Protective coatings for carbon fibers

Protective refractory nanocoatings on carbon bundles and tapes have been investigated. Processes have been developed for growing thin layers of refractory oxides—alumina, zirconia, and silica—on continuous carbon fibers and tapes using sol-gel processing. ZrC/ZrO₂ bilayer coatings have been produced by chemical vapor transport. The surface morphology, phase composition, and elemental composition of the coatings have been studied by x-ray diffraction, high-resolution scanning electron microscopy, and qualitative energy-dispersive x-ray microanalysis. The results demonstrate that the refractory oxide coatings are homogeneous along the length and perimeter of individual fibers and adhere well to the fiber surface, with no peeling. Their thickness is within 200–300 nm. The effect of the nature of the coating on the oxidation resistance of carbon materials is analyzed.