Aluminium foams a reality

Aluminium foams have a porous structure that makes them good materials to absorb sound, impacts and vibrations. The metallic nature allows their use as electromagnetic shields and makes them stable at high temperatures. Aluminium foam is metallic with many randomly distributed pores inside its structure. Researchers at Escuela Tecnica Superior de Ingenieros Industriales at the UPM have manufactured aluminium foams using calcium carbonate as a foaming agent. This material decomposes inside the molten aluminium alloy releasing carbon monoxide and carbon dioxide. These reactive gases, under the right agitation conditions, form bubbles along with aluminium oxide, calcium oxide and other complex metallic oxides that stabilise the liquid metal and modify its viscosity and surface energy to keep bubbles from merging and the liquid from draining. According to the researchers, the obtained foam has proven stable in a wide range of compositions, allowing the production of materials with different geometry and characteristics. With this foaming agent, the production of aluminium foam is a continuous process and leads to significant cost reductions since this is a cheaper product than titanium hybrid and other currently used foaming agents, a fact which will effectively multiply the many applications of these materials. The main applications of aluminium foams are found in the automotive industry, the aerospace industry as structural components in turbines and spatial cones, in the naval industry as low frequency absorbers and in construction, as sound barriers inside tunnels.