Oxidation behavior and mechanism of Al4O4C powders at 1000–1300 °C

Abstract

The high temperature non–isothermal and isothermal oxidation behavior of Al4O4C powders were investigated in the temperature range of 1000 to 1300 °C. The phase composition, micro–structure evolution, and the thickness of the oxide scale were characterized. The Al4O4C powders showed a good oxidation resistance at 1000 and 1100 °C, owing to the generation of the dense nanoscale rod–like and worm–like α–Al2O3 layer. Density functional theory (DFT) calculation illustrated that Al4O4C performed a high–temperature stability due to the strong covalent bond. The grain sizes of α–Al2O3 increased evidently at 1200 °C, and the staggered growth of α–Al2O3 particles and their corresponding volume shrinkage dominated the generation of the porous surface structure of oxidized Al4O4C powders. Subsequently, the gas phase diffused quickly through these porous structures, and thus resulted in rapid and complete oxidation of Al4O4C powders at 1300 °C. The isothermal oxidation kinetics of Al4O4C powders can be accurately described by the Carter model, and their corresponding apparent activation energy was calculated to be 350.93 kJ/mol at 1000–1300 °C.