Kinetic studies of mixed powder compact system between zinc oxide and aluminium oxide

Abstract

The addition reaction between the compacted powders of zinc oxide and aluminium oxide was studied. Both the reactants of different particles sizes were mixed in 1 - 1 molar ratio and compacted. Three particle sizes (ZnO <2 μm, Al 2O 3 < 18 μm, 84 μm) and four compaction pressures, 288 kgf/cm 2, 576 kgf/cm 2, 876 kgf/cm 2 and 1152 kgf/cm 2, were used for the studies. Conversions were measured at 800°, 900°, 1000° and 1100°C from 5 minutes to 5 hours. The reaction rate changed to a constant value after an initial phase boundary process. The mole percentage conversions increased with decrease in particle size of aluminium oxide, the increase in compaction pressure corresponding to a decrease in the initial porosity of the compact. It was also observed that the final porosity of the compact increased with increase in reaction temperature. The diffusion controlled model, Valensi-Carter model, was used to calculate the reaction rate constant equivalent. The activation energy was calculated to be 26.3–57.1 kcal/g.mole and 21.3–56.1 kcal/g.mole for the two particle sizes of aluminium oxide and for the temperature range of 800–1100°C.