Inhibition of the Oxidation of Carbon Fibres and Composites

The effect of a thin silica coating on the oxidation of carbon fibres has been investigated in the temperature range 600-1200°C. Silica was deposited by thermal cracking of an organic precursor (tetraethoxysilane). The protection of carbon fibre by the coating consists first in an almost complete, but limited in time, resistance to oxidation. Thereafter, oxidation of the carbon becomes noticeable, but at a smaller rate than for the uncoated fibre. The change in efficiency of theprotection during oxidation are discussed in terms of modification of surface properties of the carbon, total surface area and active surface area, and of thermomechanical characteristics of the carbon-coating interface.