Preparation of γ -alumina powder from kaolin derived aluminium sulphate solution and its stability by BaO addition

The synthesis of γ-alumina powder from kaolin derived aluminium sulphate solution is described and results are reported on the effect of BaO additions made by two different methods, precipitation mixing and mechanical mixing of BaCl₂.2H₂O, on the thermal stability of γ-alumina powder at high temperatures. The powders were characterised by XRD, SEM, TEM, and measurements of surface area by the BET method. It was found that powder prepared by precipitation mixing was more thermally stable at high temperatures than powder prepared by mechanical mixing, indicating that the precipitation mixing was more effective in retarding the γ-to α-alumina phase transformation at high temperature.