The H atoms in γ-phase occupied tetrahedral interstitial sites and formed a simple-cubic sub-lattice in the face-centered cubic Ti host. In order to determine to which nearest-neighbor site the diffusing H atoms jumped during their migration through the lattice, nuclear magnetic resonance measurements of the diffusion coefficient (450 to 550C) and of the proton-spin longitudinal relaxation time (80 to 550C) were carried out in TiH1.55 and TiH1.71. The respective diffusion coefficients at 500C were 3.6 x 10-7 and 1.75 x 10-7 cm2/s. These values were combined with previously determined activation energies to yield the relationships:

TiH1.55:      D (cm2/s) = 9.7 x 10-4 exp[-6100/T]

TiH1.71:     D (cm2/s) = 6.1 x 10-4 exp[-6300/T]

The ratio of the pre-exponential factors was similar to that of the vacancy concentrations. It was concluded that H motion occurred predominantly via a first-nearest neighbor jump mechanism. It was not possible to distinguish between the 2 possible jump paths.

Determination of the Hydrogen Diffusion Mechanism in γ-Titanium Hydride using Nuclear Magnetic Resonance. L.D.Bustard, R.M.Cotts, E.F.W.Seymour: Physical Review B, 1980, 22[1], 12-20

Table 168

H Diffusion in Metal Hydrides