Mg and its alloys show high potential to be applied as implant materials due to their superior properties like biodegradability,bioactivity,biocompatibility,and suitable mechanical behaviors.Nevertheless,the fast and ...Mg and its alloys show high potential to be applied as implant materials due to their superior properties like biodegradability,bioactivity,biocompatibility,and suitable mechanical behaviors.Nevertheless,the fast and uncontrolled degradation of Mg alloys in biological environment severely restricts their wide applications as biomedical materials.In comparison with alloying,surface coatings can not only improve corrosion resistance but also impart other bio-functional properties to achieve diverse clinical requirements.This review analyzes and summarizes the most recent developments in popular coating technologies,including micro-arc oxidation,electrophoretic deposition,chemical conversion,anodic oxidation,layered double hydroxide,and sol-gel coatings.Considering inevitable damages under complex service conditions,smart self-healing coatings are also introduced in each coating technology.The existing issues and future perspectives are finally discussed to facilitate applications of Mg alloys as biomedical materials in the medical industry.展开更多
This study aims to examine the effect of clay micro particles addition on the microstructure,wear and corrosion behavior of PEO coatings on AM 50 magnesium alloy.PEO coatings were prepared using an aluminate-based ele...This study aims to examine the effect of clay micro particles addition on the microstructure,wear and corrosion behavior of PEO coatings on AM 50 magnesium alloy.PEO coatings were prepared using an aluminate-based electrolyte with and without the presence of 5 g/L clay particles.The structure and composition of the coatings were evaluated using SEM,EDS and XRD.The wear investigations were conducted using a ball-on-disk tribometer at 2,5 and 10 N loads.The corrosion behavior of the coatings was examined using polarization and EIS tests in 0.5 wt.%NaCl.The results revealed that the addition of clay particles deteriorated the wear resistance of the coatings under the loads of 5 and 10 N.The SEM examinations of the worn surfaces indicated that a combination of adhesive and abrasive wear mechanisms was activated for the coating with clay particles.The poor wear performance of the clay-incorporated coating was related to its lower adhesion strength and higher roughness.The potentiodynamic polarization examinations revealed that the addition of clay particles slightly decreased the corrosion rate of the coatings.Corrosion resistance of the clay-containing coating was attributed to its compactness,as indicated by the results of EIS tests.展开更多
A gradient coating containing collagen and inorganic strontium/calcium phosphate(Sr/CaP)was fabricated on plasma-electrolytically oxidised magnesium via one-step cathodic electrodeposition.First,Sr-doped dicalcium pho...A gradient coating containing collagen and inorganic strontium/calcium phosphate(Sr/CaP)was fabricated on plasma-electrolytically oxidised magnesium via one-step cathodic electrodeposition.First,Sr-doped dicalcium phosphate dihydrate and hydroxyapatite(DCPD and HA)was deposited,followed by a collagen/CaP layer.The morphological evolution,sequential degradation behaviour,and in vitro bio-properties of the coatings were investigated.The incorporation of collagen remarkably refined the morphology of the CaP,and a more aggregated nano-spherical morphology was observed with increasing collagen concentration.Sr could partially replace Ca in the CaP crystals.Collagen combined with CaP formed a relatively stable skeletal frame,which provided sufficient barrier properties and more sites for the re-precipitation of bone tissue,as well as a more promising proliferation and differentiation ability of osteoblasts.A gradient coating that matches the requirements of bone growth at various periods is suggested for implantation.展开更多
The advent of three-dimensional(3D)printed porous Mg alloys is considered a significant milestone in the development of metal-based degradable implants.However,the poor corrosion resistance of additively manufactured ...The advent of three-dimensional(3D)printed porous Mg alloys is considered a significant milestone in the development of metal-based degradable implants.However,the poor corrosion resistance of additively manufactured Mg alloys,along with the occurrences of inflammation and bacterial infections following implantation,pose critical challenges.In this study,two drug-loaded coatings were prepared within a porous Mg alloy using in situ incorporation and post-deposition of layered double hydroxides(LDHs)to enhance corrosion resistance,antibacterial properties,and biological compatibility combined with plasma electrolytic oxidation(PEO).The results revealed that in situ incorporation of LDH capsules effectively reduced the porosity of the PEO layer and improved the long-term corrosion resistance of the coating.The postdeposited LDH layer effectively sealed the PEO layer,demonstrating highly stable corrosion resistance during 7 d electrochemical impedance spectroscopy(EIS)test,with the impedance modulus at 10^(-2) Hz stabilizing at 5×10^(5)Ω·cm^(2).After soaking,the surface morphology of the in situ drug-loaded PEO coating exhibited more cracks and defects,whereas the PEO-LDH coating maintained a relatively dense morphology.Among the tested samples,the PEO-LDH coating showed the best performance in terms of corrosion resistance,cell proliferation and differentiation capabilities,and antibacterial efficacy(>99%).Its strong compatibility with the porous structure of 3D-printed Mg alloy highlights the potential of this coating system for biomedical applications.The design strategy proposed in this study offers valuable insights for future development of drug-loaded coatings for 3D-printed porous materials.展开更多
In-situ growth of layered double hydroxide(LDH)has been considered a feasible method to further improve the corrosion protection of PEO coated Mg alloys,but the process is basically carried out in an autoclave.In this...In-situ growth of layered double hydroxide(LDH)has been considered a feasible method to further improve the corrosion protection of PEO coated Mg alloys,but the process is basically carried out in an autoclave.In this study,LDH was in-situ synthesized on PEO treated AM50 Mg by hydrothermal treatment at ambient pressure in the presence of chelating agents.Results indicated that the synergistic effect of sulfosalicylic acid(SSA)and ethylenediaminetetraacetic acid tetrasodium salt(EDTA)chelating agents is appropriate for Mg-Al LDH formation due to the sufficient quantity of highly stable Mg and Al complexes in the treatment bath.An appropriate hydrothermal treatment time was also revealed in this work,which can efficiently seal the pores and defects of PEO coating with a uniform LDH film.As a result,the corrosion protection of the coating was improved dramatically.The prolonged hydrothermal treatment is detrimental to the integrity of PEO layers.The influence of chelating agents on the LDH formation processes is supported by thermodynamic calculation of the equilibrium composition,and the formation mechanism of LDH film is discussed in depth.展开更多
Plasma electrolytic oxidation(PEO)processing of light metals has been established for decades and is in increasing industrial use,even as an alternative surface treatment to produce multifunctional coatings with envir...Plasma electrolytic oxidation(PEO)processing of light metals has been established for decades and is in increasing industrial use,even as an alternative surface treatment to produce multifunctional coatings with environmental-friendly processing concept.One of the benefits of PEO processing claimed already a couple of years ago was the ability to treat dissimilar metal joints,which can obviously improve the surface homogeneity and stability at the interface of the dissimilar components,especially impeding the galvanic corrosion due to the different electrochemical properties of each component.However,the progress and breakthrough develop slowly especially for the macro scales due to the much larger gap between each component.This literature review firstly demonstrates the still low number of studies reporting successful PEO treatment of material combination such as Mg/Al,Mg/Ti,Al/Ti and scarcely light metal combinations with steel.The main issues and challenges to performing PEO processing on the macroscale dissimilar weldments were stated.On the other hand,dissimilar metal joints also widely exist in micrometer scale in alloys and metal matrix composites(MMCs).Moreover,there is a huge knowledge base on PEO treatment of such multiphase substrates.PEO processing of such complicated mixed microstructures is reviewed as well to reveal the basic problems.To some certain degree,these PEO-related studies on alloys and MMCs can be good examples to have an insight into the coating formation mechanism on macro-scaled dissimilar metal joints.Conclusions are drawn from the micro-to macroscale.Finally,critical access to the problems is given and possible solutions and reaming limitations are discussed.展开更多
Magnesium(Mg)and its alloys present great potential to be extensively applied in different applications.However,the relatively poor resistance to corrosion and wear significantly restricts their applications in practi...Magnesium(Mg)and its alloys present great potential to be extensively applied in different applications.However,the relatively poor resistance to corrosion and wear significantly restricts their applications in practice.As one of strategies of surface treatment,micro-arc oxidation(MAO)process attracts a lot of attention,since it does not use neither expensive equipment,nor complicated manipulation.This review systematically discusses MAO mechanism and some typical models,which still need to be further developed to provide a better understanding and guide for future researchers.Subsequently,main influencing factors of MAO process are analyzed in detail.Further,some popular applications of MAO coatings are respectively reviewed,including biomedical application,decoration,thermal control,corrosion and wear resistance,and industrial applications in practice.The existing issues and future perspectives are finally discussed to further accelerate extensive applications of Mg alloys.展开更多
In this study,MgAl-V_(2) O_7^(4-) LDHs/(poly(ethyleneimine)(PEI)/MXene)_n composite films were synthesized via(ⅰ) in-situ hydrothermal growth of Mg-AL layered double hydroxides(LDHs) on AZ31 alloy followed by vanadat...In this study,MgAl-V_(2) O_7^(4-) LDHs/(poly(ethyleneimine)(PEI)/MXene)_n composite films were synthesized via(ⅰ) in-situ hydrothermal growth of Mg-AL layered double hydroxides(LDHs) on AZ31 alloy followed by vanadate intercalation reactions,and(ⅱ) the as-prepared MgAL-V_(2) O7^(4-) LDHs film was covered by layerby-layer assembly using(PEI/MXene)_n,where n=5,10,and 20.Film characterization revealed that the outer layers(PEI/MXene) were assembled on the surface by electrostatic interaction and provided a good coverage of LDHs nanosheets.But,microcracks appeared gradually on the surface and destroyed the film integrity with increasing number of PEI/MXene layers.The corrosion tests indicated that the MgAl-V_(2) O_7^(4-)LDHs/(PEI/MXene)_(10) composite films provided a better corrosion protection ability than that of n=5 and20.The outer layers(PEI/MXene) had a corrosion inhibition protective effect on MgAl-V_(2) O_7^(4-) LDHs film.This work opened a new perspective of the MXene materials for anticorrosion application via a layer-bylayer assembly method.展开更多
Coating technologies are a commonly used way to protect metals against corrosion.However,with more and more severe service environments of materials,many protective coating systems often are not environmentally friend...Coating technologies are a commonly used way to protect metals against corrosion.However,with more and more severe service environments of materials,many protective coating systems often are not environmentally friendly or toxic as in the case of chromates.Based on the world’s abundant ideal magnesium(Mg)and its alloy,the smart self-healing anticorrosive coating can autonomously restore the damaged part of the coating according to the environmental changes,strengthen the corrosion protection ability,and prolong its service life.This paper reviews the research progress of smart self-healing coatings on Mg alloys.These coatings mostly contain suitable corrosion inhibitors encapsulated into micro/nano containers.Moreover,the different self-healing mechanisms and functionalities of micro/nano containers are discussed.The micro/nano containers range from inorganic nanocontainers such as mesoporous nanoparticles(silica(SiO_(2)),titanium dioxide(TiO_(2)),etc.),over inorganic clays(halloysite,hydrotalcite-like,zeolite),to organic nanocontainers such as polymer microcapsules,nanofibers,chitosan(CS)and cyclodextrin(CD),as well as,carbon materials such as graphene and carbon nanotubes and hybrids such as metal organic frameworks.The functioning of micro/nano containers can be divided in two principal groups:autonomous(based on defect filling and corrosion inhibition)and non-autonomous(based on dynamic bonds and shape memory polymers).Moreover,multi functionalities and composite applications of various micro/nano containers are summarized.At present,significant progress has been made in the preparation methods and technologies of micro/nano containers.Achieving long-term self-healing properties of coatings sensing of coating failure and early warning after self-healing function failure can be expected as the main development direction of self-healing corrosion protection coatings in the future.展开更多
In this work,plasma electrolytic oxidation(PEO)coatings were produced on magnesium alloy AZ31 in aluminate,silicate and phosphate-based electrolytes,and followed by hydrothermal treatments in order to synthesis layere...In this work,plasma electrolytic oxidation(PEO)coatings were produced on magnesium alloy AZ31 in aluminate,silicate and phosphate-based electrolytes,and followed by hydrothermal treatments in order to synthesis layered double hydroxides(LDHs)based nanocontainers.LDHs synthesis was done in three different growth solutions(deionized water,sodium nitrate and aluminum nitrate containing solution).In frame of this work it was shown,that it was difficult to form LDHs on Si-based PEO coating,due to more stable silicate phases in comparison with aluminate and phosphate phases in respective PEO coatings.The obtained hybrid LDH/PEO coatings were characterized using SEM,EDS and GDOES,and then the corrosion protection was further investigated by EIS.Based on the obtained results,it was confirmed that,the hydrothermal treatments in Al^(3+)containing solution played an important role on overall corrosion resistance for phosphate and silicate-based PEO coatings,but not for Al-based PEO coatings.展开更多
Magnesium alloys are promising as load bearing components.They are inevitably exposed to cyclic loading and corrosive environment in actual service,which can consequently result in corrosion fatigue failure and loss o...Magnesium alloys are promising as load bearing components.They are inevitably exposed to cyclic loading and corrosive environment in actual service,which can consequently result in corrosion fatigue failure and loss of mechanical integrity of the material.Therefore,in the present study,the corrosion behavior,corrosion fatigue performance and mechanical integrity of an extruded Mg4Zn0.2Sn(wt.%)alloy were thoroughly studied in two corrosive electrolytes.Strong localized corrosion occurred when the alloy was immersed in deionized water based sodium chloride(NaCl)solution.The poor corrosion resistance of the alloy resulted in a fast deterioration of the tensile properties after pre-exposure to salt spray and a poor fatigue resistance in deionized water based NaCl solution.In comparison,the active dissolution of the substrate was sufficiently suppressed in artificial tap water based NaCl solution due to the formation of highly protective corrosion product layers.This consequently conferred longer fatigue life on the alloy in the electrolyte.Our results emphasized the influence of corrosion on the fatigue behavior and tensile properties of magnesium alloys.展开更多
The corrosion performances of the as-cast and solution-treated Mg-0.5Zn samples were investigated in 0.9%Na Cl solution and compared.From the electrochemical measurement results and corrosion morphology observations,i...The corrosion performances of the as-cast and solution-treated Mg-0.5Zn samples were investigated in 0.9%Na Cl solution and compared.From the electrochemical measurement results and corrosion morphology observations,it is found that the corrosion resistance of Mg-0.5Zn deteriorated with the extension of solution treatment duration.The main reason was the formation of Fe-Si precipitates with higher Fe concentrations during heat treatment.The Fe-Si precipitates,especially the ones with high Fe contents influenced the corrosion initiation and propagation significantly.In regard of corrosion performance,the solution-treated and then extruded sample was also performing not as good as the cast and then directly extruded sample.展开更多
High-porosity,open-cell AZ91 magnesium alloy foams of two pore sizes were fabricated by means of investment casting technology,using PUR foam patterns.Foam casting variables such as pressure,mould temperature and meta...High-porosity,open-cell AZ91 magnesium alloy foams of two pore sizes were fabricated by means of investment casting technology,using PUR foam patterns.Foam casting variables such as pressure,mould temperature and metal pouring temperature were thoroughly investigated to define the most optimal casting conditions.The mechanical properties of the fabricated foams were measured in compression tests.A potential application for the foams considered is temporary bioresorbable bone implants,therefore the mechanical properties of the foams were compared with those of cancellous bone tissue.Foams with smaller pore size and lower porosity(20 PPI and 80%±87%)exhibited mechanical properties in the lower regions of the cancellous bone property range(Young’s modulus 36.5±77.5 MPa),while foams with higher pore size and porosity(10 PPI and~90%)were found to have insufficient compression strength(Young’s modulus 11.65±23.8),but thickening their walls and lowering their porosity below 90%yielded foams with Young’s modulus between 36.5 and 77.5 MPa.Foam fractures were also investigated to determine their collapse mechanism.A series of corrosion tests in stimulated body fluid was carried out to determine their applicability as a biomaterial.The Plasma Electrolytic Oxidation(PEO)process was used in a feasibility study to examine the microstructure and chemical composition of foams with protective coating.展开更多
The influence of incorporating different sizes of Si_(3)N_(4) particles on the microstructure and corrosion properties of a phosphate-based plasma electrolytic oxidation (PEO) coating on AM50 magnesium alloy was inves...The influence of incorporating different sizes of Si_(3)N_(4) particles on the microstructure and corrosion properties of a phosphate-based plasma electrolytic oxidation (PEO) coating on AM50 magnesium alloy was investigated. The experiments for this study were performed in alkaline electrolytes containing 1 g/L KOH, 10 g/L Na_(3)PO_(4) with and without three different sized of Si_(3)N_(4) particles. The corrosion properties of PEO coatings were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 0.5 wt.% NaCl solution. Microstructure observations by SEM showed that the surface morphology and composition of the PEO coating were affected greatly by particle addition. Si_(3)N_(4) particles can still be found without decomposition in the final coating due to their high melting point.展开更多
The aim of the present study is to evaluate the effect of alloy processing and composition as well as the pH control and testing medium on the in vitro corrosion performance of Mg-Zn-Ca systems for biodegradable impla...The aim of the present study is to evaluate the effect of alloy processing and composition as well as the pH control and testing medium on the in vitro corrosion performance of Mg-Zn-Ca systems for biodegradable implants.The grain size and secondary phases were analyzed by optical microscopy,scanning electron microscopy,transmission electron microscopy,and X-ray diffraction.Scanning kelvin probe force microscopy(SKPFM)was used to analyze the Volta potential values of the second phases.The corrosion performance of the three alloys was evaluated by electrochemical and hydrogen evolution methods inα-MEM with and without organic species(i.e.complete and inorganicα-MEM).Two strategies were followed to evaluate the influence of the pH on the corrosion behavior:daily solution replacement and CO_(2)flow based pH control.For all the materials,the organic medium accelerates the corrosion process.Constant pH maintained by CO_(2)flow through the medium results in considerably higher corrosion rates for all alloys.The impact of pH is lesser on the as-cast alloys due to the barrier effect of the secondary phases,particularly pronounced in the Mg1Zn1Ca alloy which showed the lowest corrosion rate.The wrought Mg0.5Zn0.2Ca alloy that lacks the refined secondary phase network and exhibits high number of twins undergoes accelerated uniform corrosion under constant pH conditions.展开更多
This work reports the influence of alumina fiber reinforcement of an AZ91Nd MMC(metal matrix composite)on the PEO coating formation process in a sodium phosphate-based electrolyte.By comparison with the pure AZ91Nd,th...This work reports the influence of alumina fiber reinforcement of an AZ91Nd MMC(metal matrix composite)on the PEO coating formation process in a sodium phosphate-based electrolyte.By comparison with the pure AZ91Nd,the evolution of alumina fiber during the processing and the characteristics of the resultant PEO coating were investigated.The voltage response as a function of processing time was changed.Lower voltage in the presence of alumina fiber is responsible for the lower coating thickness.The morphology and phase composition of the coatings are also influenced by the incorporation of the fiber.Firstly,the fiber is embedded in the coating and interrupts the continuity of the coating.With increasing processing time,the fiber is found to be reactively incorporated in the coating.The intention to produce a MgAl_(2)O_(4)containing coating is achieved and it is mainly accumulated near the coating surface.However,due to the low number of fibers,the Al content is overall still low and only near to the fibers the MgAl_(2)O_(4)spinel phase can form.展开更多
In order to study the substrate lattice structure(Li addition)on the growth of plasma electrolytic oxidation(PEO)coatings,Mg Li alloy(11.36 wt.%of Li,cubic)and pure Mg(hexagonal)were treated under a pulsed direct PEO ...In order to study the substrate lattice structure(Li addition)on the growth of plasma electrolytic oxidation(PEO)coatings,Mg Li alloy(11.36 wt.%of Li,cubic)and pure Mg(hexagonal)were treated under a pulsed direct PEO mode in a phosphate electrolyte for different periods of time.The results revealed that the presence of Li and Li-rich phases in the cubic Mg alloy seems to be essential for the treatment result rather than the original lattice structure.A modified discharge behavior of Mg Li alloy finally led to a different microstructure of the coating.The unstable coatings of Mg Li alloy tended to dissolve rapidly though shared the similar composition to that of pure Mg.Li was incorporated only in the primary conversion products at the interface of coating/Mg Li.In spite of the advanced efficiency of energy input during processing,the more porous and thinner PEO coatings on the Mg Li alloy were less resistant to abrasion and corrosion.展开更多
The microstructures of as-cast ZK40,ZK40 with 2%(mass fraction)CaO and ZK40 with 1%(mass fraction)Y were investigated,and the intermetallic phase morphology and the distribution were characterised.By having discrete i...The microstructures of as-cast ZK40,ZK40 with 2%(mass fraction)CaO and ZK40 with 1%(mass fraction)Y were investigated,and the intermetallic phase morphology and the distribution were characterised.By having discrete intermetallic particles at the grain boundaries for the ZK40,the microstructure was modified to a semi-continuous network of intermetallic compounds along the grain boundaries for the ZK40 with CaO or Y additions.The CaO was not found in the microstructure.However,Ca was present in Ca2Mg6Zn3 intermetallic compounds which were formed during casting.Hydrogen evolution and electrochemical impedance spectroscopy tests revealed that the addition of CaO slightly enhanced the corrosion resistance whereas Y had a negative effect on the corrosion resistance of ZK40.Immersion tests showed that severe localised corrosion as well as corrosion along the intermetallic compounds played an important role in the corrosion process of ZK40-Y whereas the localised corrosion was not pronounced for ZK40 or ZK40?CaO alloys.Micro-segregation in theα-Mg matrix was notably higher for the ZK40 alloy compared with the modified alloys.The combination of this effect with a possible formation of a more stable corrosion layer for the ZK40-CaO was attributed as the main reason for an improved corrosion resistance for the ZK40-CaO alloy.展开更多
The need to combine various metals in light-weight constructions requires the development of coatings that prevent galvanic corrosion.Layered double hydroxides(LDHs)can be an example of such coatings,which were previo...The need to combine various metals in light-weight constructions requires the development of coatings that prevent galvanic corrosion.Layered double hydroxides(LDHs)can be an example of such coatings,which were previously successfully obtained in situ on individual materials.In addition,the possibility of LDH growth(including LDH growth in the presence of chelating agents)on the surface of plasma electrolytic oxidation(PEO)-coated metals was previously shown.This PEO+LDH combination could improve both corrosion and mechanical characteristics of the system.The possibility of LDHs formation in situ on the surface of PEO-coated friction stir welded(FSW)magnesium-aluminum materials(AZ31/AA5754 system was selected as a model one)was demonstrated in the presence of 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid(DHPTA)as a chelating agent,which was selected based on analysis of respective metal-ligand compounds stability.LDHs growth was achieved under ambient pressure without addition of carbonates in the electrolyte.The effectiveness of the resulting coating is shown both for corrosion resistance and hardness.展开更多
基金supported by the Chongqing Natural Science Foundation(No.CSTB2023NSCQ-MSX0512)Municipal Human Resources and Social Security Bureau(No.cx2022098)China Postdoctoral Science Foundation(Nos.2022T150767 and 2021M693708).
文摘Mg and its alloys show high potential to be applied as implant materials due to their superior properties like biodegradability,bioactivity,biocompatibility,and suitable mechanical behaviors.Nevertheless,the fast and uncontrolled degradation of Mg alloys in biological environment severely restricts their wide applications as biomedical materials.In comparison with alloying,surface coatings can not only improve corrosion resistance but also impart other bio-functional properties to achieve diverse clinical requirements.This review analyzes and summarizes the most recent developments in popular coating technologies,including micro-arc oxidation,electrophoretic deposition,chemical conversion,anodic oxidation,layered double hydroxide,and sol-gel coatings.Considering inevitable damages under complex service conditions,smart self-healing coatings are also introduced in each coating technology.The existing issues and future perspectives are finally discussed to facilitate applications of Mg alloys as biomedical materials in the medical industry.
文摘This study aims to examine the effect of clay micro particles addition on the microstructure,wear and corrosion behavior of PEO coatings on AM 50 magnesium alloy.PEO coatings were prepared using an aluminate-based electrolyte with and without the presence of 5 g/L clay particles.The structure and composition of the coatings were evaluated using SEM,EDS and XRD.The wear investigations were conducted using a ball-on-disk tribometer at 2,5 and 10 N loads.The corrosion behavior of the coatings was examined using polarization and EIS tests in 0.5 wt.%NaCl.The results revealed that the addition of clay particles deteriorated the wear resistance of the coatings under the loads of 5 and 10 N.The SEM examinations of the worn surfaces indicated that a combination of adhesive and abrasive wear mechanisms was activated for the coating with clay particles.The poor wear performance of the clay-incorporated coating was related to its lower adhesion strength and higher roughness.The potentiodynamic polarization examinations revealed that the addition of clay particles slightly decreased the corrosion rate of the coatings.Corrosion resistance of the clay-containing coating was attributed to its compactness,as indicated by the results of EIS tests.
基金National Natural Science Foundation of China(No.52101084)Guangdong Basic and Applied Basic Research Foundation,China(Nos.2023A1515011579,2020A1515110754)Guangzhou Basic and Applied Basic Research Foundation,China(No.202102020612)。
基金support from Mobility Programme of the Sino-German Center(M-0056)National Natural Science Foundation of China(52101286)+2 种基金Natural Science Foundation of Liaoning Province(2022-YGJC-16)Fundamental Research Funds for the Central Universities(N2302017)Supported by Sichuan Science and Technology Program 2023ZYD0115Shenyang Young and Middle-aged Science and Technology Innovation Talent Support Program(RC231178).
文摘A gradient coating containing collagen and inorganic strontium/calcium phosphate(Sr/CaP)was fabricated on plasma-electrolytically oxidised magnesium via one-step cathodic electrodeposition.First,Sr-doped dicalcium phosphate dihydrate and hydroxyapatite(DCPD and HA)was deposited,followed by a collagen/CaP layer.The morphological evolution,sequential degradation behaviour,and in vitro bio-properties of the coatings were investigated.The incorporation of collagen remarkably refined the morphology of the CaP,and a more aggregated nano-spherical morphology was observed with increasing collagen concentration.Sr could partially replace Ca in the CaP crystals.Collagen combined with CaP formed a relatively stable skeletal frame,which provided sufficient barrier properties and more sites for the re-precipitation of bone tissue,as well as a more promising proliferation and differentiation ability of osteoblasts.A gradient coating that matches the requirements of bone growth at various periods is suggested for implantation.
基金Natural Foundation of Science and Technology Department of Sichuan Province(2024NSFSC0949)Sichuan Science and Technology Program(2023ZYD0115)+1 种基金LiaoNing Revitalization Talents Program(XLYC2403026)Shenyang Young and Middle-aged Science and Technology Innovation Talent Support Program(RC231178).
文摘The advent of three-dimensional(3D)printed porous Mg alloys is considered a significant milestone in the development of metal-based degradable implants.However,the poor corrosion resistance of additively manufactured Mg alloys,along with the occurrences of inflammation and bacterial infections following implantation,pose critical challenges.In this study,two drug-loaded coatings were prepared within a porous Mg alloy using in situ incorporation and post-deposition of layered double hydroxides(LDHs)to enhance corrosion resistance,antibacterial properties,and biological compatibility combined with plasma electrolytic oxidation(PEO).The results revealed that in situ incorporation of LDH capsules effectively reduced the porosity of the PEO layer and improved the long-term corrosion resistance of the coating.The postdeposited LDH layer effectively sealed the PEO layer,demonstrating highly stable corrosion resistance during 7 d electrochemical impedance spectroscopy(EIS)test,with the impedance modulus at 10^(-2) Hz stabilizing at 5×10^(5)Ω·cm^(2).After soaking,the surface morphology of the in situ drug-loaded PEO coating exhibited more cracks and defects,whereas the PEO-LDH coating maintained a relatively dense morphology.Among the tested samples,the PEO-LDH coating showed the best performance in terms of corrosion resistance,cell proliferation and differentiation capabilities,and antibacterial efficacy(>99%).Its strong compatibility with the porous structure of 3D-printed Mg alloy highlights the potential of this coating system for biomedical applications.The design strategy proposed in this study offers valuable insights for future development of drug-loaded coatings for 3D-printed porous materials.
基金the financial support from National Natural Science Foundation of China(No.52071067)Mobility Programme of the Sino-German Center(M-0056)+3 种基金Shenyang Young and Middle-aged Science and Technology Innovation Talent Support Program(RC231178)Natural Science Foundation Project of Liaoning Province(2022-YGJC-16)the Fundamental Research Funds for the Central Universities(N2302019)Qianqian Chen would like to acknowledge China Scholarship Council for the award of fellowship(NO.202206080011).
文摘In-situ growth of layered double hydroxide(LDH)has been considered a feasible method to further improve the corrosion protection of PEO coated Mg alloys,but the process is basically carried out in an autoclave.In this study,LDH was in-situ synthesized on PEO treated AM50 Mg by hydrothermal treatment at ambient pressure in the presence of chelating agents.Results indicated that the synergistic effect of sulfosalicylic acid(SSA)and ethylenediaminetetraacetic acid tetrasodium salt(EDTA)chelating agents is appropriate for Mg-Al LDH formation due to the sufficient quantity of highly stable Mg and Al complexes in the treatment bath.An appropriate hydrothermal treatment time was also revealed in this work,which can efficiently seal the pores and defects of PEO coating with a uniform LDH film.As a result,the corrosion protection of the coating was improved dramatically.The prolonged hydrothermal treatment is detrimental to the integrity of PEO layers.The influence of chelating agents on the LDH formation processes is supported by thermodynamic calculation of the equilibrium composition,and the formation mechanism of LDH film is discussed in depth.
基金the China Scholarship Council(No.201708510113)for fellowship and funding.
文摘Plasma electrolytic oxidation(PEO)processing of light metals has been established for decades and is in increasing industrial use,even as an alternative surface treatment to produce multifunctional coatings with environmental-friendly processing concept.One of the benefits of PEO processing claimed already a couple of years ago was the ability to treat dissimilar metal joints,which can obviously improve the surface homogeneity and stability at the interface of the dissimilar components,especially impeding the galvanic corrosion due to the different electrochemical properties of each component.However,the progress and breakthrough develop slowly especially for the macro scales due to the much larger gap between each component.This literature review firstly demonstrates the still low number of studies reporting successful PEO treatment of material combination such as Mg/Al,Mg/Ti,Al/Ti and scarcely light metal combinations with steel.The main issues and challenges to performing PEO processing on the macroscale dissimilar weldments were stated.On the other hand,dissimilar metal joints also widely exist in micrometer scale in alloys and metal matrix composites(MMCs).Moreover,there is a huge knowledge base on PEO treatment of such multiphase substrates.PEO processing of such complicated mixed microstructures is reviewed as well to reveal the basic problems.To some certain degree,these PEO-related studies on alloys and MMCs can be good examples to have an insight into the coating formation mechanism on macro-scaled dissimilar metal joints.Conclusions are drawn from the micro-to macroscale.Finally,critical access to the problems is given and possible solutions and reaming limitations are discussed.
基金supported by the National Natural Science Foundation of China(No.52001036)the China Postdoctoral Science Foundation(No.2021M693708)+2 种基金the Chongqing Postdoctoral Scientific Research Foundation(No.cstc2020jcyjbsh X0015)the National Natural Science Foundation of China(51971040,52171101)the Natural Science Foundation of Chongqing(cstc2021jcyj-msxm X0613)。
文摘Magnesium(Mg)and its alloys present great potential to be extensively applied in different applications.However,the relatively poor resistance to corrosion and wear significantly restricts their applications in practice.As one of strategies of surface treatment,micro-arc oxidation(MAO)process attracts a lot of attention,since it does not use neither expensive equipment,nor complicated manipulation.This review systematically discusses MAO mechanism and some typical models,which still need to be further developed to provide a better understanding and guide for future researchers.Subsequently,main influencing factors of MAO process are analyzed in detail.Further,some popular applications of MAO coatings are respectively reviewed,including biomedical application,decoration,thermal control,corrosion and wear resistance,and industrial applications in practice.The existing issues and future perspectives are finally discussed to further accelerate extensive applications of Mg alloys.
基金supported by the National Natural Science Foundation of China (51971040, 51971044)the Fundamental Research Funds for the Central Universities (2020CDJQY-A007)。
文摘In this study,MgAl-V_(2) O_7^(4-) LDHs/(poly(ethyleneimine)(PEI)/MXene)_n composite films were synthesized via(ⅰ) in-situ hydrothermal growth of Mg-AL layered double hydroxides(LDHs) on AZ31 alloy followed by vanadate intercalation reactions,and(ⅱ) the as-prepared MgAL-V_(2) O7^(4-) LDHs film was covered by layerby-layer assembly using(PEI/MXene)_n,where n=5,10,and 20.Film characterization revealed that the outer layers(PEI/MXene) were assembled on the surface by electrostatic interaction and provided a good coverage of LDHs nanosheets.But,microcracks appeared gradually on the surface and destroyed the film integrity with increasing number of PEI/MXene layers.The corrosion tests indicated that the MgAl-V_(2) O_7^(4-)LDHs/(PEI/MXene)_(10) composite films provided a better corrosion protection ability than that of n=5 and20.The outer layers(PEI/MXene) had a corrosion inhibition protective effect on MgAl-V_(2) O_7^(4-) LDHs film.This work opened a new perspective of the MXene materials for anticorrosion application via a layer-bylayer assembly method.
基金supported by the National Natural Science Foundation of China(51971040,52171101)the Natural Science Foundation of Chongqing(cstc2021jcyj-msxmX0613)+1 种基金the National Natural Science Foundation of China(52001036,51971044)the Independent Research Project of State Key Laboratory of Mechanical Transmissions(SKLMT-ZZKT-2022M12).
文摘Coating technologies are a commonly used way to protect metals against corrosion.However,with more and more severe service environments of materials,many protective coating systems often are not environmentally friendly or toxic as in the case of chromates.Based on the world’s abundant ideal magnesium(Mg)and its alloy,the smart self-healing anticorrosive coating can autonomously restore the damaged part of the coating according to the environmental changes,strengthen the corrosion protection ability,and prolong its service life.This paper reviews the research progress of smart self-healing coatings on Mg alloys.These coatings mostly contain suitable corrosion inhibitors encapsulated into micro/nano containers.Moreover,the different self-healing mechanisms and functionalities of micro/nano containers are discussed.The micro/nano containers range from inorganic nanocontainers such as mesoporous nanoparticles(silica(SiO_(2)),titanium dioxide(TiO_(2)),etc.),over inorganic clays(halloysite,hydrotalcite-like,zeolite),to organic nanocontainers such as polymer microcapsules,nanofibers,chitosan(CS)and cyclodextrin(CD),as well as,carbon materials such as graphene and carbon nanotubes and hybrids such as metal organic frameworks.The functioning of micro/nano containers can be divided in two principal groups:autonomous(based on defect filling and corrosion inhibition)and non-autonomous(based on dynamic bonds and shape memory polymers).Moreover,multi functionalities and composite applications of various micro/nano containers are summarized.At present,significant progress has been made in the preparation methods and technologies of micro/nano containers.Achieving long-term self-healing properties of coatings sensing of coating failure and early warning after self-healing function failure can be expected as the main development direction of self-healing corrosion protection coatings in the future.
基金supported by the International Cooperation in Science and Technology Innovation between Governments,National Key Research and Development Program of China(No.2018YFE0116200)the National Natural Science Foundation of China(51971040,51701029)+4 种基金the Fundamental Research Funds for the Central Universities(2020CDJQY-A007)China Postdoctoral Science Foundation Funded Project(2017M620410,2018T110942)the Chongqing Postdoctoral Scientific Research Foundation(Xm2017010)G.Z.thanks also China Scholarship Council for the award of fellowship and funding(No.201806050047)M.S.and C.B.additionally thank the ACTICOAT project(Era.Net RUS Plus Call 2017,Project 477)for the financial support of this work.
文摘In this work,plasma electrolytic oxidation(PEO)coatings were produced on magnesium alloy AZ31 in aluminate,silicate and phosphate-based electrolytes,and followed by hydrothermal treatments in order to synthesis layered double hydroxides(LDHs)based nanocontainers.LDHs synthesis was done in three different growth solutions(deionized water,sodium nitrate and aluminum nitrate containing solution).In frame of this work it was shown,that it was difficult to form LDHs on Si-based PEO coating,due to more stable silicate phases in comparison with aluminate and phosphate phases in respective PEO coatings.The obtained hybrid LDH/PEO coatings were characterized using SEM,EDS and GDOES,and then the corrosion protection was further investigated by EIS.Based on the obtained results,it was confirmed that,the hydrothermal treatments in Al^(3+)containing solution played an important role on overall corrosion resistance for phosphate and silicate-based PEO coatings,but not for Al-based PEO coatings.
基金The author Pingli Jiang(CSC No.201606310043)would like to thank the financial support from China Scholarship Council(CSC)。
文摘Magnesium alloys are promising as load bearing components.They are inevitably exposed to cyclic loading and corrosive environment in actual service,which can consequently result in corrosion fatigue failure and loss of mechanical integrity of the material.Therefore,in the present study,the corrosion behavior,corrosion fatigue performance and mechanical integrity of an extruded Mg4Zn0.2Sn(wt.%)alloy were thoroughly studied in two corrosive electrolytes.Strong localized corrosion occurred when the alloy was immersed in deionized water based sodium chloride(NaCl)solution.The poor corrosion resistance of the alloy resulted in a fast deterioration of the tensile properties after pre-exposure to salt spray and a poor fatigue resistance in deionized water based NaCl solution.In comparison,the active dissolution of the substrate was sufficiently suppressed in artificial tap water based NaCl solution due to the formation of highly protective corrosion product layers.This consequently conferred longer fatigue life on the alloy in the electrolyte.Our results emphasized the influence of corrosion on the fatigue behavior and tensile properties of magnesium alloys.
基金China Scholarship Council for the award of fellowship and funding(201604910527)。
文摘The corrosion performances of the as-cast and solution-treated Mg-0.5Zn samples were investigated in 0.9%Na Cl solution and compared.From the electrochemical measurement results and corrosion morphology observations,it is found that the corrosion resistance of Mg-0.5Zn deteriorated with the extension of solution treatment duration.The main reason was the formation of Fe-Si precipitates with higher Fe concentrations during heat treatment.The Fe-Si precipitates,especially the ones with high Fe contents influenced the corrosion initiation and propagation significantly.In regard of corrosion performance,the solution-treated and then extruded sample was also performing not as good as the cast and then directly extruded sample.
文摘High-porosity,open-cell AZ91 magnesium alloy foams of two pore sizes were fabricated by means of investment casting technology,using PUR foam patterns.Foam casting variables such as pressure,mould temperature and metal pouring temperature were thoroughly investigated to define the most optimal casting conditions.The mechanical properties of the fabricated foams were measured in compression tests.A potential application for the foams considered is temporary bioresorbable bone implants,therefore the mechanical properties of the foams were compared with those of cancellous bone tissue.Foams with smaller pore size and lower porosity(20 PPI and 80%±87%)exhibited mechanical properties in the lower regions of the cancellous bone property range(Young’s modulus 36.5±77.5 MPa),while foams with higher pore size and porosity(10 PPI and~90%)were found to have insufficient compression strength(Young’s modulus 11.65±23.8),but thickening their walls and lowering their porosity below 90%yielded foams with Young’s modulus between 36.5 and 77.5 MPa.Foam fractures were also investigated to determine their collapse mechanism.A series of corrosion tests in stimulated body fluid was carried out to determine their applicability as a biomaterial.The Plasma Electrolytic Oxidation(PEO)process was used in a feasibility study to examine the microstructure and chemical composition of foams with protective coating.
文摘The influence of incorporating different sizes of Si_(3)N_(4) particles on the microstructure and corrosion properties of a phosphate-based plasma electrolytic oxidation (PEO) coating on AM50 magnesium alloy was investigated. The experiments for this study were performed in alkaline electrolytes containing 1 g/L KOH, 10 g/L Na_(3)PO_(4) with and without three different sized of Si_(3)N_(4) particles. The corrosion properties of PEO coatings were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 0.5 wt.% NaCl solution. Microstructure observations by SEM showed that the surface morphology and composition of the PEO coating were affected greatly by particle addition. Si_(3)N_(4) particles can still be found without decomposition in the final coating due to their high melting point.
基金The funding of the ADITIMAT-CM project(S2018/NMT4411,Regional Government of Madrid and EU Structural and Social Funds)PID2021-124341OB-C22(MCIU)+3 种基金the support of RYC-2017-21843the Portuguese Foundation for Science and Technology for the researcher grant(IF/01284/2015)the project CICECO-Aveiro Institute of Materials,UIDB/50011/2020&UIDP/50011/2020financed by national funds through the Portuguese Foundation for Science and Technology/MCTES
文摘The aim of the present study is to evaluate the effect of alloy processing and composition as well as the pH control and testing medium on the in vitro corrosion performance of Mg-Zn-Ca systems for biodegradable implants.The grain size and secondary phases were analyzed by optical microscopy,scanning electron microscopy,transmission electron microscopy,and X-ray diffraction.Scanning kelvin probe force microscopy(SKPFM)was used to analyze the Volta potential values of the second phases.The corrosion performance of the three alloys was evaluated by electrochemical and hydrogen evolution methods inα-MEM with and without organic species(i.e.complete and inorganicα-MEM).Two strategies were followed to evaluate the influence of the pH on the corrosion behavior:daily solution replacement and CO_(2)flow based pH control.For all the materials,the organic medium accelerates the corrosion process.Constant pH maintained by CO_(2)flow through the medium results in considerably higher corrosion rates for all alloys.The impact of pH is lesser on the as-cast alloys due to the barrier effect of the secondary phases,particularly pronounced in the Mg1Zn1Ca alloy which showed the lowest corrosion rate.The wrought Mg0.5Zn0.2Ca alloy that lacks the refined secondary phase network and exhibits high number of twins undergoes accelerated uniform corrosion under constant pH conditions.
基金China Scholarship Council for the award of fellowship and funding (No. 201708510113)。
文摘This work reports the influence of alumina fiber reinforcement of an AZ91Nd MMC(metal matrix composite)on the PEO coating formation process in a sodium phosphate-based electrolyte.By comparison with the pure AZ91Nd,the evolution of alumina fiber during the processing and the characteristics of the resultant PEO coating were investigated.The voltage response as a function of processing time was changed.Lower voltage in the presence of alumina fiber is responsible for the lower coating thickness.The morphology and phase composition of the coatings are also influenced by the incorporation of the fiber.Firstly,the fiber is embedded in the coating and interrupts the continuity of the coating.With increasing processing time,the fiber is found to be reactively incorporated in the coating.The intention to produce a MgAl_(2)O_(4)containing coating is achieved and it is mainly accumulated near the coating surface.However,due to the low number of fibers,the Al content is overall still low and only near to the fibers the MgAl_(2)O_(4)spinel phase can form.
基金China Scholarship Council for the award of fellowship and funding(NO.201708510113)the financial support from National Natural Science Foundation of China(NO.52071067 and U1737102)+1 种基金Mobility Programme of the Sino-German Center(M-0056)the Fundamental Research Funds for the Central Universities(N2002009)。
文摘In order to study the substrate lattice structure(Li addition)on the growth of plasma electrolytic oxidation(PEO)coatings,Mg Li alloy(11.36 wt.%of Li,cubic)and pure Mg(hexagonal)were treated under a pulsed direct PEO mode in a phosphate electrolyte for different periods of time.The results revealed that the presence of Li and Li-rich phases in the cubic Mg alloy seems to be essential for the treatment result rather than the original lattice structure.A modified discharge behavior of Mg Li alloy finally led to a different microstructure of the coating.The unstable coatings of Mg Li alloy tended to dissolve rapidly though shared the similar composition to that of pure Mg.Li was incorporated only in the primary conversion products at the interface of coating/Mg Li.In spite of the advanced efficiency of energy input during processing,the more porous and thinner PEO coatings on the Mg Li alloy were less resistant to abrasion and corrosion.
基金the Alexander von Humboldt foundation for the provision of financial support in the form of post-doctoral fellowship
文摘The microstructures of as-cast ZK40,ZK40 with 2%(mass fraction)CaO and ZK40 with 1%(mass fraction)Y were investigated,and the intermetallic phase morphology and the distribution were characterised.By having discrete intermetallic particles at the grain boundaries for the ZK40,the microstructure was modified to a semi-continuous network of intermetallic compounds along the grain boundaries for the ZK40 with CaO or Y additions.The CaO was not found in the microstructure.However,Ca was present in Ca2Mg6Zn3 intermetallic compounds which were formed during casting.Hydrogen evolution and electrochemical impedance spectroscopy tests revealed that the addition of CaO slightly enhanced the corrosion resistance whereas Y had a negative effect on the corrosion resistance of ZK40.Immersion tests showed that severe localised corrosion as well as corrosion along the intermetallic compounds played an important role in the corrosion process of ZK40-Y whereas the localised corrosion was not pronounced for ZK40 or ZK40?CaO alloys.Micro-segregation in theα-Mg matrix was notably higher for the ZK40 alloy compared with the modified alloys.The combination of this effect with a possible formation of a more stable corrosion layer for the ZK40-CaO was attributed as the main reason for an improved corrosion resistance for the ZK40-CaO alloy.
基金the financial support of the FUNCOAT project(Development and design of novel multifunctional PEO COATings,H2020-RISE-2019-2024,No.823942)the I2B funding in frame MUFfin projectACTICOAT project in frame of Era。
文摘The need to combine various metals in light-weight constructions requires the development of coatings that prevent galvanic corrosion.Layered double hydroxides(LDHs)can be an example of such coatings,which were previously successfully obtained in situ on individual materials.In addition,the possibility of LDH growth(including LDH growth in the presence of chelating agents)on the surface of plasma electrolytic oxidation(PEO)-coated metals was previously shown.This PEO+LDH combination could improve both corrosion and mechanical characteristics of the system.The possibility of LDHs formation in situ on the surface of PEO-coated friction stir welded(FSW)magnesium-aluminum materials(AZ31/AA5754 system was selected as a model one)was demonstrated in the presence of 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid(DHPTA)as a chelating agent,which was selected based on analysis of respective metal-ligand compounds stability.LDHs growth was achieved under ambient pressure without addition of carbonates in the electrolyte.The effectiveness of the resulting coating is shown both for corrosion resistance and hardness.
