The H mass density of the body-centred cubic Ti35Cr65−xVx alloys (x = 18, 22) was investigated as a function of pressure at various temperatures by tracing P–C isotherms from which the formation enthalpy of the γ hydride was derived (ΔH = −39kJ/mol for the Ti35Cr43V22 alloy and ΔH = −35kJ/mol for the Ti35Cr47V18 alloy). Internal friction measurements had revealed the existence of a broad H Snoek-type relaxation at around 150K (f ≈ 1kHz), which was used to glean information on H mobility. Combined Snoek and high-temperature absorption data showed that the H diffusion was described by:

Ti35Cr47V18:     D(m2/s) = 4 x 10−7exp[-0.32(eV)/kT]

Ti35Cr43V22:     D(m2/s) = 2 x 10−7exp[-0.34(eV)/kT]

The X-ray diffraction patterns confirmed a face-centred cubic lattice structure for the hydride while differential scanning calorimetry and thermal desorption spectroscopy data exhibited peaks on the temperature scale which could be attributed to structural transitions of the hydrides. The occurrence of these transitions was accounted for in terms of a previously proposed atomistic model.

Hydrogen-Storage Capacities and H Diffusion in BCC TiVCr Alloys. G.Mazzolai, B.Coluzzi, A.Biscarini, F.M.Mazzolai, A.Tuissi, F.Agresti, S.L.Russo, A.Maddalena, P.Palade, G.Principi: Journal of Alloys and Compounds, 2008, 466[1-2], 133-9