The diffusion behavior was studied by performing permeation measurements on fine-grained foils which had been produced by electrodeposition. The permeation data were analyzed by using a modified version of the Hart equation. The grain boundary diffusivity at 30C was at least 3 x 10-12m2/s. This was a factor of 40 times greater than the lattice diffusivity. However, the analysis indicated that a 1000-fold increase might not be unreasonable. The activation energy for grain boundary diffusion was 30kJ/mol. This was approximately equal to 75% of the activation energy for H diffusion in Ni monocrystals.
Grain Boundary Diffusion of Hydrogen in Nickel. T.M.Harris, R.M.Latanision: Metallurgical Transactions A, 1991, 22[2], 351-5
Table 104
Grain Boundary Diffusion of H in Ni
Material | Temperature (K) | D (cm2/s) |
small (25 grains | 298 | 7.7 x 10-10 |
large (150 grains | 298 | 4.6 x 10-10 |
98% cold-worked | 298 | 2.2 x 10-10 |
small (25 grains | 333 | 3.1 x 10-9 |
large (150 grains | 333 | 1.9 x 10-9 |
98% cold-worked | 333 | 1.1 x 10-9 |
small (25 grains | 373 | 1.3 x 10-8 |
large (150 grains | 373 | 1.2 x 10-8 |
98% cold-worked | 373 | 4.6 x 10-9 |