Effects of chelation reactions between metal alkoxide and acetylacetone on the preparation of MgAl2O4 powders by sol–gel process

Magnesium aluminate spinel (MgAl2O4) were synthesized via the sol–gel method, using magnesium aluminum double n-butoxide as precursors. The n-butoxide, prepared by the direct reaction of stoichiometric magnesium, aluminum and adequate n-butanol, was modified by acetylacetone as the chelating agent to control the speed of hydrolysis. Gel samples were identified as the mixture of Mg2Al(OH)7 and MgAl2(OH)8 phases, which converted to pure MgAl2O4 spinel phase at 800 °C. Then dense spinel ceramics with 96% of relative density were prepared by sintering in air at 1600 °C. Besides, the morphology of the powders and sintered ceramics has been investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM).

Graphical abstractThe mechanism of chelation reaction between the magnesium aluminum double alkoxide and the chelating agent acetylacetone was investigated by analyzing the FT-IR spectroscopy of the n-butoxide and the chelating products. The chelating agent acetylacetone substitutes the alkoxyl group of the double alkoxide to enhance the steric effects, and forms steady hexatomic ring to delay the hydrolysis effectively.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Nanosized MgAl2O4 spinel powders were synthesized by the sol–gel process. ► We analyzed the reaction between the chelating agent acetylacetone and the alkoxide. ► The introduction of acetylacetone succeeded in delaying the hydrolysis of alkoxide.