Blends of amorphous/crystalline nanoalumina and hydrophobic amorphous nanosilica

Abstract

Initial Al-100 and hydro-compacted amorphous/crystalline nanoalumina cAl-100 alone or in blends with hydrophobic amorphous nanosilica AM1 were characterized using low-temperature 1H NMR and IR spectroscopies, adsorption, XRD, DSC, microscopy, and cryoporometry. Mechanical treatment of weakly hydrated (0.5 g/g) nanooxides results in their hydro-compaction changing many of the material characteristics. There is overlapping of confined space effects for water bound in voids between nanoparticles with effects caused by the colligative properties of aqueous solution of trifluoroacetic acid in a chloroform medium. The interfacial phenomena determine the temperature behavior of bound water/ice depending on dispersion media features. Contact area between unfrozen water and nanooxide surface is smaller than the specific surface area due incomplete water filling of voids between hydrophilic/hydrophobic nanoparticles. In composites with cAl-100/AM1, there is a tendency of diminution of the contact area of water with hydrophobic nanosilica AM1 and hydrophobic chloroform immiscible with water. This effect changes the temperature behavior of water, which becomes more strongly bound to hydrophilic alumina. The observed effects can be of importance upon practical applications of nanooxide based composites.