Micro-arc Oxidation Electrolyte Of Medical Metal Tantalum On Film Performance

Tantalum has wide application in medical field because of its good biocompatibility.Surface performance is very important as medical material.Micro-arc oxidation technology could be used to modify the surface of Ti implant material,and thus was selected to adjust the surface property of tantalum.The surface properties of the ceramic layer fabricated with different electrolyte systems were studied.The microstructure and phase compositions of the ceramic layer were characterized.The growth mechanism of ceramic layer is discussed by studying the electrochemical impedance spectroscope(EIS)characteristics.The results show that the ceramic layer can be fabricated in the electrolyte of sodium silicate,sodium phosphate and sodium metalaluminate,silicate-phosphate,respectively.The thickest ceramic coating was fabricated in the electrolyte of sodium metalaluminate,and the ceramic coating was most roughness fabricated in the electrolyte of sodium silicate.The phase compositions of the ceramic coating formed in sodium silicate and sodium phosphate electrolyte is Ta2Os,The ceramic coating formed in sodium metaluminate electrolyte mainly consists of amorphous phase.The EIS pattern of the ceramic layer formed in different electrolyte systems and different conductivity solutions was fitted by the equivalent circuit.According to the corrosion mechanism and impedance map type of micro-arc oxide film,the R(QR(CR))model was selected for the equivalent circuit fitting.The impedance value R2 of dense film was the largest for tantalum fabricated in sodium metalaluminate electrolyte,indicating the ceramic coating is the densest.In the late stage of spark discharge,it is better to obtian the ceramic layer of tantalum when the conductivity of sodium silicate is 8 mS/cm,the conductivity of sodium metaaluminate is lOmS/cm,and the conductivity of sodium phosphate conductivity is 6 mS/cm.From above,silicate-phosphate and metaluminate-phosphate electrolyte were selected as the electrolyte used to fabricate MAO ceramic layer.The ceramic layer formed in silicate-phosphate electrolyte is relatively rough and porous,and the ceramic layer formed in metaluminate-phosphate is dense and smooth.The phase composition of the ceramic layer fabricated in the composite system is Ta2O5.