Photocatalytic properties of nano-structured TiO2 plasma sprayed coating

Nano-TiO2 photo-catalytic coatings were deposited on stainless steel 304 (50×55×3 mm3) by the atmospheric plasma spraying process. To apply nano-TiO2 powder to thermal spraying, the starting nano-TiO2 powder with 100% anatase phase was agglomerated by the spray drying process. The plasma 2nd gas (H2) flow rate and spraying distance were used as principal process parameters which controlled the heat enthalpy (heat input). When the plasma spraying was completed, the relationship among the process parameters, the characteristics of microstructure such as the anatase phase fraction and grain size of the TiO2 coatings and the photo-decomposition efficiency were investigated. The photo-decomposition efficiency of the TiO2 coatings was evaluated by the kinetics of the methylene blue aqueous solution decomposition after irradiation using ultraviolet rays lamp which excites electrons and forms holes in TiO2 coatings. It was found that TiO2 coating applied under a lower heat input, resulting in a higher anatase phase fraction and smaller anatase grain size showed the best photo-decomposition efficiency.