THE THICKNESS OF SOL-GEL SILICA COATINGS OBTAINED BY DIPPING

Silica coatings on glass slides were prepared from solutions of the same concentration, but with different H2O/TEOS ratios. The thicknesses of the liquid films deposited by the dip-coating method were calculated from those of the heat treated coatings and related to the withdrawal speed and to the properties of the solutions by means of the theoretical equations and the empirical approaches described in the literature. A modified empirical method was derived to fit the experimental thicknesses of heat treated layers. It was shown that the H2O/TEOS ratio scarcely affect the flow behavior of the solutions and differences in thickness arise from their different viscosities. Films deposited in a higher alcohol content environment exhibited smaller thickness values. © 1990.