FT-Raman Spectroscopy of Modified Tetraisopropyltitanate Hydrolysates

Abstract

Modification of metal alkoxides with complexing agents, such as carboxylic acids, which act both as a catalyst and a ligand, is commonly used in sol-gel processing to alter the hydrolysis and condensation rates of the alkoxide. Hydrolyzates produced by the reaction of modified tetraisopropyltitanate with water were X-ray-amorphous but exhibited spectra similar to the spectrum of rutile; broad bands assigned to the Eg and A1g Ti-O stretching modes of the "rutile-like" phase were obsd. at ca. 425 and 605 cm-1, resp. During peptization of the hydrolyzate with nitric acid at 60 °C, the intensity of these bands decreased substantially, and new peaks appeared at 154, 405, 515 and 630 cm-1, which were assigned to the δo-Ti-o (Eg), δo-Ti-o (B1g), vTi-o (A1g/B1g) and vTi-o (Eg) modes, resp., of anatase. However, the hydrolyzates were also found to undergo a similar phase change when processed at the same temp. in the absence of peptizing agents, but the rate of transformation was slower. The carboxylic acid also had a significant influence on the induction time for the phase change, with the transformation occurring more slowly with increasing carboxylate chain length. [on SciFinder(R)]