The short-range and long-range diffusion of H was studied by using magnetic after-effect and thermal desorption spectroscopic techniques. It was found that the substitution of Ga for Fe greatly reduced up-take and diffusion of H. The Fe17Sm2 exhibited a H-induced magnetic after-effect relaxation maximum at 190K, with a mean activation enthalpy of 0.48eV and a pre-exponential factor of 5 x 10-12s. In Fe28Ga3, the maximum was replaced by a double maximum at 200 and 250K. These peaks corresponded to activation enthalpies of 0.52 and 0.64eV, with a pre-exponential factor of 2 x 10-12s. The maxima were attributed to short-range H diffusion. Thermal desorption spectroscopic measurements at 291 to 515K indicated activation enthalpies of 0.59 and 0.75eV, respectively. The results were explained in terms of differing interstitial sites for H.

Hydrogen Diffusion in Sm2Fe17 and Sm2Fe14Ga3 Compounds. N.Mommer, J.Van Lier, M.Hirscher, H.Kronmuller: Journal of Alloys and Compounds, 1998, 270[1-2], 58-62

Figure 12

Diffusivity of H in Amorphous Alloys

(open squares: FeP13C7Cr10, filled squares: FeP13C7)

Table 81

Parameters for the Permeation of H in α-Phase Fe-V