Reaction of molten Al and of Al-20 wt. % U with water vapour

Abstract

An investigation has been made of the reaction between Al at 800–1400°C in 100 per cent or argon-diluted water vapour, and between Al-20 wt.-% U alloy at 930–1400° in 100 per cent water vapour, the total gas-phase pressure being 1 atm. Metal samples were heated and suspended in the vapour stream by the electromagnetic levitation technique, and the concentration of hydrogen liberated by reaction recorded continuously. Provided the oxide layer did not break down, oxidation was parabolic for a short interval after attainment of the working temperature but then the rate decreased more steeply; later, depending on conditions of temperature and vapour pressure, the oxidation rate became approximately constant or it fluctuated giving two types of pulse. However, if the temperature exceeded a critical value-1050° with pure argon up to ca. 1700° with 100 per cent water vapour—the rate remained at a high level owing to partial or complete oxide layer breakdown. The results are discussed in terms of hydrogen dissolving into the metal, formation of amorphous followed by crystalline oxide, oxide cracking, suboxide formation, and oxide disruption by hydrogen pockets.