Thermal decomposition, phase evolution and morphology study of combustion synthesized alumina powder – Influence of precursor pH

Abstract

Here, nanocrystalline alumina powder is prepared by the glycine-nitrate combustion method, maintaining stoichiometric fuel to oxidizer ratio and two different pH conditions. The in-situ exothermic reaction occurs between an oxidizer, and fuel found to be affected by the alkalinity of the precursor solution. During combustion synthesis, spontaneous ignition occurs with the generation of gases and foamy ashes. The ash crushed into powders and then calcined at different temperatures. Thermodynamic modelling is done to calculate the enthalpy of combustions and the number of moles of gases released from the stoichiometric chemical reactions. Different characterization techniques used to study the phase formation, surface area, microstructure and morphology of the ash and calcined alumina powders. Fine crystalline α - Al2O3 powder with high surface area formed in alkaline condition. Micrographs reveal that flaky morphology of the alumina powder changed to grain type on increasing the pH of the precursor solution.