Oxidation protection of carbon materials by acid phosphate impregnation Original Research Article

Acid phosphate impregnation, with ozone pre-treatment, improves the oxidation resistance of carbon materials (polycrystalline graphite and pitch-based carbon fiber), as shown by weight measurement in air up to 1500 °C. The impregnation involves using phosphoric acid and dissolved aluminum hydroxide in the molar ratio 12:1 and results in a rough, white and hard aluminum metaphosphate coating of weight about 20% of that of the carbon before the treatment. Without ozone pre-treatment, the impregnation is not effective. Without aluminum hydroxide, the impregnation even degrades the oxidation resistance of the carbon.