Hydrogen and deuterium mass transfer and separation during hydriding-dehydriding of palladium studied by the NERD method

The neutron induced elastic recoil detection (NERD) technique with monochromatic 14 MeV neutrons was applied to a hydrogen and deuterium concentration depth profile study during the hydriding-dehydriding process in palladium placed as a membrane or a membrane electrode within a gas or an electrolytic cell, respectively. It was found that hydrogen diffusion may be accompanied by a distinct alpha-beta interphase boundary movement to the membrane exit whereupon a sharp growth of permeation gas flux takes place. An anomalous behaviour of gas Aux was also revealed at the point of opposite beta-alpha phase transition of the Pd-D system induced by the membrane heating. Dehydriding of the Pd-membrane as well as both hydriding and dehydriding of a membrane made from a Pd-Ag alloy do not reveal any concentration gradients in the membrane bulk. A much higher H/D isotope separation factor was found in the case of Pd membrane loading with an isotope mixture, when using electrochemical hydriding compared with that observed from gas surroundings. Copyright (C) 1996 International Association for Hydrogen Energy