Production of high porosity metal foams using EPS beads as space holders

High porosity metal foams were produced using a SWS (Space holders & Whipped Slurry) process that uses EPS (Expanded polystyrene) beads as space holders and a whipped slurry of a metal powder and a water solution of PVA (Polyvinyl alcohol). First, the slurry is whipped and mixed with EPS beads, then molded, and finally frozen and left for 24 h to form a gel. After being thawed, the precursor thus obtained is desiccated, decomposed all binders and polystyrenes and sintered. The result is high porosity metal foam that maintains the molded shape. When stainless steel powder is used in this simple process, metal foams with a porosity ranging from 90% to 97%, plateau stress from 4 to 0.4 MPa and thermal conductivity from 0.5 to 0.1 W/mK are produced. Pore size can be controlled by using different sizes of EPS beads. This simple process can be used to produce metal foams of high porosity at high throughput. Also, this process can be used to reduce production costs using coarser and cheaper powder. Such coarse powder foam has lower thermal conductivity, and thus can be used as a thermal insulator. These low cost metal foams can expand these applications such as filters, thermal insulators, shock absorbers and acoustic insulators.