Magnesium coatings were fabricated on stainless steel substrates (1Cr11Ni2W2MoV) by a plane magnetron sputtering technique. The argon pressure and the substrate condition (including temperature and the substrate was r...Magnesium coatings were fabricated on stainless steel substrates (1Cr11Ni2W2MoV) by a plane magnetron sputtering technique. The argon pressure and the substrate condition (including temperature and the substrate was rotated or fixed) were varied in order to evaluate the influence of the parameters on the crystal orientation and morphology of the coating. The corrosion behavior of the coatings in 1 wt pct NaCI solution was studied by electrochemical methods. The results showed that all coatings exhibited preferred orientation (002) as the argon pressure increased from 0.2 to 0.4 Pa. The morphologies of the coatings varied with the argon pressure and with whether the substrate was rotated or fixed. The open circuit potential of the coatings was more positive than that of cast AZ91D magnesium alloy. However, the immersion test in 1 wt pct NaCI solution showed that the corrosion rates of the coatings were higher than that of cast AZ91D magnesium alloy.展开更多
The effects of substrate temperature and deposition time on the morphology and corrosion resistance of FeCoCrNiMo0.3 coating fabricated by magnetron sputtering were investigated by scanning electron microscopy and ele...The effects of substrate temperature and deposition time on the morphology and corrosion resistance of FeCoCrNiMo0.3 coating fabricated by magnetron sputtering were investigated by scanning electron microscopy and electrochemical tests.The FeCoCrNiMo0.3 coating was mainly composed of the face-centered cubic phase.High substrate temperature promoted the densification of the coating,and the pitting resistance and protective ability of the coating in 3.5wt%NaCl solution was thus improved.When the deposition time was prolonged at 500℃,the thickness of the coating remarkably increased.Meanwhile,the pitting resistance improved as the deposition time increased from 1 to 3 h;however,further improvement could not be obtained for the coating sputtered for 5 h.Overall,the pitting resistance of the FeCoCrNiMo0.3 coating sputtered at 500℃for 3 h exceeds those of most of the reported high-entropy alloy coatings.展开更多
To improve the oxidation resistance and corrosion resistance of Zr-4 alloy, titanium nitride(TiN) coatings were prepared on the Zr-4 alloy with a TiN ceramic target with different ratios of N_2. Microstructure and hig...To improve the oxidation resistance and corrosion resistance of Zr-4 alloy, titanium nitride(TiN) coatings were prepared on the Zr-4 alloy with a TiN ceramic target with different ratios of N_2. Microstructure and high-temperature properties of the TiN coated samples were studied by scanning electron microscopy(SEM), energy dispersive spectrometer(EDS), X-ray diffraction meter(XRD), X-ray photoelectron spectroscopy(XPS), heat treatment furnace and autoclaves, respectively. The x value of the TiN coatings(TiN_x) ranges from 0.96 to 1.33. After the introduction of N_2, TiN coating exhibits a weak(200) plane and a preferred(111) orientation. The coating prepared with an N_2 flow ratio of 15% shows an optimal oxidation resistance in the atmospheric environment at 800 °C. In either 1 200 °C steam environment for one hour, or deionized water at 360 °C and a pressure of 18.6 Mpa for 16 d, the opitimized TiN coated samples have no delamination or spallation; and the gains in the masses of samples are much smaller than Zr-4 alloy. These results demonstrate the effectiveness of the optimized TiN coating as the protective coating on the Zr-4 alloy under extreme conditons.展开更多
Magnesium alloys have been widely studied as materials for temporary implants,but their use has been limited by their corrosion rate.Recently,coatings have been proven to provide an effective barrier.Though only littl...Magnesium alloys have been widely studied as materials for temporary implants,but their use has been limited by their corrosion rate.Recently,coatings have been proven to provide an effective barrier.Though only little explored in the field,Atomic Layer Deposition(ALD)stands out as a coating technology due to the outstanding film conformality and density achievable.Here,we provide first insights into the corrosion behavior and the induced biological response of 100 nm thick ALD TiO_(2),HfO_(2)and ZrO_(2)coatings on AZ31 alloy by means of potentiodynamic polarization curves,electrochemical impedance spectroscopy(EIS),hydrogen evolution and MTS colorimetric assay with L929 cells.All three coatings improve the corrosion behavior and cytotoxicity of the alloy.Particularly,HfO_(2)coatings were characterized by the highest corrosion resistance and cell viability,slightly higher than those of ZrO_(2)coatings.TiO_(2)was characterized by the lowest corrosion improvements and,though generally considered a biocompatible coating,was found to not meet the demands for cellular applications(it was characterized by grade 3 cytotoxicity after 5 days of culture).These results reveal a strong link between biocompatibility and corrosion resistance and entail the need of taking the latter into consideration in the choice of a biocompatible coating to protect degradable Mg-based alloys.展开更多
Bioactive calcium phosphate coatings were prepared on AZ91D magnesium alloy in phosphating solution in order to im- prove the corrosion resistance of the magnesium alloy in Simulated Body Fluid (SBF). The surface mo...Bioactive calcium phosphate coatings were prepared on AZ91D magnesium alloy in phosphating solution in order to im- prove the corrosion resistance of the magnesium alloy in Simulated Body Fluid (SBF). The surface morphologies and compo- sitions of the calcium phosphate coatings deposited in the phosphating bath with different compositions were investigated by Scanning Electron Microscopy (SEM) with Energy Dispersive Spectrometer (EDS) and X-ray Diffraction (XRD). Results showed that the calcium phosphate coating was mainly composed of dicalcium phosphate dihydrate (CaHPO4o2H20, DCPD), with Ca/P ratio of approximately 1 : 1. The corrosion resistance was evaluated by acid drop, electrochemical polarization, elec- trochemical impedance spectroscopy and immersion tests. The dense and uniform calcium phosphate coating obtained from the optimal phosphating bath can greatly decrease the corrosion rate and hydrogen evolution rate of AZ91D magnesium alloy in SBE展开更多
Aluminum films with thickness of 8.78-20.82μm were deposited on the AZ31B magnesium alloys by DC magnetron sputtering.The influences of aluminum film on the micro-mechanical properties and corrosion behavior of the m...Aluminum films with thickness of 8.78-20.82μm were deposited on the AZ31B magnesium alloys by DC magnetron sputtering.The influences of aluminum film on the micro-mechanical properties and corrosion behavior of the magnesium alloys were investigated.The morphology of aluminum film was examined by scanning electron microscopy and the microstructure of aluminum film was analyzed by X-ray diffiactometry.Nanoindentation and nanoscratch tests were conducted to investigate their micromechanical properties.Moreover,potentiodynamical polarization test performed in 3.5%NaCl solution was carried out to study their anticorrosion performances.The results show that the surface hardness of AZ31B magnesium alloy with aluminum film is 1.38-2.01 GPa,higher than that of the magnesium alloy substrate.The critical load of Al film/AZ31B substrate is in the range of 0.68-2.77 N. The corrosion current density of AZ31B with aluminum film is 2-3 orders of magnitude less than that of bare AZ31B.And the corrosion potential with aluminum film positively shifts.Thus aluminum film can increase the corrosion resistance of Mg alloys obviously.展开更多
Chromium-plating is considered an effective method to improve surface properties of metal materials.Magnetron sputtering was applied to prepare Cr coating on AZ31 magnesium alloy and the influence of bias voltage on p...Chromium-plating is considered an effective method to improve surface properties of metal materials.Magnetron sputtering was applied to prepare Cr coating on AZ31 magnesium alloy and the influence of bias voltage on properties of Cr coating was investigated.The obtained coatings present an(110) preferred texture and have a developed columnar structure.With increasing bias voltage,the surface structure of Cr coating becomes denser.All of the Cr-coated AZ31 have much higher surface microhardness than bare AZ31.The Cr coating deposited on AZ31 at bias voltage of -150 V has a higher corrosion potential than others.The result of the immersion test shows that it decreases the damaged area compared with bare AZ31.The failure of the coated AZ31 is mainly attributed to the existence of through-thickness defects in the coating.展开更多
CrN and Cr-Al-N coatings were deposited by reactive magnetron sputtering on the glass substrate,and their corrosion behavior was studied. The electrochemical tests using both DC(polarization curves) and AC techniques(...CrN and Cr-Al-N coatings were deposited by reactive magnetron sputtering on the glass substrate,and their corrosion behavior was studied. The electrochemical tests using both DC(polarization curves) and AC techniques(EIS) were carried out on Potentiostat/Galvanstat(EG&G) in 3.5%(mass fraction) NaCl solution. After immersed into NaCl solution for 1 h,the mass of the CrN coating keeps constant with the time continuing. This can be explained by the passivation of the coating. The comparison between the corrosion potential(φcorr) of the Cr-Al-N coatings with different aluminum contents reveals that the corrosion potentials of the aluminum contain coatings are nobler than that of the CrN coatings. This means that the addition of aluminum shifts the corrosion potential to more positive potential value. Among these coatings,CrN in NaCl solution exhibits the worst corrosion resistance,while the corrosion resistance of Cr0.63Al0.37N in NaCl solution is the best. The polarization data and EIS data suggest that addition of aluminum can improve the corrosion resistance of CrN coating.展开更多
Magnesium(Mg)alloys are widely used for temporary bone implants due to their favorable biodegradability,cytocompatibility,hemocompatibility,and close mechanical properties to bone.However,rapid degradation and inadequ...Magnesium(Mg)alloys are widely used for temporary bone implants due to their favorable biodegradability,cytocompatibility,hemocompatibility,and close mechanical properties to bone.However,rapid degradation and inadequate strength limit their applicability.To overcome this,the direct current magnetron sputtering technique is employed for surface coating in Mg-based alloys using various zirconium(Zr)content.This approach presents a promising strategy for simultaneously improving corrosion resistance,maintaining biocompatibility,and enhancing strength without compromising osseointegration.By leveraging Mg’s inherent biodegradability,it has the potential to minimize the need for secondary surgeries,thereby reducing costs and resources.This paper is a systematic study aimed at understanding the corrosion mechanisms of Mg–Zr coatings,denoted Mg-xZr(x=0–5 at.%).Zr-doped coatings exhibited columnar growth leading to denser and refined structures with increasing Zr content.XRD analysis confirmed the presence of the Mg(00.2)basal plane,shifting towards higher angles(1.15°)with 5 at.%Zr doping due to lattice parameter changes(i.e.,decrease and increase of“c”and“a”lattice parameters,respectively).Mg–Zr coatings exhibited“liquidphilic”behavior,while Young’s modulus retained a steady value around 80 GPa across all samples.However,the hardness has significantly improved across all samples’coating,reaching the highest value of(2.2±0.3)GPa for 5 at.%Zr.Electrochemical testing in simulated body fluid(SBF)at 37℃ revealed a significant enhancement in corrosion resistance for Mg–Zr coatings containing 1.0–3.4 at.%Zr.Compared with the 5 at.%Zr coating which exhibited a corrosion rate of 32 mm/year,these coatings displayed lower corrosion rates,ranging from 1 to 12 mm/year.This synergistic enhancement in mechanical properties and corrosion resistance,achieved with 2.0–3.4 at.%Zr,suggests potential ability for reducing stress shielding and controlled degradation performance,and consequently,promising functional biodegradable materials for temporary bone implants.展开更多
A novel approach was developed to reduce the corrosion rate of magnesium(Mg)metal,utilising titanate coatings.Magnetron sputtering was used to deposit ca.500 nm titanium(Ti)coatings onto pure Mg discs,followed by hydr...A novel approach was developed to reduce the corrosion rate of magnesium(Mg)metal,utilising titanate coatings.Magnetron sputtering was used to deposit ca.500 nm titanium(Ti)coatings onto pure Mg discs,followed by hydrothermal conversion and ion exchange reactions to produce sodium and calcium titanate coatings.SEM confirmed the characteristic nanoporous structure of sodium and calcium titanate,with thicknesses ranging from ca.0.8 to 1.4μm.XPS analysis confirmed the presence of Ti^(4+)-O,Na-O,and Ca-O bonding,whilst Raman spectroscopy demonstrated characteristic vibrational modes(such as TiO 6 octahedral vibrations)of the sodium and calcium titanate perovskite structure.Furthermore,corrosion studies through potentiodynamic polarisation measurements demonstrated the NB/NH CaTC samples to be superior in reducing Mg degradation,compared to other samples tested,through an increase in E_(corr)from-1.49 to-1.33 V,and the reduction in corrosion current density,i corr,from 0.31 to 0.06 mA/cm^(2)for Mg and NB/NH CaTC samples,respectively.There was a clear trend noted for the NB/NH samples,which showed an increase in E corr to more positive values in the following order:Mg<Ti coated<NaTC<CaTC.These nanoporous titanate coatings have potential to be applied onto degradable plates for bone fracture fixation,or other orthopaedic applications.展开更多
Preparation of titanium film on magnesium substrate faces a challenge due to non-Fickian inter-diffusion between titanium and magnesium. Aluminum can build a bridge between titanium and magnesium. Al/Ti duplex coating...Preparation of titanium film on magnesium substrate faces a challenge due to non-Fickian inter-diffusion between titanium and magnesium. Aluminum can build a bridge between titanium and magnesium. Al/Ti duplex coatings were deposited on magnesium alloy AZ31B using magnetron sputtering (MS). The low temperature diffusion bonding behavior of the MglAl/Ti coating was investigated through SEM and its affiliated EDS. The phase structure and critical load of the coatings were examined by means of XRD and scratch tests, respectively, The results demonstrated that the bonding strength was significantly improved after a post heat treatment (HT) at a temperature of 210℃. The diffusion mechanism of the interfaces of MglAI and Al/Ti in the coating was discussed based on the analysis of formation energy of vacancies and diffusion rates. The Al/Ti dual layer enhanced the corrosion resistance of the alloy. And the HT process further increased the corrosion resistance of the coated alloy. This result implies that a post HTat a lower temperature after MS is an effective approach to enhance the bonding strength and corrosion resistance of the Al/Ti film on Mg alloys.展开更多
Depositing silver on magnesium alloy by both electroless plating and organic coatings was studied. The organic coating was made by immersing samples in organosilicon heat-resisting varnish. In this method the organic ...Depositing silver on magnesium alloy by both electroless plating and organic coatings was studied. The organic coating was made by immersing samples in organosilicon heat-resisting varnish. In this method the organic coating acts as interlayer between the substrate and silver film. When the reaction starts, silver deposits directly on the interlayer. X-ray diffraction and SEM analysis were used to determine the composition and morphology of the interlayer and silver film. The potentiodynamic polarization curves for corrosion studies of coated magnesium alloys were performed in a corrosive environment of 3.5% NaCl(mass fraction) at neutral pH (6.9). The results indicate that compared with the substrate, the corrosion resistance of coated magnesium alloys increases greatly. Moreover, the method proposed in this work is environmentally friendly, non-toxic chemicals were used. In addition, it provides a new concept for the corrosion inhibition of magnesium alloys.展开更多
文摘Magnesium coatings were fabricated on stainless steel substrates (1Cr11Ni2W2MoV) by a plane magnetron sputtering technique. The argon pressure and the substrate condition (including temperature and the substrate was rotated or fixed) were varied in order to evaluate the influence of the parameters on the crystal orientation and morphology of the coating. The corrosion behavior of the coatings in 1 wt pct NaCI solution was studied by electrochemical methods. The results showed that all coatings exhibited preferred orientation (002) as the argon pressure increased from 0.2 to 0.4 Pa. The morphologies of the coatings varied with the argon pressure and with whether the substrate was rotated or fixed. The open circuit potential of the coatings was more positive than that of cast AZ91D magnesium alloy. However, the immersion test in 1 wt pct NaCI solution showed that the corrosion rates of the coatings were higher than that of cast AZ91D magnesium alloy.
基金the National Science and Technology Major Project of China(No.2017-VII-0012-0109).
文摘The effects of substrate temperature and deposition time on the morphology and corrosion resistance of FeCoCrNiMo0.3 coating fabricated by magnetron sputtering were investigated by scanning electron microscopy and electrochemical tests.The FeCoCrNiMo0.3 coating was mainly composed of the face-centered cubic phase.High substrate temperature promoted the densification of the coating,and the pitting resistance and protective ability of the coating in 3.5wt%NaCl solution was thus improved.When the deposition time was prolonged at 500℃,the thickness of the coating remarkably increased.Meanwhile,the pitting resistance improved as the deposition time increased from 1 to 3 h;however,further improvement could not be obtained for the coating sputtered for 5 h.Overall,the pitting resistance of the FeCoCrNiMo0.3 coating sputtered at 500℃for 3 h exceeds those of most of the reported high-entropy alloy coatings.
基金Funded by the National Science and Technology Major Project of the Ministry of Science and Technology of China(2015ZX06004001-002)the Postgraduate Research and Innovation Project of the University of South China(2017XCX11)
文摘To improve the oxidation resistance and corrosion resistance of Zr-4 alloy, titanium nitride(TiN) coatings were prepared on the Zr-4 alloy with a TiN ceramic target with different ratios of N_2. Microstructure and high-temperature properties of the TiN coated samples were studied by scanning electron microscopy(SEM), energy dispersive spectrometer(EDS), X-ray diffraction meter(XRD), X-ray photoelectron spectroscopy(XPS), heat treatment furnace and autoclaves, respectively. The x value of the TiN coatings(TiN_x) ranges from 0.96 to 1.33. After the introduction of N_2, TiN coating exhibits a weak(200) plane and a preferred(111) orientation. The coating prepared with an N_2 flow ratio of 15% shows an optimal oxidation resistance in the atmospheric environment at 800 °C. In either 1 200 °C steam environment for one hour, or deionized water at 360 °C and a pressure of 18.6 Mpa for 16 d, the opitimized TiN coated samples have no delamination or spallation; and the gains in the masses of samples are much smaller than Zr-4 alloy. These results demonstrate the effectiveness of the optimized TiN coating as the protective coating on the Zr-4 alloy under extreme conditons.
文摘Magnesium alloys have been widely studied as materials for temporary implants,but their use has been limited by their corrosion rate.Recently,coatings have been proven to provide an effective barrier.Though only little explored in the field,Atomic Layer Deposition(ALD)stands out as a coating technology due to the outstanding film conformality and density achievable.Here,we provide first insights into the corrosion behavior and the induced biological response of 100 nm thick ALD TiO_(2),HfO_(2)and ZrO_(2)coatings on AZ31 alloy by means of potentiodynamic polarization curves,electrochemical impedance spectroscopy(EIS),hydrogen evolution and MTS colorimetric assay with L929 cells.All three coatings improve the corrosion behavior and cytotoxicity of the alloy.Particularly,HfO_(2)coatings were characterized by the highest corrosion resistance and cell viability,slightly higher than those of ZrO_(2)coatings.TiO_(2)was characterized by the lowest corrosion improvements and,though generally considered a biocompatible coating,was found to not meet the demands for cellular applications(it was characterized by grade 3 cytotoxicity after 5 days of culture).These results reveal a strong link between biocompatibility and corrosion resistance and entail the need of taking the latter into consideration in the choice of a biocompatible coating to protect degradable Mg-based alloys.
文摘Bioactive calcium phosphate coatings were prepared on AZ91D magnesium alloy in phosphating solution in order to im- prove the corrosion resistance of the magnesium alloy in Simulated Body Fluid (SBF). The surface morphologies and compo- sitions of the calcium phosphate coatings deposited in the phosphating bath with different compositions were investigated by Scanning Electron Microscopy (SEM) with Energy Dispersive Spectrometer (EDS) and X-ray Diffraction (XRD). Results showed that the calcium phosphate coating was mainly composed of dicalcium phosphate dihydrate (CaHPO4o2H20, DCPD), with Ca/P ratio of approximately 1 : 1. The corrosion resistance was evaluated by acid drop, electrochemical polarization, elec- trochemical impedance spectroscopy and immersion tests. The dense and uniform calcium phosphate coating obtained from the optimal phosphating bath can greatly decrease the corrosion rate and hydrogen evolution rate of AZ91D magnesium alloy in SBE
基金Project(2070950)supported by the Key Research Projects of the Ministry of Education,ChinaProject(KJ070617)supported by theChongqing Municipal Education Commission,China
文摘Aluminum films with thickness of 8.78-20.82μm were deposited on the AZ31B magnesium alloys by DC magnetron sputtering.The influences of aluminum film on the micro-mechanical properties and corrosion behavior of the magnesium alloys were investigated.The morphology of aluminum film was examined by scanning electron microscopy and the microstructure of aluminum film was analyzed by X-ray diffiactometry.Nanoindentation and nanoscratch tests were conducted to investigate their micromechanical properties.Moreover,potentiodynamical polarization test performed in 3.5%NaCl solution was carried out to study their anticorrosion performances.The results show that the surface hardness of AZ31B magnesium alloy with aluminum film is 1.38-2.01 GPa,higher than that of the magnesium alloy substrate.The critical load of Al film/AZ31B substrate is in the range of 0.68-2.77 N. The corrosion current density of AZ31B with aluminum film is 2-3 orders of magnitude less than that of bare AZ31B.And the corrosion potential with aluminum film positively shifts.Thus aluminum film can increase the corrosion resistance of Mg alloys obviously.
基金Project(200701A6305013)supported by the Natural Science Foundation of Ningbo City,China
文摘Chromium-plating is considered an effective method to improve surface properties of metal materials.Magnetron sputtering was applied to prepare Cr coating on AZ31 magnesium alloy and the influence of bias voltage on properties of Cr coating was investigated.The obtained coatings present an(110) preferred texture and have a developed columnar structure.With increasing bias voltage,the surface structure of Cr coating becomes denser.All of the Cr-coated AZ31 have much higher surface microhardness than bare AZ31.The Cr coating deposited on AZ31 at bias voltage of -150 V has a higher corrosion potential than others.The result of the immersion test shows that it decreases the damaged area compared with bare AZ31.The failure of the coated AZ31 is mainly attributed to the existence of through-thickness defects in the coating.
基金Project (50371095) supported by the National Natural Science Foundation of China
文摘CrN and Cr-Al-N coatings were deposited by reactive magnetron sputtering on the glass substrate,and their corrosion behavior was studied. The electrochemical tests using both DC(polarization curves) and AC techniques(EIS) were carried out on Potentiostat/Galvanstat(EG&G) in 3.5%(mass fraction) NaCl solution. After immersed into NaCl solution for 1 h,the mass of the CrN coating keeps constant with the time continuing. This can be explained by the passivation of the coating. The comparison between the corrosion potential(φcorr) of the Cr-Al-N coatings with different aluminum contents reveals that the corrosion potentials of the aluminum contain coatings are nobler than that of the CrN coatings. This means that the addition of aluminum shifts the corrosion potential to more positive potential value. Among these coatings,CrN in NaCl solution exhibits the worst corrosion resistance,while the corrosion resistance of Cr0.63Al0.37N in NaCl solution is the best. The polarization data and EIS data suggest that addition of aluminum can improve the corrosion resistance of CrN coating.
基金support by the project n°7225-ILLIANCE High Performing EnergyPro-jeto apoiado pelo PRR-Plano de Recuperação e Resiliência e pelos Fundos Europeus Next Generation EU,no sequência do AVISO N.°02/C05-i01/2022,Componente 5-Capital-ização e Inovação Empresarial-Agendas Mobilizadores para a Inovação Empresarialsupport by national funds through FCT-Fundação para a Ciência e a Tecnologia,under the project UID/EMS/00285/2020,ARISE-LA/P/0112/2020.
文摘Magnesium(Mg)alloys are widely used for temporary bone implants due to their favorable biodegradability,cytocompatibility,hemocompatibility,and close mechanical properties to bone.However,rapid degradation and inadequate strength limit their applicability.To overcome this,the direct current magnetron sputtering technique is employed for surface coating in Mg-based alloys using various zirconium(Zr)content.This approach presents a promising strategy for simultaneously improving corrosion resistance,maintaining biocompatibility,and enhancing strength without compromising osseointegration.By leveraging Mg’s inherent biodegradability,it has the potential to minimize the need for secondary surgeries,thereby reducing costs and resources.This paper is a systematic study aimed at understanding the corrosion mechanisms of Mg–Zr coatings,denoted Mg-xZr(x=0–5 at.%).Zr-doped coatings exhibited columnar growth leading to denser and refined structures with increasing Zr content.XRD analysis confirmed the presence of the Mg(00.2)basal plane,shifting towards higher angles(1.15°)with 5 at.%Zr doping due to lattice parameter changes(i.e.,decrease and increase of“c”and“a”lattice parameters,respectively).Mg–Zr coatings exhibited“liquidphilic”behavior,while Young’s modulus retained a steady value around 80 GPa across all samples.However,the hardness has significantly improved across all samples’coating,reaching the highest value of(2.2±0.3)GPa for 5 at.%Zr.Electrochemical testing in simulated body fluid(SBF)at 37℃ revealed a significant enhancement in corrosion resistance for Mg–Zr coatings containing 1.0–3.4 at.%Zr.Compared with the 5 at.%Zr coating which exhibited a corrosion rate of 32 mm/year,these coatings displayed lower corrosion rates,ranging from 1 to 12 mm/year.This synergistic enhancement in mechanical properties and corrosion resistance,achieved with 2.0–3.4 at.%Zr,suggests potential ability for reducing stress shielding and controlled degradation performance,and consequently,promising functional biodegradable materials for temporary bone implants.
基金This work was supported by the Engineering and Physi-cal Sciences Research Council[grant numbers EP/K029592/1,EP/L022494/1].
文摘A novel approach was developed to reduce the corrosion rate of magnesium(Mg)metal,utilising titanate coatings.Magnetron sputtering was used to deposit ca.500 nm titanium(Ti)coatings onto pure Mg discs,followed by hydrothermal conversion and ion exchange reactions to produce sodium and calcium titanate coatings.SEM confirmed the characteristic nanoporous structure of sodium and calcium titanate,with thicknesses ranging from ca.0.8 to 1.4μm.XPS analysis confirmed the presence of Ti^(4+)-O,Na-O,and Ca-O bonding,whilst Raman spectroscopy demonstrated characteristic vibrational modes(such as TiO 6 octahedral vibrations)of the sodium and calcium titanate perovskite structure.Furthermore,corrosion studies through potentiodynamic polarisation measurements demonstrated the NB/NH CaTC samples to be superior in reducing Mg degradation,compared to other samples tested,through an increase in E_(corr)from-1.49 to-1.33 V,and the reduction in corrosion current density,i corr,from 0.31 to 0.06 mA/cm^(2)for Mg and NB/NH CaTC samples,respectively.There was a clear trend noted for the NB/NH samples,which showed an increase in E corr to more positive values in the following order:Mg<Ti coated<NaTC<CaTC.These nanoporous titanate coatings have potential to be applied onto degradable plates for bone fracture fixation,or other orthopaedic applications.
基金Acknowledgements This research was financially supported by the National Natural Science Foundation of China (Grant No. 51241001), Shandong Provincial Natural Science Foundation, China (ZR2011 EMM004), Taishan Scholarship Project of Shandong Province (TS20110828), SDUST Research Fund (2014TDJH104), Joint Innovative Center for Safe and Effective Mining Technology and Equipment of Coal Resources, and Shandong Province. Thanks go to Dr. Jun CHEN, Dr. Donghua YANG and Dr. Zhenlin WANG in Chongqing University of Technology for the help in the sample preparation, corrosion and scratch tests.
文摘Preparation of titanium film on magnesium substrate faces a challenge due to non-Fickian inter-diffusion between titanium and magnesium. Aluminum can build a bridge between titanium and magnesium. Al/Ti duplex coatings were deposited on magnesium alloy AZ31B using magnetron sputtering (MS). The low temperature diffusion bonding behavior of the MglAl/Ti coating was investigated through SEM and its affiliated EDS. The phase structure and critical load of the coatings were examined by means of XRD and scratch tests, respectively, The results demonstrated that the bonding strength was significantly improved after a post heat treatment (HT) at a temperature of 210℃. The diffusion mechanism of the interfaces of MglAI and Al/Ti in the coating was discussed based on the analysis of formation energy of vacancies and diffusion rates. The Al/Ti dual layer enhanced the corrosion resistance of the alloy. And the HT process further increased the corrosion resistance of the coated alloy. This result implies that a post HTat a lower temperature after MS is an effective approach to enhance the bonding strength and corrosion resistance of the Al/Ti film on Mg alloys.
文摘Depositing silver on magnesium alloy by both electroless plating and organic coatings was studied. The organic coating was made by immersing samples in organosilicon heat-resisting varnish. In this method the organic coating acts as interlayer between the substrate and silver film. When the reaction starts, silver deposits directly on the interlayer. X-ray diffraction and SEM analysis were used to determine the composition and morphology of the interlayer and silver film. The potentiodynamic polarization curves for corrosion studies of coated magnesium alloys were performed in a corrosive environment of 3.5% NaCl(mass fraction) at neutral pH (6.9). The results indicate that compared with the substrate, the corrosion resistance of coated magnesium alloys increases greatly. Moreover, the method proposed in this work is environmentally friendly, non-toxic chemicals were used. In addition, it provides a new concept for the corrosion inhibition of magnesium alloys.