Spinellisation of magnesium and aluminium hydroxides with pressure and temperatures

An attempt has been made to study the effects of pressure and temperature on spinellisation of magnesium aluminate aggregate. The starting materials, magnesium hydroxide and aluminium hydroxide, were first characterized and then mixed for stoichiometric spinel composition. The mixed powder was then fired as loose powder and as briquettes (pressed at 1000 kg.cm−2), between 900° and 1600°C. The amount of spinellisation has been determined by X-ray diffraction method after comparing with a standard spinel sample. The results show that the briquettes have much higher spinel content and almost complete spinellisation has been obtained at 1600°C, whereas only 82.5% spinellisation was observed for the powders at the same temperature. Densification study of the briquetted samples also supports the trend of spinellisation