Preparation Of Anodic Coatings Containing Calcium,Phosphorus And Magnesium Elements On Biomedical Titanium Alloys And Study On The Influencing Regulation

Due to the low density,high specific strength and outstanding biocompatibility,titanium and its alloys are widely used for orthopedic implants.However,titanium and its alloys belong to bio-inert materials and exhibit poor bioactivity.Micro arc oxidation?MAO?,one kind of surface modification methods,can not only retain original excellent properties of titanium alloy,but also effectively improve the biological activity.Micro-arc oxide?MAO?????,??????MAO??Micro arc oxidation?film coating containing phosphorus element has good biological activity,but at present the widely used electrolytes are mostly inorganic phosphates.Therefore,in order to prepare micro-arc oxide film MAO coating containing calcium,phosphorus and magnesium elements,the organic phosphorus-phytic acid?phytic acid,one kinds of organic phosphates,?was used as the basic electrolyte in this paper with addition of the electrolytes containing calcium and magnesium.The effects of calcium salt and potassium hydroxide concentration on the properties of oxide film were comparatively studied and the best calcium salt and pH value were obtained.So we obtain the best calcium salt and pH value.In order to determine optimum processing parameters and discuss film-forming mechanism,the orthogonal experiment of four factors with three levels were used.The influences of EDTA-MgNa₂ concentration and pH value on the property of the oxide film were investigated.In addition,the existing form of the magnesium element was also researched determined.The research results are achieved as follows:?1?Five kinds of calcium salts such as Ca?CH₃COO?₂,CaO,Ca?H₂PO₄?₂,C₃H₇CaO₆P,EDTA-CaNa₂ and KOH were separately added into a base solution of 15g/L food additive phytic acid.The effects of calcium salts and KOH concentrations on the surface morphology and chemical composition of micro arc oxidation MAO coatings formed on titanium alloys were studied.The results show that calcium slats can significantly increase the phosphorus content of anodic coatings.In addition,CaO,Ca?H₂PO₄?₂ and EDTA-CaNa₂ can greatly improve the calcium content of anodic coatings.With the increase of KOH concentration,the calcium content of the oxide film increases.Both calcium slats and KOH can significantly increase the surface pore diameter of the oxide film.?2?In a base solution containing 15 g/L phytic acid and 10 g/L KOH,the influences of processing factors including EDTA-Na₂ concentration,Ca?CH₃COO?₂concentration,current density and treating time on calcium and phosphorus contents of micro arc oxidation?MAO?coatings developed on Ti6Al4V were investigated by the orthogonal experiment of four factors with three levels.Surface morphology,chemical composition and phase structure of anodic coating as well as element existing states??FTIR?XRD???????were characterized by scanning electron microscopy?SEM?,X-ray diffraction?XRD?,Fourier infrared spectrum?FTIR?and X-ray photoelectron spectroscopy?XPS?.The mechanism of calcium and phosphorus elements into anodic coatings was discussed.The results show that calcium and phosphorus elements of MAO coatings were mainly existed as CaTi O₃,PO₄^3-and HPO₄^2-.The affecting sequence of factors on calcium content of MAO coatings is Ca?CH₃COO?₂ concentration>current density>EDTA-Na₂concentration>treating time,but the order on the phosphorus content is Ca?CH₃COO?₂ concentration>treating time>current density>EDTA-Na₂concentration.The entrance mechanism of calcium and phosphorus element includes diffusion and electrophoresis.?3?Different concentrations of EDTA-MgNa₂ and KOH were separately added into a base solution containing 15 g/L phytic acid.The effects of EDTA-MgNa₂ and KOH concentration on the surface morphology,chemical composition and phase structure of micro-arc oxidation MAO film formed on Ti6Al4V alloy were studied by SEM,XRD,XPS,FT-IR and HPLC???HPLC??????,????????,????????.The results show that Mg content of the oxide film increases with the increase of EDTA-MgNa₂ and KOH concentration.EDTA-MgNa₂and KOH can also affect the surface pore diameter of the oxide film.Magnesium element of MAO coatings were mainly existed as Mg O and Mg₃?PO₄?₂.