Two-step Gas Treatment of Commercially Pure Titanium for Anatase Layer Formation

A two-step gas treatment of commercially pure titanium (CP Ti) was investigated with a focus on the formation of the anatase phase. The first step was carried out in Ar-1%C0 atmosphere at 1073 K for 0 ks or in N-2 atmosphere at 1123 K for 14.4 ks. The subsequent second step was carried out in air at 473-873 K for 0 ks and 86.4 ks. A titanium oxycarbide (TiC1-xOx) layer was formed after the first-step treatment in Ar-1% CO atmosphere, and an anatase-rich TiO2 layer was obtained after the second-step treatments in air at 673-873 K for 0 ks and at 573-773 K for 86.4 ks. In particular, single-phase anatase formed under the condition of the second step in air at 573 K for 86.4 ks. The anatase fraction in reaction layer could be controlled by varying the temperature and holding time of the second step. Both the TiN and Ti2N phases were detected as reaction products after the first step in N-2 atmosphere, and an anatase-containing TiO2 layer was obtained after the second-step treatment in air at 723 K for 86.4 ks. The formation of TiN and its oxidation at low temperatures seem to be required for the preparation of an anatase-containing TiO2 layer on Ti.