Thermostable SiCO@BN sheets with enhanced electromagnetic wave absorption

Due to the extremely low transmission loss, hexagonal boron nitride (h-BN) is always used as a permeable material for electromagnetic wave (EMW). However, an excellent electromagnetic absorption is achieved from two-dimensional BN based absorber just because of the polymer-derived SiCO ceramic coating on BN sheets. This novel SiCO coated BN absorber (SiCO@BN) possesses a unique core-hell structure, which acts as an electromagnetic resonant cavity for EMW absorption. The as-prepared SiCO@BN ceramics not only inherit the low density, card-structure, and good impedance matching from the BN ceramic, but also demonstrates a broad absorption because of SiCO coating layer. According to the dielectric constant, the calculated minimum reflection loss (RLmin) could reach -55.6 dB at 8.7 GHz with a thickness of 4 mm, and the broadest effective bandwidth (EBW) is nearly 6 GHz (12-17.9 GHz) at a thickness of 2.5 mm. In addition, the SiCO@BN absorbers have a good high-temperature oxidation resistance with a mass loss beneath 1.3% even after the heating process at 1000 degrees C in the air. The associating RLmin and EBW are still -40 dB with the thickness of 4 mm and 4.8 GHz (8.9-13.7 GHz) with the thickness of 3 mm, respectively. Thence, these properties allow SiCO@BN absorber serving as a unique material under extreme environment, such as the exhaust nozzle of high speed aircraft.