ELECTROCHEMICAL SYNTHESIS AND CHARACTERIZATION OF Tа2Si OBTAINED FROM CHLORIDE-FLUORIDE MELTS

In this work, the possibility of electrochemical synthesis of tantalum silicides, in particular Ta2Si, using chloride-fluoride melts NaCl–KCl–K2TaF7–K2SiF6 as an electrolytic medium was investigated. The influence of key process parameters, such as temperature, melt composition and potential, on the phase composition and morphology of the final products was studied. Based on thermodynamic calculations that take into account the Gibbs energy of formation of the corresponding compounds, as well as a complex of voltammetric studies, including cyclic voltammetry, the mechanism of electrochemical reduction of tantalum and silicon ions to Ta2Si was established. This confirms the effectiveness of using chloride-fluoride melts for the direct synthesis of tantalum silicides. It was experimentally shown that the ratio of the volumetric concentrations of tantalum and silicon in the melt does not affect the stoichiometry of the cathodic reduction products. Regardless of the initial ratio, the main product of electrolysis is Ta2Si, which indicates the thermodynamic advantage of the formation of this particular phase under the studied conditions. Electrolysis on nickel cathodes produced Ta2Si powders and coatings that differ in morphology and particle size. The phase composition and morphology of the synthesized products were confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of current density on the deposition rate and quality of the obtained materials was studied. In particular, in a NaCl–KCl melt containing 2 wt.% K2SiF6 and 5 wt.% K2TaF7, at a current density in the range of 0.1–0.2 A/cm² and a temperature of 700 °C, powders with a porous structure consisting of agglomerates of small dendritic particles were obtained. The optimal current density range of 0.03–0.08 A/cm² for the deposition of homogeneous and dense Ta2Si coatings with characteristic globular elements has been determined. The results obtained demonstrate the significant potential of electrochemical synthesis from chloride-fluoride melts for obtaining tantalum silicides with controlled phase composition and morphological characteristics, which opens up prospects for their application in various high-tech industries, including microelectronics, wear-resistant and corrosion-resistant coatings, and high-temperature materials.