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

Developing microwave absorbers that simultaneously achieve high absorption efficiency and improved corrosion resistance remains challenging, particularly under corrosive environments containing chloride ions. Herein, we designed a multilayered FI@SiO 2 @TiO 2 composite using flake carbonyl iron (FI) as the core and a sol-gel strategy based on heterointerface engineering. Electrochemical measurements reveal that the corrosion rate of FI@SiO 2 @TiO 2 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 SiO 2 @TiO 2 dual-shell structure, which effectively suppresses the diffusion of corrosive species and inhibits electrochemical reactions at the metal surface. Electromagnetic characterization shows that FI@SiO 2 @TiO 2 achieves a minimum reflection loss (RL min ) of −65.01 dB at 4.18 GHz with a thickness of 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.