Micro-Arc oxidation of Ti in a solution of sulfuric acid and Ti+3 salt

A comparative study was performed on the behavior of titanium electrode in a sulfuric acid solution with and without Ti+3 during micro-arc oxidation under the constant current density control regime. The composition and microstructure of the obtained micro-arc films were analyzed using scanning electron microscopy, glancing-angle X-ray diffractometry, Raman and energy-dispersive X-ray spectroscopies. We have shown that addition of a Ti+3 salt extends the region of current densities (j(a)) can be used for micro-arc oxidation of Ti and results in an obvious change of sparking behavior from extensive, large and long-played sparks to numerous, small and short sparks. As a consequence, the titania films formed in the Ti+3-containing solutions are relatively thick, more uniform, composed of almost pure crystalline anatase and rutile phases of TiO2, and contain a network of evenly distributed small pores. It has also been shown that these films are promising for applications in catalysis, sensors and optoelectronics. The Raman spectra indicate that an increase in the electrolysis time of titanium in the Ti+3-containing solution leads to the increase in rutile content, as expected. (c) 2007 Elsevier B.V. All rights reserved.