Analysis of equilibrium vapor pressure of hydrogen in Pd doped Ti-based quasicrystal

Abstract

The metastable Ti53-xZr27Ni20Pdx and Ti53Zr27-xNi20Pdx (x=0, 2, 4, 6, 8) quasicrystals were prepared by using a rapidly quenching method, and their technical potential for hydrogen storage application was evaluated by measuring an equilibrium vapor pressure at evaluated temperature. The quasi-lattice constant decreased from 5.12 to 5.06 A when Zr were replaced by 8 at. % of Pd. The coherence length decreased from 100 to 90 A when Ti were replaced by 8 at. % of Pd, and it decreased from to 80 A when Zr were replaced by 8 at. % of Pd. These results demonstrated that Pd destabilizes the quasicrystal structure. To absorb hydrogen, a series of pressure-composition-temperature (P-c-T) curves for hydrogen was measured from Ti53Zr27Ni20 quasicrystals at 200, 250 and 300 C. The maximum value of hydrogen to host metal atom ratio (H/M) was 1.6 at 200 C. However the equilibrium vapor pressure was too low (remains lower than 0.1 Torr). To increase the equilibrium vapor pressure of Ti-Zr-Ni quasicrystals, Pd was added with a few atomic concentrations. As results of P-c-T curves of Ti53-xZr27Ni20Pdx and Ti53Zr27-xNi20Pdx (where x=0 to 8) at 300 C, the equilibrium vapor pressure increased from 0.05 to 0.3 Torr. After the hydrogen absorption, the lattice constants increased from 5.12 to 5.36 A and the coherence lengths increased from 100 to 240 A for Ti53Zr27Ni20 quasicrystals. No hint of the hydride phase was found after hydrogen absorption. An analysis of the differential scanning calorimeter (DSC) results revealed that the absorbed hydrogen atoms desorbed from 140 to 465 C.