Crystal structure and protium absorption properties of La-rich La(Ni, M)x (x=3-4.7) (M=Al, Co, Mn, Si) melt-spun ribbons

The present study describes the rapid quenching effects on the solid-solution range of La(Ni, M)(x) (x=3-4.7) (M=Al, Co, Mn, Si) alloys prepared by melt-spinning and discusses their protium (hydrogen atom) absorption properties. It is found that the single phase with CaCu5 crystal structure extends to LaNi4.65 compositional alloys. When x in LaNi5-x becomes smaller, the alloy acquires better protium absorption properties including easier activation, better flatness of plateau region and a good hydrogen storage capacity comparable to those of LaNi5 homogenized sample. On adopting a melt-spinning technique it is easy to form single phase of CaCu5 type-structure for La-rich non-stoichiometric La-Ni-M alloys such as La(Ni, M)(x) (x=3-4.7) (M=Al, Mn, Si) alloys. The readiness of forming a single phase CaCu5 type-structure in melt-spun La-Ni-M alloys is in order of Al greater than or equal to Si>Mn>Co. The phases formed and protium absorption properties of La-rich LaNi4.5M0.2 melt-spun alloys are studied. It was found that LaNi4.5M0.2 alloys had better protium absorption properties such as easier activation than the LaNi4.65 binary alloy and as good hydrogen storage capacity as that of homogenized LaNi3. (C) 1999 Elsevier Science S.A. All rights reserved.