Influence of post-process annealing temperature on structural, optical, mechanical and corrosion properties of mixed TiO2 -WO3 thin films

The paper focuses on the comparative studies on the structural, optical, corrosion and mechanical properties of TiO2, WO3 and mixed TiO2-WO3, i.e. (Ti0.68W0.32)O-x and (Ti0.41W0.59)O-x thin film coatings. Oxide thin films were prepared from WO3 and Ti3O5 pellets by electron beam evaporation method and were additionally annealed at 600 degrees C and 800 degrees C using tubular furnace. The microstructure of prepared coatings was analysed using scanning electron microscopy and X-ray diffraction. The transparency of as-deposited thin films was high, while annealing caused significant decrease of the transmission of TiO2 and WO3 coatings. In the case of mixed oxides such post-process treatment did not cause severe change of the optical properties. The corrosion properties of the thin films were examined by an analysis of the voltammetric curves, while mechanical properties were determined by nanoidentation measurements. The hardness of the (Ti0.41W0.59)O-x film was approx. 3.42 GPa, but after annealing at 800 degrees C it increased to H-it = 14.6 GPa. Preparation of the mixed titanium-tungsten oxidethin films caused a decrease of the electrochemical activity. The Ti6Al4V substrate coated with (Ti0.41W0.59)O-x thin filmannealed at 800 degrees C exhibited the best corrosion properties among stprepared thin-film coatings.