Engineerable 3D@1D FeSi@SiC composites with superior high-temperature-resistant low-frequency electromagnetic wave absorption

With the increasing demands for high-temperature resistance and superior electromagnetic wave absorption in complex environments, developing effective low-frequency (2–8 GHz) absorbers remains challenging, especially for magnetic composites with high magnetic content and dispersibility. This study proposes a hummingbird acoustic resonance mixing (HAM) strategy to fabricate FeSi@SiC composites. Compositing soft magnetic FeSi with high-surface-area nano-SiC enhances electromagnetic loss and improves the high-temperature stability of the composite material due to the partial protection of FeSi by SiC. The optimized composite achieves a minimum reflection loss of −35.9 dB and a qualified absorption efficiency of 3.9 GHz at only 3 mm thickness, along with maintained structural integrity at 800 °C. Enhanced low-frequency absorption is revealed to stem from a large-small size magnetic-dielectric structure, a high density of confined magnetic units and strong magnetic coupling, which collectively promote magnetic loss. This work introduces a new approach to designing low-frequency electromagnetic wave absorbers with high-temperature oxidation resistance by precisely tuning their dielectric and magnetic constituents, and elucidates the underlying low-frequency magnetic attenuation mechanism along with its potential applications.