Study On Microwave Synthesis Of Hydroxyapatite Coating By Electrophoretic Deposition

Due to low self-bonding strength, bonding strength and large particle size,hydroxyapatite (Ca10(PO4)6(OH)2, HA)/titanium alloy composite material is restricted inmedical applications. In this paper, a submicron HA coating was fabricated on medicalTi6Al4V surface by the combination of electrophoretic deposition and microwavesynthesis. The parameters of HA suspension, electrophoretic deposition and microwavesynthesis were studied and optimized. The morphology, phase structure and biologicalproperties of the coating were studied by scanning electron microscopy (SEM), X-raydiffraction (XRD) and SBF experiment.Using n-butanol as a dispersion medium, adding12mL/L triethanolamine and adjustingpH value to6, the suspension was stable and suit for obtaining a uniform coating byelectrophoretic deposition with concentration of20g/L. And the suspension can meet therequirements of depositing HA coating.By studying the parameters of electrophoretic deposition, the results showed that theamount of coating deposition increased with the deposition time, the early growth wasrapid, then the rate slowed down. Poor coating uniformity firstly were obtained, due to thelate suspended particulates have time to look for space, the coating became uniform withdeposition time increasing. The amount of coating deposition was increasing as thevoltage increased while the growth rate became slow. In order to obtain a more uniformcoating, the loading voltage should be tens of volts lager than the high threshold voltagedriving the particle. As the electrode distance decreased, the amount of coating depositionwas increasing while the increasing rate began to be gentler afterwards.By studying the parameters of microwave synthesis, the results showed that the surfaceof coating was not excessive oxidation and the coating had a relatively high strength at1200℃for30min when the argon was used as a protective atmosphere. The heating rateis5°C/min. What’s more, the HA coating didn’t decomposed completely.The results on microwave synthesis of nanostructure HA coating by electrophoreticdeposition showed that the HA wasn’t found in the composition of the coating when deposition time was1min, while there was HA at5min. When deposition time was5min,through the analyzing the phase structure of the coating, it was proved that a gradientcoating was obtained by microwave inducement. The gradient coating can be divided intothree sections: the inner layer which was composed of TiO2and TiO, the middle layer thatcontained a minute amount of CaTiO3and the top layer constituted mainly HA and CaO.Deposition voltage from70V to200V, the cracks of the coating gradually became moreand larger, and the particles were uncompact, so the degree of sintering reduced and themechanical properties of the coating decrease. In order to ensure the uniformity anddensity of the coating, the deposition voltage should be100V. Electrode distanceincreased from5mm to15mm, the density degree of became higher while thetransformation of the coating composition is not large, and HA existed. In order to obtainthe higher density degree, electrode distance should select15mm.Under the optimal microwave synthesis conditions, here were the electrophoreticdeposition optimal parameters: the deposition time was5min, deposition voltage was100V, electrode distance was15mm. Coatings obtained in this parameter were used inSBF experiment, the HA coating surface could induce the growth of bone-like apatite aftereight-days’ immersion. This result showed that HA coatings obtained by electrophoreticdeposition and microwave synthesis were bioactive.