Filters with < 100 nm radius pores for gas separation formed by high-energy ion irradiation of polymers

In the industry, often gases have to be separated from each other for clean ing and other purposes. In principle, this can be achieved by passing a gas mixture through a filter system when the filter pore diameter is very smal l being comparable to the size of the mean free path of the gases. Such wel l-defined pores can be fabricated by high-energy ion irradiation of polymer s, combined with chemical etching of the resulting damage in the polymer. P olyimide foil was irradiated with high-energy lead ions. The pores were evo lved from the ion tracks by exposing the polymer to a chemical etching agen t. The pore radius was determined by scanning electron microscopy (SEM). Th e shape of the pores through the foil was determined by filling them electr ochemically with metal, cutting them into small pieces and investigating th e edges again by SEM. The results showed that uniform cylindrical pores wit h radii below 100 nm could be formed. Using the gas mixture CO/CO2 as a mod el system for the gas separation the filters were tested for their efficien cy. The gas mixture was pumped through the filter and analysed by gas chrom atography. The results show that a separation of the gas mixture is possibl e. Filters fabricated by ion irradiation may act as efficient gas separator s. (C) 2001 Elsevier Science B.V. All rights reserved.