The diffusion of H in 5N-purity polycrystalline material was investigated by using isothermal and constant heating-rate desorption techniques. The latter technique was used to clarify the effects of microstructural trap states upon the apparent diffusivity. The isothermal desorption of H from annealed uniformly-charged cylindrical specimens was controlled by bulk diffusion. The data at 30 to 600C obeyed:

D (cm2/s) = 1.75 x 10-4 exp[-3.9(kcal/mol)/RT]

The constant heating-rate desorption spectra revealed 3 distinct trapping states, with desorption energies of 15.3, 43.5 and 84.8kJ/mol. These trapping states were associated with interstitial lattice sites, dislocations and vacancies, respectively.

G.A.Young, J.R.Scully: Acta Materialia, 1998, 46[18], 6337-49