Journal of Industrial and Engineering Chemistry, Vol.9, No.6, 728-734, November, 2003
Synthesis of Monolithic Titania-Silica Composite Aerogels with Supercritical Drying Process
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Monolithic titania-silica composite aerogels have been prepared by complexation and impregnation methods. In the case of complexation method, monolithic titania-silica composite aerogels had good transparency and homogeneity. Particularly. the sot-get reaction rate was successfully controlled by modifying tetrabutyl orthotitanate (TBOT) with acetylacetone. and the resulting titania-silica composite aerogel had very hid specific surface area. From UV-vis diffuse reflectance spectra and FT-IR spectra, it was evident that the resulting titania-silica composite aerogels had homogeneous Si-O-Ti bonds. However, they had more crack and shrinkage than those prepared by impregnation method after supercritical drying and calcination. It was possible to produce crack-free titania-silica composite aerogels by impregnation method, but those composite aerogels showed some drawbacks of low Ti contents and non-uniformly distributed Ti phase. We have investigated the influence of addition of various polymers on the synthesis of monolithic aerogel. As a result, it was possible to enhance the hardness of gel network and consequently get a crack-free titania-silica composite aerogel.
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