The stability of aluminum foams at accumulation and condensation stages in gas injection foaming process

Abstract

Abstract The gas injection foaming process is divided into four stages to discuss the foam stability problem. OM, SEM, BSE and other technologies were adopted to analyze the influence of ceramic particles and oxide film on foam stability. Results indicate the oxide film on bubble surface can effectively prevent the ceramic particles from absorbing to the gas/liquid interface and avoid particles piercing the surface of liquid films. Furthermore, nano-sized oxide film also can spread at the gas/liquid interface continuously. When foams are severely deformed at accumulation stage, oxide film can protect the foams. At foam condensation stage, drainage will cause foams to rupture. Oxide film builds a framework for foams. It limits the space and flow direction of drainage. It also prevents particles from being pushed to the surface of cell walls during the solidification process. At the same time, ceramic particles increase the viscosity of melt and slow drainage. With the help of the above-mentioned mechanisms, foams can keep intact during solidifying.