Selection of blowing agent for metal foam production: A review

Abstract

Metal foams are cellular solids in which gas is uniformly distributed throughout the metal matrix. One of the cheapest ways of evolving the gas is introducing the blowing agent in parent metal in liquid state. A blowing agent is defined as a material that decomposes under the presence of heat and releases gas which then propels the foaming process. The quality of final foam is influenced by several parameters such as composition, size and volume fraction of the blowing agent used. Different chemicals which can evolve gases such as carbonates and metal hydrides fit into the description of blowing agent. Hydrides during decomposition releases H₂ gas while carbonates release CO₂ or CO gases which are responsible for foaming process. To produce good quality metal foam, the blowing agent must be a compound that does not detriment the foam metallic matrix and must have decomposition temperature closed to the melting point of the metal. This review paper covers the manufacturing processes which uses blowing agent in the formation of metal foam. Furthermore, the paper provides the detail information about the foaming physics, blowing agent’s type and selection criteria of blowing agents to produce amorphous metal foam.