SiBNC_x ceramics derived from single source polymeric precursor with controllable carbon structures for highly efficient electromagnetic wave absorption at high temperature

Precursor derived ceramic with controllable carbon content has the advantages of high temperature and adjustable dielectric properties, which has significant potential for the research the high temperature microwave absorbing materials. In this contribution, a series of single-source SiBNC_x precursors are obtained using NH₃, n-butylamine, and dichlorodiphenylsilane with n-butylamine as the carbon source ammonolysis trichlorosilylamino-dichloroborane (TADB) monomer and polymerization. Adjusting the carbon content of precursors directly leads to phase composition and performance differences of SiBNC_x ceramics. For SiBNC_x ceramics with no carbon or low-carbon content, it had almost no effect on electromagnetic waves. The transmission rate ranged from 98% to 78% in 2–18 GHz. When SiBNC_x ceramics with carbon-rich structure, the tanδ of pyrolytic ceramics increased significantly, which has an obvious loss on electromagnetic wave. The minimum reflection coefficient (RC_min) values reached −64.75 dB, and the effective absorption bandwidth (EAB) was 3.8 GHz in the X band at room temperature. Importantly, EAB of the SiBNC_x ceramics still cover more than 50% of the X band, RC_min can be as low as −24.9 dB at 600 °C. The strategy offers a new method to accurately control high temperature electromagnetic performance from molecular structure.