Hydrogen Absorption and Structural Analysis of TiZrNiV Quasicrystals

Abstract

Ti-based quasicrystals are known to store a high capacity of hydrogen exceeding the density of liquid hydrogen. Because TiZrNi quasicrystals contain a large number of tetrahedral sites formed with Ti and Zr atoms that are chemically favorable to hydrogen, these materials retain strong advantages for hydrogen storage applications in structurally and chemically. In fact, TiZrNi quasicrystals are known to absorb hydrogen maximum of the hydrogen to host metal ratio (H/M) value of near 2.0. The critical disadvantage, however, is that the equilibrium vapor pressure of hydrogen is very low (less than 1 Torr). To overcome this engineering drawback, we added a small amount of vanadium (V) in Ti53-XZr27Ni20Vx, alloys (where x = 0 to 15) and rapidly quenched the molten ingots to form quasicrystals, and investigated the effects of V in terms of changes of structure, the H/M values, and an equilibrium vapor pressure of hydrogen. As the results, an equilibrium vapor pressure significantly increased from 0.84 to 2.16 Torr while the maximum H/M value decreased from 1.32 to 1.11 as increasing x = 0 to 8. After hydrogenation, the main peaks shifted evenly to the lower angle of 2 theta in X-ray diffraction patterns with uniform expansion of the quasilattice constants which demonstrates that hydrogen atoms homogeneously diffused into the samples. A Laves phase starts to form at x = 13 and the samples completely transformed to the phase at x = 15 suggesting the similarity between the quasicrystal and the Laves phase.