Effects of SiC contents on the dielectric properties of SiO2f/SiO2 composites fabricated through a sol-gel process

SiC powders have been synthesized through a combustion process using Si powders and carbon black as starting materials. As a C-enriched α-SiC solid solution, the prepared SiC powders contain antisite defects of CSi and graphite state of sp2C, revealing good real part ε′ and imaginary part ε″ of permittivity. Subsequently, SiO2f/SiO2 composites are fabricated via a sol-gel process employing three-dimensional braided quartz fiber fabrics as a skeleton and a mixture of high-purity silica sol and the synthesized SiC powders as slurry. The effects of the SiC contents on the dielectric properties of the composites are investigated. The real and imaginary parts of the complex permittivity (ε′ and ε″) of the composites increase first before they decrease with an increasing SiC content from 0 to 40 wt.%. The maximum ε′ and ε″ are obtained at the SiC content of 20 wt.% in the range of 8–18 GHz, and the bandwidth with the reflectivity below − 10 dB of the SiO2f/SiO2 composite with 20 wt.% SiC powders is 5 GHz, which can well meet the requirements as good microwave absorbing materials.