The diffusion of H was measured, at temperatures of between 270 and 365K, by using the alternating pulsed field-gradient nuclear magnetic resonance technique. The diffusivity of H in LaNi4.8Sn0.2H5.8 was characterized by a higher mobility and a lower activation enthalpy than those found for LaNi5.0H6.0. The diffusivities at 300K were 9.2 x 10-12 and 4.6 x 10-12m2/s in LaNi4.8Sn0.2H5.8 and LaNi5.0H6.0, respectively. The overall results could be described by the expressions:

LaNi5.0H6.0:      D (m2/s) = 3.4 x 10-7 exp[-0.29(eV/kT]

LaNi4.8Sn0.2H5.8:      D (m2/s) = 3.6 x 10-8 exp[-0.22(eV/kT]

The nuclear magnetic resonance spin-lattice relaxation rates were measured, using the same samples, at temperatures ranging from 100 to 350K. The data were found to be consistent with regard to the activation enthalpies for long-range diffusion in both alloys. The hopping rates corresponded to long-range diffusion, and both sets of measurements indicate a more rapid motion in the Sn-containing material.

Nuclear Magnetic Resonance Studies of Hydrogen Diffusion in LaNi5.0H6.0 and LaNi4.8Sn0.2H5.8. G.Majer, U.Kaess, R.C.Bowman: Physical Review B, 1998, 57[21], 13599-603

Figure 21

Diffusivity of H in Ni5La

Figure 22

Diffusivity of H in Ni60Nb40

(open squares: cold-rolled, filled squares: as-quenched)