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 LaNi_4.65 compositional alloys. When x in LaNi_5-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≥Si>Mn>Co. The phases formed and protium absorption properties of La-rich LaNi_4.5M_0.2 melt-spun alloys are studied. It was found that LaNi_4.5M_0.2 alloys had better protium absorption properties such as easier activation than the LaNi_4.65 binary alloy and as good hydrogen storage capacity as that of homogenized LaNi₅.