Synthesis and micro structural investigations of titania–silica nano composite aerogels

We have synthesized titania–silica (TiO2–SiO2) aerogel composites with 20 wt%, 50 wt% and 65 wt% TiO2 by sol–gel method and investigated their microstructure in detailed using variety of techniques. X-ray diffraction showed formation of the anatase phase of TiO2 in nano-crystalline form which was confirmed by the broadening of Raman spectra. FTIR studies indicated that TiO2 is structurally incorporated in to the lattice of silica with formation of the Si–O–Ti linkage. Small angle X-ray scattering study indicated the presence of larger aggregates with rough surfaces. A systematic variation in the morphology of the larger grains and constituting smaller particles (of typical size about 20 nm) with increase in TiO2 content has been noticed. Pictures from TEM indicated that TiO2 is confined to the pores in the host silica gel, resulting in formation of TiO2 nano-crystallites leading to high surface area. Nitrogen-physisorption studies further confirmed that the TiO2 particles occupy the pores of gel matrix resulting in reduction in the average pore diameter with increasing TiO2 content. The results from all the techniques clearly suggested that the variations in the microstructure of the composites as prepared by sol–gel method will have significant impact on the optical and catalytic performance of the TiO2.