Formation of anatase on commercially pure Ti by two-step thermal oxidation using N₂-CO gas

The phase of a TiO₂ layer formed on commercially pure Ti by two-step thermal oxidation using N₂-CO gas was investigated. The oxidation process comprised two steps: treatment in an N₂-(0.1, 1 and 5)%CO atmosphere and treatment in air. ATi(C,N,O) phase was formed after the first-step treatment conducted at 873-1123 K. In the second step, the oxidation of this phase at 573-773 K resulted in the formation of an anatase phase, while its oxidation at 873K resulted in the formation of a single rutile phase. An increase in the CO partial pressure in the first step lowered the temperature for anatase phase formation. Further, in the second step, a single-phase anatase layer was formed at temperatures of 623 and 673 K.