Synthesis of Ti-Zr-Ni amorphous and quasicrystal powders by mechanical alloying, and their electrochemical properties

Mechanical alloying of Ti(45)Zr(38-x)Ni(17+x) and Ti(45-x)Zr(38)Ni(17+x) (0 <= x <= 8) elemental powders produced an amorphous phase, but subsequent annealing converted the amorphous phase into an icosahedral quasicrystal phase, along with a Ti(2)Ni-type phase. The discharge capacities, measured in a three-electrode cell at room temperature for both the amorphous and quasicrystal electrodes, increased with increasing Ni substitution for Zr or Ti. The highest discharge capacities, which were about 60 mAh/g for the amorphous electrode and 100 mAh/g for the quasicrystal electrode, were obtained from (Ti(45)Zr(30)Ni(25)) after substitution of Ni for Zr. For the Ti(45)Zr(30)Ni(25) composition, the discharge performance of the quasicrystal electrode was stable over charge/discharge cycling, but that of the amorphous electrode gradually decreased with cycling. The structure of the quasicrystal phase in the electrodes was stable, even after 15 charge/discharge cycles, but the amorphous phase converted to a (Ti, Zr)H(2) f.c.c. hydride.