| Zn-Cu alloys were prepared by powder metallurgy method with Zn and Cu powder as initial materials.The effects of pressing pressure,sintering temperature,Cu contents on porosity,sintering density,compressive strength and microhardness were investigated.The microstructure and phase composion of the Zn-Cu alloys with different Cu contents was observed and analyzed.The corrosion resistance of the Zn-Cu alloys was investigated.The Zn-Cu alloys were multiply modified by micro-arc oxidation and coating graphene oxide?GO?film.The influences of oxidation current intensity,oxidation time,contents of Cu element on oxidation voltages,film microstructure and thickness of the Zn-Cu alloys were studied.The phase constitution and corrosion resistance of the oxidated films on the Zn-Cu alloys were analyzed and tested.The microstructure of the composite coating of the Zn-Cu alloys at different GO concentration was observed.The growth mechanism of the HA coating on the GO film in simulated body fluids was analyzed.The microstructure,phase composition,bonding property of HA with the Zn-Cu alloys matrix were observed and analyzed.The results show that with the increase of Cu contents or sintering temperature the porosities of the Zn-Cu alloys decrease,but their sintering density,compressive strength and microhardness all increase.The porosities of the Zn-Cu alloys decrease,but their sintering desnity and microhardness both increase by increasing pressing pressure.When the Zn-2.5Cu alloys were sintered at 390?with pressing pressure of 100MPa,the porosity,compressive strength and microhardness of sintered products are 2.4%,165.8MPa and 75.25HV,respectively.SEM analysis shows when Cu elements are added in the Zn matrix,the sintered products have finer grain size and higher sintering density.XRD and EDS analysis show the Zn-2.5Cu alloys are composed of?phase,but the Zn-3.0Cu alloys are composed of?and?phases.The corrosion resistance test shows that with the increase of Cu content,the self-corrosion potential of the Zn-Cu alloys first increases and then decreases,but the passivation current density first decreases and then increases.The self-corrosion potentials of the Zn-2.5Cu alloys comes to the maximum of-1.0485V and the passivation current density comes to the minmum of 4.6304×10-5A·cm-2.At the same time,its stable corrosion rate is0.076 mm·a-1 and its weight loss are minimal.The results of micro-arc oxidation show that with the increase of oxidation current intensity or oxidation time,U1,U2,U3 during micro-arc oxidation process and the film thickness all increase.With the increase of Cu content,U1,U2,U3 and film thickness first decrease and then increase.The oxidation film of the Zn-2.5Cu alloys has small and uniform pores at oxidation current intensity of 3A,oxidation time of 2min and Cu content of 2.5wt%.The oxidation film with the thickness of 61.9?m has the best quality.XRD and EDS analysis indicate that the micro-arc oxidation coating is mainly composed of Zn O,Zn2Si O4,Zn?OH?2phases.The self-corrosion potential,passivation current density,corrosion rate of the Zn-2.5Cu alloys after micro-arc oxidation are-0.58419V,9.5056×10-8A·cm-2,0.019mm·a-1,respectively corrosion rates of the Zn-2.5Cu alloys after micro-arc oxidation match with those of implanted biodegradable materials,so micro-arc oxidation can further controll the degradation rate of the Zn-Cu alloys.When GO concentration is 1.5mg/m L,uniform GO film can be formed on the surface of the Zn-2.5Cu alloys after micro-arc oxidation by drip coating method.The fold morphology of GO thin layer and a lot of oxygen group can better induce HA crystal nucleus to form dense packing.After immersed in SBF for 4d,compared with micro-arc oxidated surface,a film of dense HA layer can be formed on the micro-arc oxidated/GO composite surface.The HA layers have better bonding property with Zn-2.5Cu matrix,which shows that the micro-arc oxidated/GO composite surface has better biological activity. |
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