SYNTHESIS OF SIO2-TIO2 XEROGELS BY SOL-GEL PROCESS

A new method to synthesize SiO2-TiO2 gels by sol-gel process has been developed. This technique uses tetraisopropylorthotitanate [Ti(O'Pr)(4 )] and tetraethylorthosilicate [TEOS]: they are mixed in the same solv ent and then directly hydrolysed. This one-step reaction is possible b ecause of the use of 2-methoxyethanol, a protic polar solvent. This al cohol plays two different specific roles: it acts as a solvent as well as a stabilizer of titanium alkoxide towards the hydrolysis-precipita tion reaction. So, by an accurate adjustment of the quantity of methox yethanol in the mixture, we can control the reactivity of the titanium precursor. Monolithic and transparent xerogels were obtained whatever the composition. Three monolithic SiO2-TiO2 gels containing 20, 50 an d 75 mol% of TiO2 were prepared and studied in details. By using the T G-DSC analysis, we can follow the evolution of the loss of water and o rganic residues. The structural evolution of gels during calcination i s characterized by IR spectroscopy and X-Ray diffraction.