Defective magnesium oxide: Synthesis and studies of structure formation

The method for the synthesis of defective magnesium oxide by hydration of initial MgO in a magnesium acetate solution followed by drying and calcining is suggested. The mechanism of the formation of defective magnesium oxide is studied by IR spectroscopy, UV-VIS diffuse-reflectance spectroscopy, X-ray diffraction analysis, electron microscopy, and thermogravimetry. It is shown that a metastable Mg(OH) x . . AC Y . nH 2 O (I) compound with a structure of magnesium hydroxide is formed in a MgAc 2 solution during the hydration of MgO. At 235°C, this compound is rearranged into Mg(OH) x . AC y hydroxyacetate (II) of a variable composition, which depends on the degree of substitution of acetate groups for hydroxyl groups and is responsible for the rate of solid-phase transformations. Less stable hydroxyacetates begin to transform to defective magnesium oxide at 335°C, and this transformation is completed at 370°C. The modification of magnesium oxide with admixed acetate ions occurs during the formation of its structure. At high temperatures, acetate ions in the MgO structure are converted into carbonate ions, which are retained in MgO after calcination at 1000°C.