Improvement in properties and air oxidation resistance of carbon materials by boron oxide impregnation Original Research Article

Boron oxide (B2O3) has been impregnated into a high-density isotropic graphite block and a felt carbon fiber reinforced carbon composite (CC composite). Impregnation was carried out at 1200 °C under a pressure of 15 MPa for 1 hour. The bulk density of the original graphite and CC composite increased by 12% and 20% respectively as a result of impregnation, the mechanical properties of these materials were improved significantly, and the thermal conductivity slightly increased. Gas permeability was reduced by B2O3 impregnation to the order of 10−5 cm2/s from 10−1 cm2/s of the original graphite, and to 10−2 cm2/s from 10 cm2/s of the original CC composite. Oxidation loss by air of both B2O3-impregnated materials appeared to be almost suppressed at temperatures below 800 °C. Serious oxidation loss was observed in both the impregnated materials by exposing to air for several hours at 850 °C because of loss of B2O3 from the specimen.