Porous Metals and Metallic Foams: Current Status and Recent Developments

Cellular metals and metallic foams are metals with pores deliberately integrated in their structure. The terms cellular metals or porous metals are general expressions referring to metals having large volume of porosities, while the terms foamed metal or metallic foams applies to porous metals produced with processes where foaming take place. Besides, the term metal sponge refers to highly porous materials with complex and interconnected porosity where the porosity cannot be subdivided into well defined cells. Porous metals and metallic foams have combinations of properties that cannot be obtained with dense polymers, metals and ceramics or polymer and ceramic foams. For example, the mechanical strength, stiffness and energy absorption of metallic foams are much higher than those of polymer foams. They are thermally and electrically conductive and they maintain their mechanical properties at much higher temperatures than polymers. Besides, they are generally more stable in harsh environments than polymer foams. As opposed to ceramics, they have the ability to deform plastically and absorb energy. If they have open porosity, they are permeable and can have very high specific surface areas, characteristics required for flow-through applications or when surface exchange are involved.