The Study On The Performance Of Hydroxyapatite Film Prepared On The TC4Titanium Alloy By Microarc Oxidation

In this paper, the porous oxidation film rich in Ca and P elements withbiocompatibility was prepared on the TC4Titanium alloy by microarc oxidation andhydrothermal treatment. The effect of oxidation time,electrical parameter and thetemperature, time, pH of hydrothermal treatment on thickness, roughness, surfacemorphology, phase composition, Ca、P comparative content, Ca/P and substratebonding force for biological-activity micro-arc oxidation film in Calcium andPhosphorus containing solution was investigated. The relationship between the tissuestructure and property was preliminary studied. The biocompatibility was evaluatedby simulated body fluid immersion experiment.The results showed that: the part of the micro-arc oxidation film that near thebase was dense and the further part was loose, this structure not only makes theoxidation film had good biological activity for biological cells adhering to, but alsomakes the film combined with the base tightly and provided strong corrosionresistance. The oxidation film wasmainly composed of anatase, rutile and brookiteTiO2and amorphous calcium phosphate compounds. The thickness, roughness, Ca、Pcomparative content, Ca/P of the micro-arc oxidation film than with the oxidationtime, pulse current density and duty ratio increased, decreased with the increase ofimpulse frequency. The substrate bonding force for biological-activity micro-arcoxidation film with the oxidation time, the pulse electric current density and duty ratioincreased showed a trend of decrease after the first increase and decreased with theincrease of pulse frequency.The change of the micro-arc oxidation film’s thickness and roughness were notobvious after hydrothermal treatment, and had hydroxyapatite crystals generated onthe film’s surface. As the temperature and time of the hydrothermal treatmentincreased, the Ca、P comparative content and Ca/P of the oxidation film reduced,while that of the hydroxyapatite generated on the surface increased,and the Ca/P ofthe hydroxyapatite was up to1.67. With the pH of hydrothermal liquid increased, theCa、P comparative content and Ca/P of the hydroxyapatite showed a trend of decreaseafter the first increase, preferential growth orientation of hydroxyapatite crystals wasrestrained, length-diameter ratio diminished，had good crystal structure stability, andthe hydroxyapatite crystals which had medium size were well-distributed.The wettability of the TC4Titanium alloy base improved after microarc oxidation and hydrothermal treatment. Water contact angles (WCAs) changed from29.55°。to14.58°after microarc oxidation, then after the hydrothermal treatment, theWCAs changed to0°. The wettability of oxidation film can directly affect itsbiological activity, the better wettability the film had, the higher biological activity itgot. After5weeks’ simulated body fluid immersion experiment, both of the microarcoxidation group and the hydrothermal treatment group had calcium phosphategenerated on the surface of titanium alloy, while the TC4titanium alloy withouttreatment got none. Compared with the microarc oxidation treatment, on the surfaceof the titanium alloy with hydrothermal treatment, calcium phosphate generatedearlier and the amount of which was larger.The property of the oxidation film prepared by microarc oxidation andhydrothermal treatment was affected by the technological parameter of the microarcoxidation and hydrothermal treatment, and was closely related to the tissue structureof the oxidation film. The oxidation film had biological activity and biocompatibility.The substrate bonding force was about30N, when the technological parameter wereas follows: the oxidation time:12min, the pulse current density:7A·dm-2, impulseduty ratio:50%, frequebcy:500Hz. The substrate bonding force was about12N, whenafter4h hydrothermal treatment at160℃, pH=12, and the hydroxyapatite crystalswere well-distributed. The results of simulated body fluid immersion experimentshowed that the biocompatibility and biological activity of the oxidation film preparedby the microarc oxidation and hydrothermal treatment were better than that preparedby the microarc oxidation. The bonding force between the substrate and the oxidationfilm which prepared by microarc oxidation and hydrothermal treatment was good,what’s more, the oxidation film had excellent biocompatibility. In conclusion, themethod was applicable to surface activation treatment of titanium alloy implants.