FeTiO3 with band gap of 2.85 eV was added into TiO2 powder to improve the visible light responsivity of TiO2 in this study. The compositions and photocatalytic activity of plasma sprayed TiO2, TiO2-30%FeTiO3, TiO2-50%FeTiO3 and FeTiO3 coatings were investigated. The influence of FeTiO3 compound on the charge carrier separation and recombination in the TiO2-FeTiO3 coating was discussed. The FeTiO3 coating plasma sprayed under the arc current of 400 A consisted of rutile TiO2, FeTiO3, Fe2TiO5, and thermally metastable Fe2Ti3O9 and γ-Fe2O3. TiO2-30%FeTiO3 coating sprayed under the arc current of 400 A, which contained anatase TiO2, rutile TiO2 and FeTiO3, had good photocatalytic activity. The relative deposition rate of TiO2-30%FeTiO3 powder under the arc current of 400 A was approximate to 4 μm/pass. For the low band gap of pure FeTiO3 compound, the existence of FeTiO3 could improve the photocatalytic activity of anatase TiO2 when FeTiO3 contacts coherently with it, which was explained using a proposed two-steps electron transfer model.
Blasting is a substrate processing technique during which spherical or granular materials made of metal or ceramics are jetted against the surface of substrate using compressed air. Blasting causes a variety of effects to appear on the substrate because the blasting material collides at high speed on the surface of substrate. As causes of influences exerted on the substrate, colliding pressure or particle shapes of the blasting material are conceivable. Results of this investigation are summarized as follows. In the range of blasting distance h at 10 - 150 mm, the maximum colliding pressure Pmax became highest at h = 10 mm. Moreover, the blasting surface area increased with an increase of h. Pmax went up as the blasting pressure ξ increased, and suddenly dropped with an increase of h. The colliding pressure P was hardly affected by the type and particle size of blasting material, but was greatly influenced by ξ and h. The arc height H was larger with steel shot than with steel grit. Shot had greater influences than grit on work hardening. Under the peening effect by blasting, work hardening was induced and the fatigue strength σf increased. The removal ratio of specimen are different in each particle size.
Bonding characteristics of mild steel to cast iron using electron beam welding (EBW) process are investigated from the viewpoint of microstructure and mechanical properties. When the electron beam is radiated to a cast iron, remelting of the surface and corresponding rapid cooling take place, and it results in formation of brittle fine-cementite structure whose hardness is over 700 Hv. As Ni is an alloying element that may prevent formation of cementite, we compare two kinds of welding methods with Ni addition. One method is EBW process, radiating the electron beam to a thin plate made of spheroidal graphite cast iron with a high Ni content after the plate inserts between cast iron and steel, and other one is a metal active gas (MAG) welding process using a Fe-Ni wire. Bonding tensile strength by EBW process is higher than that by MAG welding process. In case of welding of cast iron and other metallic material, EBW process is found to be more advantageous than MAG welding process.
The SrTiO3 and La-doped SrTiO3 coatings were deposited by synthetic plasma spraying onto steel substrates. The aim of the study was the improvement of these plasma-sprayed coating properties by modifying the microstructures through re-melting processes with 1kW CO2 lasers. It revealed that the laser treatment of the La-doped SrTiO3 layers was dramatically improved to the dielectric properties and electric conductivities. The experimental results have demonstrated that the synthetic plasma process has a great potential for the integrated fabrications of the electric devices.