Coating of Open Cell Foams
- Publication date
- Publisher
Abstract
The interior surfaces of three-dimensional open cell
foams were coated by a combination of dip coating and spin coating.
Glycerol/water solutions were used as model Newtonian liquids, and
the coating processes were studied on open cell carbon foams with
10 or 30 pores per inch (PPI). The amount of liquid retained in the
foam structures after dip coating increased with withdrawal speed
and coating viscosity, as expected from the conventional understanding
of dip coating onto nonporous substrates such as flat plates and rods.
However, the liquid retention and hence average coating thickness
increased with surface tension, a result counter to the observation
with coating onto nonporous substrates. Pockets of liquid were observed
after dip coating and results with coatings of alumina suspension
showed that after drying, the trapped liquid can block pore windows.
Spinning the foams after dip coating resulted in uniform liquid distribution
and uniform coatings. Foams were placed in a special apparatus and
rotated using a commercial spin coater. The liquid layer thickness
decreased with spinning time and rotational speed, and increased with
the liquid viscosity, results consistent with spin coating theory.
The coating thickness after spinning was not affected by the initial
dip coating procedure. The dip and spin process was also used to create
γ-alumina
and zeolite coatings, which are of interest for catalysis applications