Electrodeposition of cobalt-nickel material libraries

Cobalt-nickel material libraries were electrodeposited in two different types of modified Hull cells. Chloride and sulphate based electrolyte baths, the influence of the overall applied current density, cobalt concentration in the bath and addition of citrate as complexing agent were studied. The experiments suggested a higher cobalt content in the deposits for relatively low overall applied current densities and higher Co2+ concentrations in the electrolyte bath. For the vast majority of the cobalt-nickel material libraries, a transition from anomalous to normal co-deposition behaviour was found as a result of the current density gradient establishing in the Hull cell during electroplating. Further examination was carried out by scanning electron microscopy (SEM), revealing a changing surface morphology within a material library depending on the cobalt content and the current density. X-ray diffraction (XRD) showed separate and mixed face-centred cubic (fcc) and hexagonal close-packed (hcp) crystallographic structures. Cobalt-nickel composition gradient obtained from two different Hull cell modifications including SEM micrographs of the material library deposited in the lying Hull cell.