(SiC-Si3N4)w/SiBCN composite ceramics with tunable electromagnetic properties

In this study, composite ceramics with tunable electromagnetic properties were developed based on SiC-Si3N4 hybrids. First, SiC-Si3N4 whisker preforms with various SiC whisker (SiCw) concentrations were prepared by the nitridation of Si in SiCw-Si powder compacts. The in-situ-grown Si3N4 whiskers (Si3N4w) were dispersed uniformly in the voids inside the interconnected network formed by SiCw. The whisker reinforcements effectively toughened the SiBCN matrix through interface debonding, crack deflection and whisker pullout mechanisms. The electromagnetic properties of the composite ceramics can be tuned by adjusting the composition of (SiC-Si3N4)w preforms. The composite ceramic with 31.9 vol% SiCw exhibited the broadest effective absorption bandwidth (EAB) of 2.9 GHz in X band. Furthermore, a multilayer radar absorbing structure (RAS) composed of ceramic composites with gradient electromagnetic parameters was constructed to further improve the absorption properties. By adjusting the structure of the RAS, the resulting EAB of the RAS covered the entire X band.