Measurements of the Hydrogen Absorption Pressurecomposition Isotherms IN Ti/Zr-Based Quasicrystals

The first hydrogen absorption pressure-composition isotherms (p-c-T) were measured in quasicrystalline Ti 45 Zr 38 Ni 17 . No evidence for a pressure plateau was found, indicating a distribution of energies for the hydrogen in interstitial sites. Fits to the p-c-T data confirmed this, giving energy peaks at -0.19 eV with a full width at half maximum (half-width) of 0.06 eV, and at -0.09 eV with a half-width of 0.08 eV. This is in contrast with the broad site energy distribution that is characteristic of a metallic glass. in agreement, fits to data taken from amorphous Ti 45 Zr 27 Ni 20 Si 8 gave a single broad energy distribution at -0.10 eV with a half-width of 0.35 eV. Based on the weighted averages of the site energies for the pure components, the energies assigned to the tetrahedral sites in the Ti 44 Zr 40 Ni 16 1/1 approximant phase are in qualitative agreement with the measured data for the quasicrystal, supporting a local structural similarity between these two phases. Almost all of the absorbed hydrogen can be desorbed at 650°C in one hour by pumping, without transforming the quasicrystal phase and without powdering the rapidly-quenched samples.