Analysis of the Morphology, Structure and Hardness of TiO₂ Anodized with HCl and the Incorporation of K₂Cr₂O₇ in the Solution

Abstract

It was possible to obtain TiO2 doped with K and Cr by electrochemical anodizing technique. An unexplored synthesis route was considered where the electrolyte used for the anodization was HCl and K2Cr2O7 as the precursor of the incorporated metals. Subsequently, the heat treatment temperatures of 400, 500, 600, 600, 700 and 800 °C were varied in order to observe the morphological, structural and hardness changes of the obtained films. The presence of nanotubes was observed on the anodized surface and the samples were annealed at 400, 500 and 600 °C, and grain formation for the samples were annealed at 700 and 800 °C. The presence of K and Cr in the TiO2 structure, together with the temperature changes, favored the transformation of anatase to rutile, which gave a hardness improvement of up to 4.8 times more compared to that of titanium without any treatment.