Titanium dioxide (TiO 2 ) is a promising material for photocatalyst coating. However, it was difficult to fabricate TiO 2 coatings which have excellent photocatalyst property by thermal spray processes. Because anatase phase of TiO 2 transforms into rutile phase under high temperature i.e. the photocatalyst property of TiO 2 declines by heating. In this study, TiO 2 photocatalyst coatings were fabricated by cold spraying. Agglomerated TiO 2 powder with 100% anatase phase was injected into nitrogen or helium gas stream and deposit onto steel substrate. It was possible to fabricate TiO 2 coatings with anatase phase and dense microstructure. The deposition efficiency was increased with gas temperature. The photocatalytic property of the coatings was evaluated by NOx elimination test. From the results, it became clear that cold sprayed TiO 2 coatings had excellent photocatalyst property.

Self designed cold spray equipment was installed in the laboratory and deposition behavior of sprayed individual metallic particles on the substrate surface was fundamentally investigated. As a preliminary experiment, pure Cu particles were sprayed on mirror polished stainless steel and Al alloy substrate surfaces. Process parameters changed systematically were particles diameter, working gas, gas pressure, gas temperature and substrate temperature, and effect of these parameters on the flattening or adhesive behavior of an individual particle was precisely investigated. Deposition ratio on substrate surface was also evaluated on these parameters. From the results obtained, it was quite noticeable that the higher substrate temperature brought about higher deposition rate of Cu particles even under the condition with particles temperature kept at room temperature. This tendency was promoted more effectively by using helium instead of air or nitrogen as a working gas. Both higher velocity and temperature of the particles sprayed are the necessary conditions for the higher deposition ratio in the cold spraying. However, instead of particles heating, substrate heating may bring about the equivalent effect for the deposition of the particles. This finding is quite new and has never been reported.