Surface modification of titanium by hydrothermal treatment

Abstract

The chemical-hydrothermal combined synthesis of TiO₂ and CaTiO₃ films on pure Ti substrates was examined with a focus on crystallinity and surface morphology of the films. Pure Ti disks were chemically treated with H₂O₂/HNO₃ solutions at 353 K for 5–60 min in order to introduce a TiO₂ layer with low crystallinity on the surface. The samples were then hydrothermally treated in an autoclave at 453 K for 12 h. Anatase-type TiO₂ and perovskite-type CaTiO₃ films with high crystallinity were obtained upon treatment with distilled water and an aqueous solution of Ca(OH)₂, respectively. Cracks in the TiO₂ precursor films disappeared after hydrothermal treatment. Uniform and crack-free films could be obtained by the present process. In addition, in vitro formation of hydroxyapatite (HAp) on the films was investigated. Obtained samples were immersed in SBF (Simulated Body Fluid), adjusted to 310 K. A light HAp precipitate could be observed on non-surface modified Ti after six days of immersion. In contrast, precipitate formed after only two days on the present oxide film. The present surface modification was confirmed to drastically promote deposition of HAp on the surface of Ti.