The Gorsky-effect technique was used to study the diffusion of H in Nb, and the effect of N upon this process. In the case of out-gassed samples (N concentration below 0.01%), the H diffusivity could be described by the sum of 2 exponentials; one of which predominated at 0 to 300C while the other predominated at -50 to-100C:
D (cm2/s) = 5.2 x 10-4 exp[-0.125(eV)/kT] + 5 x 10-5 exp[-0.062(eV)/kT]
The presence of up to 0.55%N decreased the H diffusivity, and it was suggested that N in Nb suppressed the fast low-temperature diffusion process.
Influence of Nitrogen on the Diffusion Coefficient of Hydrogen in Niobium. W.Muenzing, J.Völkl, H.Wipf, G.Alefeld: Scripta Metallurgica, 1974, 8[11], 1327-30
Table 94
Parameters for H Diffusion in NbHx
x | Do (cm2/s) | E (eV) |
0.10 | 3.2 x 10-4 | 0.115 |
0.33 | 4.9 x 10-4 | 0.142 |
0.55 | 1.0 x 10-3 | 0.168 |
0.70 | 7.2 x 10-4 | 0.174 |
0.89 | 5.6 x 10-4 | 0.164 |