2006 Volume 47 Issue 3 Pages 849-853
Titanium dioxide (TiO2) coatings were prepared by chemical conversion treatment of aluminum in (NH4)2TiF6 with H2O2, and the sintering of the coating was prepared to immobilize the photocatalyst on aluminum. Coatings were also formed in this solution at room temperature. To identify the coating structure, coating analysis was carried out using an infrared absorption spectrum analyzer. Based on the infrared absorption results, a component of the coating was found in the hydrolysis product of peroxo titanium fluoride. Furthermore, the coating analysis was carried out using X-ray diffractometry (XRD), and non-sintered coating was amorphous; however, the coating sintered by 673 K was anatase-type titanium dioxide.
In the forming process of the conversion treatment in (NH3)2TiF6 and H2O2, first, the generated F− in the bath reacted with the aluminum. At the same time, hydrogen ions on the aluminum surface were consumed because hydrogen gas was generated. Thus, the pH of the interface became alkali. The hydrolysis of the titanium peroxo fluoride was deposited on the aluminum because pH increased on the surface.
The coating sintered at 473 K had the highest activity. The photocatalytic activity of the coating sintered at 623 K was lower than the coating heated at 473 K, which is attributed to TiO2 aggregation This forming process of the coating is low cost because of the useless electrolytic decomposition process. Furthermore, practical industry is expected because immobilized substances on aluminum can easily be decomposed at low temperatures.
