Investigation of oxidation–reduction processes of nickel hydroxide precipitation and their carbothermical reduction

Most of the known methods for the chemical production of nickel nano- and microparticles, nickel oxides and hydroxides use various reducing agents and solvents, which are often toxic to the environment. As a rule, these methods are energy-consuming, lengthy and multi-stage, requiring complex equipment. Therefore, the development of a simple and “green” process for the synthesis of nickel-containing particles, including those with magnetic properties, remains one of the priority tasks. In this paper, a new physicochemical method for oxidation–reduction contact deposition of nickel(II) hydroxide nano–microparticles on the surface of magnesium particles from aqueous solutions of nickel-containing electrolyte is proposed. This method is based on the local corrosion of microgalvanic cells’ formation with predominant hydrogen depolarization. The proposed method was used to obtain nickel(II) hydroxide samples and study their morphology using SEM, as well as their phase composition using XRD analysis. It has been proven that the shape and structure of the resulting Ni(OH)₂ particles depend on the contact deposition conditions: depending on the surface state of the magnesium particles as a reducing agent, it is possible to obtain both plate-shaped α/β-Ni(OH)₂ particles and three-dimensional β-Ni(OH)₂ “flowers” with different degrees of crystallinity.