For many applications of open-celled ceramic or metal foams such as metal melt filtration, catalyst support, reformers, porous burner and absorber structures of solar receivers, the structural and therewith related physical properties have to be adjusted within narrow limits.
Although open-celled or more general network-like structures can be generated by 3D printing, the replication technique based on reticulated polymeric foams is still the most efficient process. Those polymeric foams or templates are available in a wide range of cell sizes from some hundred micrometres up to some millimetres for the coarsest. While the choice of the template defines the structural parameters in general, the foam properties like cell sizes, strut lengths and thicknesses of course depend on the amount of ceramic or metal material that is applied during the coating process (Schwarzwalder method) and the shrinkage of the material during the thermal treatment. The structural parameters are directly connected to the pressure losses and geometrical surface area.
A detailed knowledge of the foam structure can help to optimize its properties and to adjust them for a certain application. Intensive studies have been performed investigating the relation between the structural characteristics and the physical properties like pressure drop and geometrical surface area. In addition, also the identification and characterisation of closed cells based on a comparatively easy optical measurement setup has been in focus of this investigation.
Giving an overview of methods for describing the foam structure, this presentation will show some new techniques for the characterisation of open-celled foams that are applicable for the polymeric templates as well as the sintered ceramic or metal parts.