The migration of H was investigated, by means of quasi-elastic neutron scattering, at temperatures of 165 to 300K. A transition from a high-temperature activation energy of 0.106eV, to a low-temperature activation energy of 0.068eV, was observed in this region. The value of the low-temperature activation energy was confirmed by neutron scattering experiments. At temperatures below 250K, the results of scattering experiments yielded the relationship:
D (cm2/s) = 1.2 x 10-4 exp[-0.069(eV)/kT]
Investigation of the Anomalous Temperature Dependence of the Self-Diffusion Constant of Hydrogen in Niobium by Quasielastic Neutron Scattering. D.Richter, B.Alefeld, A.Heidemann, N.Wakabayashi: Journal of Physics F, 1977, 7[4], 569-74
Table 90
Diffusivity of H into Polycrystallinea Nb
Temperature (C) | D (cm2/s) |
200 | 4.1 x 10-7 |
250 | 1.1 x 10-6 |
300 | 2.2 x 10-6 |
600 | 5.9 x 10-5 |
650 | 7.2 x 10-5 |
700 | 9.2 x 10-5 |
a: grain-size = 0.26mm