A STUDY OF THE FORMATION OF SILICA-SUPPORTED MIXED MAGNESIUM-MANGANESE SPINEL OXIDES FROM MULTICOMPONENT GELS

The effects of thermal treatment on composite materials prepared by th e gelation of sols comprising large concentrations of metal oxide prec ursor salts have been investigated, in order to determine the composit ional and thermal requirements for forming spinel magnesium manganates in such systems. The preparative technique has been found to give ris e to derived gel materials in which the metal oxide phase, in the form of regular spherical particles, is dispersed throughout a continuous silica matrix. Silica-supported mixed magnesium and manganese spinel o xide phases were obtained for systems comprising at least 30 wt% metal nitrate after heating to temperatures between 700 and 850-degrees-C, but not without concomitant formation of Mn2O3 and modification of the silica network by magnesium.