Abstract: Electromagnetic wave (EMW) absorption materials effectively synergize room temperature (RT) and high-temperature absorption are essential for harsh environments applications such as stealth aircraft and aerodynamically heated components of aero-engines. Herein, an ingenious multiscale design strategy is proposed by combining the SiC_f/SiBCN composite with metastructure to achieve synergy RT and high-temperature absorption. Firstly, as the skeleton material, the microstructure, electromagnetic parameters, and high-temperature EMW absorption performance of the SiC_f/SiBCN composite have been systematically investigated. After optimizing the metastructure and corresponding geometric parameters, the SiC_f/SiBCN composite with a frustum pyramid structure has exhibited exceptional broadband and temperature-insensitive absorption characteristics. The effective absorption bandwidth (EAB) of optimized SiC_f/SiBCN-based metamaterial reaches 34.8 GHz (5.2-40 GHz, covering 96.7 % within the tested frequency band) at RT, while the EAB remains 12.5 GHz (5.5-18 GHz, covering 89 % within the tested frequency band) even at 1100 °C. Notably, it maintains stable absorption against oblique incidence (within 40 °) under transverse electric polarization. The broadband absorption mechanism of the wide temperature domain and the oblique incidence is ascribed to optimized gradient impedance matching and multiple attenuation resulting from multiscale design. This study points to the avenue for fabrication of high-performance EMW absorption metamaterial that synergizes broadband, wide temperature domains, as well as oblique incidence insensitivity.

Key words: SiC_f/SiBCN composite, Metamaterial, Wide temperature domain, Impedance matching, Electromagnetic wave absorption