Study Of Bioactive Coatings On The Surface Of Titanium By Micro-arc Oixdation

Titanium alloy Ti-6Al-4V is the most important biomedical metal materials, and widelyused in the repair and replacement of the hard tissues, such as the joints of the human body,bones. However, if we implant titanium and titanium alloy directly in the human body, it willhave some problems, such as low biological activity, low adhesion strength and long healingtime. Coating hydroxyapatite on the surface of the material is the most common methodwhich can improve the biological activity of the medical titanium alloy and promote thecombination of human bone tissue. But the brittleness, low adhesion strength with the matrixand the crack reduce the coating’s effect. In this paper, in order to improve thebiocompatibility of titanium alloy, we use micro-arc oxidation technology in the preparationof HA coating on the titanium surface.We make up four kinds of electrolytic solutions with different proportions: Potassiumhydrogen phosphate （K₂HPO₄·3H₂O） and calcium phosphate （Ca₃（PO₄）₂）, potassiumhydrogen phosphate （K₂HPO₄·3H₂O） and calcium-silicate （CaSiO₃）, potassium hydrogenphosphate （K₂HPO₄·3H₂O） and calcium acetate（（CH₃COO）2Ca H₂O）, potassium hydrogenphosphate （K₂HPO₄·3H₂O） and calcium hydroxide Ca（OH）₂. By controlling the micro-arcoxidation time, electrolyte composition ratio, electrolyte concentrtion, etc, we can completethe preparation of porous coating containing calcium and phosphorus on the surface oftitanium alloy. We also use scanning electron microscopy （SEM）, the spectrum analyzer（EDX）, universal tensile testing machine and simulated body fluid experiments studying thesurface morphology, the composition, adhesion strength, bio-compatibility of the coatingand other properties.The results show that: After the micro-arc oxidation, the electrolytes with differentcompositions will form the coatings with different ratio of calcium and phosphorus. And thishas great influence on biological activity. In addition, the micro-arc oxidation time, theelectrolytes concentration has great influence on the morphology of the coatings andadhesion strength. The adhesion strength of the film can be achieved49.6Mpa. After soakedin the simulated body fluid （SBF） for7days and15days, respectively, the surface of thefilm generated hydroxyapatite. This indicates that the coating has good bone induction.