Formation of Metastable Co-Ni Alloy Nanowires in Electrodeposition.

The effect of potential on the crystal structure and composition of Co-Ni alloy nanowires is studied by XRD, FE-SEM and EDX. The deposited alloy nanowires are metastable fcc phase Co84.45Ni15.55 at -3.0 V and stable hcp phase Co80.75Ni19.25 at -1.6 V. The formation of the metastable fcc alloy nanowires can be attributed to smaller critical clusters formed at the high potential, as the smaller critical clusters favor fcc structure because of the significant surface energy effect. The content of Co inside nanowires increases with increasing potential. This can be understood by the polarization curves of depositing Co and Ni nanowires, which show that the current density ratio of Ni to Co at -1.6 V (0.88) is higher than that at -3.0 V (0.73).