An approach to predict the solid film thickness possibly yielded from an alumina sol-gel liquid film

The Landau-Levich-Derjaguin (LLD) equation is widely used to predict the thickness of wet layer deposited on substrate by dip-coating. But it cannot effectively predict the solid film thickness yielded from the sol-gel liquid layer. Considering the solid content, the amount of solution sticking to the surface of substrate and the density of the sol-gel derived solids materials are the main factors determining the solid film thickness, a new approach capable of directly predicting what an oxide film thickness of a liquid layer on the substrate could yield without really sintering at high temperature was developed. It was found that the predicted and measured thicknesses for both compact and porous Al₂O₃ films were in good accordance. The approach uses very common testing techniques and does not concern the aspects such as solution composition, Newtonian or non-Newtonian fluid, withdrawal speed, viscosity, and liquid-vapor surface tension, etc. So the method is much timesaving and economical, and will be a good supplement for thickness determination techniques, especially under some circumstances where use of SEM, XRR, ellipsometer analyses are limited.