Long-Term Oxidation of Ti2AlC in Air and Water Vapor at 1000–1300°C Temperature Range
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The long-term isothermal oxidation behavior of bulk Ti2AlC in air and 100 water vapor has been investigated in the 1000-1300C temperature range. The kinetics, for oxidation up to 120 hours, follows a cubic rate law in both environments - air and water vapor. The kinetics was found to be slightly faster for hydrothermal oxidation compared to oxidation in air, especially below 1100C. However, there is little variation between the activation energies for oxidation in air (approximately 279 kJm3+) and in 100 water vapor (approximately 261 kJm3+). Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction show that oxidation of Ti2AlC forms mostly a continuous and stable layer of -Al2O3, along with a thin surface layer of rutile-TiO2in both environments. However, the thin TiO2layer volatilizes by forming gaseous TiO(OH)2in the presence of water vapor at high temperatures (>1200°C). At short-term oxidation and lower temperatures, diffusion of hydroxyl ions is proposed to be the rate limiting mechanism under hydrothermal conditions. Above 1100°C, the diffusion of oxide ions through Al2O3layer becomes the rate limiting step and humidity has little effect on the overall oxidation kinetics of Ti2AlC. © 2011 The Electrochemical Society.
author list (cited authors)
Basu, S., Obando, N., Gowdy, A., Karaman, I., & Radovic, M.