INHIBITION OF THE OXIDATION OF CARBON CARBON COMPOSITES BY BROMINATION

Bromination by exposure to bromine vapor at room temperature was effective for inhibiting the oxidation of carbon-carbon composites in the form of PAN-based carbon fibers impregnated with resin, which was subsequently carbonized at 1000 or 2000°C. The oxidation rate was decreased by up to 43%. In addition, electrical resistivity was decreased by up to 39%. However, the tensile modulus was decreased by 16-17% and tensile strength was decreased by 17-20%; the ductility was not affected. The increased oxidation resistance may be due to bromine adsorption or the electron transfer from graphite to bromine. The bromine resided in the matrix of the composite, particularly in pores within the matrix. Bromination was also attempted by the electrochemical method, but it resulted in negligible weight uptake in the carbon-carbon composite. Carbon-carbon composites that had been graphitized at 2700°C were damaged by bromination. © 1990.