Gradient multilayer interface–coupled FeNi@C@SiO2 for enhanced anti–corrosion and preeminent microwave absorption

Developing high–efficient microwave absorbing (MA) materials with anti–corrosion (AC) properties to tackle the harsh hygrothermal marine conditions remains a challenge. Herein, we employed catalytic chemical vapor deposition and the Stöber technique to fabricate gradient multilayer interface–coupled FeNi@C@SiO2 composites, guided by the hetero–interface engineering. The resulting composites exhibited exceptional MA properties and AC behavior. Specifically, they showcased a remarkable effective absorption bandwidth of 6.27 GHz at 1.40 mm, outperforming that of FeNi (3.80 GHz). This improved bandwidth was attributed to the electron conduction pathway provided by the C layer, which facilitated electron migration and hopping. The C@SiO2 layer, containing defects and –OH functional groups, induced abundant dipole polarization and optimizes the impedance matching of FeNi. Furthermore, the RCS reduction value of FeNi@C@SiO2 could reach 16.73 dB·m2. Moreover, the corrosion rate of FeNi@C@SiO2 was 7.48 × 10−11 m/s, significantly lower than that of FeNi (1.29 × 10−10 m/s). This reduction was primarily due to the intrinsic inertness and impermeability of the C@SiO2 layer, effectively isolating the corrosive medium from the substrate. This investigation presents a novel point of reference for the advancement of bifunctional MA materials intended to cope with extreme environments.