Nanocrystalline titanium oxide by sol–gel method : the role of the solvent removal step

TiO2 particles have been prepared by following a sol gel preparative route using titanium(IV) isopropoxide as the starting compound. HCl was employed as the catalyst of the polycondensation reaction in the gel formation at 25degreesC and at constant ionic strength. Three different series of dried precursors were obtained by: (i) evaporating the solvent in oven at 80degreesC (xerogels), (ii) reaching supercritical conditions for the fluid (aerogels), or (iii) freeze drying (cryogel). All the samples were calcined at 300 and 600degreesC, for the same length of time (6 h). The powders were characterized for phase composition crystallinity (XRD), surface area porosity (BET), water and solvent content (TGA). The role played by the conditions of the solvent elimination, at the end of the sol gel reaction, in affecting the physico-chemical properties of the powders is discussed.