• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Greatly enhanced corrosion/wear resistances of epoxy coating for Mg alloy through a synergistic effect between functionalized graphene and insulated blocking layer

    2024-04-18 13:44:40XueLiChuLiZouTong
    Journal of Magnesium and Alloys 2024年1期

    Z.Y.Xue ,X.J.Li ,J.H.Chu ,M.M.Li ,D.N.Zou ,L.B.Tong,b,?

    a School of Metallurgical Engineering, Xi’an University of Architecture and Technology, Xi’an 710055, China

    b State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha 410082, China

    Abstract 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.

    Keywords: Mg alloy;Functionalized graphene;Epoxy coating;Corrosion/wear resistance;Blocking layer.

    1.Introduction

    Magnesium (Mg) and its alloys are widely used in the fields of automobile and aerospace [1,2]because of their outstanding properties,such as low density,high damping,high specific strength and electromagnetic shielding [3,4].However,Mg alloys are prone to corrosion due to the negative standard electrode potential and the porous native oxide film,which cannot effectively prevent the infiltration of corrosive media,especially in some environments such as chlorine ions or CO2[5,6].Therefore,it is significant to solve the problem of poor corrosion resistance and achieve the wide range of applications of Mg alloys.

    The improvement of corrosion resistance is limited by intrinsic drawbacks of Mg alloy,which cannot be solved from the perspective of composition design [7].Many surface coating technologies have been applied to Mg alloy,such as chemical conversion,anodic oxidation and so on [8–11].However,these approaches are generally toxic or high-energy consumptive during the preparation process [12].Furthermore,the adhesion ability of the coating with Mg alloy substrate is an important issue,which determines the service life.Therefore,it is necessary to develop a low-cost and environmentfriendly coating with high adhesive strength and excellent anti-corrosion performance for Mg alloy.

    Organic coatings with the characteristics of low cost,simple operation and excellent performance have been widely used in the fields of corrosion and protection [13].Epoxy resin (EP) is an organic matter with outstanding chemical inertia and adhesion force [14,15].Unfortunately,the volatile organic compounds (VOCs) produced during the curing process cause environmental pollution [16].Therefore,EP is modified to disperse in a continuous aqueous phase,as small particles or droplets to avoid the use of organic solvents [17].The emergence of waterborne epoxy resin (WEP) solves this problem and attracts much attention.However,the volatilization of solvent inevitably brings shrinkage of resin coating,which becomes the diffusion path of corrosive medium.After adding various nanofillers,such as inorganic particles (SiO2,TiO2) or silane coupling agents [18–20],the compactness of resin can be improved and the diffusion of the corrosive medium can be hindered.

    Compared with the conventional inorganic particles,graphene is a two-dimensional material with high hardness,superior conductivity,impermeability and chemical inertia[21–23],which has become a novel candidate for nanofillers in the field of organic anti-corrosive coating.Graphene has a higher specific surface area than nanoparticles,which means that it has better performance under the same addition amount[24].Unfortunately,the dispersion of graphene in the resin is poor,and the agglomerated graphene will significantly reduce the corrosion resistance [25].In contrast,graphene oxide (GO) sheets contain many oxygen-containing functional groups,which can become active sites for chemical modification and graft new functional groups to form functionalized graphene (FG).The selection of new functional groups is the key to improving the dispersion of FG sheets in organic coatings.Jiang et al.[26]reported GO sheets were functionalized with polyethyleneimine (PEI) to improve their dispersion in WEP.The coating was fabricated on carbon steel,which effectively enhanced its corrosion resistance.The galvanic corrosion effect between the graphene/GO sheets and carbon steel substrate can be significantly hindered due to its high standard electrode potential.However,for other metals,such as Mg,Al,Zn and so on [27,28],the intensive galvanic corrosion behaviors derived from the graphene/GO sheets often accelerate their dissolution behaviors.

    At present,there are hardly any reports about graphene(or GO)/WEP hybrid coating for Mg alloy due to its strong reducibility (reaction capacity with GO sheet),how to solve the galvanic corrosion between the GO sheets and Mg alloy substrate has been facing a significant challenge.According to previous reports,the Ce-based conversion (Ce) film has nontoxic,which contents the requirements of the coating for environmental protection [29].The preparation process is facile and easy to operate.There is a strong adhesion between the film and the substrate,providing a good transition for the outer layer [30].The insulation of the Ce film can effectively avoid galvanic corrosion between the graphene sheet and Mg alloy [31].In addition,new Mg-Zn-Ca series alloys have attracted much attention because of their low cost and excellent mechanical properties [32].However,the existence of the Ca2Mg6Zn3phase generally leads to the accelerated dissolution of the alloy,which may be solved through the construction of graphene-based protection coating [33].

    In the current study,the dispersion ability of GO sheets in WEP will be improved by chemical modification,the WEP/FG coating has been fabricated on the Mg-Zn-Ca alloy.The existence of Ce film effectively isolates the contact between the FG sheets and the substrate to avoids the galvanic corrosion.The microstructure evolution and corrosion/wear properties of the composite coatings are systematically investigated,and the corresponding mechanisms will be deeply discussed.Therefore,this article will pave a new avenue for designing the homogenous protection coating with superior multi-functional performances for highly chemically active metallic materials.

    2.Experimental procedures

    2.1. Substrate and coatings

    The preparation process of Mg alloy with the double-layer composite coating is sketched in Fig.1,which includes Ce film pretreatment on Mg alloy and subsequent WEP coating process.The substrate was machined from extruded Mg-3.0Zn-0.5Ca alloy (wt.%) with a diameter and height of 15 and 10 mm respectively in this study.For the sake of dislodging the oxide film on the surface,the Mg alloy was firstly used SiC abrasive paper from 80 to 2000 and diamond polishing paste,and then ultrasonically cleaned with acetone for 20 min.

    Fig.1.The details of the preparation process of the composite coating.

    The Ce(NO3)3·6H2O was dissolved in deionized water with a 1.0 mg/ml concentration and Mg alloy was immersed in the solution for 1 h.The as-received sample was taken out of the solution and then placed in the drying box (50?C) for 1 h.Ce film is evenly connected to the Mg alloy substrate in the form of Ce3+.Finally,the sample was put into a drying oven at 80?C for 30 min to form a more stable Ce4+[34].

    The GO sheets were prepared by the Hummers method,and the FG sheets were obtained through the PEI modification of GO sheets reported by Jiang et al.[26].The FG powder (18 mg) was dispersed in ethanol by ultrasonic treatment to form the suspension and then dropped into the WEP(10 g).The mixture was stirred vigorously for 30 min to remove ethanol and stirred slowly for 1 h to mix the solution.Next,the curing agent(2 g)was added to the WEP and stirred for 1 min.The mixture was put into a vacuum drying oven and defoamed at 25?C for 5 min.The final mixture was grafted on the sample with Ce film by spin-coating method,with speed rotation of 60 and 2500 rpm for 10 and 15 s respectively,and each sample was 3 times.Compared with dip coating,the surface of the spin coating sample is flattening.Furthermore,the filling orientation can be controlled by centrifugal force.Then,the Ce/WEP/FG coated Mg alloy was cured at room temperature for 2 h and heat cured at 60?C for 3 h.In addition,the WEP,WEP/FG and Ce/WEP coatings,as comparative specimens,were fabricated according to the same method.

    2.2. Characterization

    After Au plated treatment,the surface topography,fracture surface,and wear track of the composite coatings were observed by scanning electron microscopy (SEM,Gemini SEM 300,ZEISS,Germany).The fracture surface of the coating was obtained by thinning and tearing the sample.The threedimensional images were obtained by the atomic force microscope(AFM,SPA400,Japan)under the contact mode,and the value of roughness was calculated by the SPI3800N analysis software.The chemical structure was analyzed by the attenuated total reflection Fourier transformed infrared (ATR-FTIR,Nicolet Summit,America) over a frequency range of 600–3500 cm-1at room temperature.The appearance of scratches caused by wear was observed by a confocal laser scanning microscope (Hybrid L7,Lasertec,Japan).

    The electrochemical measurements were obtained by the Gamry Reference 600+(Gamry Instruments,USA) through electrochemical tests,and the sample was immersed in the 3.5 wt.% NaCl aqueous solution.A typical three-electrode electrochemical system was used to form a complete working system.Pt is the counter electrode,saturated calomel electrode (SCE) is the reference electrode and the sample (1 cm2exposed area) is the working electrode.An open-circuit potential test was conducted for 300 s to stabilize the working system.The electrochemical impedance spectroscopy (EIS)was recorded at scan frequency between 106and 10-2Hz at room temperature.The impedance spectra were fitting and analyzed by ZsimpleWin software.The potentiodynamic polarization measurements were conducted on the sample polarized from -2.0 to -1.3 V by a direct current signal with the scan rate of 5.0 mV·s-1.The corrosion parameters including corrosion current and corrosion potential were calculated by the Tafel extrapolation method.

    The wear measurements were obtained by rotating friction and wear testing machine at room temperature.The applied load was 4.0 N and the sliding speed of the steel ball was 0.07 ms-1.Then,the confocal laser scanning microscope was used to obtain the cross-sectional depth,width and area of scratches to calculate the wear rate.

    3.Results

    3.1. Macrostructure

    As shown in Fig.2a,for the sample with GO sheets addition of 0.15%,there is an obvious particle agglomeration phenomenon in the coating.GO sheets are difficult to disperse in WEP,due to the intensiveπ-πinteraction.In Fig.2b,under the same addition amount,no obvious aggregation occurs in the coating,indicating that through the PEI modification of the GO sheets,new functional groups are grafted onto the GO sheets and more evenly dispersed in WEP coating.

    Fig.2.Macroscopic morphologies of (a) Ce/WEP/GO and (b) Ce/WEP/FG coatings.

    3.2. Microstructure

    Fig.3 shows the surface morphologies of the composite coatings.For the WEP coating,there are some visible defects with a diameter of about 15 μm (Fig.3a).With the addition of FG sheets,the surface morphology becomes flat.However,there are a large number of holes on the surface,the size of which is 10~50 μm (Fig.3b).For the Ce/WEP coating,the surface is more wrinkled and the number of holes is significantly reduced than WEP (Fig.3c).Compared with the other samples,the defects of the Ce/WEP/FG coating nearly disappear and the compactness is remarkably improved(Fig.3d).

    Fig.3.The SEM images of surface morphologies of (a) WEP,(b) WEP/FG,(c) Ce/WEP and (d) Ce/WEP/FG coatings.

    The cross-sectional morphologies are shown in Fig.4.For the WEP coating,some cracks appear,whose thickness is 16.7 μm (Fig.4a).After FG sheets addition,no obvious cracks appear,while some huge holes can be observed,which run through the coating,the thickness is significantly increased to 46.4 μm (Fig.4b).For the Ce/WEP coating,the cracks can still be observed on the cross-section,indicating that the Ce film cannot improve the internal structure,while the thickness is 11.8 μm (Fig.4c).Through the design of the Ce film,no cracks and holes can be observed within the Ce/WEP/FG coating,and the thickness is dramatically decreased to 17.7 μm(Fig.4d),compared with that of WEP/FG coating (without Ce film).

    Fig.4.The cross-sectional SEM images of (a) WEP,(b) WEP/FG,(c)Ce/WEP and (d) Ce/WEP/FG coatings.

    As shown in Fig.5,the ATR-FTIR shows the detail of chemical bonds within the different coatings.The characteristic peaks of WEP coating appear at ~2927 cm-1,~1507 cm-1,~1238 cm-1corresponding to the C–H stretching vibration,benzene ring skeleton stretching vibration,the O–H bending vibration,respectively.The intensity ratio of the absorption bands around ~3403 cm-1(O–H stretching vibration) and 1735 (C=O stretching vibration) is increased,suggesting that FG sheets are successfully added to the coating.Some new peaks appear at 1608 cm-1(N–C=O stretching vibration),1456 cm-1(CH2scissoring),1298 cm-1(C–N stretching vibration),and 758 cm-1(N–H wag),implying that the PEI molecules have successfully been grafted on the GO sheets through chemical bonding.

    Fig.5.ATR-FTIR,the left image shows the full range and the right image is related to the magnified peaks.

    3.3. Corrosion properties

    As shown in Fig.6a,the corrosion resistances of bare Mg alloy,WEP,WEP/FG,Ce/WEP,Ce/WEP/GO and Ce/WEP/FG coatings are evaluated by EIS analysis.The Nyquist plot of bare Mg alloy appears exhibits two capacitance loops,in which the high-frequency is related to the double electric layer and the low-frequency is derived from the natural oxidation film.The appearance of the secondary capacitance loop means that the oxide film provides a particularly protective effect [35].Generally speaking,the corrosion resistance is mainly determined by the high-frequency capacitance loop.The larger dimension means better performance [36,37].By comparing the capacitance loop in the high-frequency region,the WEP exhibits specific corrosion resistance,and the radius of WEP is much higher than that of bare Mg alloy,which is due to the protection of robust barrier [38].The WEP/FG shows a large radius than WEP,indicating better corrosion resistance.After the assembly of Ce film,the radius of Ce/WEP is higher than of WEP/FG,implying the design of the Ce film is effective.Due to the agglomeration of GO sheets,the performance of Ce/WEP/GO is not obviously improved.Finally,Ce/WEP/FG coating shows the best anti-corrosion performance in all samples.

    Fig.6.The electrochemical measurements of Mg alloy samples with different coatings,(a) Nyquist plots,(b) potentiodynamic polarization curves.

    Fig.6b shows the potentiodynamic polarization curves of different samples,and the corresponding data are fitted via Tafel extrapolation in Table 1.The value ofPican be calculated according to the previous report [39].

    Table 1 The fitting result of samples of potentiodynamic polarization curves.

    Bare Mg alloy shows the highest corrosion current density of 1.15×10-5A/cm2,the corrosion rate of 0.26 mm/y.Compared with bare Mg alloy,the value oficorrdecreases by 2 or 4 orders of magnitude for WEP,WEP/FG,Ce/WEP,Ce/WEP/GO and Ce/WEP/FG,respectively.The WEP,WEP/FG,Ce/WEP and Ce/WEP/GO coatings show the reducedicorrof 2.19×10-7,5.05×10-8,2.45×10-8and 2.06×10-8A/cm2andPiof 5.00×10-3,1.15×10-3,5.60×10-4and 4.70×10-4mm/y,respectively.It is worth noting that theicorrandPivalues of Ce/WEP/FG coating are dramatically reduced to 5.33×10-9A/cm2and 1.22×10-4mm/y.The existence of the coating effectively decreases the corrosion rate,the order of corrosion rate is Ce/WEP/FG

    The electrochemical corrosion process is further explained through the equivalent circuit.The fitting curves and circuit diagrams are shown in Fig.7,and the corresponding results are shown in Table 2.TheRsis the solution resistance,Rtis the charge transfer resistance andRfis the film resistance[40].TheCPEfrepresents the capacitance of the films andCPEdlrepresents the capacitance of the electric double layer at the interface of Mg alloy and the electrolyte solution,which are determined byY(f,dl)and n(f,dl) values,respectively.The value ofndetermines the properties ofCPE,a value of 0 and 1 represents resistor and capacitor.Rtreflects the dissolution of Mg alloy,which directly determines the corrosion rate[41].TheCfrepresents the capacitance of the coating.For the WEP,WEP/FG and Ce/WEP,the value ofRtof 7.47×103,1.78×105and 1.12×106Ωcm2are improved than Mg alloy of 6.36×102Ωcm2.In contrast,the most noticeable increase is the Ce/WEP/FG of 3.08×106Ωcm2,which shows the most outstanding corrosion resistance.

    Table 2 The fitting result of EIS spectra of Mg alloy samples with different coatings.

    Fig.7.EIS fitting plots of (a) bare Mg alloy,(b) WEP,(c) WEP/FG,(d) Ce/WEP and (e) Ce/WEP/FG.The equivalent circuit of (f) bare Mg alloy,WEP and WEP/FG and (g) Ce/WEP and Ce/WEP/FG.

    3.4. Tribological properties

    As shown in Fig.8a,the friction and wear experiments are carried out on the samples,and the coefficient of friction(COF) curves are obtained.The COF value of bare Mg alloy is gradually stabilized ~0.3 after the running-in stage.The COF value of WEP and WEP/FG coating is similar to that of bare Mg alloy,implying that the coating has failed and cannot protect the Mg alloy.For the Ce/WEP and Ce/WEP/FG,the COF value is increased to 0.4~0.5.By calculating the friction data,the wear rate (WR) is shown in Fig.8b.Compared with bare Mg alloy,the wear rate of WEP/FG coating is slightly decreased.The design of the Ce film effectively reduces the wear rate of the sample.However,the addition of FG sheets within Ce/WEP increases the wear rate to a certain degree,and the detailed mechanisms will be discussed in the following section.

    Fig.8.The friction measurements performed on different samples,(a) the evolution of COF during the wear test,(b) the comparison of WR value.

    Fig.9 shows the morphologies of wear tracks in the samples without and with the composite coatings.For bare Mg alloy,many grooves and ridges can be observed as significant features of abrasive wear (Fig.9a).The scratch width is 1176 μm,the depth is 60 μm,and the cross-sectional area is calculated as ~46,902 μm2(Fig.9b-c).For the WEP and WEP/FG coatings,the local regions fall off (Fig.9d and e).The WEP coating aggravates the wear process and enlarges the wear area to ~58,599 μm2.(Fig.9f).The WEP/FG provides slight protection,and the cross-sectional area of wear track for the WEP/FG coating is remarkably decreased to~44,410 μm2(Fig.9g-i).The scratch surface of Ce/WEP coating is flat,and a few flakes are found (Fig.9j).The wear rate is dramatically reduced,and the coating exhibits an excellent protection ability during the wear process (Fig.9k-l).The scratch surface is almost continuous for the Ce/WEP/FG coated sample,and Mg alloy fragments are hardly observed(Fig.9m).In addition,the scratch width is decreased to~1043 μm and the depth is 6 μm (Fig.9n-o).

    Fig.9.SEM surface morphologies,OM images and 3D profiles of wear tracks of different samples: (a) (b) (c) bare Mg alloy,(d) (e) (f) WEP,(g) (h) (i)WEP/FG,(j) (k) (l) Ce/WEP and (m) (n) (o) Ce/WEP/FG.

    4.Discussion

    4.1. Corrosion mechanisms

    Generally speaking,GO sheets are difficult to disperse in WEP,due to the intensiveπ-πinteraction (Fig.2).The functionalization of GO sheets is beneficial to the dispersibility within organic matter and enhances the barrier effect of their coatings [42].In this study,the GO sheets modified by PEI molecules can be uniformly dispersed in the WEP and effectively hinder aggregation.The -NH2functional groups of FG sheets occur in the ring-opening reaction with the epoxy group of the WEP (Fig.5).With the further occurrence of the reaction,the interfacial interaction results in the enhanced dispersion capacity.The uniformity and compactness of the coating are effectively improved.

    The aggregation of GO sheets is reduced through functionalization,which will lead to the intensive “l(fā)abyrinth effect”and improve the anti-corrosion performances of their coatings[43].Unfortunately,it is found that the corrosion resistance of the WEP/FG is opposite to the expected results.The electrode potential values of Mg alloy and the FG sheets are -2.37 V[44]and 0.4~0.6 V [45],respectively,which leads to galvanic corrosion between the coating and substrate.Similar to GO sheets [45],the oxygen-containing groups of FG sheets are decreased and the reduction reaction occurs to form reduced functionalized graphene (RFG).The detailed corrosion process of Mg alloy is usually expressed by Eqs.(2)~(4):

    In order to explore whether the galvanic corrosion occurs between the coating and the substrate,more information is obtained through the immersion experiments.As shown in Fig.10a and b,the original WEP and WEP/FG exhibits poor corrosion resistance.However,the capacitive loops are increased after immersion.It may relate to the accumulation of corrosion products.Subsequently,the dimension of capacitive loops of WEP is gradually decreased with the increased immersion time,which confirms that it is constantly corroded.The WEP/FG still has a certain protection capability,which may be that the corrosion products repair the caused by galvanic corrosion and strengthen the labyrinth effect.For the Ce/WEP and Ce/WEP/GO coatings,the corrosion resistance is decreased with the increased immersion time,which does not provide effective protection for the Mg substrate (Fig.10c and d).The corrosion resistance of Ce/WEP/FG decreases with the increase of immersion time,while the performance is still higher than that of other samples (Fig.10e).

    Fig.10.The Nyquist plots of samples with different immersion time in 3.5 wt% NaCl and (a) WEP,(b) WEP/FG,(c) Ce/WEP,(d) Ce/WEP/GO and (e)Ce/WEP/FG.

    The effect of galvanic corrosion is remarkably weakened by the Ce film,which is composed of Ce(OH)4and CeO2.At the initial stage of immersion,the film is mainly composed of Ce3+hydroxides.With the increase of immersion time,Ce3+transforms to a more stable Ce4+to form Ce(OH)4.A further reaction that Ce(OH)4is converted to CeO2occurs.The detailed formation process of Ce film is usually expressed by Eqs.(5)~(7) [46]:

    EP has a high viscosity and is viscous or solid at room temperature.In order to meet the application requirements,EP is usually dissolved in the solvent.In the curing process,the volatilization of solvent inevitably leads to shrinkage of the coating [47],which becomes the diffusion channel of the corrosive medium and reduces the corrosion resistance of the coating (Fig.11a).For the WEP/FG,the FG sheets and Mg alloy substrate form a microcell structure through the WEP.The water molecules become the conductor in the whole system,resulting in the galvanic corrosion on the surface of Mg alloy.The water vapor overflow from the galvanic corrosion process may cause many gas holes,becoming the diffusion channel of the corrosive medium.However,more diffusion channels cannot make the corrosion resistance of the coating worse than pure WEP,indicating that FG sheets remain an intensive barrier effect (Fig.11b).Through the design of the Ce film,the corrosion resistance of the Ce/WEP is improved(Fig.6a),due to the enhanced compactness (Fig.11c).For the Ce/WEP/FG,the Ce film and FG sheets addition exhibit a synergistic effect.The WEP/FG can only provide protection for the substrate to a certain degree,and Ce film makes up for the defects of WEP/FG and further improves the performance,because it can be acted as an insulating layer,effectively isolating the galvanic corrosion between FG sheets and the substrate and reducing the generation of gas holes.With the addition of FG sheets,the defects inside the coating disappear,which is conducive to improving corrosion resistance.In addition,the FG sheets are impermeable,which hinders the penetration of the corrosive medium and leads to the labyrinth effect (Fig.11d).To sum up,the Ce film can effectively prevent the galvanic corrosion between the coating and the substrate.The corrosion medium is blocked by the impermeable FG sheets,which prolongs the diffusion path of the corrosion medium and improves the corrosion resistance.Finally,the synergistic effect derived from Ce film and hybrid FG sheets dramatically enhances the protection ability of composite coating.

    Fig.11.The corrosion protection mechanisms of (a) WEP,(b) WEP/FG,(c) Ce/WEP and (d) Ce/WEP/FG coatings.

    4.2. Wear mechanisms

    The wear data show that the Ce/WEP and Ce/WEP/FG coatings play a positive role in the wear resistance of bare Mg alloy.However,the improvement of wear resistance of samples without the Ce film is limited.This section will discuss the influence of the Ce film on wear resistance.In general,according to the conventional Archard Eq.(8) [48],the effect of friction coefficient and hardness to wear rate can be obtained.

    whereWRVis worn volume,lis the load,dis the sliding distance.fandhare the COF and harness,respectively.Due to the different samples having the same values oflandd,the values offandhhave a more significant impact on the wear rate.The result shows that the lower COF value of bare Mg alloy cannot lead to better wear resistance.However,the samples with higher COF values exhibit superior wear resistance.This phenomenon indicates that other factors may play the critical roles.

    The protective performance of the coating is related to the adhesion of the coating.As shown in Fig.12,the separation of the WEP and WEP/FG coating from the substrate can be observed,indicating the poor adhesion abilities (Fig.12a and b).As the steel ball is continuously pressed into the coating,local areas fall off and leave their original position.For the Ce/WEP and Ce/WEP/FG coating,there is almost no interval between the coating and the substrate,indicating that the design of Ce film has a positive impact on the adhesion of the coating (Fig.c and d).

    Fig.12.SEM interfacial morphologies between the coating and Mg alloy substrate: (a) WEP,(b) WEP/FG,(b) Ce/WEP,(c) Ce/WEP/FG coatings.

    As shown in Fig.13,the wear protection mechanism is demonstrated.For the WEP,it may be that the WEP becomes an abrasive particle during friction,which aggravates the abrasive wear (Fig.13a).However,this phenomenon disappears with the addition of FG sheets.It may be that FG sheets play a particular lubricating role (Fig.13b).The design of the Ce film prevents galvanic corrosion and improves the adhesion and compactness of the coating.The AFM images show the surface roughness of the coating.The Ce/WEP coating exhibits a higher surface roughness of 123 nm than the Ce/WEP/FG coating of 22 nm.The rough surface dramatically reduces the contact area between steel ball and coating,resulting in the low friction resistance(Fig.13c).Furthermore,the hardness of the coating is related to the addition of FG sheets,while this effect is not obvious because of the small amount [49].Due to the insufficient hardness of the coating,the FG sheets cannot be fixed in their original position and begins to slide with the shear force of the steel ball [50].FG sheets have high hardness,which can be acted as abrasive particles and causes further damage to the coating (Fig.13d).

    Fig.13.The wear protection mechanisms of (a) WEP,(b) WEP/FG,(c) Ce/WEP and (d) Ce/WEP/FG coatings.

    5.Conclusion

    The dispersion of GO sheets in the WEP coating is improved by PEI modification,which effectively increases the diffusion path of corrosive medium and forms the “l(fā)abyrinth effect”.However,galvanic corrosion exists between the coating and bare Mg alloy,which can be effectively isolated through the design of the Ce film.The synergistic effect between the FG sheets addition and blocking layer simultaneously improves the corrosion and wear resistances of the WEP coating.In addition,it must be emphasized that the current study still retains some challenges,such as the hybridization of FG sheets leads to an inevitable sacrifice of wear resistance and cannot achieve the desired effect,which may be related to its low content,and further research is needed in the coming future.

    Notes

    There are no conflicts to declare.

    Acknowledgements

    This work was supported by the National Natural Science Foundation of China (Grant number 51771178),Shaanxi Outstanding Youth Fund project (Grant number 2021JC-45),Key international cooperation projects in Shaanxi Province(Grant number 2020KWZ-007),the Major Program of Science and Technology in Shaanxi Province (Grant number 20191102006) and Open Fund of State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body(Grant number 32115019).

    亚洲av国产av综合av卡| av在线观看视频网站免费| 日本与韩国留学比较| 国产女主播在线喷水免费视频网站| 26uuu在线亚洲综合色| 26uuu在线亚洲综合色| 精品国产三级普通话版| 男女边摸边吃奶| 99久久精品一区二区三区| 精品久久久精品久久久| 久久人人爽av亚洲精品天堂 | tube8黄色片| 免费在线观看成人毛片| 99久久人妻综合| 欧美激情久久久久久爽电影| 日韩一本色道免费dvd| 成人毛片a级毛片在线播放| 久久久久久久久久成人| 51国产日韩欧美| 精品久久久精品久久久| 亚洲av电影在线观看一区二区三区 | 最近最新中文字幕大全电影3| 美女高潮的动态| 女人十人毛片免费观看3o分钟| 激情五月婷婷亚洲| 亚洲国产欧美人成| 日本av手机在线免费观看| 亚洲精品成人av观看孕妇| a级一级毛片免费在线观看| 国产免费一级a男人的天堂| 最近最新中文字幕免费大全7| 噜噜噜噜噜久久久久久91| 成人漫画全彩无遮挡| 麻豆国产97在线/欧美| 99re6热这里在线精品视频| 国产一区有黄有色的免费视频| 国产人妻一区二区三区在| 日韩免费高清中文字幕av| 欧美性感艳星| 国产精品爽爽va在线观看网站| 最近中文字幕高清免费大全6| 乱系列少妇在线播放| 伊人久久国产一区二区| 亚洲国产高清在线一区二区三| 国产精品无大码| 精品久久久久久电影网| 久久久久精品久久久久真实原创| av在线蜜桃| 人人妻人人看人人澡| 久久精品国产亚洲av天美| 婷婷色av中文字幕| 99热6这里只有精品| 直男gayav资源| 免费大片黄手机在线观看| 肉色欧美久久久久久久蜜桃 | 欧美日韩综合久久久久久| 久久久精品免费免费高清| 欧美一级a爱片免费观看看| 国产爽快片一区二区三区| 91精品国产九色| 日本熟妇午夜| 日本色播在线视频| 亚洲内射少妇av| 在线观看美女被高潮喷水网站| 97超视频在线观看视频| 免费看光身美女| 高清在线视频一区二区三区| 晚上一个人看的免费电影| 久久精品国产亚洲网站| 国产伦在线观看视频一区| 看十八女毛片水多多多| 欧美激情久久久久久爽电影| 少妇猛男粗大的猛烈进出视频 | 能在线免费看毛片的网站| 欧美少妇被猛烈插入视频| 能在线免费看毛片的网站| 中文在线观看免费www的网站| 久久亚洲国产成人精品v| 99精国产麻豆久久婷婷| 免费观看在线日韩| 久久久久久久久久久丰满| 久久精品国产亚洲av天美| av黄色大香蕉| 黄色视频在线播放观看不卡| 春色校园在线视频观看| 观看免费一级毛片| 十八禁网站网址无遮挡 | 黄色一级大片看看| 婷婷色麻豆天堂久久| 深夜a级毛片| 亚洲av日韩在线播放| 日韩国内少妇激情av| 国产精品不卡视频一区二区| 久久久精品免费免费高清| 波多野结衣巨乳人妻| 久久久久久久久久久丰满| 老司机影院毛片| 高清日韩中文字幕在线| 男插女下体视频免费在线播放| av黄色大香蕉| 三级经典国产精品| 婷婷色麻豆天堂久久| 亚洲欧美精品专区久久| 纵有疾风起免费观看全集完整版| 国产精品.久久久| 成人高潮视频无遮挡免费网站| 日本av手机在线免费观看| 在线观看美女被高潮喷水网站| 六月丁香七月| 直男gayav资源| 波多野结衣巨乳人妻| 91狼人影院| 91精品国产九色| 色视频www国产| videossex国产| 精品久久久精品久久久| 亚洲欧美一区二区三区国产| 欧美成人精品欧美一级黄| 超碰97精品在线观看| 波多野结衣巨乳人妻| 国产乱人视频| 狂野欧美激情性xxxx在线观看| 久久久久国产精品人妻一区二区| 国产日韩欧美亚洲二区| 人妻 亚洲 视频| 久热这里只有精品99| 色5月婷婷丁香| 日日摸夜夜添夜夜添av毛片| kizo精华| 亚洲欧美成人精品一区二区| 久久久久久久久久成人| 国产精品一区二区在线观看99| 色综合色国产| 亚洲怡红院男人天堂| 热99国产精品久久久久久7| 另类亚洲欧美激情| 国产精品久久久久久久电影| 亚洲成人精品中文字幕电影| 色网站视频免费| 国产免费福利视频在线观看| 亚洲精品视频女| 视频区图区小说| 国产精品秋霞免费鲁丝片| 少妇裸体淫交视频免费看高清| 女人十人毛片免费观看3o分钟| 91久久精品国产一区二区三区| 99热国产这里只有精品6| 欧美日韩精品成人综合77777| 中文欧美无线码| 亚洲国产av新网站| 免费在线观看成人毛片| 亚洲在久久综合| 免费av毛片视频| 插阴视频在线观看视频| 国产一级毛片在线| 女人被狂操c到高潮| 亚洲精品中文字幕在线视频 | 一级毛片我不卡| 免费观看的影片在线观看| 亚洲美女搞黄在线观看| 中国美白少妇内射xxxbb| 色网站视频免费| 日韩欧美 国产精品| 精品酒店卫生间| 波野结衣二区三区在线| 神马国产精品三级电影在线观看| 亚洲欧美精品自产自拍| 丰满乱子伦码专区| 成人亚洲精品av一区二区| 小蜜桃在线观看免费完整版高清| kizo精华| 91狼人影院| 欧美激情久久久久久爽电影| 大香蕉久久网| 在线a可以看的网站| .国产精品久久| 日本与韩国留学比较| 国产成人91sexporn| 日韩不卡一区二区三区视频在线| 永久免费av网站大全| 成人毛片60女人毛片免费| 久久久久久九九精品二区国产| 亚洲成人精品中文字幕电影| av一本久久久久| 精品99又大又爽又粗少妇毛片| 一级毛片黄色毛片免费观看视频| 日韩大片免费观看网站| 久久6这里有精品| 国产精品嫩草影院av在线观看| 国产精品熟女久久久久浪| 国产免费视频播放在线视频| 最近手机中文字幕大全| av女优亚洲男人天堂| 成人鲁丝片一二三区免费| 亚洲国产精品国产精品| 岛国毛片在线播放| 精品熟女少妇av免费看| 两个人的视频大全免费| 1000部很黄的大片| 日韩av不卡免费在线播放| 亚洲熟女精品中文字幕| 精品久久久久久电影网| 久久精品国产亚洲网站| 日韩在线高清观看一区二区三区| 国产精品久久久久久久电影| 亚洲一区二区三区欧美精品 | 欧美精品国产亚洲| 噜噜噜噜噜久久久久久91| 日本av手机在线免费观看| 最后的刺客免费高清国语| 日韩电影二区| 纵有疾风起免费观看全集完整版| 国产精品av视频在线免费观看| 亚洲精品乱久久久久久| 一区二区三区四区激情视频| 日本av手机在线免费观看| 国语对白做爰xxxⅹ性视频网站| 精品久久久精品久久久| 久久精品国产亚洲av天美| 亚洲欧美日韩东京热| 人妻制服诱惑在线中文字幕| 久久久午夜欧美精品| 91在线精品国自产拍蜜月| 免费少妇av软件| 寂寞人妻少妇视频99o| 久久久久久久久大av| 男女边吃奶边做爰视频| 国产黄a三级三级三级人| 国产av国产精品国产| 成人无遮挡网站| 久久久久国产精品人妻一区二区| tube8黄色片| 中国美白少妇内射xxxbb| 中文天堂在线官网| 欧美精品国产亚洲| 国精品久久久久久国模美| 亚洲欧美一区二区三区国产| 免费av不卡在线播放| 大片电影免费在线观看免费| 亚洲不卡免费看| 亚洲av国产av综合av卡| 亚洲av电影在线观看一区二区三区 | 五月玫瑰六月丁香| 男女国产视频网站| 国模一区二区三区四区视频| 久久精品久久久久久久性| 久久久久久久国产电影| 国产毛片在线视频| 久久热精品热| 大片电影免费在线观看免费| 麻豆乱淫一区二区| 熟女av电影| 免费看a级黄色片| 色吧在线观看| 亚洲第一区二区三区不卡| 少妇丰满av| eeuss影院久久| 欧美性感艳星| 啦啦啦啦在线视频资源| 又爽又黄a免费视频| 成年女人看的毛片在线观看| 久久99热这里只有精品18| 春色校园在线视频观看| 三级经典国产精品| 亚洲精品久久午夜乱码| 色5月婷婷丁香| 国产精品久久久久久精品电影| 国产美女午夜福利| 亚洲色图av天堂| 噜噜噜噜噜久久久久久91| 性色av一级| 国产白丝娇喘喷水9色精品| 一本—道久久a久久精品蜜桃钙片 精品乱码久久久久久99久播 | 青春草国产在线视频| 搞女人的毛片| 欧美日韩一区二区视频在线观看视频在线 | 欧美潮喷喷水| 日本熟妇午夜| 边亲边吃奶的免费视频| 国产欧美另类精品又又久久亚洲欧美| 久久午夜福利片| 男女那种视频在线观看| av在线观看视频网站免费| 在线 av 中文字幕| 欧美日韩一区二区视频在线观看视频在线 | 大片免费播放器 马上看| 夜夜爽夜夜爽视频| 三级国产精品欧美在线观看| 一边亲一边摸免费视频| 男女边吃奶边做爰视频| 一个人观看的视频www高清免费观看| 一本久久精品| 欧美成人精品欧美一级黄| 成人高潮视频无遮挡免费网站| 成人黄色视频免费在线看| 爱豆传媒免费全集在线观看| 午夜老司机福利剧场| 国产精品麻豆人妻色哟哟久久| 亚洲精品日韩在线中文字幕| 国产亚洲精品久久久com| 国产成人一区二区在线| 久久久久久国产a免费观看| 国产爽快片一区二区三区| 日韩一本色道免费dvd| 国精品久久久久久国模美| 国产久久久一区二区三区| 可以在线观看毛片的网站| .国产精品久久| 国产真实伦视频高清在线观看| 99热网站在线观看| 能在线免费看毛片的网站| 国产在线一区二区三区精| 国产成人精品福利久久| 国产成人91sexporn| 日韩亚洲欧美综合| 制服丝袜香蕉在线| 热99国产精品久久久久久7| 成人亚洲欧美一区二区av| 亚洲欧美日韩卡通动漫| 国产精品国产av在线观看| 亚洲精品成人久久久久久| 一区二区三区乱码不卡18| 国产成人a区在线观看| 国产免费福利视频在线观看| 看非洲黑人一级黄片| 一个人观看的视频www高清免费观看| 午夜激情福利司机影院| 人妻一区二区av| 亚洲成人精品中文字幕电影| 欧美精品国产亚洲| 亚洲欧美日韩另类电影网站 | 18+在线观看网站| 久久人人爽人人爽人人片va| 国产成人a区在线观看| 99久久中文字幕三级久久日本| 亚洲精品国产av蜜桃| 国产精品偷伦视频观看了| 在现免费观看毛片| av福利片在线观看| 国产高清有码在线观看视频| 国产高清三级在线| 97人妻精品一区二区三区麻豆| 国产成人a∨麻豆精品| 国产成年人精品一区二区| 美女cb高潮喷水在线观看| 国产高清三级在线| 精品国产露脸久久av麻豆| 最近最新中文字幕免费大全7| 毛片一级片免费看久久久久| 久久久久久久亚洲中文字幕| 亚洲欧美精品自产自拍| 在线观看三级黄色| 亚洲人与动物交配视频| 亚洲图色成人| 1000部很黄的大片| 精品久久久久久久末码| 欧美日本视频| 久久精品综合一区二区三区| 国产91av在线免费观看| 哪个播放器可以免费观看大片| 国产乱来视频区| 午夜福利高清视频| 成人无遮挡网站| 国产精品.久久久| 少妇猛男粗大的猛烈进出视频 | 中文精品一卡2卡3卡4更新| 国产视频内射| 亚洲欧美成人精品一区二区| 国产精品福利在线免费观看| 春色校园在线视频观看| 久热这里只有精品99| 欧美日韩在线观看h| 国产成人a∨麻豆精品| 欧美极品一区二区三区四区| 亚洲国产日韩一区二区| 国产一区二区三区av在线| 日本av手机在线免费观看| av在线app专区| 九九在线视频观看精品| 在线观看三级黄色| 香蕉精品网在线| 白带黄色成豆腐渣| 国产精品av视频在线免费观看| 春色校园在线视频观看| 人人妻人人澡人人爽人人夜夜| 18禁在线播放成人免费| 免费大片黄手机在线观看| 日日摸夜夜添夜夜爱| 国产精品.久久久| 六月丁香七月| 日本-黄色视频高清免费观看| 一级毛片我不卡| 全区人妻精品视频| 亚洲精品久久午夜乱码| 小蜜桃在线观看免费完整版高清| 久久精品国产自在天天线| 国产亚洲av嫩草精品影院| av在线老鸭窝| 国产午夜福利久久久久久| 黄片wwwwww| 婷婷色综合www| 成人综合一区亚洲| 汤姆久久久久久久影院中文字幕| 中国国产av一级| 联通29元200g的流量卡| 97在线视频观看| 亚洲欧美成人精品一区二区| 69人妻影院| 三级经典国产精品| 大香蕉97超碰在线| 纵有疾风起免费观看全集完整版| 热99国产精品久久久久久7| 午夜福利网站1000一区二区三区| av在线天堂中文字幕| videos熟女内射| 交换朋友夫妻互换小说| 久久人人爽av亚洲精品天堂 | 超碰av人人做人人爽久久| 久久久久久久大尺度免费视频| 99久久九九国产精品国产免费| 精品国产三级普通话版| 最近手机中文字幕大全| 伦精品一区二区三区| 欧美一区二区亚洲| 五月开心婷婷网| 最后的刺客免费高清国语| 制服丝袜香蕉在线| 秋霞在线观看毛片| 亚洲天堂av无毛| 国产91av在线免费观看| 亚洲精品乱久久久久久| 小蜜桃在线观看免费完整版高清| 99九九线精品视频在线观看视频| 国产成人一区二区在线| 性插视频无遮挡在线免费观看| 亚洲成色77777| 一区二区三区免费毛片| 看免费成人av毛片| 18禁在线播放成人免费| 国产色婷婷99| 少妇人妻一区二区三区视频| 性插视频无遮挡在线免费观看| 日本三级黄在线观看| 久久热精品热| 亚洲高清免费不卡视频| 午夜视频国产福利| 最近最新中文字幕免费大全7| 久久久久精品性色| 女人久久www免费人成看片| 嫩草影院精品99| 91精品一卡2卡3卡4卡| 午夜免费鲁丝| 精品国产露脸久久av麻豆| 亚洲欧美中文字幕日韩二区| 亚洲成人精品中文字幕电影| 干丝袜人妻中文字幕| 91aial.com中文字幕在线观看| 国产老妇伦熟女老妇高清| 国产成人freesex在线| 国产黄a三级三级三级人| 国产黄色视频一区二区在线观看| 免费观看在线日韩| tube8黄色片| 亚洲精品成人久久久久久| 99热这里只有是精品在线观看| 超碰97精品在线观看| 女人久久www免费人成看片| 在线观看三级黄色| 九九爱精品视频在线观看| 国产午夜福利久久久久久| 成人特级av手机在线观看| 美女高潮的动态| 成人毛片a级毛片在线播放| 老司机影院成人| 久久女婷五月综合色啪小说 | 欧美日韩视频高清一区二区三区二| 国产大屁股一区二区在线视频| 欧美日韩视频精品一区| 极品少妇高潮喷水抽搐| 欧美少妇被猛烈插入视频| 成人欧美大片| 国产综合精华液| 在线a可以看的网站| 男人和女人高潮做爰伦理| 欧美精品一区二区大全| 国产一级毛片在线| 99久久中文字幕三级久久日本| 欧美97在线视频| 久久影院123| 91狼人影院| 精品少妇久久久久久888优播| 国产精品人妻久久久久久| 欧美国产精品一级二级三级 | 小蜜桃在线观看免费完整版高清| 日本免费在线观看一区| 草草在线视频免费看| 男插女下体视频免费在线播放| 精品人妻一区二区三区麻豆| av在线观看视频网站免费| 18禁裸乳无遮挡免费网站照片| a级一级毛片免费在线观看| 国产精品久久久久久精品电影| 少妇人妻精品综合一区二区| 深夜a级毛片| 尤物成人国产欧美一区二区三区| av又黄又爽大尺度在线免费看| 狠狠精品人妻久久久久久综合| 婷婷色麻豆天堂久久| 久热久热在线精品观看| 五月玫瑰六月丁香| 国产又色又爽无遮挡免| 丝袜美腿在线中文| 国产精品久久久久久久电影| 国产亚洲一区二区精品| 亚洲国产精品专区欧美| 免费av观看视频| 国产亚洲91精品色在线| 中文在线观看免费www的网站| 国产永久视频网站| 日韩制服骚丝袜av| 中文字幕亚洲精品专区| 国产永久视频网站| 亚洲欧美中文字幕日韩二区| 大话2 男鬼变身卡| 日韩欧美精品免费久久| 黄色日韩在线| 日韩av免费高清视频| av在线老鸭窝| 哪个播放器可以免费观看大片| 大片免费播放器 马上看| 一级毛片aaaaaa免费看小| 免费播放大片免费观看视频在线观看| 成年人午夜在线观看视频| 久久久久久久久久久免费av| 久久久久久久精品精品| 亚洲在线观看片| 精品人妻视频免费看| 久久久久国产精品人妻一区二区| 全区人妻精品视频| 午夜老司机福利剧场| 亚洲av国产av综合av卡| 久久精品国产a三级三级三级| 精品国产乱码久久久久久小说| 免费黄色在线免费观看| 纵有疾风起免费观看全集完整版| av国产久精品久网站免费入址| 国产探花在线观看一区二区| 亚洲欧美精品自产自拍| 久久6这里有精品| 国产又色又爽无遮挡免| 亚洲av免费在线观看| 建设人人有责人人尽责人人享有的 | 婷婷色综合大香蕉| 国产乱来视频区| 亚洲精品成人久久久久久| 精品视频人人做人人爽| av在线播放精品| 永久免费av网站大全| 18禁动态无遮挡网站| 2018国产大陆天天弄谢| 亚洲经典国产精华液单| 最近的中文字幕免费完整| 草草在线视频免费看| 99热这里只有精品一区| 亚洲国产精品专区欧美| 国产日韩欧美亚洲二区| 成人国产av品久久久| 91久久精品国产一区二区三区| 久久精品国产a三级三级三级| 婷婷色麻豆天堂久久| 国产爽快片一区二区三区| 一级片'在线观看视频| www.av在线官网国产| 大香蕉97超碰在线| 少妇被粗大猛烈的视频| 男女无遮挡免费网站观看| av卡一久久| 精品人妻偷拍中文字幕| av在线app专区| av一本久久久久| 不卡视频在线观看欧美| av国产精品久久久久影院| 欧美区成人在线视频| 国语对白做爰xxxⅹ性视频网站| 亚洲欧美日韩东京热| 日日摸夜夜添夜夜爱| 老女人水多毛片| 亚洲综合色惰| 男插女下体视频免费在线播放| 成人亚洲精品av一区二区| 国产高潮美女av| 插阴视频在线观看视频| 国产老妇女一区| 久久精品久久精品一区二区三区| 亚洲性久久影院| 成人漫画全彩无遮挡| 成年女人看的毛片在线观看| 久久久久网色| 视频区图区小说| 亚洲欧美成人精品一区二区| 亚洲av免费高清在线观看| 少妇被粗大猛烈的视频| 免费av观看视频| 国产精品熟女久久久久浪| av播播在线观看一区| 欧美成人午夜免费资源| 日韩三级伦理在线观看| 97超碰精品成人国产| 久久精品久久精品一区二区三区| 伦精品一区二区三区| 亚洲精品久久午夜乱码| 看免费成人av毛片| 国产av国产精品国产| 久久久久久久久久人人人人人人| 久久99热这里只频精品6学生|