Photo-catalytic decomposition of tetrachloroethylene (C2Cl4) by plasma sprayed TiO2 coatings

Abstract

TiO2 coatings were prepared on a stainless mesh net by plasma spraying using agglomerated TiO2 powder. Since TiO2 powders are well known as photo-catalytic materials, the photo-catalytic TiO2 coatings on mesh net are used for purification of water containing tetrachloroethylene (C2Cl4). It was found that TiO2 agglomerated powders could be deposited on mesh net and approximately 35 percent anatase ratio could be obtained by 400 A plasma spraying. It was possible to obtain approximately 100 micrometer thicknesses on the stainless mesh net substrate when plasma spraying was carried out at 800 A, while the coating thickness drastically decreased at 400 A. In terms of photo-catalytic properties, retaining the anatase phase ratio in the TiO2 coatings is essential to achieve photo-catalytic decomposition of 10 ppm C2Cl4 solution. It was found that the anatase ratio decreased gradually with increasing arc current and pass count, while the coating thickness increased with increasing arc current. This means that 0.2 micrometer agglomerated powders showed a lower susceptibility to heat effects and provided higher photo-catalytic activity. It was cleared that the anatase ratio had large influence on the photo-catalytic activity. These coatings showed photo-catalytic degradation of C2Cl4 solution. As a result of photo-catalytic experiments, it was shown that tested C2Cl4 solution is decomposed in moderately shorter times, to the extent that 10 ppm C2Cl4 was decomposed to less than 1 ppm after 7.2 ks of 400 A plasma sprayed coating. Thermal spraying on stainless mesh net could imply both new applications and possibilities for photo-catalytic degradation of C2Cl4 solution.