Shaiderov D. Electrodeposition of nickel and composites from electrolytes based on deep eutectic solvents

The thesis is devoted to the electrodeposition of nickel and Ni/TiO2 composite coating from a special kind of ionic liquids, deep eutectic solvents based on choline chloride, ethylene glycol and NiCl2 (as hexahydrate). It is found that the growth of water content in low-temperature ionic liquids leads to a decrease in density, surface tension, viscosity and an increase in conductivity. An increase in the concentration of Ni(II) ions results in an increase of density, surface tension and viscosity and a decrease of electrical conductivity. It is shown that electrodeposition / electrodissolution reactions on Ni electrodes in liquid mixtures occur as an irreversible electrochemical processes, and the addition of water reduces the rate of charge transfer in the reaction of electrodeposition of Ni. An increase in temperature, a decrease in density and the introduction of additional water provide to fabrication of high-quality coatings. The current efficiency of Ni electrodeposition reaction reaches 90–100%. The content of the titania dispersed phase in composite coatings depends on the TiO2 concentration in the plating bath, the applied current density, and the stirring rate; it may reach 2.35 wt %. Keywords: electrodeposition, nickel, nickel coatings, composites, choline chloride, nickel chloride, ethylene glycol, ionic liquids, deep eutectic solvents.