Ti/Zr-based quasicrystals - formation, structure and hydrogen storage properties

Most common in Al-3d transition metal(TM) alloys, icosahedral quasicrystals (i-phase) are also found frequently in Ti/Zr-TM alloys. The Ti-TM-Si-O quasicrystals are metastable, produced only by rapid quenching, and are extremely disordered. In contrast, Ti-Zr-Ni i-phases are well ordered and stable, produced by relatively low temperature annealing, nearly 300°C below the melting temperature. Important for both basic and practical reasons, Ti/Zr-based quasicrystals can absorb significant quantities of hydrogen, up to two hydrogen atoms for each metal atom. The formation and structures of these quasicrystals and closely related complex crystal phases are discussed. The hydrogenation properties of these quasicrystals are presented and shown to be competitive with materials in current use for hydrogen storage and battery applications. Results from recent studies using hydrogen as a probe of the local structure of the quasicrystal and crystal approximant are presented.