The Study On The Fabrication Of K₂O·nTiO₂/TiO₂ Coating By Electrochemical Technique

After studying the recent researches on the activation of the Ti biomaterials, a K₂ O·nTiO₂/TiO₂ bio-ceramic coating on the surface of titanium was prepared successfully by an in situ electrochemical technique in this study. The fabrication process contains two steps. Firstly, a titanium oxide coating was gained by anodisation. Then the surface topography was observed by SEM and the microstructure was analyzed by TEM. Secondly, a K₂ O·nTiO₂ layer was fabricated by electrochemical method on the base of the titanium oxide. The surface topography and composition-of-phases were researched by SEM and XRD. Analyze and confirm the effects of the factors such as temperature, current density, electrolyte concentration and reaction time. Finally, the bioactivity of the coating was evaluated by SBF cultivation. At last a K₂ O·nTiO₂/TiO₂ bio-ceramic coating was fabricated on Ti-39Nb-3.7Zr by the same method. The results indicated:1. Fabricate a titanium oxide layer by anodisation. The TEM result shows that it is a rutile TiO₂ film, and the crystalline is not fine. In the same electrolyte solution, the thickness of the TiO₂ film increased and the colors were changed as the voltage rised.2. In the KOH solutions, as the concentration increases, the breakdown voltage and the thickness of the film formed before breakdown decrease, but the increasing rate of the thickness mounts up.3. In the K₂ CO3 solutions, the change of the concentration has little affection on the increasing rate of the thickness. When the voltage reaches to the certain value many micro-pits appear on the surface. And the micro-pits turn to be bigger and deeper with the raise of the voltage.4. The Ti electrodes breakdown at the same voltage in three different HNO3 solutions. And the amount of the corrosion pits is reduced while the treating voltage rises.5. Fabricate the K₂ (Ti8 O17) in situ on the titanium oxide by an electrochemical technique. And the crystalline is not well. Analyze the effects of different factors to the formation of the K₂ (Ti8 O17) shows that: temperature>current density>solution concentration>reaction time.6. The TiO₂ films got in different solutions have an important effect on the subsequent formation of the K₂ (Ti8 O17). The microstructures of the K₂ (Ti8 O17) obtained after being anodized in KOH, HNO3 and K2 CO3 are respectively villiform, reticular and sharply reticular.7. Confirm the best treating process is: (1) gain the TiO₂ film in 0.5mol/L K2 CO3 room temperature solution at 20V for 20min; (2) treat the sample in 90℃3mol/L KOH solution with constant current 2mA/cm2 for half an hour.8. Cultivate the samples in SBF. And study the deposition of Ca, P on the different surface. The results testify that the K2 (Ti8 O17) with sharply reticular formation is propitious to deposit Ca, P. So it has fine bioactivity.9. The amount of the corrosion pits obtained on the Ti-39Nb-3.7Zr is obviously more than that on the Ti sample after anodisation. A layer of potassium titanate with reticular formation is fabricated by the same electrochemical method. It proves that the method is also adequate for the Ti alloy. At the same time the research verifies the rules about the effects of different factors that have defined in the former experiments.10. The study proves that the electrochemical technique is feasible and efficient, and it has broad application in surface modification of the implant materials.