Application of New Organic Fuels in the Direct MgAl2O4 Combustion Synthesis

Abstract

AbstractThe paper presents a new version of MgAl2O4 solution‐combustion synthesis, based on the individual reactivity of Mg(NO3)2 and Al(NO3)3 with respect to various fuels. Beside the traditionally used fuels (urea, glycine, β‐alanine), new organic reducing agents [monoethanolamine, triethanolamine, tris(hydroxymethyl)aminomethane and triethylenetetramine] have also been used. The study of the individual reactivities of Mg(NO3)2 and Al(NO3)3 with respect to each of the previously mentioned fuels suggested that there is a predilection of the two metal nitrates for certain fuels: urea is the optimum fuel for Al(NO3)3, whereas monoethanolamine represents the most suitable fuel for Mg(NO3)2. It has been shown by X‐ray diffraction and thermal analysis that the use of a single fuel in the MgAl2O4 low‐temperature combustion synthesis leads to the formation of an amorphous powder. In this case, the formation of pure crystalline MgAl2O4 requires a subsequent thermal treatment at 900 °C with 1 h soaking time. On the other hand, the use of fuel mixtures containing urea and monoethanolamine or urea and β‐alanine proved to be the rational solution for the direct formation of MgAl2O4. It has been shown that, by using the above‐mentioned fuel mixtures, one can obtain pure nanocrystalline MgAl2O4 straight from the combustion reaction, no additional calcination being necessary. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)