The tracer diffusion of H in body-centered cubic TiHx phases, with x = 0.57 or 0.70, was measured at temperatures ranging from 620 to 830K by using the nuclear magnetic resonance pulsed field gradient spin-echo technique. It was found that the results could be described by the expressions:

x = 0.57:     D (cm2/s) = 7.8 x 10-4 exp[-0.155(eV/atom)/kT]

x = 0.70:     D (cm2/s) = 6.3 x 10-4 exp[-0.147(eV/atom)/kT]

The diffusion parameters were compared with those for other body-centered cubic transition metal hydrides. All were found to have large H-diffusion coefficients, which decreased as the H concentration was increased. Although an increase in H concentration caused an increase in activation energy over most of the concentration range, the maximum value of the activation energy did not exceed 0.190eV/atom. In contrast, it was noted that most face-centered cubic transition metal hydrides had activation energies which were higher, by a factor of 3 or more, and diffusion coefficients which were smaller by 2 or more orders of magnitude.

Tracer Diffusion Coefficients of Hydrogen at High Concentration in BCC Host Metal Lattices. E.H.Sevilla, R.M.Cotts: Journal of the Less-Common Metals, 1987, 129, 223-8

Table 169

Diffusion of H in Ti and Ti-V Alloys