A phenomenological description of the rate of the aluminum/oxygen reaction in the reaction-bonding of alumina

The isothermal reaction kinetics of aluminum oxidation in loose Al/Al2O3 powder was studied in the temperature range 455–555 °C using thermogravimetry. The powder compositions ranged from 30 to 65 vol.% aluminium, with average Al particle sizes in the range 1.4–2.7 μm The oxygen mole fraction was varied between 20 and 100%. It was found that only 70–80% of the aluminum can be oxidized below the melting point of 660 °C. The weight gain curves were well fitted by assuming that the rate of oxidation was first order with respect to the amount of aluminum, which can be oxidized below 660 °C, left in the sample. The reaction rate was observed to be independent of both the partial pressure of oxygen and the aluminum particle size. It was shown that the same kinetics relationship could also be applied to a broad range of experimental oxidation data in the literature, yielding a common value of the Arrhenius constant and activation energy. The kinetic model was successfully applied to the controlled processing of RBAO powder compacts for constant temperature hold and constant reaction rate cases.