Investigation On The Corrosion Resistance And Antibacterial Properties Of Biodegradable Magnesium-based Metals

Mgnesium-based metal,as a novel biodegradable metallic material,attracts more and more attention in the fields of biomedical materials.However,its rapid degradation under physiological conditons and bacterial infection during implantation process seriously limit its application in the clinic.Even though magnesium–based metal degradation produces strong alkaline environments and shows special antibacterial property,it potential application disappears while comprising compatibility.In this thesis,a novel surface modification was adopted to improve antibacterial property on the basis of enhancement of corrosion resistance.In the meantime,the corrosion resistance,antibacterial propery and microbiological corrosion of pure magnesim,WE43 and ZK60 magnesium alloys were systematically researched.The corrosive and anti-micribial mechanism is explored.In the first part of the thesis,the effects of Zr and O plasma immersion ion implantation on the corrosion behaviour and antimicrobial properties of ZK60 Mg alloy are investigated.Electrochemical experiment has been used to investigate the effect of implantation parameters on the corrosion behaviour.The result showed that the best implantation parameter was Zr PIII(0.5h)followed by O PIII(3h).Then the optimized sample was characterized by XPS,Contact angle measurements,AFM,and Nanoindentation and elastic modulus.These results showed that a smooth,hydropholic and Zr O2-containing surface film is fabricated on ZK60 magnesium alloy by dual zirconium and oxygen ion implantation.The implantation layer can block the dispersion and penetration of the electrolyte effectively and improve corrosion resistance of the substrate.Moreover,the amount of adherent staphylococcus aureus on the Zr&O PIII and Zr PIII samples diminished remarkably compared to the untreated control,suggesting the improved antibacterial performance after PIII.This might be associated with the the formation of Zr O2 with antibacterial property as well as enhanced surface hydrophobility and diminished roughness.In addition,PIII improved surface nano hardness and elastic modulus.In the second part of the thesis,Mg,WE43 and ZK60,were utilized to investigate the relationship between corrosion resistance and antibacterial propertiesand explored to the effect of microorganism on corrosion property.Electrochemical impedance spectra and polarization curves were utilized to suggest the corrosion resistance of three kinds of magnesium in simulated body fluid(SBF),tryptone soy broth(TSB)and phosphate buffer solution(PBS)respectively as followes: WE43 > Mg> ZK60.The antibacterial effects against Staphylococcus aureus and Escherichia coli were evaluated by the plate spread method.The results showed that the order of antibacterial properties is ZK60 > WE43 > Mg.By means of electrochemical corrosion analysis,the effects of microbes on corrosion of magnesium-based metals were researched.The results revealed that the corrosion rates of ZK60 and WE43 were accelerated in the bacterial environments,but that of magnesium was slowed down,which was mainly attributed to their different microstructrue.