Synthesis and properties of inorganic composite coatings containing detonation nanodiamonds

Electrodeposition from solutions based on Cr(III) compounds of composite chromium coatings with denotation nanodiamond (DND) particles and composite coatings (CCs) of silicon dioxide-DND obtained using the sol-gel method is studied. Physicomechanical properties and composition of these composite coatings (CCs) are investigated. It is found that the presence of DND particles produces a significant effect on chromium coatings and causes a 1.4-fold increase in their microhardness. Herewith, brittleness of coatings decreases. DND content in CCs reaches final values (12-14 vol % or 6.4-7.2 wt %) at an increase in the DND concentration in the solution to 30 g/L. The performed studies allow establishing the optimum DND concentration in chromium-plating solutions (17 g/L) and in CCs (10.5 vol % or 5.6 wt %) that provides the maximum microhardness and minimum brittleness of chromium-DND coatings. Application of thin films from SiO2 sols modified by DND particles is studied. Dependences of microhardness and optical transmission of samples with coatings on the sol composition are established. The optical concentration of DND corresponding to the maximum coating microhardness is 0.5 wt %. An increase in DND content in the solution above 0.5 wt % causes a drastic decrease in the microhardness and optical transmission of samples with coatings and an increase in microbrittleness.