(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 (SiC_w) concentrations were prepared by the nitridation of Si in SiC_w-Si powder compacts. The in-situ-grown Si₃N₄ whiskers (Si₃N_4w) were dispersed uniformly in the voids inside the interconnected network formed by SiC_w. 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% SiC_w 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.