Calcination effect on magnesium hydroxide and aluminium hydroxide for the development of magnesium aluminate spinel

Spinellisation and densification of magnesium aluminate spinel was studied. Magnesium hydroxide and aluminium hydroxide were calcined separately between 900 and 1600°C. Stoichiometric mixtures of the uncalcined and calcined materials were sintered between 1550°C to 1750°C. Spinellisation was found to be reduced with increasing calcination temperature but sintering at 1750°C produces similar spinellisation for different batches due to higher diffusivities of the diffusing species. Above 99% spinellisation was obtained for the uncalcined batch sintered at 1750°C. Densification was also found to be greatly dependent on calcination temperature. Control of reactivity by calcination and slower rate of sintering have reduced the negative effects of the single stage sintering and a maximum of 91% densification has been found for the batch with materials calcined at 1400°C. ©