The Surface Properties of the Silica-Titania System Prepared by the Hydrolysis of Metal Alkoxides

The surface and bulk properties of silica-titania systems, prepared by the co-hydrolysis of silicon ethoxide and titanium tetrabutoxide, were investigated by measuring the heat of immersion, the adsorption of nitrogen, water, and ammonia, the X-ray diffraction, the DTA, and the TGA. It was found that the addition of silica to titania has a large suppressive effect on the crystal growth of anatase and on the transformation of anatase to rutile. The heat of immersion, the surface hydrophilicity (the surface area by water adsorption/the surface area by nitrogen adsorption) and the amount of ammonia adsorbed gave inverted sigmoid curves when the titania content was varied. Especially, the shape of the curve of the change in the heat of immersion coincides approximately with that of the surface hydrophilicity.