4. Porous and permeable products

Powder metallurgy enables us to produce metals with a volume porosity of over 95%. From a structural point of view, tamped balls of the same diameter give a porosity of 26% in face-centered cubic assembly and 32% in face-centered cubic assembly. With a powder of identical spherical grains, compacted by vibration, an intermediate porosity is obtained, and the two systems can be recognized locally.

If higher porosities are required, different structures have to be created, either from spherical powders, or with filamentous particles or particles approximating such shapes.