Nanofilter for hydrogen purification

The application of polymeric membranes in combination with metallic films can be used for gas purification, in particular hydrogen (Int J Hydrogen Energy 27(2) (2002) 905), whose molecules are very small. The affinity of hydrogen to certain metals supports its flow, but restricts the permeation of other gases. However, the flow rate is very small in dense membranes. Attempts have been made to etch nuclear tracks created in polymeric foils, from both sides in a very controlled way such that conical etched pits meet at their vertices. This has been characterized by gas permeation measurements. The low density of 106–108 tracks/cm2 is generated by a 60 MeV carbon ion beam at the NSC Pelletron, New Delhi. The primary ion fluence of 1010/cm2 was reduced by means of a gold absorber foil. The gas flow rate has shown a considerable improvement along with the selectivity of hydrogen over the carbon dioxide where the molecular sizes of 0.21 and 0.4 nm, respectively, are separable.