Nanoporous Metal Foams as Efficient Particulate Filters*

Nanostructured metal foams offer exciting potential for applications in diverse fields such as catalysts, electronics, heat exchange, structural materials, and filtration due to their extremely high surface to volume ratios. We have achieved metallic foams with tunable porosity and density (0.1%-30% of bulk density)[1] using electrochemical methods, with strong mechanical stability. Uniaxial compression tests reveal varying structural strengths depending on the relative density. Additional physical characteristics and applications have been explored. We have also investigated using such foams as efficient filtration membranes for micron and sub-micron sized particles. Over 99% of airborne micron-sized particles are found to be filtered after passing through just 1 mm of metallic foam. The foams are also found to be extremely effective for filtering out 0.2-0.4 micron sized nanoparticles. When filtering such deep submicron particles, the pressure drops across the foams are found to be comparable to an N-95 respirator for the same level of filtration.

[1] D. A. Gilbert, et al, Chem. Mater. 29, 9814 (2017).