Impurity Control of Ti Complex Solution for Solution/Suspension Hybrid Spray Coating

This study aimed to investigate the impact of impurities on the mechanical and chemical properties of TiO2 coatings produced from recycled powders via a solution plasma spray technique. The objective was to enhance the biocompat-ibility and bioactivity of Cp-Ti or TiO2 coatings for biomedical applications, specifically to improve the adhesion between natural human tissues and arti-ficial components. In this research, we developed a solution precursor plasma spray (SPPS) method utilizing water-soluble titanium complex powder derived from recycled titanium alloy debris. This method facilitates the direct injec-tion of the solution into the plasma jet to generate TiO2 coatings. SEM/EDX analyses, XPS observations, Raman spectroscopy, and XRD measurements were conducted to assess the effects of chemical treatment on impurity reduction and the resultant coating properties. Despite the presence of impurities in the recycled titanium complex, the SPPS TiO2 coatings demonstrated effective photocat-alytic functionality. The coatings generated hydroxyl radicals upon exposure to both UV and visible light, indicating their potential application in antibacte-rial treatments. The presence of oxygen-deficient Magneli phases (TiO2−x) in the coatings may enhance their photocatalytic activities. Density functional the-ory (DFT) calculations were performed to examine the effects of lattice strain on the bandgap energy, revealing that only Ti2O3 exhibited a narrow bandgap among the Magneli phases studied. These findings suggest new opportunities for utilizing recycled titanium in advanced coating applications while addressing environmental concerns associated with titanium waste.