Pressure-composition-temperature curves and structure stability induced by hydrogen in TiZrNi quasicrystals

초록

To evaluate the potential applications of Ti-based quasicrystals as hydrogen storage materials, metastable Ti53-xZr27Ni20Pdx (x = 0, 2, 4, 6) quasicrystals were prepared by a rapid quenching method and equilibrium vapor pressures for hydrogen were measured. Pressure-composition-temperature curves measured in Pd-added TiZrNi quasicrystals revealed a significantly increased equilibrium vapor pressure for hydrogen with increasing Pd concentration, while hydrogen loading capacity decreased. After hydrogen absorption, no hydride phase was found for samples made with less than x = 4. The main peaks shifted to the lower angle of 2 in X-ray diffraction patterns, demonstrating that the quasi-lattice constants increased from 5.13 to 5.38 angstrom after hydrogenation. The quasi-lattice constants linearly expanded with increasing absorption amount of hydrogen. Interestingly, analyzing the full width at half maximum values of the main peaks in the X-ray diffraction patterns showed that the coherence lengths of the quasicrystals significantly increased from 120 to 240 angstrom after hydrogenation, presumably due to kinetic rather than thermal factors.

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