Heterointerface-engineered FI@SiO2@TiO2 composites for simultaneous microwave absorption and corrosion resistance

Developing microwave absorbers that simultaneously deliver high absorption efficiency and robust corrosion resistance remains challenging in complex marine environments with high humidity and salt fog. Herein, we designed a multilayered FI@SiO2@TiO2 composite using flake carbonyl iron (FI) as the core and a sol–gel strategy based on hetero-interface engineering. Electrochemical measurements reveal that the corrosion rate of FI@SiO2@TiO2 is nearly two orders of magnitude lower than that of pristine FI, reaching as low as 0.012 mm/year. This enhanced corrosion resistance mainly arises from the dense and chemically inert SiO2@TiO2 dual-shell structure, which effectively suppresses the diffusion of corrosive species and inhibits electrochemical reactions at the metal surface. Electromagnetic characterization shows that FI@SiO2@TiO2 achieves a minimum reflection loss (RLmin) of −65.01 dB at 2.23 mm, along with a maximum effective absorption bandwidth (EAB) of 4.53 GHz at only 1.36 mm. Such excellent performance predominantly originates from engineered heterogeneous interfaces, which induce abundant interfacial and dipolar polarization and markedly improve impedance matching of the flake iron core. Furthermore, electromagnetic simulations based on COMSOL and CST corroborate the positive role of the dual-shell architecture in optimizing impedance matching and reducing radar reflection. This work offers a practical strategy for fabricating dual-functional microwave absorbers capable of delivering high absorption efficiency together with sustained corrosion resistance.