Enhanced Microwave Absorption and Corrosion Resistance of Flaky Carbonyl Iron by Acoustic Resonance-Assisted SiO2 Coating

In this study, SiO 2 -coated flaky carbonyl iron powder (FCIP@SiO 2 ) composites with varying coating ratios were successfully fabricated using an acoustic resonance-assisted modification method. The effects of the SiO 2 coating on electromagnetic properties, microwave absorption performance, thermal stability, and corrosion resistance were systematically investigated. Electromagnetic characterization revealed that the SiO 2 coating effectively regulated the balance between conduction and polarization, optimized impedance matching, and suppressed excessive conductive losses, thereby improving microwave absorption. Notably, with a thickness of 4.0 mm, the FCIP@SiO 2 -5% sample achieved a remarkable minimum reflection loss of − 24.57 dB at 2.08 GHz (S-band), significantly outperforming the pristine FCIP. Regarding thermal stability, thermogravimetric analysis demonstrated that the dense SiO 2 shell significantly enhanced oxidation resistance. The onset oxidation temperature of the FCIP@SiO 2 -5% sample was delayed to 227.80 °C (an increase of ~ 83.5 °C compared to uncoated FCIP), and it exhibited the lowest total mass gain at 900 °C. Electrochemical tests indicated enhanced corrosion resistance, with the corrosion potential positively shifting from − 0.906 V to − 0.818 V. Graphical