Low‐Temperature Chemical Synthesis of Nanocrystalline MgAl₂O₄ Spinel Powder

Abstract

Nanocrystalline MgAl 2 O 4 spinel powder was synthesized by pyrolysis of complex compounds of aluminum and magnesium with triethanolamine (TEA). The soluble metal ion-TEA complexes formed the precursor material on complete dehydration of the complexes of aluminum-TEA and magnesium-TEA. Single-phase MgAl 2 O 4 spinel powder resulted after heat treatment of the precursor material at 675°C. The precursor and the heat-treated powders were characterized by X-ray diffractometry (XRD), differential thermal and thermogravimetric analysis, and transmission electron microscopy (TEM). The average crystallite size as measured from the X-ray line broadening was around 14 nm and the average particle size from TEM studies was around 20 nm.

Application of New Organic Fuels in the Direct MgAl2O4 Combustion Synthesis

“…Moreover, it was assumed that the gaseous by-products of the combustion reaction are CO 2 , H 2 O and N 2 . In all samples stoichiometric metal nitrate/fuel molar ratios were used, according to reactions (16)(17)(18)(19)(20)(21)(22)(23)(24). The procedures were designed in order to obtain 0.070 mol (9.940 g) of magnesium aluminate, MgAl 2 O 4 .…”

“…This means that the exothermic effect, which occurs during the combustion reactions containing fuel mixtures (reactions 23 and 24), is considerably more intense than the one occurring in the traditional combustion reactions involving the use of a single fuel (reactions [16][17][18][19][20][21][22].…”

“…That is why one of the major research directions in the field of materials science is represented by the development of new more efficient synthesis methods. As a result, several different methods have been suggested for the MgAl 2 O 4 synthesis: the ceramic method, [9,10] mechanochemical synthesis, [11,12] sol-gel, [13][14][15] thermal decomposition of complex combinations, [16,17] coprecipitation, [18,19] Pechini, [20] SHS (self-propagating high-temperature synthesis) [21] etc. Yet, in all these in the MgAl 2 O 4 low-temperature combustion synthesis leads to the formation of an amorphous powder.…”

Low temperature synthesis of magnesium oxide and spinel powders by a sol-gel process

“…Although some methods, such as hydrothermal synthesis, plasma spray decomposition of oxides could be used to prepare high-purity oxide powders. However, these techniques have not received much commercial importance because of the use of expensive raw materials and many processing steps 9,10 . In this paper, a relatively simple, efficient, low-cost aqueous solgel process based on the in situ generation of water soluble metal complexes with magnesium chloride, aluminum nitrate and citric acid as raw materials has been developed to synthesize fine magnesium oxide and spinel powders.…”

Sintering, mechanical and refractory properties of MA spinel prepared via co-precipitation and sol–gel techniques

“…Over the last few decades, numerous techniques have been used to prepare high purity magnesium aluminate spinel powder, addressing chemical homogeneity, control of stoichiometry, fine particle size, narrow particle size distribution, and minimum particle agglomeration with high surface area. These include hydrothermal synthesis [16], co-precipitation [17][18][19][20][21][22][23][24][25], microemulsion technique [26], microwave-assisted combustion processing [27], plasma spray decomposition [28,29], sol-gel of double or semi-alkoxides [30][31][32][33], the citrate-nitrate route [34,35], organic gel-assisted citrate process [36], aerosol method [37], freeze drying [38], decomposition of organometallic compounds [39][40][41][42], mechaniochemical synthesis [43][44], mechanical activation [45] and others [46][47][48].…”