STABLE TI-BASED QUASI-CRYSTAL OFFERS PROSPECT FOR IMPROVED HYDROGEN STORAGE

The desorption of hydrogen from a novel material, a T45Zr38Ni17-H quas icrystal, was observed using high-temperature powder x-ray diffraction , demonstrating the potential utility of Ti-based quasicrystals in pla ce of crystalline or amorphous hydrides for hydrogen storage applicati ons. The maximum observed change in hydrogen concentration was from 61 at. %, corresponding to a hydrogen-to-metal ratio (H/M) of 1.54, at 9 1 degrees C to less than 2.5 at, % (H/M=0.025) at 620 degrees C. The o nset temperature of desorption is below 350 degrees C. Surface oxidati on was found to promote the formation of crystalline hydride phases. H ighly oxidized samples transformed to a mixture of the C14 Laves and C 15 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 th e stability of the Ti45Zr38Ni17 quasicrystal at very low hydrogen conc entrations, and temperatures as high as 661 degrees C. This is the fir st evidence for a stable Ti-based quasicrystal and for reversible hydr ogen storage in a quasicrystalline phase. (C) 1996 American Institute of Physics.