Influence of Pr(NO3)3 doping on the microstructure and corrosion resistance of TC4 micro-arc oxidation coating
Titanium alloy has become the most widely used implant material in clinical field due to its high specific strength and mechanical properties.However,titanium alloy,as a bioinert material,has relatively weak binding ability of bone tissue,so it needs to be properly modified to provide its surface activation properties and improve its binding strength with bone,then it would shorten the healing cycle.Therefore,the production of bioactive coatings on the surface of titanium alloy has become a key technical problem for the clinical application of titanium alloy.Aiming at the problems of biological inertness and poor corrosion resistance of TC4 alloy,this paper attempted to apply micro-arc oxidation technology to synthesize TiO2 composite coating doped with hydroxyapatite(HAp)on the surface of TC4 alloy,so Pr(NO3)3 was introduced into the electrolytic liquid system of calcium and phosphorus salts.The influence of Pr(NO3)3 doping amount on the phase composition,surface morphology,surface roughness,contact angle and electrochemical polarization curve of TC4 micro-arc oxidation coating was investigated.The research results showed that TiO2 composite coatings containing hydroxyapatite(HAp)can be directly synthesized on the surface of TC4 alloy by micro-arc oxidation technology.With the increase of Pr(NO3)3 doping amount in the electro-lytic liquid,the content of rutile phase TiO2 and hydroxyapatite phase in the coating increased.The surface roughness and contact angle of the Pr-doped coating showed a trend of decreasing first and then increasing.Compared with the undoped Pr(NO3)3 specimen,the corrosion current density of Pr-doped coating decreased.When the doping amount of Pr(NO3)3 reached 0.009 mol/L,the corrosion current density of the coating was the lowest,which was about 182.54 nA/cm2,so the corrosion resistance was the best.
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