Hetero-interfaces strategy based on Fe3O4 microspheres to construct multi-band tunable and anticorrosive absorbers

The development of Fe₃O₄ in the fields of electromagnetic wave absorption (EMA) is severely hindered by its narrow bandwidth and environmental tolerance. Herein, we introduce dielectric components and favorable hetero-interface engineering on Fe₃O₄ to promote the EMA and broaden an effective absorption bandwidth (EAB). Before incorporation of dielectric component, Fe₃O₄ microspheres show a high-effective EMA in C and X bands with the strongest reflection loss (RL) of 70.40 dB at 8.86 GHz and a corresponding EAB of 5.3 GHz (5.3−10.6 GHz). Upon the introduction of dielectric SiO₂ or TiO₂ coating, the tailored permittivity and the enhanced dielectric loss are obtained by reinforcing the interface polarization. Meanwhile, the structural feature imparts desirable impedance matching and multiple reflection and scattering absorption. As a result, Fe₃O₄@SiO₂ exhibits outstanding EMA performances in C, X, and Ku bands, including an impressive EAB of 6.5 GHz (11.5–18.0 GHz) covering the whole Ku band with only 2.5 mm. Fe₃O₄@TiO₂ achieves a broaden EAB of 8.4 GHz with 3.0 mm, which is better than those of many Fe₃O₄-based absorbers previously reported. More importantly, both SiO₂ and TiO₂ coating efficiently enhance the marine anticorrosion properties of Fe₃O₄, making it a superior EMA material with strong and wide absorbing features for EMA applications.