Plasma Electrolytic Formation of WO<sub>3</sub>-CuO or WO<sub>3</sub>-CuWO<sub>4</sub> Oxide Layers on Titanium

Abstract

The oxide layers on titanium were formed by plasma electrolytic oxidation technique in acid aqueous electrolytes containing sodium tungstate and copper acetate. The coatings with WO3-CuO or WO3-CuWO4 oxide layers have been formed in the electrolytes with H2C2O4 (pH~6) or H2SO4 (pH~4) accordingly. The coatings with WO3-CuWO4 have a developed surface architecture. The surface is constructed from coral-like structures with lamellar nanocrystals containing copper tungstate and tungsten oxide. The layers of tungsten oxide nanocrystals occupy the depressions between these structures. The band gap of the mixed WO3CuWO4 oxide layers is 2.8 eV.