Study of titanium oxide sol-gel condensation using small angle X-ray scattering.

Transparent gels prepared from an acid solution of TiOCl(2) in N,N-dimethylformamide (DMF) and water have been studied by small-angle X-ray scattering (SAXS). The sol-gel transformation of the titanium inorganic polymer was studied as a function of chemical composition of the sol and of the annealing time. Quantitative information was obtained by modeling the SAXS data with the Burford and Beaucage models. From the fits to the data, the radius of gyration of the primary particles, the so-called building blocks, the size xi of the homogeneous objects forming a fractal network in the gel, and the fractal dimension of the gel were obtained. We found fractal dimensions varying between D(f) = 1.75 and 2.2 and a radius of gyration of the building blocks equal to R(g) = 0.46 nm, which remained almost constant for all studied samples. The analysis of the homogeneous domain size xi as a function of the annealing time shows the existence of an incubation time preceding the rapid growth of the aggregates at high titanium concentration.