Measurements of permeation of hydrogen isotopes through α-iron by pressure modulation and ion bombarding

Permeation response of hydrogen and deuterium through α-iron under the condition of pressure modulation was measured to determine the diffusion coefficient which contained no surface effects. The diffusion coefficients of hydrogen isotopes are obtained between 500 and 1000 K. Permeation under hydrogen ion bombardment was also studied to extend the temperature range of diffusion coefficient measurements. The ratio of the diffusion coefficients of hydrogen isotopes (DH/DD) depends on the temperature; the value of the ratio approaches unity with increasing temperature. This behavior differs from that of common fcc metals in which the value of the ratio approaches √2 with increasing temperature. The isotope effect of hydrogen diffusivity in α-iron can not be explained by the classical rate theory, and the quantum-mechanical correction is needed. (author)