Comparative Study of TiO2 Photocatalyst Coatings Fabricated by Cold Spray and Suspension HVOF Spray Processes

Titanium dioxide (TiO₂) is a promising material for photocatalyst applications. However, it is difficult to fabricate high performance TiO₂ photocatalyst coatings by conventional thermal spray processes due to thermal phase transformation from anatase to rutile. The anatase structure possesses much higher photocatalytic activity than the rutile. The phase transformation temperature is lower than the melting temperature of TiO₂ i.e. it is impossible to obtain anatase structured coating by conventional thermal spray process. Recently, on the other hand, TiO₂ coatings with high photocatalytic performance have been reported using cold spray or suspension thermal spray processes. In this study, photocatalytic and mechanical properties of TiO₂ coatings fabricated by cold spray and suspension HVOF spray processes were compared with same evaluation methods. The cold sprayed coating exhibited higher photocatalytic activity and deposition efficiency. However, the suspension sprayed coating showed higher mechanical properties. Furthermore, microstructural observations for each coating revealed the deposition mechanisms of anatase structured TiO₂ coatings.