Preparation and dielectric properties of carbon-coated SiC fibers

A carbon coating of 100nm thick was prepared on the surface of SiC fibers by chemical vapor deposition method. The effect of fabrication temperature on microstructure of carbon coating and on the body conductivity, permittivity of carbon-coated fiber was studied. Scanning electron microscopy and Raman microscopy were employed to investigate the surface morphology and microstructure of the coatings. The results show that when fabrication temperature increases from 800°C to 900°C, the crystallization degree and the grain size of carbon coatings increase and the body conductivity of SiC filament also increases from 0.745Ω^-1·cm^-1 to 6.289Ω^-1·cm^-1. The real part of complex permittivity of SiC woven sheet increases from 90 to 132, imaginary part from 87 to 150, respectively, and the dielectric dissipation fraction increases from 0.95 to 1.14 at the same time. The increase of the real part and imaginary part has connection with the increased density of current carrier and missed conductivity, respectively. The changes above are attributed to the conductivity increases of the carbon coatings on SiC fibers. The dissipation derived from direct current conductivity is the primary mechanism of the dissipation above all.