Hydrogenation of titanium-based quasicrystals.

Abstract

Measurements of hydrogen loading and unloading in a quasicrystal are reported. The icosahedral phase (i phase) in a Ti-Zr-Ni alloy demonstrates hydrogen absorption from the gas phase at a temperature of 260 \ifmmode^\circ\else\textdegree\fi{}C and a pressure of 40 atmospheres. The incorporation of hydrogen causes the quasilattice to expand, with an increase in quasilattice constant of almost 7%, from ${\mathit{a}}_{\mathit{i}}$=5.18 to 5.52 \AA{}. Similar abilities for storing hydrogen are found in high-order crystalline approximant and amorphous phases of like composition. Of the phases examined, the i phase absorbs the most hydrogen, giving a hydrogen atom to metal atom ratio ([H]/[M]) of 1.6. Initial studies indicate that hydrogen desorption is hindered by phase transitions to stable hydride phases. Hydrogen loading at lower temperatures with higher ${\mathrm{H}}_{2}$ pressures favors higher [H]/[M] ratios for the i phase and the crystal approximant, and also minimizes the growth of more stable crystalline hydride phases.