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.