The hydrogen solubility and the hydrogen permeability of pure niobium at high temperatures were investigated in order to analyze the hydrogen diffusion coefficient during hydrogen permeation. It was shown that the hydrogen dissolution reaction into niobium metal did not obey Sieverts' law at practical hydrogen permeation pressures. The hydrogen diffusion coefficient during hydrogen permeation through pure niobium at high temperatures was evaluated from the linear relationship between the normalized hydrogen flux and the hydrogen concentration difference. It was found that the hydrogen diffusion coefficient under the practical condition was much lower than the reported values measured for dilute hydrogen solid solutions. Surprisingly, the hydrogen diffusion was found to be faster in Pd–Ag alloy with the face-centred cubic crystal structure, than in pure niobium with the body-centred cubic crystal structure at 773K during the hydrogen permeation.

Analysis of Hydrogen Diffusion Coefficient during Hydrogen Permeation through Pure Niobium. G.X.Zhang, H.Yukawa, N.Watanabe, Y.Saito, H.Fukaya, M.Morinaga, T.Nambu, Y.Matsumoto: International Journal of Hydrogen Energy, 2008, 33[16], 4419-23