Multivariate analysis of the size dependence of monodisperse silica particles prepared according to the sol-gel technique

The dependence of the size of the silica particles produced by a sol-gel process on constituent concentrations, reaction temperature and time was studied using reduced factorial design 2(6-2). Much information is obtained with a few experiments. The data obtained are interpreted using: multiple regression analysis. To account for the experimental results two models based on particle diameter and the other on total particle area are suggested. The full model with cross terms based on particle diameter explains 97.5% of the variation in particle size, while the model including the experimental variables explains only 18.4%. The full model based on total particle area explains 98.4% of the variance, while the model including only the main variables (tetraethyl orthosilicate and water concentration) explains 90%. The models are non-linear, suggesting that at least one of the variables is non-linear. The effects of changed levels of variables are explained on the basis of changed reaction rates. (C) 1997 Elsevier Science B.V.