption of -50.1, -59.83, -55.87 and -51.91 dB in the S, C, X and Ku bands, respectively. The maximum radar cross-sectional reduction reaches 35.44 dB m^-2 when the incident θ is 20°, testifying its impressive performance. Surprisingly, this EWA material also shows a remarkable resistance to oxidation and corrosion derived from the tightly coated carbon layers. This work provides new insight into the design of multi-band and stable EWA materials for practical application.

Key words: Multi-scale structure, Heterogeneous interface, Multiple bands, Magnetic-dielectric composites, Electromagnetic waves absorption