Stable Ti-based quasicrystal offers prospect for improved hydrogen storage

The desorption of hydrogen from a novel material, a Ti₄₅Zr₃₈Ni₁₇-H quasicrystal, was observed using high-temperature powder x-ray diffraction, demonstrating the potential utility of Ti-based quasicrystals in place of crystalline or amorphous hydrides for hydrogen storage applications. The maximum observed change in hydrogen concentration was from 61 at. %, corresponding to a hydrogen-to-metal ratio (H/M) of 1.54, at 91°C to less than 2.5 at. % (H/M=0.025) at 620°C. The onset temperature of desorption is below 350°C. Surface oxidation was found to promote the formation of crystalline hydride phases. Highly oxidized samples transformed to a mixture of the C14 Laves and C15 Laves crystalline hydrides, and the Ti₂Ni phase. When the oxidation was less severe, a reversible transformation between the quasicrystal and crystalline hydride phases was clearly observed, demonstrating the stability of the Ti₄₅Zr₃₈Ni₁₇ quasicrystal at very low hydrogen concentrations, and temperatures as high as 661°C. This is the first evidence for a stable Ti-based quasicrystal and for reversible hydrogen storage in a quasicrystalline phase.