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 m agnesium oxide is studied by LR spectroscopy, W-VIS diffuse-reflectanc e spectroscopy, X-ray diffraction analysis, electron microscopy, and t hermogravimetry. 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 MgAc2 solution during the hydration of MgO. At 235 degrees C, this co mpound is rearranged into Mg(OH)(x) . Ac-y hydroxyacetate (II) of a va riable composition, which depends on the degree of substitution of ace tate groups for hydroxyl groups and is responsible for the rate of sol id-phase transformations. Less stable hydroxyacetates begin to transfo rm to defective magnesium oxide at 335 degrees C, and this transformat ion is completed at 370 degrees C. The modification of magnesium oxide with admired acetate ions occurs during the formation of its structur e. At high temperatures, acetate ions in the MgO structure are convert ed into carbonate ions, which are retained in MgO after calcination at 1000 degrees C.