FRACTAL ANALYSIS OF POLYMERIC AND PARTICULATE TITANIA AEROGELS BY ADSORPTION

Polymeric and particulate titania (TiO2) aerogels with high surface ar eas were prepared from sol-gel derived TiO2 lyogels via freeze-drying as well as CO2 supercritical drying. The surface fractal dimensions of these aerogels were evaluated with two methods based on physisorption , one by Avnir and Pfeifer, and the other, the modified form of the Fr enkel-Halsey-Hill (FHH) equation. The two approaches yielded almost id entical results. The surface fractal dimensions measured are approxima tely 2.7 and 2.8 for polymeric and particulate TiO2 aerogels, respecti vely, thereby indicating that the fractal surfaces of particulate aero gels are slightly more irregular than those of polymeric aerogels.