A processing route for dip-coating and characterization of multi-structured ceramic foam

Abstract Ceramic foam materials have received great attention in recent years for their light weight, thermal/electrical insulation, high crack tolerance and good machinability properties. However, some applications demand higher mechanical strength, better resistivity of the surface against mechanical impact or improved abrasion resistance. In this paper, the feasibility of dip coating 89 vol% porous, green alumino-silicate foam bars with dimensions in the centimeter range was studied and a dip coating route was proposed. The surface morphology of uncoated and coated foam bars was first analyzed by scanning electron microscopy (SEM) and later detailed using the Gelsight TM method. Mechanical properties were determined by 4-point bending. A dense coating layer with a uniform thickness and good interfacial adhesion was obtained over the foam. Consequently, a three-fold increase in the flexural strength was measured for coated parts. In addition, the versatility of the developed dip coating route was demonstrated coating samples of bigger size like panels as well as complex geometries like cylindrical crucibles.