| Simulation of gelation occurring during ceramic membrane
formation by sol-gel process is reported. The main cause for
gelation in this case is the suction of liquid from the sol by a
porous substrate. When aggregation takes place by random
collisions only and there is no liquid removal, the gelation
takes place uniformly in the liquid. However, when gelation
results from the removal of liquid from the surface, a clear
gradient in concentration from the interface to the bulk is
seen. The structure formed shows maximum compactness at
the interface and it progressively becomes more open as the
distance from the interface increases. As the liquid removal
rate increases, the structure as a whole becomes more
compact and as the pH increases the structure becomes more
open. The shapes of the pores in the structure of gels formed
exhibit directionality, i.e. the pores tend to be perpendicular
to the surface of the liquid removal which may be advantageous
for a system like the ceramic membrane. |
