Influence of Water–Organic Medium on the Phase Composition of Modified Aluminum Oxide Systems in Electrochemical Synthesis of Precursors

Abstract

Possessing a high complex of mechanical and functional properties: tensile strength, hardness, wear resistance, corrosion resistance, heat resistance and bio-inertness, Al₂O₃–ZrO₂ systems are an effective material used for the manufacture of products that operate in harsh conditions. The main problem with currently used production methods is the limitations caused by the aggregability of particles. One of the approaches to reducing the degree of their aggregation is the use of organic or mixed aqueous-organic media. At the same time, the question of the influence of the solvent on the phase composition and structure of the forming precursor of the oxide system remains open. In this regard, the aim of the work is to identify patterns of influence of the solvent composition and electrolysis conditions on the chemical and phase composition of the final product and some of its physicochemical characteristics. The synthesis of precursors of oxide systems was carried out using a diaphragm-free coaxial electrolyzer reactor, where the cathode is Kh18N10T steel, and the soluble anode is 99.95% aluminum. Water–isopropyl alcohol solutions in various ratios, containing 0.5 M NaCl to ensure activation of the anode surface and Zr(NO₃)₄ were used as electrolytes. It was found that during the process of electrolysis with anodic dissolution of aluminum the use of a mixed solvent (water-isopropanol) makes it possibleallows, to regulate the content of bound water in the sediment, the ratio of the zirconium dioxide and aluminum oxide phases in the aluminum oxide system, and also to contribute to a reduction in particle size. In this case, the total amount of aluminum oxides in the oxide system Al₂O₃–ZrO₂ decreases, and the total amount of zirconium oxides increases (the dominant phase is tetragonal zirconium dioxide, the content of which in the product reaches 49% with an isopropanol content of 40 vol % in the initial electrolyte solution).