Chemical-Hydrothermal Synthesis of Zr-Containing Titanium Oxide Film on CP-Ti

Abstract

Titanium and its alloys have been employed in bone plates/screws, which must be removed after recovery. Conduction of bone occurs on the surface of Ti alloys that reside in the body for a long period. This can lead to re-fracture of cured bone in removal operations. On the other hand, bone has been reported not to be formed on the surface of Zr alloys. The purpose of this study was to synthesize Zr-containing TiO2 film on commercial purity titanium (CP-Ti) by chemical-hydrothermal treatment. In addition, apatite formation on the films in Hanks’ solution and bone conduction in the tibiae of rats were also investigated. CP-Ti substrates were chemically treated with H2O2/HNO3 aqueous solutions at 353 K for 20 min. The substrates were hydrothermally treated with ZrOCl2/NH3/hydroxy acid aqueous solutions in a Teflon-lined autoclave at 453 K for 12 h. The hydroxy acid was selected to be C3H6O3 (lactic acid), C4H6O6 (tartaric acid) or C6H8O7 (citric acid). In the hydrothermal treatment without hydroxy acid, the surface product was anatase-type TiO2. In contrast, when hydroxy acid was added the surface of Ti was covered homogeneously with a Zr-containing TiO2 film. Some of the Zr (OH)4 sol in the solution is thought to have dissolved into the solution by coordinate bonding with hydroxy acid carboxyl groups, leading to incorporation of Zr as ZrO2 into the TiO2. The product films suppressed the apatite precipitation in the Hanks’ solution soaking. In animal test, the small amount of ZrO2 effectively suppressed the bone conduction.