Formation and Physicochemical Properties of Composite Electrochemical Coatings of Tin–Nickel Alloy with Silicon Dioxide Incapsulated by Nanosized Titanium Dioxide

The "SiO2 core–TiO2 shell" composite particles are synthesized and their properties are studied. Using the method of X-ray diffraction analysis, it is found that titanium dioxide in the composite is in the anatase crystal modification with crystallites 6–8 nm in size. The core–shell composites with a titanium dioxide content of 32 wt % have a specific surface area of 220 m2/g and a sorption volume of about 0.3 cm3/g. The effect of SiO2 core–TiO2 shell composite introduced into the electrolyte on the cathodic polarization of the electrochemical deposition of Sn–Ni alloy in the fluoride–chloride electrolyte is determined using the method of voltammetry. The morphology (SEM) and phase composition (XRD) of electrochemical coatings, which were deposited from the electrolytes with various concentrations of the composite, are studied. It is shown that the introduced SiO2 core–TiO2 shell composite has an effect on the activation energy of electrodeposition of the coatings based on the tin–nickel alloy. The concentration of SiO2 core–TiO2 shell composite in the electrolyte should be 2 g/dm3. The titanium content in the coating is 0.19 wt %. The dependence of microroughness and hardness of the coatings on the concentration of the composite in the electrolyte is studied.