INFLUENCE OF THE SURFACE CONDITIONS ON PERMEATION IN THE DEUTERIUM-MANET SYSTEM

The condition of the surfaces is of crucial importance for the deuteri um permeation through materials. In this work a study of the surface c onstants for the adsorption (sigma k(1)) and release (sigma k(2)) of d euterium under different surface conditions on the martensitic steel D IN 1.4914 (MANET) has been carried out. The growth of an oxide surface layer (Cr2O3) of about 25-30 nm in a MANET sample, heat treated in an oxidizing environment, compared to the bare MANET that have a 'natura l' oxide of about 5 nm has provoked a reduction of both the permeation rate and the recombination coefficient (about 3 orders of magnitude). In addition, the permeation governing process has changed from diffus ion-limited to surface-limited. The measurements of the permeation rat e of deuterium were performed by a gas-phase permeation technique over the temperature range 574-746 K and for deuterium driving pressures i n the range from 3 to 10(5) Pa.