HYDROLYSIS CONDENSATION MECHANISM OF A 2-STEP SOL-GEL PROCESS OF MIXTURES OF TEOS AND TEOG

The effect of the addition of tetraethoxygermanate (TEOG) on the hydrolysis-condensation mechanism of a two-step silica-sol-gel process was investigated. Gelation time versus hydrolysis time curves were recorded for mixtures of TEOS, ethanol and water to which TEOG was added. It was found that TEOG reacts with silanols under ethanol formation. Because TEOG has four reactive groups, it is efficient in cross-linking chains, which implies that, in general, its addition results in shorter gelation times. At high TEOG concentrations, an unexpected dissolution of the previously obtained gel was observed.