Foam formation mechanisms in particle suspensions applied to metal foams

At first glance, metal foams appear to be peculiar. On the one hand, they show a high stability with life times of minutes up to hours. On the other hand, metal foams should be highly unstable due to capillary forces. Generally, the cell structures show odd cell configurations. In addition, the cell walls are thick, about 100 μm, and exhibit pronounced local swellings and indents.In this paper, we show that this apparent discrepancy is a direct consequence of an underlying foam stabilization mechanism for metals which is based on a barrier effect induced by particles confined in cell walls. Numerical simulation based on a lattice Boltzmann model shows how particles get confined within cell walls and induce a repulsive disjoining pressure there. This disjoining pressure is responsible for the high foam stability generally observed. The identified stabilization mechanism also explains the presence of irregular cell structures generally observed for metal foams and represents the basis for further developments.