Molotovska L. Electrochemical synthesis of chromium silicides in chloride-fluoride melts

Due to the acid-base interactions in the molten NaCl-KCleut-K2SiF6-K2CrO4 mixture was formed the oxofluoride complexes of chromium [CrO2F4]2- and silicon [SiO2F2]2-. The oxofluoride complexes of chromium and silicon have similar deposition potentials that provides the necessary conditions of their joint electrochemical discharge and electrochemical synthesis of chromium silicides occured in a kinetic mode. Besides, it was found that the rate-limiting stage during the currentless transfer of silicon to the surface of metals of VI B group in molten (NaCl-KCl)eut-NaF-Na2SiF6 mixture with the presence of Si is the diffusion in the solid phase driven mainly by silicon atoms. The optimal conditions (composition of the melt, the duration of the currentless deposition) were determined for single-phase CrSi2 coatings obtaining. It was shown that the use of sodium metal in joint reduction of chromium and silicon compounds in a molar ratio of 3:1, 5:3, 1:1 and 1:2 in the CrCl3-Na2SiF6 system favors the formation of dispersed single phase powders of chromium silicides Cr3Si, Cr5Si3, CrSi, and CrSi2, respectively, with particle size < 1 micron.