SYNTHESIS AND CHARACTERIZATION OF MULLITE AEROGELS

A serious problem in the production of homogeneous binary gels is the different reactivity of the alkoxides used. In the special case of silicon alkoxides and aluminium alkoxides, the difference is some orders of magnitude. A common procedure to decrease the reactivity is the complexation of the alkoxide by a chelating agent, e.g., beta-diketones. Particle formation in the system aluminium-sec-butylate-beta-diketone-TEOS in an alcoholic solution was studied by SAXS and IR spectroscopy to learn more about the effect of chelation. The most important effect of the chelating agent was shown to be the reduction of the number of possible condensation sites. Some gels were prepared and supercritically dried. Translucent aerogels were obtained under suitable hydrolysis conditions.