GROSKY EFFECT CONSEQUENCES OF LATTICE EXPANSIVE STRAIN GRADIENTS IN DIFFUSION OF HYDROGEN IN METALS

Among transition metals forming hydrides of a metallic type, palladium and certain palladium alloys have been preferentially utilised as mem branes for hydrogen purification - in view of their relative resistanc es to embrittlement, high solubilities for hydrogen, as derivable from quite comprehensive p - c (n) - T relationships, and accompanying hig h values of hydrogen diffusion coefficients. As fairly recent points o f interest, uphill effects corresponding to temporary localised hydrog en permeation against overall hydrogen concentration gradients have be en observed in studies with membranes of Pd, Pd77Ag23 and Pd81Pt19. Th ese uphill effects have been associated with hydrogen migrations induc ed by Gorsky Effects resulting from developments of gradients of latti ce strain produced by the expansive effects of the permeating hydrogen interstitials. An outline is presented of experimental methods and re sults of measurements together with some theoretical and technological correlations.