Home – Home – Jornals – Chemistry for Sustainable Development 2020 number 1

A sequence of changes in X-ray patterns on heating of MgAl₂O₄ precursors synthesized by different methods is considered. It is shown that the presence of only spinel phase peaks can cause the erroneous conclusion of a single-phase nature of the product and thus explain its low sinterability. Mechanochemical treatment of the stoichiometric mixture of aluminum and magnesium hydroxides yields precursors, which form the powders of single-phase spinel with a crystallite size of 15-30 nm (depending on the composition of the gas medium) when heated at 1000 ^оC for an hour. Additional disaggregation of spinel powders through low-intensity mechanical treatment (10 g , 5 min) in ethanol gives rise to increased sinterability and allows attaining 95 % density at no more than 1350 ^оC, which is sufficient for successive densification by means of hot isostatic pressing. However, vacuum sintering is less efficient, leading to low density due to residual alkoxy groups enclosed in gas-tight aggregates which are formed in the course of the treatment with ethanol.