Solution combustion synthesis of MgAl2O4 using fuel mixtures

The paper reveals a new perspective concerning the rational fuel selection and the logical elaboration of the recipes for the MgAl2O4 solution combustion synthesis. It was shown that Mg(NO3)2·6H2O and Al(NO3)3·9H2O exhibit different behavior with respect to urea, glycine and β-alanine. Urea proved to be the most adequate fuel for Al(NO3)3·9H2O, while β-alanine proved to be the most appropriate fuel for Mg(NO3)2·6H2O. Considering that there is a predilection of metal nitrates with respect to these fuels, in the case of MgAl2O4 combustion synthesis best results were achieved when fuel mixtures (urea and β-alanine, urea and glycine) were used. The use of fuel mixtures allowed the formation of pure, nanocrystalline MgAl2O4 directly from the combustion reaction, without any subsequent annealing step. The use of a single fuel (urea, glycine or β-alanine) led to the formation of an amorphous powder, which required further annealing in order to achieve the formation of crystalline MgAl2O4.