Chemical Hydrothermal Treatment Research Articles

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

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.

化学・水熱複合処理によるチタン表面の生体活性制御

化学・水熱複合処理によるチタン表面の生体活性制御

Photo-induced formation of hydroxyapatite on TiO 2 synthesized by a chemical–hydrothermal treatment

The formation of hydroxyapatite (HAp) on TiO 2 surfaces under continuous ultraviolet (UV) irradiation was investigated. Pure Ti substrates were chemically treated with H 2O 2/HNO 3 at 353 K for 20 min to form a TiO 2 gel layer. The specimens were then hydrothermally treated with an aqueous NH 3 solution in an autoclave at 453 K for 12 h. An adhesive and sufficiently crystallized anatase-type TiO 2 film could be synthesized on the Ti surface. The specimens were immersed in simulated body fluid in darkness or under UV irradiation with a centered wavelength of λ = 365 nm. Under dark conditions, a thin homogeneous HAp film was formed, with just a few spherical clusters of HAp. The UV illumination promoted the formation of HAp clusters, which may be due to the generation of functional Ti–OH or Ti–O groups on the TiO 2 surface. On the other hand, the UV light produced electron-hole pairs in the TiO 2, and the photogenerated holes that migrated to the surface repelled the Ca 2+ ions in the solution. As a consequence, the UV irradiation suppressed the formation of a HAp thin film.

Chemical-Hydrothermal Synthesis of Bioinert ZrO<SUB>2</SUB>-TiO<SUB>2</SUB> Films on Pure Ti Substrates and Proliferation of Osteoblast-Like Cells

The synthesis of bioinert oxide films on pure Ti surfaces by chemical-hydrothermal treatment was investigated. Some pure Ti substrates were chemically treated with H2O2/HNO3 to form a TiO2 gel layer prior to hydrothermal treatment. Two types of solutions in the hydrothermal treatment were prepared: Zr(OH)4 gel dispersed NH3/CH3CH(OH)COOH solution and Zr dissolved NH3/CH3CH(OH)COOH solution. A uniform layer of very fine crystals were formed on the surfaces of the specimens subjected to the hydrothermal treatment. Sharp peaks attributed to TiO2 and/or ZrO2 appeared after the hydrothermal treatment. ZrO2-TiO2 composite films were successfully produced on the Ti surface by hydrothermal treatment with the Zr(OH)4 gel dispersed NH3/CH3CH(OH)COOH solution at 453 K for 12 h, following the chemical treatment. The proliferation of osteoblast-like MC3T3-E1 cells was also investigated. The cells were observed to have spread their pseudopodiums. The cell density increased monotonically with incubation period for all specimens. The proliferation of cells was strongly influenced by the surface roughness; the cell densities increased with decreasing roughness in the range of Ra ¼ 20{80 nm. Furthermore, the surface products with TiO2 showed a relatively low rate of proliferation. The strong attachment of cells to the surface may hinder cell migration. [doi:10.2320/matertrans.MAW200910]