Modification of alumina bubbles with ammonium aluminum sulphate

Ammonium aluminum sulphate was introduced to modify alumina bubbles by the wet chemical method. Distribution of ammonium aluminum sulphate, in situ decomposition characteristics, microstructure and mechanical properties of the modified alumina bubbles were investigated by SEM, XRD, BET and by a purposely designed experimental device for the measurement of compressive resistance. Experimental results showed that an ammonium aluminum sulphate thin film was formed on the surface of the alumina bubbles, at the same time, ammonium aluminum sulphate also infiltrated into the flaws and cavities of the alumina bubbles. After heat-treated at 900 °C, the ammonium aluminum sulphate on the alumina bubbles could be in situ decomposed to γ-Al2O3 with high activity. The compressive resistance of the modified alumina bubbles was enhanced from 15.6N to 38.7N after heat-treatment at 1700 °C for 2 h.