Study of the hydrogen-induced amorphization in the LaNi2.28 alloy

Abstract

To understand the fundamental reason leading to the poor stability of LaNi_2.28 hydrogen storage alloy, the cycling behavior of LaNi_2.28 alloy under hydrogen has been investigated. The present study describes the hydrogen-induced amorphization (HIA) of LaNi_2.28 alloy. The phase composition, microstructure and morphology of the phases are observed and analyzed using X-ray diffraction and scanning electron microscopy. The crystal structure and chemical composition of the amorphized alloy show that HIA is found in the sample at different cycles of the hydrogenation process. During the first hydrogenation cycle, the degree of HIA is indeclinable with the increased cycle. In addition, the formation processes of amorphous alloys, the occurrence of HIA and the relationship between the structure of the hydrogen-induced amorphous alloy and the stability of LaNi_2.28 are given. The conclusions can be summarized as follows: 2LaNi_2.28 + H₂ → LaNi_2.28H_x (amorphous) + LaNi₅H_y + LaH₂, and amorphous LaNi_2.28H_x and LaNi₅H_y can desorb 50% hydrogen of the absorption capacity of LaNi_2.28, and the absorption–desorption capacity is stable after the first cycle.