In the present study, anatase TiO 2 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 TiO 2 -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 TiO 2 to Ti 3 O 5 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 TiO 2 -Al particles was observed compared with the case of using pure TiO 2 particle. These results suggest that a chemical reaction between TiO 2 and Al occurs during thermal spraying.

The polyethylene terephtalate (PET) is widely utilized for high performance as a food and beverage container due to its excellent mechanical and chemical properties. The consumption of PET material is expected to increase more rapidly. Consequently, the recycling of waste PET is urgently needed to reduce environmental problems and economic costs. The purpose of this research is to endow waste PET materials with a new function by spraying of metal and ceramics such as Cu and TiO 2 . The recycled PET plate substrate for plasma spraying was prepared from waste PET bottles. It is found that Cu and TiO 2 powder could be sprayed on the surface of the recycled PET plate without heat damage and transformation of the substrate. In specific spray conditions, the implantation of melted Cu and TiO 2 particles, which retained their original shape, into the PET substrate was also observed and this is an unusual phenomenon in plasma spraying. In this research, the possibility of production of functional PET plates with electric conductivity and wear resistance was found by controlling the plasma spray conditions.

Two types of rutile and anatase powders are used for the deposition of TiO2 coatings. The effects of plasma spraying conditions on the structure of TiO2 coatings are investigated in order to clarify controlling factors of the phase formation and to aim at the development of effective photo-catalyst TiO2. It is found that the amount of anatase TiO2 in the coating is influenced by spray parameters. The decrease of the heat input to spray droplet and an increase in the cooling speed during droplet deposition will increase the amount of the anatase TiO2 in the coating. As a photo-catalyst, the coating deposited under limited plasma power and by HVOF spraying using anatase powder is effective for the decomposition of acetaldehyde gas.