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 BN interphase and Si₃N₄ matrix were deposited on the corrugated structure fiber preform by chemical vapor infiltration to obtain corrugated structure SiC_f/Si₃N₄. Through fiber pretreatment process and SiC matrix deposition, three samples show different dielectric properties. The ε′ and ε′′ at 10 GHz under 600 °C are 14.4, 11.3, 13.7 and 26.1, 6.4, 17.4, respectively. The regulation of high-temperature dielectric properties enables the corrugated structure SiC_f/Si₃N₄ exhibits an effective absorption bandwidth (EAB) of 7.6 GHz at 1000 °C. In addition, the EAB covers 4-6 GHz frequency range, while the average reflection loss in 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.