LAYER THICKNESS
The theoretical wet layer thickness corresponds to the height of the doctor blade’s edge, or the spiral geometry, respectively. However, the wet layer is sheared during the layer application due to the surface tension of the sol, the wetting behavior and the rheological properties of the sol (dynamic viscosity) and the coating speed. This has the consequence, that the practical wet layer thickness is only 60 to 70 % of the theoretical ones. The final, dried layer thickness
of course also depends on the solid content and the densification behavior of the sol.
An analytical model for the film thickness as a function of the process parameters has been proposed by Chan, Ko and Yan [6].
In [7], the fluid mechanic associated with the flow of the sol-gel-slurry during the doctor blading process is analyzed.