Electrodeposition of cobalt–nickel material libraries

Abstract

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 Co 2þ 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.

Cobalt–nickel material libraries obtained from electrodeposition using citrate or glycine as additives

“…With increasing overall applied current density, this transition is shifted toward higher x positions, and thus the total amount of cobalt in the material libraries is raised. An opposite effect has been found for cobalt–nickel material libraries electrodeposition without additives (). A possible explanation might be the adsorption of metal‐complex species on the substrate.…”

“… fabricated copper–nickel material libraries in a Hull cell via pulsed electrodeposition. Using a similar approach, cobalt–nickel material libraries have been prepared galvanostatically from chloride and sulfate‐based electrolyte solutions ().…”

Preparation and investigation of combinatorially electrodeposited zinc-nickel, zinc-cobalt, and zinc-nickel-cobalt material libraries

“…it is seen, that at the highest x positions on the material library (very low current density) the zinc content decreased below this 5 % mark, indicating a normal co‐deposition behaviour. It has been reported before, that very low current densities permit normal co‐deposition of alloy systems, which are known to undergo anomalous co‐deposition under most plating conditions . At very low plating rates the system is considered to be closer to equilibrium state, favouring reduction of the thermodynamically more noble metal, which is cobalt in this case.…”

“…The length of the cathode was 76 mm, which was inclined by an angle of 50 towards the 49 mm long anode. A detailed description is given elsewhere .…”

“…More recently, Srinivas et al reported on the preparation of Ni–Cu material libraries by pulse‐plating , . Moreover, Co–Ni material libraries were prepared with an addition of citrate or glycine to the electrolyte bath and without bath additives . It is well‐known, that alloying zinc with iron group metals (Fe, Co, Ni) improves mechanical properties and corrosion resistance compared to pure zinc coatings.…”