Ion-driven permeation was used to determine the diffusivity, rather than gaseous or electrochemical charging. The steady-state permeation rate and the diffusion coefficient tended to decrease with increasing fluence, because of changes in the surface or sub-surface regions. It was found that the results could be described by the expression:

D (m2/s) = 3.9 x 10-7 exp[-38.6(kJ/mol)/RT]

at temperatures of between 500 and 1100K.

Y.Furuyama, T.Tanabe, S.Imoto: Journal of the Japan Institute of Metals, 1986, 50[8], 688-94

Table 153

Parameters for H Isotope Diffusion in Ni Single Crystals at 670 to 1270K