N.K. Acharya

The titanium-coated polymeric membranes for hydrogen recovery

Abstract The polymeric membranes are commercially used for gas separation. The important parameters for their commercial application are good permeabilities and permselectivities. These parameters have a strong dependence on the free volume properties of the material. The membranes alone are generally not suitable when high product purity and recovery is desired. However, the titanium-coated polymeric membranes can solve the problem. Hydrogen molecules when diffuse through metals like titanium and palladium, break into atomic form and recombine after recovery. The binding of metallic clusters on the polymeric material is improved partially by heat treatment, however, good results are obtained by dissolving the coated membranes and recasting them. The permeability of hydrogen in comparison to air has been found to increase 2–5 times.

Nanofilter for hydrogen purification

Abstract 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 10 6 – 10 8 tracks / cm 2 is generated by a 60 MeV carbon ion beam at the NSC Pelletron, New Delhi. The primary ion fluence of 10 10 / cm 2 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.

Transport through track etched polymeric blend membrane

Polymer blends of polycarbonate (PC) and polysulphone (PSF) having thickness, 27 μm, are prepared by solution cast method. The transport properties of pores in a blend membrane are examined. The pores were produced in this membrane by a track etching technique. For this purpose, a thin polymer membrane was penetrated by a single heavy ion of Ni7+ of 100 MeV, followed by preferential chemical etching of the ion track. Ion permeation measurements show that pores in polymeric membrane are charged or neutralized, which depends upon the variation in concentration of the solvent. TheV-Icurve at concentration, N/10, shows that the pores are negatively charged, whereas at concentration, N/20, the linear nature ofV-I curve indicates that the pores approach towards neutralized state and on further concentration, N/40, the pores become fully neutralized, consequently the rectifier behaviour of pores has been omitted.The gas permeability of hydrogen and carbon dioxide of this membrane was measured with increasing etching time. The permeability was measured from both the sides. Permeability at the front was larger than the permeability at the back which shows asymmetric behaviour of membranes.

Effect of temperature and α-irradiation on gas permeability for polymeric membrane

In the present study the polyethersulphone (PES) membranes of thickness (35 ±2) μm were prepared by solution cast method. The permeability of these membranes was calculated by varying the temperature and by irradiation of α ions. For the variation of temperature, the gas permeation cell was dipped in a constant temperature water bath in the temperature range from 303–373 K, which is well below the glass transition temperature (498 K). The permeability of H2 and CO2 increased with increasing temperature. The PES membrane was exposed by a-source (95Am241) of strength (1 μ Ci) in vacuum of the order of 10−6 torr, with fluence 2.7 × 107 ions/cm2. The permeability of H2 and CO2 has been observed for irradiated membrane with increasing etching time. The permeability increases with increasing etching time for both gases. There was a sudden change in permeability for both the gases when observed at 18 min etching. At this stage the tracks are visible with optical instrument, which confirms that the pores are generated. Most of pores seen in the micrograph are circular cross-section ones.

Characterization of track etched membranes by gas permeation

The application of polymeric membrane in combination with the metallic films can be used for the gas purification; in particular, the hydrogen where the molecular size is very small. The affinity of hydrogen to certain metals assists the flow of hydrogen, however, restricts the permeation of other gases. However, the flow rate is very small in the dense membranes. Attempts have been made to etch the nuclear tracks of the polymeric membranes in a very controlled way to achieve the conical etched tracks to meet the vertex. This has been characterized by gas permeation measurements.

Irradiation of large area Mylar membrane and characterization of nuclear track filter

Ion irradiation of Si8+ ion beam of 100 MeV was scattered by a gold foil on a Mylar membrane of 25 Μm thickness in the form of film roll (width, 12.5 cm and length, 400 cm) at the Nuclear Science Centre, New Delhi. The characterization of etched nuclear tracks was carried out by gas permeation measurements. The samples cut from the film roll of required size for permeability measurements were etched in a controlled manner in a constant temperature bath of 6N NaOH solution. The opening of the conical etched tracks was characterized by hydrogen gas permeation.