SURFACE FREE-ENERGY OF CARBON-FIBERS WITH CIRCULAR AND NONCIRCULAR CROSS-SECTIONS COATED WITH SILICON-CARBIDE

Mesophase pitch-based carbon fibers with circular and non-circular (ri bbon, C-shaped) cross sections were coated with a thin, approximately 100-150 nm SiC-layer, using a CVD technique. The sur face free energy of the uncoated and SiC-coated carbon fibers was determined by measuri ng the contact angle of a variety of liquids with known polar and disp ersive components of their total surface free energy. It was shown tha t the polar and dispersive components of the total surface free energy of the carbon fibers depends strongly on both the SiC-layer as well a s on the shape of the cross section.