Hydrothermal Synthesis of Bioinert TiO₂-ZrO₂ Films on Ti Substrates with Zr-dissolved Alkaline Solutions

Abstract

Titanium and its alloys have been used in bone plates/screws; these are designed to be removed after recovery. However, bone can sometimes bond to surface of implanted materials that remain in the body for long periods of time. This can lead to re-fracture of newly repaired bone during operations to remove the implants. The purpose of the present study was to synthesize bioinert films, including ZrO₂ on pure Ti surfaces and to investigate hydroxyapatite (HAp) formation on the synthesized films in simulated body fluid (SBF). Pure Ti disks were chemically treated with H₂O₂/HNO₃ aqueous solutions at 353 K for 20 min. The disks were hydrothermally treated with ZrOCl₂/NH₃/C₆H₈O₇ (citric acid) aqueous solutions at 453 K for 12 h. The specimens were immersed in SBF, which was maintained at 310 K. After being soaked for different periods of time, the surfaces were observed by SEM. In the hydrothermal treatment with ZrOCl₂/NH₃ aqueous solution, the surface product was anatase-type TiO₂. On the other hand, when citric acid was added the surface of Ti was covered homogeneously with a TiO₂-ZrO₂ composite film. This surface suppressed the precipitation of HAp during SBF soaking.