THE MODELING OF HYDROGEN TRANSPORT IN METALS AND ITS APPLICATION TO THE EVALUATION OF HYDROGEN PERMEATION AND INVENTORIES

Hydrogen transport behavior in metals is discussed with a conventional transport model which takes into account diffusion in the bulk and hydrogen recombination at surfaces as principal rate-determining steps. The present model will allow one to evaluate the permeation rate and bulk inventory of hydrogen isotopes at steady state. But, with the application of an appropriate surface-bulk potential energy diagram, the model can be extended to evaluate surface inventories as well. When the recombination process is the rate-determining step, the state of the surface, especially the presence of impurities, plays an important role. It is shown how a change of surface composition due to ion implantation is reflected in an anomalous transient transport behavior known as the "permeation spike".