ALUMINA VOLATILITY IN WATER VAPOR AT ELEVATED TEMPERATURES: APPLICATION TO COMBUSTION ENVIRONMENTS

摘要

The volatility of alumina in high temperature water vapor was determined by measuring weight loss of sapphire coupons at temperatures between 1250 and 1500℃, water vapor partial pressures between 0.15 and 0.68 atm in oxygen, at one atmosphere total pressure, and a gas velocity of 4.4 cm/s. The variation of the volatility with water vapor partial pressure was consistent with Al(OH)_3(g) formation. The enthalpy of reaction to form Al(OH)_3(g) from alumina and water vapor was found to be 210+-20 kJ/mol. Surface rearrangement of ground sapphire surfaces increased with water vapor partial pressure, temperature and volatility rate. Recession rates of alumina due to volatility were determined as a function of water vapor partial pressure and temperature to evaluate limits for use of alumina in long term applications in combustion environments.