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

Abstract

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 25 °C and at constant ionic strength. Three different series of dried precursors were obtained by: (i) evaporating the solvent in oven at 80 °C (xerogels), (ii) reaching supercritical conditions for the fluid (aerogels), or (iii) freeze drying (cryogel). All the samples were calcined at 300 and 600 °C, 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.