Comparative Study of the Effects of Nano ZnO and CuO on the Biodegradation,Biocompatibility,and Antibacterial Properties of Micro-arc Oxidation Coating of Magnesium Alloy

This research systematically examined the degradation,antibacterial effects,and biocompatibility of micro-arc oxidation(MAO)coatings with nano CuO and ZnO on extruded Mg alloys.Both copper(Cu)and Zinc(Zn)possess antibacterial properties.The findings demonstrated that adding ZnO will appreciably reduce the degradation rate of MAO-coating alloy due to the self-sealing micro holes.CuO+MAO coating exhibited excellent antibacterial performance,with an antibacterial rate of over 90%within 6 h co-cultured with Staphylococcus aureus.Similarly,the antibacterial rate of ZnO+MAO coating reached 90%after 12 h co-culture.Cytotoxicity test using MG63 cell indicated that the incorporation of CuO and ZnO did not notably affect the cell viability rate of the coating.Moreover,after 14 days of culture,the CuO+MAO and ZnO+MAO coated samples exhibited higher alkaline phosphatase(ALP)activity than the MAO-coated and uncoated samples,suggesting favorable osteogenic properties.

Effects of microstructure on the torsional properties of biodegradable WE43 Mg alloy

Torsional properties are important performance parameters for bone screw applications,but they are seldom studied,especially for newly developed biodegradable Mg alloys.In this study,WE43 Mg alloy with different microstructures was achieved by equal channel angular pressing(ECAP)and heat treatment,and their torsional properties were studied.In addition,tensile properties were also tested as a comparison.The results indicated that grain refinement led to higher torsional strength and ductility,while the second phases improved the torsional strength but reduced the ductility.The texture was strengthened after ECAP,as a result the tensile strength increased,but the torsional strength did not increase and even decreased,especially for 2-pass ECAP sample with a typical basal fiber texture.The basal plane orientation deviation from the extrusion direction after 4-pass ECAP resulted in higher torsional strength and lower torsional ductility,but lower tensile strength and higher tensile ductility were obtained.This implied that a strong fiber texture would reduce the torsional strength but improve the torsional ductility,which was different from its effect on tensile properties.

Influence of stamping on the biodegradation behavior of Mg–2Zn-0.5Nd (ZN20) sheet

Stamping processing is commonly used to form medical devices and implant.However,for biodegradable Mg alloy,the stamping will influence the degradation behavior because of the change in microstructure after stamping.So in this study,the As-rolled Mg–2Zn-0.5Nd alloy(ZN20)was processed by stamping.The microstructure,crystallographic orientation and corrosion performance of this processing method was investigated to reveal the influence of the stamping process on the degradation rate of Rolled Mg–2Zn–Nd(ZN20).The degradation rate was measured by immersion of the Mg–2Zn-0.5Nd alloy in simulated body fluid using Electrochemical Impedance Spectroscopy,Potentiodynamic polarization and mass loss.The in vitro degradation result shows that the degradation rate of the Rolled Mg–2Zn-0.5Nd increased from 0.2 mm/year to 0.5 mm/year after stamping processing.The result reveals that the activation of the{101‾2}tension twin during stamping can remarkably weaken the{0001}basal texture and have a significant influence on the corrosion rate of Stamped Mg–2Zn-0.5Nd sheet.After removing the deformation by annealing,the degradation rate was reduced to 0.15 mm/year.This work is expected to prompt better microstructural design of biomedical Mg in order to control its degradation behavior for biomedical application.

Microstructural Evolution and Biodegradation Response of Mg–2Zn–0.5Nd Alloy During Tensile and Compressive Deformation

The effect of deformation behavior on the in vitro corrosion rate of Mg–2Zn–0.5 Nd alloy was investigated experimentally after uniaxial tensile and compressive stress.The microstructure and texture were characterized using electron backscattered diffraction and X-ray diffraction,while potentiodynamic polarization and immersion tests were used to investigate the corrosion response after deformation.The result reveals that applied compressive stress has more dominant effect on the corrosion rate of Mg–2 Zn–0.5 Nd alloy as compared to tensile stress.Both tensile and compressive strains introduce dislocation slip and deformation twins in the alloy,thereby accelerating the corrosion rate due to the increased stress corrosion related to dislocation slips and deformation twins.The{10ī2}tension twinning and prismatic slip were the major contributors to tensile deformation while basal slip,and{10ī2}tension twin were obtainable during compressive deformation.The twinning activity after deformation increases with the plastic strain and this correlates with the degradation rate.