STRAIN GRADIENT EFFECTS ON HYDROGEN PERMEATION THROUGH HYDRIDED METALS

Analyses of experimentally determined rates of hydrogen permeation through bulk lattice structures of membranes have commonly been broadly discussed in terms of Fickian principles. More recent studies of hydrogen permeation through membranes have indicated circumstances where there are increased needs of appreciation of additional concurrent influences of the expansion effects of the hydrogen interstitials. Evidence for this extended viewpoint has been provided by results of studies with suitably surface-activated membranes of palladium and certain palladium/silver and palladium/platinum alloys. These studies have revealed indications in the form of Uphill Effects and associated reductions of steady stage permeation rates which have indicated that the effects of interstitial hydrogen lattice expansions have been to produce components of hydrogen permeation flux in opposition to concentration gradient flux components.