Diffusion of Hydrogen and Deuterium in High Purity Iron between 222 and 322 K

Abstract

Diffusion coefficients of hydrogen and deuterium in high purity iron were measured by an electrochemical alternating current method at temperatures between 222 and 322 K . In this method, the diffusion coefficient can be evaluated from the frequency response of the phase difference between an anodic permeation current and a cathodic charging current by eliminating the surface effect from the permeation process. The diffusion coefficient of hydrogen in iron is proposed to be DH(m2⁄s)=4.90×10−8exp(−4200(J⁄mol)⁄RT). The activation energies of diffusion for the two hydrogen isotopes were equal at 4200 J/mol. And the isotope ratio of pre-exponential factors, D0H⁄D0D, was determined to be 1.24, which was a little smaller than the classical ratio 1.41. At low temperatures, the trapping effect by lattice imperfections was observed, and it was more remarkable for deuterium than for hydrogen.