Abstract
In the present study, anatase TiO2 photo-catalytic coatings were fabricated by plasma and HVOF spraying. In order to prevent the transformation from anatase to rutile phase, lower heat input conditions were adopted. For the improvement of bondability between coatings and substrate, anatase TiO2-Al agglomerated powder was used for the experiment. The microstructures of the coatings were characterized with SEM and XRD analysis, and the photo-catalytic characteristics of coatings were evaluated by the decomposition rate of acetaldehyde gas. Due to the addition of aluminum, thick coatings were formed even at lower heat input conditions in both plasma and HVOF spraying. The results of XRD analysis for the plasma sprayed coatings, however, indicated the disappearance of anatase phase and deoxidization of TiO2 to Ti3O5 or magnetite phase. On the other hand, high anatase/rutile ratio and high photo-catalytic efficiency were achieved for the coatings formed by HVOF spraying. The temperature measurements of flying particles were also carried out using DPV-2000. As results, significant increase in temperature of TiO2-Al particles was observed compared with the case of using pure TiO2 particle. These results suggest that a chemical reaction between TiO2 and Al occurs during thermal spraying.
