In this study,a calcium-phosphate coating was formed on a Mg-Mn-Ce alloy by the plasma electrolytic oxidation(PEO).The antibiotic vancomycin,widely used in the treatment of infections caused by Staphylococcus aureus(S...In this study,a calcium-phosphate coating was formed on a Mg-Mn-Ce alloy by the plasma electrolytic oxidation(PEO).The antibiotic vancomycin,widely used in the treatment of infections caused by Staphylococcus aureus(S.aureus),was impregnated into the coating.Samples with vancomycin showed high bactericidal activity against S.aureus.The mechanical and electrochemical properties of the formed coatings were studied,as well as in vitro cytotoxicity tests and in vivo tests on mature male rats were performed.According to SEM,EDS,XRD and XPS data,coatings had a developed morphology and contained hydroxyapatite,which indicates high biocompatibility.The analysis of roughness of coatings without and with vancomycin did not reveal any differences,confirming the high roughness of the samples.During electrochemical tests,an increase in corrosion resistance by more than two times after the application of PEO coatings was revealed.According to the results of an in vivo study,after 28 days of the implantation of samples with calcium phosphate PEO coating and vancomycin,no signs of inflammation were observed,while an inflammatory reaction developed in the area of implantation of bare alloy,followed by encapsulation.Antibiotic release tests from the coatings show a sharp decrease in the concentration of the released antibiotic on day 7 and then a gradual decrease until day 28.Throughout the experiment,no significant deviations in the condition and behavior of the animals were observed;clinical tests did not reveal a systemic toxic reaction.展开更多
The Sr/F co-doped CaP(Sr/F-CaP)coatings were prepared by micro-arc oxidation(MAO)under different voltages to modify the microstructure and corrosion behavior of Mg-4Zn-1Mn alloy.The surface and interface characteristi...The Sr/F co-doped CaP(Sr/F-CaP)coatings were prepared by micro-arc oxidation(MAO)under different voltages to modify the microstructure and corrosion behavior of Mg-4Zn-1Mn alloy.The surface and interface characteristics investigated using scanning electron microscopy(SEM)and energy dispersive X-ray spectrometer(EDS)showed that the MAO coatings displayed uneven crater-like holes and tiny cracks under lower voltage,while they exhibited relatively homogeneous crater-like holes without cracks under higher voltage.The thickness of MAO coatings increased with increasing voltage.The corrosion behavior of Mg-4Zn-1Mn alloy was improved by the MAO coatings.The MAO coatings prepared under 450 V and 500 V voltages possessed the best corrosion resistance with regard to the electrochemical corrosion tests and immersion corrosion tests,respectively.The MAO coatings fabricated under 450-500 V could provide a better corrosion protection effect for the substrate.展开更多
The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification proc...The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification process,which cannot provide sufficient protection.In the current study,we design a double-layer epoxy composite coating on Mg alloy with enhanced anti-corrosion/wear properties,via the spin-assisted assembly technique.The outer layer is functionalized graphene(FG)in waterborne epoxy resin(WEP)and the inner layer is Ce-based conversion(Ce)film.The FG sheets can be homogeneously dispersed within the epoxy matrix to fill the intrinsic defects and improve the barrier capability.The Ce film connects the outer layer with the substrate,showing the transition effect.The corrosion rate of Ce/WEP/FG composite coating is 2131 times lower than that of bare Mg alloy,and the wear rate is decreased by~90%.The improved corrosion resistance is attributed to the labyrinth effect(hindering the penetration of corrosive medium)and the obstruction of galvanic coupling behavior.The synergistic effect derived from the FG sheet and blocking layer exhibits great potential in realizing the improvement of multi-functional integration,which will open up a new avenue for the development of novel composite protection coatings of Mg alloys.展开更多
Magnesium(Mg)alloys are lightweight materials with excellent mechanical properties,making them attractive for various applications,including aerospace,automotive,and biomedical industries.However,the practical applica...Magnesium(Mg)alloys are lightweight materials with excellent mechanical properties,making them attractive for various applications,including aerospace,automotive,and biomedical industries.However,the practical application of Mg alloys is limited due to their high susceptibility to corrosion.Plasma electrolytic oxidation(PEO),or micro-arc oxidation(MAO),is a coating method that boosts Mg alloys'corrosion resistance.However,despite the benefits of PEO coatings,they can still exhibit certain limitations,such as failing to maintain long-term protection as a result of their inherent porosity.To address these challenges,researchers have suggested the use of inhibitors in combination with PEO coatings on Mg alloys.Inhibitors are chemical compounds that can be incorporated into the coating or applied as a post-treatment to further boost the corrosion resistance of the PEO-coated Mg alloys.Corrosion inhibitors,whether organic or inorganic,can act by forming a protective barrier,hindering the corrosion process,or modifying the surface properties to reduce susceptibility to corrosion.Containers can be made of various materials,including polyelectrolyte shells,layered double hydroxides,polymer shells,and mesoporous inorganic materials.Encapsulating corrosion inhibitors in containers fully compatible with the coating matrix and substrate is a promising approach for their incorporation.Laboratory studies of the combination of inhibitors with PEO coatings on Mg alloys have shown promising results,demonstrating significant corrosion mitigation,extending the service life of Mg alloy components in aggressive environments,and providing self-healing properties.In general,this review presents available information on the incorporation of inhibitors with PEO coatings,which can lead to improved performance of Mg alloy components in demanding environments.展开更多
Mg alloys are considered the most promising engineering materials because of their unique properties.However,the uncontrolled corrosion rate of these alloys limits their applications.Therefore,in this study,a micro-ar...Mg alloys are considered the most promising engineering materials because of their unique properties.However,the uncontrolled corrosion rate of these alloys limits their applications.Therefore,in this study,a micro-arc oxidation layer was used as a transition layer to“directly”grow a zinc-based metal-organic framework(MOF)composite coating on the surface of a Mg alloy(AZ91D).Herein,the two zeolitic imidazolate framework(ZIF-8)coatings with different morphologies were separately prepared by homologous metal oxide induction and a one-step in-situ growth method.The superhydrophobic composite coating showed strong hydrophobicity and self-cleaning properties,which could prevent the penetration of water and corrosive ions(Cl^(−))into the surface of AZ91D.Electrochemical tests demonstrated that the super-hydrophobic composite coatings greatly enhanced the corrosion resistance of AZ91D,and the corrosion current density decreased from 10^(−5)to 10^(−9)A/cm^(2).These results indicate that the ZIF-8 coatings are beneficial for improving the hydrophobicity and enhancing the corrosion resistance of Mg alloys.Therefore,MOF composite coatings provide a new strategy that can be used to prepare multifunctional anticorrosion coatings on metal substrates.展开更多
Layered double hydroxide(LDH)coatings on magnesium(Mg)alloys shine brightly in the field of corrosion protection because of their special ion-exchange function.State-of-the-art steam coating as a type of LDH film prep...Layered double hydroxide(LDH)coatings on magnesium(Mg)alloys shine brightly in the field of corrosion protection because of their special ion-exchange function.State-of-the-art steam coating as a type of LDH film preparation technique has emerged in recent years because only pure water is required as the steam source and its environmentally friendly LDH coating fits the current need for green development.Moreover,this coating can effectively inhibit the corrosion of the Mg alloy substrate due to the chemical bonding between the coating and the Mg alloy substrate.This review systematically explains cutting-edge advancements in the growth mechanism and corrosion behavior of LDH steam coatings,and analyzes the advantages and limitations of the steam-coating method.The influencing factors including pressure,CO_(2)/CO_(3)^(2-),aluminum content of the substrate alloy,solution type,and acid-pickling pretreatment,as well as the post-treatment of steam-coating defects,are comprehensively elucidated,providing new insights into the development of the in situ steam-coating technique.Finally,existing issues and future prospects are discussed to further accelerate the widespread application of Mg alloys.展开更多
Mg and its alloys have been introduced as promising biodegradable materials for biomedical implant applications due to their excellent biocompatibility, mechanical behavior, and biodegradability. However, their suscep...Mg and its alloys have been introduced as promising biodegradable materials for biomedical implant applications due to their excellent biocompatibility, mechanical behavior, and biodegradability. However, their susceptibility to rapid corrosion within the body poses a significant challenge and restricts their applications. To overcome this issue, various surface modification techniques have been developed to enhance the corrosion resistance and bioactivity of Mg-based implants. PEO is a potent technique for producing an oxide film on a surface that significantly minimizes the tendency to corrode. However, the inevitable defects due to discharges and poor biological activity during the coating process remain a concern. Therefore, adding suitable particles during the coating process is a suitable solution. Hydroxyapatite(HAp)has attracted much attention in the development of biomedical applications in the scientific community. HAp shows excellent biocompatibility due to its similarity in chemical composition to the mineral portion of bone. Therefore, its combination with Mg-based implants through PEO has shown significant improvements in their corrosion resistance and bioactivity. This review paper provides a comprehensive overview of the recent advances in the preparation, characterization, corrosion behavior and bioactivity applications of HAp particles on Mg-based implants by PEO.展开更多
Featuring low density and high specific strength, magnesium(Mg) alloys have attracted wide interests in the fields of portable devices and automotive industry. However, the active chemical and electrochemical properti...Featuring low density and high specific strength, magnesium(Mg) alloys have attracted wide interests in the fields of portable devices and automotive industry. However, the active chemical and electrochemical properties make them susceptible to corrosion in humid, seawater, soil,and chemical medium. Various strategies have revealed certain merits of protecting Mg alloys. Therein, engineering self-repairing coatings is considered as an effective strategy, because they can enable the timely repair for damaged areas, which brings about long-term protection for Mg alloys. In this review, self-repairing coatings on Mg alloys are summarized from two aspects, namely shape restoring coatings and function restoring coatings. Shape restoring coatings benefit for swelling, shrinking, or reassociating reversible chemical bonds to return to the original state and morphology when coatings broken;function self-repairing coatings depend on the release of inhibitors to generate new passive layers on the damaged areas. With the advancement of coating research and to fulfill the demanding requirements of applications, it is an inevitable trend to develop coatings that can integrate multiple functions(such as stimulus response, self-repairing, corrosion warning,and so on). As a novel carrier and barrier, porous solids, especially covalent organic frameworks(COFs), have been respected as the future development of self-repairing coatings on Mg alloys, due to their unique, diverse structures and adjustable functions.展开更多
The high activity of metallic magnesium and alloys limits its potential in biomedical applications;in recent years,extensive efforts have been devoted to modulating this reactivity.In this work,we present Mg(OH)_(2) a...The high activity of metallic magnesium and alloys limits its potential in biomedical applications;in recent years,extensive efforts have been devoted to modulating this reactivity.In this work,we present Mg(OH)_(2) and TiO_(2)barrier coatings to reduce the degradation of magnesium alloy(Mg-Ca-Zn)surfaces.These coatings were deposited by the anodization method and the spin-coating technique,respectively.The anodized layer was coated with TiO_(2)generated from the hydrolysis of 3%weight of TTIP(Ti[OCH(CH_(3))_(2)]_(4),Titanium(IV)isopropoxide)in 2-Propanol deposited by the spin-coating method.Studying the degradation in Ringer’s solution by electrochemical impedance spectroscopy and OCP revealed a 98%reduction in pittings in uncoated samples after 14 days of immersion.The p H measurements revealed that the TiO_(2)coating reduced the alkalization of the physiological environment,keeping the pH at 6.0 values.In vitro studies of two types of bacteria(E.coli and S.aureus)exhibited zones of inhibition in the agar and activity bactericidal(kill time test).The mechanisms behind the improved degradation resistance and enhanced antibacterial activity are presented and discussed here.Surface modification with Mg(OH)_(2)/TiO_(2)coatings is a promising strategy to control the biodegradation of magnesium implants for bone regeneration.展开更多
Works on exploring an environmentally clean method for producing an Mg,Al-hydrotalcite(Mg6Al2(OH) 16CO3·4H2O) layer and/or calcium carbonate(CaCO3) layer on Mg alloy in a carbonic acid solution system(aqueous HCO...Works on exploring an environmentally clean method for producing an Mg,Al-hydrotalcite(Mg6Al2(OH) 16CO3·4H2O) layer and/or calcium carbonate(CaCO3) layer on Mg alloy in a carbonic acid solution system(aqueous HCO3-/CO3 2-or Ca 2+ /HCO3-) at 50℃ were reviewed.Conversion treatment for the Mg,Al-hydrotalcite conversion coating was as follows.Mg alloy was treated first in acidic HCO3-/CO3 2-aqueous for precursor layer formation on Mg alloy surface and then in alkaline HCO3-/CO3 2-aqueous to form a crystallized Mg,Al-hydrotalcite coating.Duration of an Mg,Al-hydrotalcite coating on Mg alloy surface was reduced from 12 h to 4 h by the conversion treatment.On the other hand,for reducing the formation time of CaCO3 coating on Mg alloy,the aqueous Ca 2+ /HCO3-with a saturated Ca 2+ content was employed for developing a CaCO3 coating on Mg alloy.A dense CaCO3 coating could yield on Mg alloy surface in 2 h.Corrosion rate(corrosion current density,Jcorr) of the Mg,Al-hydrotalcite-coated sample and CaCO3-coated AZ91D sample was 7-10μA/cm 2,roughly two orders less than the Jcorr of the as-diecast sample(about 200μA/cm 2) . No corrosion spot on the Mg,Al-hydrotalcite-coated sample and CaCO3-coated sample was observed after 72 h and 192 h salt spray test,respectively.展开更多
Recently,developing bioactive and biocompatible materials based on Mg and Mg-alloys for implant applications has drawn attention among researchers owing to their suitable body degradability.Implementing Mg and its all...Recently,developing bioactive and biocompatible materials based on Mg and Mg-alloys for implant applications has drawn attention among researchers owing to their suitable body degradability.Implementing Mg and its alloys reduces the risk of long-term incompatibility with tissues because of their close mechanical properties and no need for re-operation to remove the implant.Nevertheless,the degradation rate of the implant needs to be controlled because production of hydrogen gas and accumulation of its bubbles increases local pH around the implants.To confine the integrity of implants and the body,the corrosion concern in the body fluid requires to be addressed.Surface modification as one of the effective strategies can improve corrosion resistance.Besides,it creates a suitable surface for bone grafting and cell growth.The development of proper surface-coated implants needs appropriate techniques and approaches.Plasma electrolytic oxidation(PEO)coating can provide long-term protection by providing a ceramic layer and improving the implant’s biocompatibility.Herein,a general review of in-vivo and in-vitro evaluation of PEO coatings on Mg and Mg-alloys has been carried out.Recent advances in surface modification on Mg and Mg-alloys have been discussed,however,the need for reliable laboratory models to predict in-vivo degradation is still valid.展开更多
Magnesium(Mg)and its alloys have received much attention in a lot of areas due to their special chemical and physical properties.Nevertheless,high corrosion rates are a limiting factor.The plasma electrolytic oxidatio...Magnesium(Mg)and its alloys have received much attention in a lot of areas due to their special chemical and physical properties.Nevertheless,high corrosion rates are a limiting factor.The plasma electrolytic oxidation(PEO)technique is a simple approach to place an oxide film on the surface of light metals like Mg alloys.This method has been considered for controlling the rate of corrosion and improving some other properties.On the other hand,PEO coatings cannot make enough protection of Magnesium alloys for a long time due to porosity and fine cracks.Therefore,PEO-based composite coatings are used to make adequate corrosion protection on the Mg alloys surface.The popularity of these coatings is due to their good corrosion resistance,simplicity,high coating capability,and cost-effectiveness in complex segments.Formation of an organic layer on the surface of PEO coating is one of the effective methods to close the defects and thus prevent the corrosive species penetration into the substrate.Coating the PEO coating with a polymer layer can be a good solution to control the amount of damage and improve the corrosion and abrasion resistance.In addition,PEO coating can eliminate the problems of insufficient adhesion of polymer coatings and is considered as a suitable base for composite coatings.This review paper presents the corrosion and abrasion behavior of the PEO/Polymer dual coating system on Mg alloys.Given the fundamental role of coatings thickness and morphology in wear and corrosion behavior,these aspects have been highly discussed in this study.展开更多
Micro-arc oxidation (MAO) method was used for the surface modification of an Mg-5wt.%Li alloy. Ceramic coatings were in-situ fabricated on the Mg-Li alloy. The morphology feature,phase composition,and corrosion-resist...Micro-arc oxidation (MAO) method was used for the surface modification of an Mg-5wt.%Li alloy. Ceramic coatings were in-situ fabricated on the Mg-Li alloy. The morphology feature,phase composition,and corrosion-resistance of the formed ceramic coatings were studied by SEM,XRD,and electrochemical methods,respectively. The results showed that the coatings produced in a sodium silicate solution system were composed of MgO and Mg2SiO4. The ceramic coating became thicker and the content of Mg2SiO4 phase increase...展开更多
The microstructure of Mg-8Zn-4Al-1Ca aged alloy was investigated by TEM and HRTEM. The results show that the hardening produced in the Mg-8Zn-4Al-1Ca alloy is considerably higher than that in the Mg-8Zn-4A1 alloy. A d...The microstructure of Mg-8Zn-4Al-1Ca aged alloy was investigated by TEM and HRTEM. The results show that the hardening produced in the Mg-8Zn-4Al-1Ca alloy is considerably higher than that in the Mg-8Zn-4A1 alloy. A dense dispersion of disc-like Ca2Mg6Zn3 precipitates are formed in Mg-8Zn-4Al-1Ca alloy aged at 160 ℃ for 16 h. In addition, the lattice distortions, honeycomb-looking Moir＆#233; fringes, edge dislocations and dislocation loop also exist in the microstructure. The precipitates of alloy aged at 160 ℃ for 48 h are coarse disc-like and fine dispersed grainy. When the alloy is subjected to aging at 160 ℃ for 227 h, the microstructure consists of numerous MgZn2 precipitates and Ca2Mg6Zn3 precipitates. All the analyses show that Ca is a particularly effective trace addition in improving the age-hardening and postponing the formation of MgZn2 precipitates in Mg-8Zn-4Al alloy aged at 160 ℃.展开更多
Rapidly solidified（RS） Mg-6Zn-1Y-1Ce ribbons were prepared by single roller melt-spinning technique.Transmission electron microscopy and energy dispersive X-ray spectroscopy were employed to characterize the microst...Rapidly solidified（RS） Mg-6Zn-1Y-1Ce ribbons were prepared by single roller melt-spinning technique.Transmission electron microscopy and energy dispersive X-ray spectroscopy were employed to characterize the microstructure of RS ribbons.The results show that there is high density of particles distributed within grains and at grain boundaries in the region near wheel side.The particle density is decreased in the middle region and free surface region.The alloy is predominantly composed of supersaturated--Mg solid solution,T phase and W phase;meanwhile,a few icosahedral quasicrystalline and Mg4Zn7 particles are also observed.The T phase is confirmed having a body-centered orthorhombic structure that is transformed from the body-centered tetragonal structure Mg12Ce phase due to the partial substitution of Mg atoms by Zn.展开更多
A longstanding quest in material science has been the development of superhydrophobic coating based on a single material, without the requirement of fluorination or silane treatment. In this work, the micro-arc oxidat...A longstanding quest in material science has been the development of superhydrophobic coating based on a single material, without the requirement of fluorination or silane treatment. In this work, the micro-arc oxidation(MAO) coating as transition layer can effectively enhance the bonding force of the superhydrophobic coating. The semiconductor@metal organic frameworks(MOFs) core-shell structure was synthesized by a simple self-templating method, and obtained ZnO@2-methylimidazole zinc salt(ZIF-8) nanorods array on magnesium(Mg)alloy. ZnO nanorods not only act as the template but also provide Zn^(2+) for ZIF-8. In addition, we proved that the ligand concentration,synthesis time and temperature are the keys to the preparation of ZnO@ZIF-8 nanorods. As we expect, the ZnO@ZIF-8 nanorods array can trap air in the gaps to form an air layer, and the coating exhibits superhydrophobic properties(154.81°). Excitingly, ZnO@ZIF-8 nanorods array shown a superhydrophobic property, without the requirement of fluorination or silane treatment. The results shown that the coating has good chemical stability and self-cleaning performance. Meanwhile, the corrosion resistance has been significantly improved, R_(ct) was increased from 1.044×10^(3) to 1.414×10^(6) Ω/cm^(2) and I_(corr) was reduced from 4.275×10^(-5) to 5.611×10^(-9)A/cm^2. Therefore, the semiconductor@MOFs core-shell structure has broad application prospects in anti-corrosion.展开更多
Plasma electrolytic oxidation（PEO） was developed as a bond coat for air plasma sprayed（APS） nanostructure ZrO2 as top coat to enhance the corrosion resistance and antibacterial activity of Mg alloy. Corrosion beha...Plasma electrolytic oxidation（PEO） was developed as a bond coat for air plasma sprayed（APS） nanostructure ZrO2 as top coat to enhance the corrosion resistance and antibacterial activity of Mg alloy. Corrosion behavior and antibacterial activities of coated and uncoated samples were assessed by electrochemical tests and agar diffusion method toward Escherichia coli（E. coli） bacterial pathogens, respectively. The lowest corrosion current density and the highest charge transfer resistance, phase angle and impedance modulus were observed for PEO/nano-ZrO2 coated sample compared with those of PEO coated and bare Mg alloys. Nano-ZrO2 top coat which has completely sealed PEO bond coat is able to considerably delay aggressive ions transportation towards Mg alloy surface and significantly enhances corrosion resistance of Mg alloy in simulated body fluid（SBF） solution. Moreover, higher antibacterial activity was also observed in PEO/nano-ZrO2 coating against bacterial strains than that of the PEO coated and bare Mg alloys. This observation was attributed to the presence of ZrO2 nanoparticles which decelerate E. coli growth as a result of E. coli membranes.展开更多
基金supported by Russian Science Foundation Grant no.22-73-10149,https://rscf.ru/project/22-73-10149/supported by the Russian Science Foundation Grant no.23-13-00329,https://rscf.ru/project/23-13-00329/。
文摘In this study,a calcium-phosphate coating was formed on a Mg-Mn-Ce alloy by the plasma electrolytic oxidation(PEO).The antibiotic vancomycin,widely used in the treatment of infections caused by Staphylococcus aureus(S.aureus),was impregnated into the coating.Samples with vancomycin showed high bactericidal activity against S.aureus.The mechanical and electrochemical properties of the formed coatings were studied,as well as in vitro cytotoxicity tests and in vivo tests on mature male rats were performed.According to SEM,EDS,XRD and XPS data,coatings had a developed morphology and contained hydroxyapatite,which indicates high biocompatibility.The analysis of roughness of coatings without and with vancomycin did not reveal any differences,confirming the high roughness of the samples.During electrochemical tests,an increase in corrosion resistance by more than two times after the application of PEO coatings was revealed.According to the results of an in vivo study,after 28 days of the implantation of samples with calcium phosphate PEO coating and vancomycin,no signs of inflammation were observed,while an inflammatory reaction developed in the area of implantation of bare alloy,followed by encapsulation.Antibiotic release tests from the coatings show a sharp decrease in the concentration of the released antibiotic on day 7 and then a gradual decrease until day 28.Throughout the experiment,no significant deviations in the condition and behavior of the animals were observed;clinical tests did not reveal a systemic toxic reaction.
文摘The Sr/F co-doped CaP(Sr/F-CaP)coatings were prepared by micro-arc oxidation(MAO)under different voltages to modify the microstructure and corrosion behavior of Mg-4Zn-1Mn alloy.The surface and interface characteristics investigated using scanning electron microscopy(SEM)and energy dispersive X-ray spectrometer(EDS)showed that the MAO coatings displayed uneven crater-like holes and tiny cracks under lower voltage,while they exhibited relatively homogeneous crater-like holes without cracks under higher voltage.The thickness of MAO coatings increased with increasing voltage.The corrosion behavior of Mg-4Zn-1Mn alloy was improved by the MAO coatings.The MAO coatings prepared under 450 V and 500 V voltages possessed the best corrosion resistance with regard to the electrochemical corrosion tests and immersion corrosion tests,respectively.The MAO coatings fabricated under 450-500 V could provide a better corrosion protection effect for the substrate.
基金the National Natural Science Foundation of China(Grant number 51771178)Shaanxi Outstanding Youth Fund project(Grant number 2021JC-45)+2 种基金Key international cooperation projects in Shaanxi Province(Grant number 2020KWZ-007)the Major Program of Science and Technology in Shaanxi Province(Grant number20191102006)Open Fund of State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body(Grant number 32115019)。
文摘The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification process,which cannot provide sufficient protection.In the current study,we design a double-layer epoxy composite coating on Mg alloy with enhanced anti-corrosion/wear properties,via the spin-assisted assembly technique.The outer layer is functionalized graphene(FG)in waterborne epoxy resin(WEP)and the inner layer is Ce-based conversion(Ce)film.The FG sheets can be homogeneously dispersed within the epoxy matrix to fill the intrinsic defects and improve the barrier capability.The Ce film connects the outer layer with the substrate,showing the transition effect.The corrosion rate of Ce/WEP/FG composite coating is 2131 times lower than that of bare Mg alloy,and the wear rate is decreased by~90%.The improved corrosion resistance is attributed to the labyrinth effect(hindering the penetration of corrosive medium)and the obstruction of galvanic coupling behavior.The synergistic effect derived from the FG sheet and blocking layer exhibits great potential in realizing the improvement of multi-functional integration,which will open up a new avenue for the development of novel composite protection coatings of Mg alloys.
文摘Magnesium(Mg)alloys are lightweight materials with excellent mechanical properties,making them attractive for various applications,including aerospace,automotive,and biomedical industries.However,the practical application of Mg alloys is limited due to their high susceptibility to corrosion.Plasma electrolytic oxidation(PEO),or micro-arc oxidation(MAO),is a coating method that boosts Mg alloys'corrosion resistance.However,despite the benefits of PEO coatings,they can still exhibit certain limitations,such as failing to maintain long-term protection as a result of their inherent porosity.To address these challenges,researchers have suggested the use of inhibitors in combination with PEO coatings on Mg alloys.Inhibitors are chemical compounds that can be incorporated into the coating or applied as a post-treatment to further boost the corrosion resistance of the PEO-coated Mg alloys.Corrosion inhibitors,whether organic or inorganic,can act by forming a protective barrier,hindering the corrosion process,or modifying the surface properties to reduce susceptibility to corrosion.Containers can be made of various materials,including polyelectrolyte shells,layered double hydroxides,polymer shells,and mesoporous inorganic materials.Encapsulating corrosion inhibitors in containers fully compatible with the coating matrix and substrate is a promising approach for their incorporation.Laboratory studies of the combination of inhibitors with PEO coatings on Mg alloys have shown promising results,demonstrating significant corrosion mitigation,extending the service life of Mg alloy components in aggressive environments,and providing self-healing properties.In general,this review presents available information on the incorporation of inhibitors with PEO coatings,which can lead to improved performance of Mg alloy components in demanding environments.
基金supported by Guangxi Natural Science Foundation of China(No.2020GXNSFAA159011)National Natural Science Foundation of China(No.51664011)Guangxi Key Laboratory Foundation of China(No.EMFM20211120).
文摘Mg alloys are considered the most promising engineering materials because of their unique properties.However,the uncontrolled corrosion rate of these alloys limits their applications.Therefore,in this study,a micro-arc oxidation layer was used as a transition layer to“directly”grow a zinc-based metal-organic framework(MOF)composite coating on the surface of a Mg alloy(AZ91D).Herein,the two zeolitic imidazolate framework(ZIF-8)coatings with different morphologies were separately prepared by homologous metal oxide induction and a one-step in-situ growth method.The superhydrophobic composite coating showed strong hydrophobicity and self-cleaning properties,which could prevent the penetration of water and corrosive ions(Cl^(−))into the surface of AZ91D.Electrochemical tests demonstrated that the super-hydrophobic composite coatings greatly enhanced the corrosion resistance of AZ91D,and the corrosion current density decreased from 10^(−5)to 10^(−9)A/cm^(2).These results indicate that the ZIF-8 coatings are beneficial for improving the hydrophobicity and enhancing the corrosion resistance of Mg alloys.Therefore,MOF composite coatings provide a new strategy that can be used to prepare multifunctional anticorrosion coatings on metal substrates.
基金This work was supported by the National Natural Science Foundation of China through the projects 51601108 and 52071191。
文摘Layered double hydroxide(LDH)coatings on magnesium(Mg)alloys shine brightly in the field of corrosion protection because of their special ion-exchange function.State-of-the-art steam coating as a type of LDH film preparation technique has emerged in recent years because only pure water is required as the steam source and its environmentally friendly LDH coating fits the current need for green development.Moreover,this coating can effectively inhibit the corrosion of the Mg alloy substrate due to the chemical bonding between the coating and the Mg alloy substrate.This review systematically explains cutting-edge advancements in the growth mechanism and corrosion behavior of LDH steam coatings,and analyzes the advantages and limitations of the steam-coating method.The influencing factors including pressure,CO_(2)/CO_(3)^(2-),aluminum content of the substrate alloy,solution type,and acid-pickling pretreatment,as well as the post-treatment of steam-coating defects,are comprehensively elucidated,providing new insights into the development of the in situ steam-coating technique.Finally,existing issues and future prospects are discussed to further accelerate the widespread application of Mg alloys.
文摘Mg and its alloys have been introduced as promising biodegradable materials for biomedical implant applications due to their excellent biocompatibility, mechanical behavior, and biodegradability. However, their susceptibility to rapid corrosion within the body poses a significant challenge and restricts their applications. To overcome this issue, various surface modification techniques have been developed to enhance the corrosion resistance and bioactivity of Mg-based implants. PEO is a potent technique for producing an oxide film on a surface that significantly minimizes the tendency to corrode. However, the inevitable defects due to discharges and poor biological activity during the coating process remain a concern. Therefore, adding suitable particles during the coating process is a suitable solution. Hydroxyapatite(HAp)has attracted much attention in the development of biomedical applications in the scientific community. HAp shows excellent biocompatibility due to its similarity in chemical composition to the mineral portion of bone. Therefore, its combination with Mg-based implants through PEO has shown significant improvements in their corrosion resistance and bioactivity. This review paper provides a comprehensive overview of the recent advances in the preparation, characterization, corrosion behavior and bioactivity applications of HAp particles on Mg-based implants by PEO.
基金the financial support from the National Natural Science Foundation of China(No.52222510)Key Research and Development Program of Shandong Province,China(No.2021ZLGX01)。
基金the financial support from the National Natural Science Foundation of China (Nos.52204389,U19A2084 and 52234009)the National Key Research and Development Program (No.2022YFE0122000)Program for the Central University Youth Innovation Team。
文摘Featuring low density and high specific strength, magnesium(Mg) alloys have attracted wide interests in the fields of portable devices and automotive industry. However, the active chemical and electrochemical properties make them susceptible to corrosion in humid, seawater, soil,and chemical medium. Various strategies have revealed certain merits of protecting Mg alloys. Therein, engineering self-repairing coatings is considered as an effective strategy, because they can enable the timely repair for damaged areas, which brings about long-term protection for Mg alloys. In this review, self-repairing coatings on Mg alloys are summarized from two aspects, namely shape restoring coatings and function restoring coatings. Shape restoring coatings benefit for swelling, shrinking, or reassociating reversible chemical bonds to return to the original state and morphology when coatings broken;function self-repairing coatings depend on the release of inhibitors to generate new passive layers on the damaged areas. With the advancement of coating research and to fulfill the demanding requirements of applications, it is an inevitable trend to develop coatings that can integrate multiple functions(such as stimulus response, self-repairing, corrosion warning,and so on). As a novel carrier and barrier, porous solids, especially covalent organic frameworks(COFs), have been respected as the future development of self-repairing coatings on Mg alloys, due to their unique, diverse structures and adjustable functions.
基金financed by the FOMIX-Yucatán 2008-108160,CONACYT LAB-2009-01-123913,292692,294643,188345,and 204822 projectsthe financial support received from CONACYT。
文摘The high activity of metallic magnesium and alloys limits its potential in biomedical applications;in recent years,extensive efforts have been devoted to modulating this reactivity.In this work,we present Mg(OH)_(2) and TiO_(2)barrier coatings to reduce the degradation of magnesium alloy(Mg-Ca-Zn)surfaces.These coatings were deposited by the anodization method and the spin-coating technique,respectively.The anodized layer was coated with TiO_(2)generated from the hydrolysis of 3%weight of TTIP(Ti[OCH(CH_(3))_(2)]_(4),Titanium(IV)isopropoxide)in 2-Propanol deposited by the spin-coating method.Studying the degradation in Ringer’s solution by electrochemical impedance spectroscopy and OCP revealed a 98%reduction in pittings in uncoated samples after 14 days of immersion.The p H measurements revealed that the TiO_(2)coating reduced the alkalization of the physiological environment,keeping the pH at 6.0 values.In vitro studies of two types of bacteria(E.coli and S.aureus)exhibited zones of inhibition in the agar and activity bactericidal(kill time test).The mechanisms behind the improved degradation resistance and enhanced antibacterial activity are presented and discussed here.Surface modification with Mg(OH)_(2)/TiO_(2)coatings is a promising strategy to control the biodegradation of magnesium implants for bone regeneration.
基金Project supported by the Ministry of Education Under the ATU Plan
文摘Works on exploring an environmentally clean method for producing an Mg,Al-hydrotalcite(Mg6Al2(OH) 16CO3·4H2O) layer and/or calcium carbonate(CaCO3) layer on Mg alloy in a carbonic acid solution system(aqueous HCO3-/CO3 2-or Ca 2+ /HCO3-) at 50℃ were reviewed.Conversion treatment for the Mg,Al-hydrotalcite conversion coating was as follows.Mg alloy was treated first in acidic HCO3-/CO3 2-aqueous for precursor layer formation on Mg alloy surface and then in alkaline HCO3-/CO3 2-aqueous to form a crystallized Mg,Al-hydrotalcite coating.Duration of an Mg,Al-hydrotalcite coating on Mg alloy surface was reduced from 12 h to 4 h by the conversion treatment.On the other hand,for reducing the formation time of CaCO3 coating on Mg alloy,the aqueous Ca 2+ /HCO3-with a saturated Ca 2+ content was employed for developing a CaCO3 coating on Mg alloy.A dense CaCO3 coating could yield on Mg alloy surface in 2 h.Corrosion rate(corrosion current density,Jcorr) of the Mg,Al-hydrotalcite-coated sample and CaCO3-coated AZ91D sample was 7-10μA/cm 2,roughly two orders less than the Jcorr of the as-diecast sample(about 200μA/cm 2) . No corrosion spot on the Mg,Al-hydrotalcite-coated sample and CaCO3-coated sample was observed after 72 h and 192 h salt spray test,respectively.
文摘Recently,developing bioactive and biocompatible materials based on Mg and Mg-alloys for implant applications has drawn attention among researchers owing to their suitable body degradability.Implementing Mg and its alloys reduces the risk of long-term incompatibility with tissues because of their close mechanical properties and no need for re-operation to remove the implant.Nevertheless,the degradation rate of the implant needs to be controlled because production of hydrogen gas and accumulation of its bubbles increases local pH around the implants.To confine the integrity of implants and the body,the corrosion concern in the body fluid requires to be addressed.Surface modification as one of the effective strategies can improve corrosion resistance.Besides,it creates a suitable surface for bone grafting and cell growth.The development of proper surface-coated implants needs appropriate techniques and approaches.Plasma electrolytic oxidation(PEO)coating can provide long-term protection by providing a ceramic layer and improving the implant’s biocompatibility.Herein,a general review of in-vivo and in-vitro evaluation of PEO coatings on Mg and Mg-alloys has been carried out.Recent advances in surface modification on Mg and Mg-alloys have been discussed,however,the need for reliable laboratory models to predict in-vivo degradation is still valid.
文摘Magnesium(Mg)and its alloys have received much attention in a lot of areas due to their special chemical and physical properties.Nevertheless,high corrosion rates are a limiting factor.The plasma electrolytic oxidation(PEO)technique is a simple approach to place an oxide film on the surface of light metals like Mg alloys.This method has been considered for controlling the rate of corrosion and improving some other properties.On the other hand,PEO coatings cannot make enough protection of Magnesium alloys for a long time due to porosity and fine cracks.Therefore,PEO-based composite coatings are used to make adequate corrosion protection on the Mg alloys surface.The popularity of these coatings is due to their good corrosion resistance,simplicity,high coating capability,and cost-effectiveness in complex segments.Formation of an organic layer on the surface of PEO coating is one of the effective methods to close the defects and thus prevent the corrosive species penetration into the substrate.Coating the PEO coating with a polymer layer can be a good solution to control the amount of damage and improve the corrosion and abrasion resistance.In addition,PEO coating can eliminate the problems of insufficient adhesion of polymer coatings and is considered as a suitable base for composite coatings.This review paper presents the corrosion and abrasion behavior of the PEO/Polymer dual coating system on Mg alloys.Given the fundamental role of coatings thickness and morphology in wear and corrosion behavior,these aspects have been highly discussed in this study.
文摘Micro-arc oxidation (MAO) method was used for the surface modification of an Mg-5wt.%Li alloy. Ceramic coatings were in-situ fabricated on the Mg-Li alloy. The morphology feature,phase composition,and corrosion-resistance of the formed ceramic coatings were studied by SEM,XRD,and electrochemical methods,respectively. The results showed that the coatings produced in a sodium silicate solution system were composed of MgO and Mg2SiO4. The ceramic coating became thicker and the content of Mg2SiO4 phase increase...
基金Project(51141007)supported by the National Natural Science Foundation of ChinaProject(E2013501096)supported by Hebei Province Natural Science Foundation,China
文摘The microstructure of Mg-8Zn-4Al-1Ca aged alloy was investigated by TEM and HRTEM. The results show that the hardening produced in the Mg-8Zn-4Al-1Ca alloy is considerably higher than that in the Mg-8Zn-4A1 alloy. A dense dispersion of disc-like Ca2Mg6Zn3 precipitates are formed in Mg-8Zn-4Al-1Ca alloy aged at 160 ℃ for 16 h. In addition, the lattice distortions, honeycomb-looking Moir＆#233; fringes, edge dislocations and dislocation loop also exist in the microstructure. The precipitates of alloy aged at 160 ℃ for 48 h are coarse disc-like and fine dispersed grainy. When the alloy is subjected to aging at 160 ℃ for 227 h, the microstructure consists of numerous MgZn2 precipitates and Ca2Mg6Zn3 precipitates. All the analyses show that Ca is a particularly effective trace addition in improving the age-hardening and postponing the formation of MgZn2 precipitates in Mg-8Zn-4Al alloy aged at 160 ℃.
基金Project (50271054) supported by the National Natural Science Foundation of ChinaProject (20070700003) supported by the Doctorate Programs Foundation of Ministry of Education of China+1 种基金Project (102102210031) supported by the Science and Technologies Foundation of Henan Province,ChinaProject (2010A430008) supported by the Natural Science Foundation of Henan Educational Committee of China
文摘Rapidly solidified（RS） Mg-6Zn-1Y-1Ce ribbons were prepared by single roller melt-spinning technique.Transmission electron microscopy and energy dispersive X-ray spectroscopy were employed to characterize the microstructure of RS ribbons.The results show that there is high density of particles distributed within grains and at grain boundaries in the region near wheel side.The particle density is decreased in the middle region and free surface region.The alloy is predominantly composed of supersaturated--Mg solid solution,T phase and W phase;meanwhile,a few icosahedral quasicrystalline and Mg4Zn7 particles are also observed.The T phase is confirmed having a body-centered orthorhombic structure that is transformed from the body-centered tetragonal structure Mg12Ce phase due to the partial substitution of Mg atoms by Zn.
基金financially supported by Guangxi Natural Science Foundation of China (No.2020GXNSFAA159011)National Natural Science Foundation of China (No.51664011)。
文摘A longstanding quest in material science has been the development of superhydrophobic coating based on a single material, without the requirement of fluorination or silane treatment. In this work, the micro-arc oxidation(MAO) coating as transition layer can effectively enhance the bonding force of the superhydrophobic coating. The semiconductor@metal organic frameworks(MOFs) core-shell structure was synthesized by a simple self-templating method, and obtained ZnO@2-methylimidazole zinc salt(ZIF-8) nanorods array on magnesium(Mg)alloy. ZnO nanorods not only act as the template but also provide Zn^(2+) for ZIF-8. In addition, we proved that the ligand concentration,synthesis time and temperature are the keys to the preparation of ZnO@ZIF-8 nanorods. As we expect, the ZnO@ZIF-8 nanorods array can trap air in the gaps to form an air layer, and the coating exhibits superhydrophobic properties(154.81°). Excitingly, ZnO@ZIF-8 nanorods array shown a superhydrophobic property, without the requirement of fluorination or silane treatment. The results shown that the coating has good chemical stability and self-cleaning performance. Meanwhile, the corrosion resistance has been significantly improved, R_(ct) was increased from 1.044×10^(3) to 1.414×10^(6) Ω/cm^(2) and I_(corr) was reduced from 4.275×10^(-5) to 5.611×10^(-9)A/cm^2. Therefore, the semiconductor@MOFs core-shell structure has broad application prospects in anti-corrosion.
基金the financial support for this work from the National Natural Science Foundation of China(Nos.U1764254,51871166)the Tianjin Natural Science Foundation,China(No.20JCYBJC00620)。
基金the Universiti Teknologi Malaysia (UTM) for providing research facilities and financial support under Grants No:(1)UTM-Research University Grant (RUG) (Q.J130000.2524.16H35),and (2)Nippon Sheet Glass (NSG) R.J130000.7324.4B300
文摘Plasma electrolytic oxidation（PEO） was developed as a bond coat for air plasma sprayed（APS） nanostructure ZrO2 as top coat to enhance the corrosion resistance and antibacterial activity of Mg alloy. Corrosion behavior and antibacterial activities of coated and uncoated samples were assessed by electrochemical tests and agar diffusion method toward Escherichia coli（E. coli） bacterial pathogens, respectively. The lowest corrosion current density and the highest charge transfer resistance, phase angle and impedance modulus were observed for PEO/nano-ZrO2 coated sample compared with those of PEO coated and bare Mg alloys. Nano-ZrO2 top coat which has completely sealed PEO bond coat is able to considerably delay aggressive ions transportation towards Mg alloy surface and significantly enhances corrosion resistance of Mg alloy in simulated body fluid（SBF） solution. Moreover, higher antibacterial activity was also observed in PEO/nano-ZrO2 coating against bacterial strains than that of the PEO coated and bare Mg alloys. This observation was attributed to the presence of ZrO2 nanoparticles which decelerate E. coli growth as a result of E. coli membranes.
