Hierarchical impedance-matched PyC@SiC_nws@SiBCN ceramic foam with triple-layered architecture for broadband microwave absorption

Porous carbon-based microwave absorbers demonstrate significant potential due to their lightweight characteristics and tunable dielectric properties, despite persistent challenges including narrow bandwidth, structural fragility, and thermal instability. In this study, an innovative PyC@SiC_nws@SiBCN ceramic foam was fabricated via a two-step impregnation process, followed by polymer-derived ceramic conversion through pressureless pyrolysis. The effects of SiC_nws content and pyrolysis temperature on microstructure, dielectric behavior, and microwave absorption were comprehensively investigated. Results demonstrate that heat treatment modulates the composition and multi-dimensional heterogeneous interfaces, and the optimal absorber exhibits exceptional performance with a minimum reflection loss of −58.4 dB at 11.0 GHz and ultra-wide EAB of 4.2 GHz (covering the entire X-band) at merely 4.5 mm thickness. The three-layered coating structure composed of PyC, SiC_nws, and SiBCN enables effective regulation of impedance matching through dielectric gradient distribution and induces multiple interfacial polarization losses synchronously, providing new insights into the structural engineering of ceramic foams for microwave absorbers.