Morphological and structural features of individual and composite nanooxides with alumina, silica, and titania in powders and aqueous suspensions

Abstract

Morphological, structural, and adsorptive characteristics of such fumed oxides as alumina, silica, composite silica/alumina and alumina/silica/titania were studied using a variety of experimental methods. Heating of nanooxides caused several processes resulting in the temperature dependent structural changes of the materials because of changes in the amounts of intact and dissociatively adsorbed water not only at the surface of the nanoparticles but also in their volume that lead to changes in the oxide matrix structure. These processes dependent on the composition of nanooxides are much stronger for nanosilica than for alumina or composite oxides. The morphology of primary nanoparticles is more stable on different treatments than the structure of secondary and ternary particles. The amounts of water adsorbed onto the nanooxides from air correspond to the amounts of water strongly bound (unfrozen at T < 273 K) to the oxide surfaces in aqueous suspensions.