Microwave absorbing properties of carbon fibers modified with BN/SiC composite coatings

Abstract

BN coating were prepared firstly on carbon fibers by dip-coating process using boric acid and urea as raw materials. Then, SiC coating were deposited on BN coating surface by chemical vapor deposition process using methyltrichlorosilane as precursor. Finally, BN/SiC composite coatings modified carbon fibers were obtained. The oxidation resistance, dielectric and microwave absorption properties, and microstructure of the BN/SiC composite coatings modified carbon fibers were investigated. The results showed that the thickness of the BN and SiC coating on the surface of carbon fibers were about 0.1 μm and 0.7 μm, respectively. After being modified by BN/SiC composite coatings, the initial and final oxidation temperatures of the modified carbon fibers were increased from 560℃ and 780℃ to 790℃ and above 1200℃, respectively. The dielectric properties of the modified carbon fibers changed significantly, and the microwave absorption properties were improved. Compared with the uncoated carbon fibers, the lowest reflectivity of the BN/SiC composite coatings modified carbon fibers with the thickness of 2 mm reduced to -13.3 dB, and the bandwidth (less than -10 dB) increased to 2.5 GHz.