Influence of reaction conditions on sol-precipitation process producing silicon oxide particles

The influence of TEOS, water, and ammonia concentrations on the sol-precipitation process for producing silicon oxide particles was investigated. When the hydrolysis and condensation were assumed as simple first-order reactions, the hydrolysis and condensation reaction coefficients were enhanced with an increase in the ammonia concentration due to its catalytic role in the reactions. Likewise, the increased hydrolysis coefficient with increased TEOS and water concentrations, as the reactant species, was due to the assumption of a simple first-order reaction for the hydrolysis. The dependency of the hydrolysis and condensation coefficients on the reaction conditions was estimated based on a function of the TEOS, water and ammonia concentrations, and was found to be in good agreement with the experimental data. The particle size of the silicon oxide increased with an increase in the TEOS, water and ammonia concentrations because of the promotion of hydrolysis and condensation reactions. By using correlations for the hydrolysis and condensation coefficients, the influence of the reaction conditions on the particle size was accurately predicted in line with the experimental data for the wide range of reaction conditions applied in the present study. (C) 2002 Elsevier Science Ltd and Techna S.r.l. All rights reserved.