Abstract

Metallic foams are used as inexpensive precursors to light-weight porous solids. Unlike their aqueous counterparts, there are no surfactants available to stabilize metallic foams and, consequently, they coarsen rapidly due to the repeated coalescence of adjacent gas bubbles. Time scales for coarsening are controlled by thinning and rupture processes in individual lamellae (the thin liquid films separating adjacent gas bubbles), which are described in detail using matched asymptotic approximations and stability analysis. One important result of these analyses is an improved prediction for the conditions at rupture immediately proceeding a coalescence event. Another important result is that these analyses lead naturally to a macroscopic description of metallic foam, involving several bubbles. I will present a network theory for two-dimensional foam in which individual lamellae are coupled through conservation conditions at Plateau borders, where multiple lamellae are joined. The aim of this network theory is to model the large-scale evolution of metallic foams and to predict their coarsening behaviour.