Effect of Cr and Co additives on microstructure and electrochemical performance of Zr(NiVMn)(2)M-0.1 alloys

Zr-based Laves alloys of Zr(NiVMn)(2)M-0.1 (M=Cr or Co) were prepared by an are melting process. The effect of the Cr or Co additive on the microstruc ture and electrochemical performance of the Zr(NiVMn)(2)M-0.1 Laves phase h ydride electrode alloys was investigated. Microstructure observation showed that the morphology of the Zr(NiVMn)(2)Cr-0.1 alloy was dendritic, while t he morphology of the Zr(NiVMn)(2)Co-0.1 alloy was of equiaxial grains. The XRD results showed that both alloys consisted of the predominant C14 and C1 5 Laves phases, and the minor Zr7Ni10, Zr9Ni11 non-laves phases. There is n o big difference in the amount of Laves phase in these two alloys as they w ere prepared under the same solidification conditions. The effect of the Cr or Co additive on phase composition and phase abundance of the obtained Zr (NiVMn)(2)M-0.1 alloys was quite similar. The electrochemical properties of the Zr(NiVMn)(2)M-0.1 alloys were dependent on the microstructures obtaine d. The electrode prepared from the alloy with equiaxial grain showed less a ctivation cycles, higher discharge capacity and poorer cycle stability than those prepared from the alloy with dendrite structure. The microstructure- dependent electrochemical properties are also discussed. (C) 2000 Elsevier Science S.A. All rights reserved.