The cycle stabilities of the as-cast and quenched La2Mg(Ni0.85Co0.15)9Mx (M = B, Cr, Ti; x = 0, 0.1) hydrogen storage alloys

The PuNi3-type La2Mg (Ni0.85Co0.15)9Mx (M = B, Cr, Ti; x = 0, 0.1) hydrogen storage electrode alloys were prepared by casting and rapid quenching. The electrochemical cycle stabilities and microstructures of the as-cast and quenched alloys were measured and determined. The effects of B, Cr, Ti and rapid quenching on the microstructures and electrochemical properties of the alloys were investigated in detail. The obtained results show that the as-cast alloys are composed of the (La, Mg)Ni3 phase (PuNi3-type) and the LaNi5 phase as well as a small amount of the LaNi2 phase. A trace of the Ni2B phase exists in the as-cast alloy containing boron, and the Ni2B phase in the alloy nearly disappears after rapid quenching. The relative amount of each phase in the alloys changes with varying quenching rate. The addition of B, Cr enhances the cycle stabilities of the alloys, whereas the addition of Ti reduces the cycle stabilities of the alloys. Rapid quenching increases the cycle stabilities of the alloys, the cycle stabilities of the alloys increase monotonously with the increase of the quenching rate.