A process for the synthesis of nanostructured metallic hollow spherical particles, in which the metal is deposited onto sacrificial masks formed in a polymeric colloidal solution by the electroless autocatalytic deposition method. Deposition releases only gaseous products (N2 and H2) during the oxidation thereof, which evolve without leaving contaminants in the deposit. The particulate material includes nanostructured metallic hollow spherical particles with average diameter ranging from 100 nm to 5 μm and low density with respect to the massic metal. A process for compacting and sintering a green test specimen are also described.