High temperature electromagnetic wave absorption properties of SiC_f/Si₃N₄ composite induced by different SiC fibers

Ceramic matrix composites are potential electromagnetic (EM) wave absorbing materials for high temperature applications, and the critical problem is to obtain temperature insensitive absorption characteristics in broadband. In this study, the double layer SiC fiber reinforced composite with ZMI-SiC_f/Si₃N₄ as lossy layer and SLF-SiC_f/Si₃N₄ as impedance matching layer, has been constructed via the chemical vapor infiltration method. The designed SiC_f/Si₃N₄ composite with the thickness of 4.2 mm, which processes uniformly continuous microstructure and hierarchical permittivity, shows greatly enhanced EM wave absorbing performance of measured reflection loss less than −8 dB in whole X and Ku band at the room temperature. The thickness dependent absorbing properties of the SiC_f/Si₃N₄ composite are investigated, which are found to be highly correlated to the combining mode of the lossy and matching layers. Particularly, the temperature dependent absorption characteristics indicate that the fabricated SiC_f/Si₃N₄ composite keeps relatively reliable high temperature absorbing performances up to 600 °C. The temperature insensitive absorption characteristics should be mostly attributed to the enhanced compensating effect of the decreased interfacial polarization loss with increasing temperature induced by multiple interfaces, as well as the unchanged geometric structure of the designed composite.