Design and structure-dependent electromagnetic absorption performance of silkworm cocoon-templated C_f @Co₃Fe₁/α-SiO₂/α-SiC_w/C composite

Aiming at the defects of carbon-based/ceramic-based composite microwave absorbers, such as the difficulty in balancing strong absorption and broadband absorption under a thinner coating thickness, using silkworm cocoon fibers (SC _f ) as templates, the C _f @Co₃Fe₁/α-SiC _w /α-SiO₂/C composite was successfully prepared by hydrothermal method, pyrolysis reduction and solid-state reaction. A series of characterizations confirmed that it takes the silkworm cocoon-derived C _f as the core, the Co₃Fe₁ on the surface of C _f obtained by thermal reduction as the magnetic loss component, and the lightweight, porous and multi-scale α-SiC _w /α-SiO₂/C as the shell, which have abundant heterogeneous structural interfaces. It exhibits paramagnetic behavior, with a minimum reflection loss (RL _min) of −71.71 dB with a loading ratio of 50 wt. %, corresponding to a coating thickness and matching frequency of 2.30 mm and 13.27 GHz, respectively. When the coating thickness is 2.10 mm, its maximum effective absorption bandwidth (EAB _max) reaches nearly 4 GHz (12.65–16.62 GHz). The density functional theory (DFT) calculations and radar cross-section (RCS) simulations confirmed its multi-component synergistic attenuation mechanism and superior EMW absorption performance, attributed to interface/dipole polarization, conductance loss, and magnetic resonance. This sample can meet the stringent requirements for strong absorption capabilities in certain scenarios.