Cold Spray Construction of Nanostructured Titania Coatings for Photocatalytic Applications

Nano-titania (TiO2) has drawn considerable attention for decades for its excellent photocatalytic activity. The use of photocatalyst TiO2 in the form of surface coating is usually desired for long-term recyclable photocatalytic performances. Yet deposition of the coatings with appropriate nanostructures persists challenging. Thermal spray processing usually triggered loss of photocatalytic anatase in the coatings. To retain anatase structure from starting TiO2 powder, in this study, cold spray was employed to deposit TiO2 nanostructured coatings using TiO2 nanoparticles as the starting feedstock. The mechanically blended Al-7.5 wt.% TiO2 powder was used as the feedstock for the coating fabrication, and Al was used as the binder for the nano-TiO2 particles. The coatings containing anatase phase were successfully fabricated and showed good long-term recyclable performance and service life. After methylene blue degradation testing for three times, the photocatalytic efficiency of the coatings still remained over 90% of the initial photocatalytic efficiency. After high-pressure gas purge and flame sweep processing, the coatings retained the initial nanostructures at their surfaces. The cold spray technical route might open a new window for making the coatings of temperature-sensitive nanosized particles for functional applications