REDUCTION OF ALUMINUM OXIDE BY PROPELLANT COMBUSTION GASES AT HIGH TEMPERATURES,

The effect of hydrogen on crystalline Al2O3 was studied at pressures ranging from 2 mm to approximately atmospheric at 1700-1800C. At the higher pressures there was no observable reduction of the alumina in the presence of hydrogen alone. However, when graphite was also present, aluminum carbide was formed at an appreciable rate. The formation of the carbide is explained on the basis of a reaction between graphite and H2 to form methane, which reduces the alumina. At very low pressures hydrogen alone did reduce alumina appreciably, but the product was not identified. Alumina was also reduced at a small but observable rate by carbon monoxide at 1700C and a pressure of approx. 0.5 atm. The implications of these phenomena for propulsion are discussed with reference to their effects on propellant performance and missile detection. Author