Ts. Dobrovolska

Intermetallics as key to spiral formation in In–Co electrodeposition. A study based on photoelectron microspectroscopy, mathematical modelling and numerical approximations

This paper reports on spiral pattern formation in In–Co electrodeposition. We propose an approach to the understanding of this process based on: (i) compositional and chemical-state distribution analysis by high-resolution photoelectron microspectroscopy and (ii) a mathematical model able to capture the morphological features highlighted in the experiments. Microspectroscopy—complemented by electrochemical, structural and morphological characterisations—combined with mathematical modelling, analytical and numerical investigations, converge in pointing out the key role played by intermetallic electrodeposition in spiral formation.

Electrodeposition of silver-indium alloy from cyanide-hydroxide electrolytes

It is shown that periodical spatio-temporal structures, consisting of phases with different indium content, are observed on the electrode surface during silver-indium alloy deposition from cyanide electrolytes in galvanostatic mode. The effect of electrolysis conditions on the silver-indium alloy appearance and morphology is studied, using optical and scanning electron microscopy; the phase composition of the obtained heterogeneous coatings, overall deposition rate, coating roughness, and microhardness are determined.

Electrodeposition of gold–indium alloys

The gold–indium alloy system has a number of intermetallic, differently coloured phases, of interest to the jewellery industry, and giving rise to the name blue gold. The present study is aimed at finding out the effect of electrolysis conditions on the morphology, elemental and phase composition of the Au–In alloy coatings from different electrolytes – with cyanide, acetate and glycine – as well as establishing the conditions for formation and observation of spatio-temporal structures on the surface of the electrode, similar to those observed during the electrodeposition of other indium alloys with silver, cobalt and palladium. It was established, that blue coloured matt coatings could be obtained from acetate–citrate electrolytes and the process of electrodeposition of gold–indium alloy from glycine electrolytes is a very promising one because of the possibility to obtain a variety of spatio-temporal structures on the surfaces of the electrode which could allow the comparison with other known cases of electrodeposition of similar structures in many other alloy systems.

Self-organisation phenomena during electrodeposition of palladium–indium alloys

The present investigation was focussed on determining the appropriate electrolyte for the deposition of palladium–indium alloy in a wide range of indium content and to investigate the possibility of observing spatio-temporal structures on the electrode surface. From polarisation experiments, it was established that the palladium–indium phase deposits at more positive potentials than the pure metals and this results at low current densities (0.1–0.3 A dm−2) in the content of the coatings being about 9–17 wt-% In. In the coatings obtained the formation of spatio-temporal structures during electrodeposition of palladium–indium alloys was observed for the first time. The period of the structures is 50–200 µm. The optically different areas of the structures show similar elemental and phase content as well as similar morphology. X-ray analysis of the sample with spatio-temporal structures shows superposition and coincidence of the spectra of the phases Pd and Pd0.85In0.15. This result is in agreement with those obtained during investigation of other electrodeposited alloys (Аg–In, Ag–Sb, Ag–Cd, In–Co, etc.) with spatio-temporal structures, which appear when simultaneously deposition of two phases with identical crystal lattice takes place.