Corrugated structure SiC_f/Si₃N₄ composite with high-temperature broadband microwave absorption through the regulation of high-temperature dielectric properties

The optimization of impedance matching by the absorbing structure can significantly broaden the absorption bandwidth. However, the high dielectric properties of SiC_f/Si₃N₄ composites at high temperatures resulted in the attenuation of absorption performance. Herein, the strategy of regulating the high-temperature dielectric properties of SiC_f/Si₃N₄ was proposed to enhance the high-temperature absorption performance of corrugated structure SiC_f/Si₃N₄. The boron nitride (BN) interphase and Si₃N₄ matrix were deposited on the corrugated structure fiber preform by chemical vapor infiltration (CVI) to obtain corrugated structure SiC_f/Si₃N₄. Through the fiber pretreatment process and SiC matrix deposition, the three samples show different dielectric properties. The real part (ε′ ) and image part (ε′′) of permittivity at 10 GHz at 600 °C are 14.4, 11.3, and 13.7 and 26.1, 6.4, and 17.4, respectively. The regulation of high-temperature dielectric properties enables the corrugated structure SiC_f/Si₃N₄ to exhibit an effective absorption bandwidth (EAB) of 7.6 GHz at 1000 °C. In addition, the EAB covers the 4–6 GHz frequency range, while the average reflection loss in the low-frequency region (4–8 GHz) is less than −13 dB. Excellent broadband and low-frequency absorption performance depends on a good match between the corrugation structure and dielectric properties. This work provides a new method for improving the absorption performance at high temperatures.