High temperature electromagnetic wave absorption properties of SiCf/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 broad-band. In this study, the double layer SiC fiber reinforced composite with ZMI-SiCf/Si3N4 as lossy layer and SLF-SiCf/Si3N4 as impedance matching layer, has been constructed via the chemical vapor infiltration method. The designed SiCf/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 SiCf/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 SiCf/Si3N4 composite keeps relatively reliable high temperature absorbing performances up to 600 degrees 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.