Biomass conversion offers an efficient approach to alleviate the energy and environmental issues.Electrochemical oxidation of 5-hydroxymethylfurfural(HMF)has attracted tremendous attention in the latest few years for ...Biomass conversion offers an efficient approach to alleviate the energy and environmental issues.Electrochemical oxidation of 5-hydroxymethylfurfural(HMF)has attracted tremendous attention in the latest few years for the mild synthesis conditions and high conversion efficiency to obtain 2,5-furan dicarboxylic acid(FDCA),but there still remain problems such as limited yield,short cycle life,and ambiguous reaction mechanism.Despite many reviews highlighting a variety of electrocatalysts for electrochemical oxidation of HMF,a detailed discussion of the structural modulation of catalyst and the underlying catalytic mechanism is still lacking.We herein provide a comprehensive summary of the recent development of electrochemical oxidation of HMF to FDCA,particularly focusing on the mechanism studies as well as the advanced strategies developed to regulate the structure and optimize the performance of the electrocatalysts,including heterointerface construction,defect engineering,single-atom engineering,and in situ reconstruction.Experimental characterization techniques and theoretical calculation methods for mechanism and active site studies are elaborated,and challenges and future directions of electrochemical oxidation of HMF are also prospected.This review will provide guidance for designing advanced catalysts and deepening the understanding of the reaction mechanism beneath electrochemical oxidation of HMF to FDCA.展开更多
The poor corrosion resistance of magnesium(Mg)and its alloys limits their application in various fields.Micro arc oxidation(MAO)coatings can improve the corrosion resistance,but the pore defects and low surface hardne...The poor corrosion resistance of magnesium(Mg)and its alloys limits their application in various fields.Micro arc oxidation(MAO)coatings can improve the corrosion resistance,but the pore defects and low surface hardness make them susceptible to wear and accelerated corrosion during usage.In this study,a ZrO_(2)nanoparticles doped-MAO coating is prepared on the ZK61 Mg alloy by utilizing an MgF_(2)passivation layer to prevent ablation.The ZrO_(2)nanoparticles re-melt and precipitate due to local discharging,which produces evenly dispersed nanocrystals in the MAO coating.As a result,the hardness of the MAO coating with the appropriate ZrO_(2)concentration increases by over 10 times,while the wear rate decreases and corrosion resistance increases.With increasing ZrO_(2)concentrations,the corrosion potentials increase from−1.528 V of the bare ZK61 Mg alloy to−1.184 V,the corrosion current density decreases from 1.065×10^(–4)A cm^(–2)to 3.960×10^(–8)A cm^(–2),and the charge transfer resistance increases from 3.41×10^(2)Ωcm^(2)to 6.782×10^(5)Ωcm^(2).Immersion tests conducted in a salt solution for 28 d reveal minimal corrosion in contrast to severe corrosion on the untreated ZK61 Mg alloy.ZrO_(2)nanoparticles improve the corrosion resistance of MAO coatings by sealing pores and secondary strengthening of the corrosion product layer.展开更多
Severe tool wear and poor surface quality are the main problems during micro machining of cemented carbide.In this work,an innovative hybrid process of laser-induced oxidation assisted micro milling(LOMM)was proposed ...Severe tool wear and poor surface quality are the main problems during micro machining of cemented carbide.In this work,an innovative hybrid process of laser-induced oxidation assisted micro milling(LOMM)was proposed to solve the problems.A nanosecond laser was utilized to induce oxidation of the WC-20%Co material,producing loose oxide which was easy to remove.The micro machinability of the material was improved by laser-induced oxidation.The oxidation mechanisms of cemented carbide were studied.A microgroove with a depth of 2.5 mm and aspect ratio of 5 was fabricated successfully.The milling force,surface quality and tool wear mechanisms were investigated.For comparison,a microgroove was also fabricated with conventional micro milling(COMM)using identical milling parameters.Results revealed that in LOMM the milling force and tool wear rate were extremely low during removing the oxide.The machined surface quality and dimensional accuracy achieved by LOMM were superior to those obtained by COMM.The surface roughness Saof the microgroove bottom reached 88 nm in LOMM,while the cross-sectional geometry of the microgroove was a trapezoid.Perpendicularity of the microgroove sidewall machined by LOMM was better than that by COMM.The tool wear forms in LOMM were coating spalling and slight tool nose breakage.Compared with COMM,the tool life in LOMM was prolonged significantly.It indicates that the proposed hybrid process is an effective and efficient way to fabricate high aspect ratio micro-features with high dimensional accuracy.展开更多
A composite coating containing hexagonal boron nitride（hBN） particles and titanium oxide（TiO_2） was formed on the surface of Ti-6Al-4V alloy via micro-arc oxidation（MAO）. The effect of quantity of the hBN-partic...A composite coating containing hexagonal boron nitride（hBN） particles and titanium oxide（TiO_2） was formed on the surface of Ti-6Al-4V alloy via micro-arc oxidation（MAO）. The effect of quantity of the hBN-particles added into electrolyte on microstructure, composition, and wear behavior of the resulting composite coatings was investigated. Microstructure, phase composition, and tribological behavior of the resulting MAO coatings were evaluated via scanning electron microscopy, X-ray diffraction, and ball-on-disc abrasive tests. The results reveal that the TiO_2/hBN composite coating consisting of rutile TiO_2, anatase TiO_2, and an hBN phase was less porous than particle-free coating. Furthermore, the presence of hBN particles in the MAO coating produced an improved anti-friction property. The composite coating produced in the electrolyte containing 2 g/L of hBN particles exhibited the best wear resistance.The outer loose layer of the MAO coatings was removed by a mechanical polishing process, which led to a significant improvement in the wear resistance and anti-friction properties of the MAO coatings and highlighted an essential lubricating role of hBN particles in the composite coatings. However, wear mechanism of the MAO coatings was not relevant to the presence of hBN particles, where fatigue wear dominated the anti-fraction properties of the MAO coatings with and without hBN particles.展开更多
Magnesium(Mg)and its alloys have become a hot research topic in various industries owing to the specific physical and chemical properties.However,high corrosion rate is considered the key lifetime-limiting.Plasma elec...Magnesium(Mg)and its alloys have become a hot research topic in various industries owing to the specific physical and chemical properties.However,high corrosion rate is considered the key lifetime-limiting.Plasma electrolytic oxidation(PEO)method is a simple strategy to deposit an oxide layer on the surface of light metals such as magnesium alloys,to control corrosion rate and promote some other properties,depending on their performances.Nevertheless,their features including their micropore size,distribution,and interconnectivity,and microcracks have not been improved to an acceptable level to support long-term performances of the magnesium-based substrates.Studies have introduced micro/nano-enabled approaches to enhance various properties of PEO coatings such as corrosion resistance,tribological properties,self-healing ability,bioactivity,biocompatibility,antibacterial properties,or catalytic performances.These strategies consist of incorporating of micro and nanoparticles into the PEO layers to produce multi-functional surfaces or the formation of multi-layered coatings to cover the defects of PEO coatings.In this perspective,the present paper aims to overview various nano/micro-enabled strategies to promote the properties of PEO coatings on magnesium alloys.The main focus is given to the functional changes that occurred in response to the incorporation of various types of nano/micro-structures into the PEO coatings on magnesium alloys.展开更多
In order to improve the osseointegration and antibacterial activity of titanium alloys,micro/nano-structured ceramic coatings doped with antibacterial element F were prepared by plasma electrolytic oxidation(PEO)proce...In order to improve the osseointegration and antibacterial activity of titanium alloys,micro/nano-structured ceramic coatings doped with antibacterial element F were prepared by plasma electrolytic oxidation(PEO)process on Ti6Al4V alloy in NaF electrolyte.The influence of NaF concentration(0.15-0.50 mol/L)on the PEO process,microstructure,phase composition,corrosion resistance and thickness of the coatings was investigated using scanning/transmission electron microscopy,energy dispersive spectroscopy,atomic force microscopy,X-ray diffractometer,and potentiodynamic polarization.The results demonstrated that Ti6Al4V alloy had low PEO voltage(less than 200 V)in NaF electrolyte,which decreased further as the NaF concentration increased.A micro/nano-structured coating with 10-15μm pits and 200-800 nm pores was formed in NaF electrolyte;the morphology was different from the typical pancake structure obtained with other electrolytes.The coating formed in NaF electrolyte had low surface roughness and was thin(<4μm).The NaF concentration had a small effect on the phase transition from metastable anatase phase to stable rutile phase,but greatly affected the corrosion resistance.In general,as the NaF concentration increased,the surface roughness,phase(anatase and rutile)contents,corrosion resistance,and thickness of the coating first increased and then decreased,reaching the maximum values at 0.25 mol/L NaF.展开更多
Micro arc oxidation(MAO) coatings doped with graphene oxide(GO) were prepared on pure titanium by adding GO and sodium dodecyl benzene sulfonate(SDBS) into a sodium silicate solution. The as-deposited coatings were co...Micro arc oxidation(MAO) coatings doped with graphene oxide(GO) were prepared on pure titanium by adding GO and sodium dodecyl benzene sulfonate(SDBS) into a sodium silicate solution. The as-deposited coatings were comparatively analyzed by scanning electron microscopy(SEM), energydispersive X-ray spectroscopy(EDS) and X-ray diffraction(XRD). The binding forces of the MAO, MAO+GO and MAO+GO+SDBS three coatings were measured by a scratch tester. The mechanical property of the three coatings was analyzed using the nano-indentation technique. The corrosion resistance of the coatings was tested by the electrochemical system in 3.5% NaCl solution. The photocatalytic activity of the prepared samples was evaluated by determining the degradation of methylene blue(MB) solution. The results showed that compared to the MAO coating, the morphologies and phase compositions of MAO+GO and MAO+GO+SDBS composite coatings were significantly different. These two composite coatings all had superior photocatalytic activity. Especially, the MAO+GO composite coating still had enhanced binding force and excellent corrosion resistance. Furthermore, the relationship between the microstructure and the properties of these three MAO coatings was analyzed.展开更多
NiMo catalyst exhibits excellent catalytic performance in the electrooxidation of 5-hydroxymethylfurfural(HMF)to produce high-value 2,5-furandicarboxylic acid(FDCA).Although metallic nickel is known to undergo reconst...NiMo catalyst exhibits excellent catalytic performance in the electrooxidation of 5-hydroxymethylfurfural(HMF)to produce high-value 2,5-furandicarboxylic acid(FDCA).Although metallic nickel is known to undergo reconstruction into high-valent species during the reaction,the dynamic evolution of molybdenum components in NiMo catalyst and their mechanistic roles in catalytic reaction remain unclear.In this study,the structural evolution of NiMo alloy during HMF electrooxidation is systematically investigated.Operando analyses reveal that under anodic polarization,molybdenum undergoes oxidative dissolution in the form of MoO_(4)^(2-),concurrently driving the generation of high-valent Ni^(3+)species.Meanwhile,the dissolved MoO_(4)^(2-)re-adsorbs on the catalyst surface,forming a unique interfacial structure with Ni^(3+).Electrochemical results demonstrate that this surface structure facilitates a synergistic effect between the MoO_(4)^(2-)and high-valent Ni^(3+),enhancing the adsorption and activation of HMF molecules.Therefore,the NiMo alloy exhibits excellent catalytic performance,with a high FDCA selectivity of 99.0%.This study provides new insights into the relationship between the catalyst reconstruction process and enhancement of catalytic performance.展开更多
BACKGROUND Gastric cancer(GC)is a type of cancer which causes high cancer-related mortality.Surgical operation and systematic chemical therapies are primary choices for the treatment of GC patients with advanced stage...BACKGROUND Gastric cancer(GC)is a type of cancer which causes high cancer-related mortality.Surgical operation and systematic chemical therapies are primary choices for the treatment of GC patients with advanced stages,however,the 5-year overall survival is only around 30%.AIM To investigate the role of mesenchymal stem cell(MSC)-derived long non-coding RNAs(lncRNA)NKILA in fatty acid oxidation and chemoresistance in GC cells,mediated through the miR-485-5p/STAT3 pathway.METHODS GC cell lines(AGS and MKN45)were co-cultured with human bone marrowderived MSCs were cultured.The MSC identity was confirmed by flow cytometry(CD73,CD90,CD105>95%positive,CD34,CD45 negative).Co-culture of GC cells and MSCs was performed in Transwell plates,where MSCs were placed in the upper chamber and GC cells in the lower chamber for 72 hours.For transfections,pcDNA-NKILA vectors,shSTAT3,and miR-485-5p mimics were utilized.Colony formation,apoptosis assays(Annexin V/PI staining),sphere formation,and flow cytometry were performed to evaluate cell proliferation,stemness,and chemoresistance.qPCR was used to analyze gene expression(Sox2,Oct4,CD133,LIN28,NKILA),and Western blotting assessed protein levels of stemness markers.Luciferase reporter assays were conducted to confirm miR-485-5p/STAT3 interactions,and biotin-labeled RNA pulldown was used to assess RNA-protein binding.Fatty acid oxidation was evaluated using a CPT1 activity assay andβ-oxidation rate detection.ATP levels were measured to assess the energetic status of GC cells.Clinical GC tissue samples were collected from patients at our hospital for validation.RESULTS MSCs were found to enhance the stemness and chemoresistance of GC cells.Co-culturing MKN45 and AGS cells with MSCs significantly increased sphere-forming ability and the expression of key cancer stem cell markers(SOX2,Oct4,LIN28,CD133),indicating that MSCs promote stem-like properties.Flow cytometry confirmed an enrichment of CD44+and CD133+subpopulations in MSC-treated GC cells.Additionally,MSC co-culture reduced chemotherapy-induced apoptosis and enhanced cell proliferation,suggesting a protective role in chemotherapy resistance.MSC-derived lncRNA NKILA further promoted stemness and chemoresistance,enhancing expression of stem cell markers and protecting cells from oxaliplatin and 5-FU-induced apoptosis.MSC co-culture also induced fatty acid oxidation in GC cells,as shown by increased CPT1 activity,β-oxidation rates,and ATP levels.NKILA mediated these effects by upregulating STAT3,which was confirmed to regulate fatty acid oxidation and chemoresistance.NKILA’s interaction with miR-485-5p further promoted STAT3 expression and fatty acid oxidation,reinforcing its role in maintaining stemness and enhancing chemoresistance.CONCLUSION MSCs enhance the stemness and chemoresistance of GC cells by secreting lncRNA NKILA,which promotes fatty acid oxidation through STAT3 activation.NKILA modulates the miR-485-5p/STAT3 axis,thereby increasing energy metabolism and supporting cancer stem cell properties.Targeting NKILA or the miR-485-5p/STAT3 pathway offers potential therapeutic strategies to overcome chemoresistance in GC.展开更多
The feasibility of the formation of a liquid plasma catalysis system through micro arc oxidation（MAO） under AC power with titanium-aluminum alloy electrodes was investigated.In the decolorization of organic dyeing w...The feasibility of the formation of a liquid plasma catalysis system through micro arc oxidation（MAO） under AC power with titanium-aluminum alloy electrodes was investigated.In the decolorization of organic dyeing wastewater simulated with Rhodamine B,Ti-Al alloy electrodes were superior over Ti electrodes and Al electrodes.The optimal molar percentage of Ti in alloy electrodes was 70%and the optimal decolorization rate was up to 88.9%if the additive suitable for Al was added into the solution to be treated.The decolorization rates were the same in the case of the alloy-alloy electrodes and alloy-Al electrodes.The proportion of the effects of plasma,TiO2 catalyzer during MAO and H2O2 after MAO in decolorization has been obtained.With the catalysis of TiO2 formed on the electrodes,the reaction rate was improved by a maximum of 95%and the decolorization rate was improved by a maximum of 71.6%.Based on the spectral analysis,the plasma catalysis mechanism has been studied.展开更多
Magnesium and its alloys have been used in many industries, but they are reactive and require protection against aggressive environments. In this study, oxide coatings were applied on AZ91D magnesium alloy using micro...Magnesium and its alloys have been used in many industries, but they are reactive and require protection against aggressive environments. In this study, oxide coatings were applied on AZ91D magnesium alloy using micro-arc oxidation （MAO） process. Then, in order to seal the pores of the MAO coatings, the samples were immersed in cerium bath for different times. The surface morphologies and compositions of the coatings were analyzed by scanning electron microscopy （SEM） and X-ray energy dispersive spectroscopy （EDS）, respectively. The corrosion behavior of the coatings was investigated with electrochemical impedance spectroscopy （EIS） and potentiodynamic polarization tests in 3.5 wt.% NaCl solution. The amount of the porosity of the coating was measured by electrochemical method. It was found that the sealing treatments by immersion in cerium bath successfully sealed the pores of the MAO coatings. The results of the corrosion tests showed that the MAO coating which was sealed in Ce bath for 10 min enhanced the corrosion resistance of the substrate significantly. Furthermore, this coating had the lowest amount of the porosity among the coatings.展开更多
Calcium phosphate(CaP) coatings were prepared on Mg–8Li–2Ca magnesium alloy by micro-arc oxidation(MAO) in an alkaline Na_3PO_4–Ca[C_3H_7O_6P] base solution at the different applied voltages. Scanning electron micr...Calcium phosphate(CaP) coatings were prepared on Mg–8Li–2Ca magnesium alloy by micro-arc oxidation(MAO) in an alkaline Na_3PO_4–Ca[C_3H_7O_6P] base solution at the different applied voltages. Scanning electron microscope and X-ray diffraction were employed to characterize the microstructure and phase composition of the coatings, respectively. The corrosion resistance of the coatings was assessed by potential dynamic polarization curves, electrochemical impedance spectroscopy and hydrogen evolution experiment in simulated body fluids solution. The friction and wear properties were evaluated by friction and wear testing machine. The results demonstrate that the coating surface is porous and mainly composed of MgO, Ca_5(PO_4)_3(OH) and CaH_2P_2O_5. With the increase in voltage, the corrosion resistance and wear resistance of the MAO coating are both enhanced. The corrosion current density of the MAO coating decreases about two orders of the magnitude compared to the substrate. Additionally, wear and corrosion mechanisms are discussed.展开更多
Ceramic coatings were prepared on AZ91 D Mg alloy by micro-arc oxidation （MAO） in aluminate electrolytes, with Al2O3 nano-additive suspending at different concentrations. Effects of nano-additive concentration on th...Ceramic coatings were prepared on AZ91 D Mg alloy by micro-arc oxidation （MAO） in aluminate electrolytes, with Al2O3 nano-additive suspending at different concentrations. Effects of nano-additive concentration on the structure, phase composition, hardness and anti-corrosion property of the MAO coatings were analyzed by scanning electron microscopy, X-ray diffraction, micro-hardness test and electrochemical method, respectively. The results revealed that Al2O3 nano-particles were mostly incorporated into ceramic coating chemically, transferred into MgAl2O4, rather than being trapped mechanically during MAO process. With the increase of Al2O3 concentration, the voltage-time response, content of MgAl2O4, hardness and anti-corrosion property increased. However, when the concentration varied from 10 g/L to 15 g/L, these behaviors and properties changed only a little. This result indicated that, after the concentration of Al2O3 nano-additive reaching 10 g/L, the incorporation of Al2O3 nano-particles turned into a saturation state, due to the complex process during MAO treatment. Therefore, 10 g/L might be a proper concentration for MAO coating to incorporate Al2O3 nano-particles,展开更多
To improve the surface corrosion resistance of the alumina films fabricated by micro-arc oxidation （MAO）,Al2O3 coatings at different current densities （5,7 and 10 A/dm 2） were produced on aluminum alloys by adding...To improve the surface corrosion resistance of the alumina films fabricated by micro-arc oxidation （MAO）,Al2O3 coatings at different current densities （5,7 and 10 A/dm 2） were produced on aluminum alloys by adding SiC nano-particles into electrolyte during MAO process.The morphology and phase composition of the coatings were investigated by scanning electron microscopy （SEM） and X-ray diffraction （XRD）,respectively.Furthermore,the corrosion performance of the coatings was evaluated via a three-electrode system in a 3.5 wt pct NaCl solution.From the obtained morphology of alumina coatings,it was believed that the Al2O3 coatings embedded with SiC nano-particles were formed.The electrochemical impedance spectroscopy （EIS） plots and potentiodynamic polarization plots of the Al2O3 coatings with and without SiC nano-particles at different current densities reveal that the Al2O3 coatings with SiC nano-particles formed at 10 A/dm 2 showed the better corrosion resistance than the other coatings produced at 5 and 7 A/dm 2.展开更多
Micro-arc oxidized Cu-incorporated TiO2 coatings （Cu-TiO2） were prepared in the Ca, P, Cu-containing electrolyte to obtain an implant material with superior biological activity and antibacterial property. The surfac...Micro-arc oxidized Cu-incorporated TiO2 coatings （Cu-TiO2） were prepared in the Ca, P, Cu-containing electrolyte to obtain an implant material with superior biological activity and antibacterial property. The surface topography, phase, and element composition of the TiO2 and Cu-TiO2 coatings were characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and energy-dispersive X-ray spectrometry （EDS）, respectively. Staphylococcus aureus （S. aureus） was selected to evaluate the antibacterial property of the Cu-TiO2 coatings, whereas osteoblastic MG63 cells were cultured on the coatings to investigate the biological activity. The obtained results demonstrated that Cu element was successfully incorporated into the porous nano-structured TiO2 coatings, which did not alter apparently the surface topography and phase composition of the coatings as compared to the Cu-free TiO2 coatings. Moreover, the antibacterial studies suggested that the Cu-incorporated TiO2 coatings could significantly inhibit the adhesion of S. aureus. In addition, the in vitro biological evaluation displayed that the adhesion, proliferation and differentiation of MG63 cells on the Cu-incorporated coatings were enhanced as compared to those on the Cu-free coatings and Ti plates. In conclusion, the innovative Cu-incorporated nano-structured TiO2 coatings on Ti substrate with excellent antibacterial property and biological activity are promising candidates for orthopedic implant.展开更多
To improve the surface wear resistance of the ceramic coating fabricated by micro-arc oxidation （MAO） on AZ91D magnesium alloy,ceramic coatings embedded with SiC nano-particles at different current frequency （500 H...To improve the surface wear resistance of the ceramic coating fabricated by micro-arc oxidation （MAO） on AZ91D magnesium alloy,ceramic coatings embedded with SiC nano-particles at different current frequency （500 Hz,700 Hz,and 900 Hz） were produced during the MAO process.The morphology and phase composition of the coatings were investigated by scanning electron microscopy （SEM）,field emission scanning electron microscopy （FESEM）,and X-ray diffraction （XRD）.The surface roughness of the coatings was characterized by confocal laser scanning microscopy （CLSM）.Simultaneously,the tribological properties of the composite coatings were evaluated by using a universal materials tester （UMT）.The results shows that the wear resistance of the ceramic coatings with SiC nano-particles was improved significantly compared to the ceramic coatings without SiC nano-particles.Furthermore,the composite coating formed at current frequency 900 Hz showed the better wear resistance than the others.展开更多
Compound ceramic coatings with the main crystalline of Al_2TiO_5（in the as-prepared coating without treatment） were prepared in situ on the surface Ti-6Al-4V alloy by means of pulsed bipolar micro-arc oxidation in N...Compound ceramic coatings with the main crystalline of Al_2TiO_5（in the as-prepared coating without treatment） were prepared in situ on the surface Ti-6Al-4V alloy by means of pulsed bipolar micro-arc oxidation in Na AlO_2 solution. For the purpose of studying the antioxidation properties of the samples, the coated samples treated in argon and the as-coated samples were calcined in air at 1000 °C. And the related characteristics were investigated by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and X-ray fluorescence（XRF） spectroscopy, respectively. The results show that, when it was calcined in air for 1 h, Al_2TiO_5in the as-prepared coating decomposed and transformed into α-Al_2O_3 and rutile TiO_2.However, after almost 4 h in argon, Al_2TiO_5in the asprepared coating decomposed and the final coating surface contents are completely α-Al_2O_3, and those of the middle interface are mainly Al_2O_3 and Ti_2O_3. The morphologies of the coatings after calcination in argon and air are different.High-temperature oxidation occurred violently in the alloy substrate without coatings. Furthermore, the weight gain curves of the as-prepared samples and the coated samples treated in argon both show a parabolic shape.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
Micro-arc oxidation(MAO)coatings were fabricated on AZ31 magnesium alloy and the effect of Na2CO3 on the energy consumption was studied.The results show that the concentration of Na2CO3 has a critical effect on the di...Micro-arc oxidation(MAO)coatings were fabricated on AZ31 magnesium alloy and the effect of Na2CO3 on the energy consumption was studied.The results show that the concentration of Na2CO3 has a critical effect on the discharge behavior of MAO process.With increasing the Na2CO3 concentration in the electrolyte,the arcing voltage and working voltage decrease.A proper concentration is needed to achieve the highest growth rate of the coatings and the lowest energy consumption per unit coating volume.The addition of Na2CO3 decreases the arcing and working voltage of MAO discharge.It is attributed to that the Na2CO3 leads to much more micropores due to the decomposition of MgCO3 to produce more gas.展开更多
In order to prepare ornamental and anti-corrosive coating on aluminum alloys, preparation technology of black micro-arc ceramic coatings on Al alloys in silicate based electrolyte was studied. The influence of content...In order to prepare ornamental and anti-corrosive coating on aluminum alloys, preparation technology of black micro-arc ceramic coatings on Al alloys in silicate based electrolyte was studied. The influence of content of Na2WO4 and combination additive in solution on the performance of black ceramic coatings was studied; the anticorrosion performances of black ceramic coatings were evaluated through whole-immersion test and electrochemical method in 3.5% NaCl solution at different pH value; SEM and XRD were used to analyze the surface morphology and phase constitutes of the black ceramic coatings. Experimental results indicated that, without combination additives, with the increasing of Na2WO4 content in the electrolyte, ceramic coating became darker and thicker, but the color was not black; after adding combination additive, the coating turned to be black; the black ceramic coating was multi-hole form in surface. There was a small quantity of tungsten existing in the black ceramic coating beside α-Al2O3 phase and β-Al2O3 phase. And aluminum alloy with black ceramic coating exhibited excellent anti-corrosion property in acid, basic and neutral 3.5% NaCl solution.展开更多
基金National Natural Science Foundation of China(22272150,22302177)Major Program of Zhejiang Provincial Natural Science Foundation of China(LD22B030002)+2 种基金Zhejiang Provincial Ten Thousand Talent Program(2021R51009)Public Technology Application Project of Jinhua City(2022-4-067)Self Designed Scientific Research of Zhejiang Normal University(2021ZS0604)。
文摘Biomass conversion offers an efficient approach to alleviate the energy and environmental issues.Electrochemical oxidation of 5-hydroxymethylfurfural(HMF)has attracted tremendous attention in the latest few years for the mild synthesis conditions and high conversion efficiency to obtain 2,5-furan dicarboxylic acid(FDCA),but there still remain problems such as limited yield,short cycle life,and ambiguous reaction mechanism.Despite many reviews highlighting a variety of electrocatalysts for electrochemical oxidation of HMF,a detailed discussion of the structural modulation of catalyst and the underlying catalytic mechanism is still lacking.We herein provide a comprehensive summary of the recent development of electrochemical oxidation of HMF to FDCA,particularly focusing on the mechanism studies as well as the advanced strategies developed to regulate the structure and optimize the performance of the electrocatalysts,including heterointerface construction,defect engineering,single-atom engineering,and in situ reconstruction.Experimental characterization techniques and theoretical calculation methods for mechanism and active site studies are elaborated,and challenges and future directions of electrochemical oxidation of HMF are also prospected.This review will provide guidance for designing advanced catalysts and deepening the understanding of the reaction mechanism beneath electrochemical oxidation of HMF to FDCA.
基金supported by the Postdoctoral Fellowship Program of CPSF(No.GZC20231545)the China Postdoctoral Science Foundation(Nos.2024T170557 and 2023M742224)+6 种基金the Shanghai Post-doctoral Excellence Program(No.2023440)the National Natural Science Foundation of China(Nos.52127801,52401101,and 22205012)the Shenzhen Basic Research Project(Nos.JCYJ20210324120001003,JCYJ20200109144608205)the Guangdong Basic and Applied Basic Research Foundation(Nos.2020A1515011301 and 2021A1515012246)the IER Foundation(Nos.IERF202201 andIERF202202),the City University of Hong Kong Donation Research(No.DON-RMG 9229021)the Hong Kong PDFS-RGC Postdoctoral Fellowship Scheme(Nos.PDFS2122–1S08 and CityU 9061014)the Hong Kong HMRF(Health and Medical Research Fund)(Nos.2120972 and CityU 9211320).
文摘The poor corrosion resistance of magnesium(Mg)and its alloys limits their application in various fields.Micro arc oxidation(MAO)coatings can improve the corrosion resistance,but the pore defects and low surface hardness make them susceptible to wear and accelerated corrosion during usage.In this study,a ZrO_(2)nanoparticles doped-MAO coating is prepared on the ZK61 Mg alloy by utilizing an MgF_(2)passivation layer to prevent ablation.The ZrO_(2)nanoparticles re-melt and precipitate due to local discharging,which produces evenly dispersed nanocrystals in the MAO coating.As a result,the hardness of the MAO coating with the appropriate ZrO_(2)concentration increases by over 10 times,while the wear rate decreases and corrosion resistance increases.With increasing ZrO_(2)concentrations,the corrosion potentials increase from−1.528 V of the bare ZK61 Mg alloy to−1.184 V,the corrosion current density decreases from 1.065×10^(–4)A cm^(–2)to 3.960×10^(–8)A cm^(–2),and the charge transfer resistance increases from 3.41×10^(2)Ωcm^(2)to 6.782×10^(5)Ωcm^(2).Immersion tests conducted in a salt solution for 28 d reveal minimal corrosion in contrast to severe corrosion on the untreated ZK61 Mg alloy.ZrO_(2)nanoparticles improve the corrosion resistance of MAO coatings by sealing pores and secondary strengthening of the corrosion product layer.
基金the National Natural Science Foundation of China(No.51705249)the China Postdoctoral Science Foundation(No.2019M661823)+1 种基金the Aeronautical Science Foundation of China(No.2017ZE52047)the 111 Project on Key Technology in Sustainable Manufacturing(No.B16024)。
文摘Severe tool wear and poor surface quality are the main problems during micro machining of cemented carbide.In this work,an innovative hybrid process of laser-induced oxidation assisted micro milling(LOMM)was proposed to solve the problems.A nanosecond laser was utilized to induce oxidation of the WC-20%Co material,producing loose oxide which was easy to remove.The micro machinability of the material was improved by laser-induced oxidation.The oxidation mechanisms of cemented carbide were studied.A microgroove with a depth of 2.5 mm and aspect ratio of 5 was fabricated successfully.The milling force,surface quality and tool wear mechanisms were investigated.For comparison,a microgroove was also fabricated with conventional micro milling(COMM)using identical milling parameters.Results revealed that in LOMM the milling force and tool wear rate were extremely low during removing the oxide.The machined surface quality and dimensional accuracy achieved by LOMM were superior to those obtained by COMM.The surface roughness Saof the microgroove bottom reached 88 nm in LOMM,while the cross-sectional geometry of the microgroove was a trapezoid.Perpendicularity of the microgroove sidewall machined by LOMM was better than that by COMM.The tool wear forms in LOMM were coating spalling and slight tool nose breakage.Compared with COMM,the tool life in LOMM was prolonged significantly.It indicates that the proposed hybrid process is an effective and efficient way to fabricate high aspect ratio micro-features with high dimensional accuracy.
基金the Open Foundation of National Defense Key Discipline Laboratory of Light Alloy Processing Science and Technology (Grant No.gf201401001)the National Natural Science Foundation of China (Grant No.51171154)
文摘A composite coating containing hexagonal boron nitride（hBN） particles and titanium oxide（TiO_2） was formed on the surface of Ti-6Al-4V alloy via micro-arc oxidation（MAO）. The effect of quantity of the hBN-particles added into electrolyte on microstructure, composition, and wear behavior of the resulting composite coatings was investigated. Microstructure, phase composition, and tribological behavior of the resulting MAO coatings were evaluated via scanning electron microscopy, X-ray diffraction, and ball-on-disc abrasive tests. The results reveal that the TiO_2/hBN composite coating consisting of rutile TiO_2, anatase TiO_2, and an hBN phase was less porous than particle-free coating. Furthermore, the presence of hBN particles in the MAO coating produced an improved anti-friction property. The composite coating produced in the electrolyte containing 2 g/L of hBN particles exhibited the best wear resistance.The outer loose layer of the MAO coatings was removed by a mechanical polishing process, which led to a significant improvement in the wear resistance and anti-friction properties of the MAO coatings and highlighted an essential lubricating role of hBN particles in the composite coatings. However, wear mechanism of the MAO coatings was not relevant to the presence of hBN particles, where fatigue wear dominated the anti-fraction properties of the MAO coatings with and without hBN particles.
文摘Magnesium(Mg)and its alloys have become a hot research topic in various industries owing to the specific physical and chemical properties.However,high corrosion rate is considered the key lifetime-limiting.Plasma electrolytic oxidation(PEO)method is a simple strategy to deposit an oxide layer on the surface of light metals such as magnesium alloys,to control corrosion rate and promote some other properties,depending on their performances.Nevertheless,their features including their micropore size,distribution,and interconnectivity,and microcracks have not been improved to an acceptable level to support long-term performances of the magnesium-based substrates.Studies have introduced micro/nano-enabled approaches to enhance various properties of PEO coatings such as corrosion resistance,tribological properties,self-healing ability,bioactivity,biocompatibility,antibacterial properties,or catalytic performances.These strategies consist of incorporating of micro and nanoparticles into the PEO layers to produce multi-functional surfaces or the formation of multi-layered coatings to cover the defects of PEO coatings.In this perspective,the present paper aims to overview various nano/micro-enabled strategies to promote the properties of PEO coatings on magnesium alloys.The main focus is given to the functional changes that occurred in response to the incorporation of various types of nano/micro-structures into the PEO coatings on magnesium alloys.
文摘In order to improve the osseointegration and antibacterial activity of titanium alloys,micro/nano-structured ceramic coatings doped with antibacterial element F were prepared by plasma electrolytic oxidation(PEO)process on Ti6Al4V alloy in NaF electrolyte.The influence of NaF concentration(0.15-0.50 mol/L)on the PEO process,microstructure,phase composition,corrosion resistance and thickness of the coatings was investigated using scanning/transmission electron microscopy,energy dispersive spectroscopy,atomic force microscopy,X-ray diffractometer,and potentiodynamic polarization.The results demonstrated that Ti6Al4V alloy had low PEO voltage(less than 200 V)in NaF electrolyte,which decreased further as the NaF concentration increased.A micro/nano-structured coating with 10-15μm pits and 200-800 nm pores was formed in NaF electrolyte;the morphology was different from the typical pancake structure obtained with other electrolytes.The coating formed in NaF electrolyte had low surface roughness and was thin(<4μm).The NaF concentration had a small effect on the phase transition from metastable anatase phase to stable rutile phase,but greatly affected the corrosion resistance.In general,as the NaF concentration increased,the surface roughness,phase(anatase and rutile)contents,corrosion resistance,and thickness of the coating first increased and then decreased,reaching the maximum values at 0.25 mol/L NaF.
基金Funded by the National Natural Science Foundation of China(No.51571114)the Key Research and Development Plan of Shaanxi Province-Industrial Project(No.2018GY-127)
文摘Micro arc oxidation(MAO) coatings doped with graphene oxide(GO) were prepared on pure titanium by adding GO and sodium dodecyl benzene sulfonate(SDBS) into a sodium silicate solution. The as-deposited coatings were comparatively analyzed by scanning electron microscopy(SEM), energydispersive X-ray spectroscopy(EDS) and X-ray diffraction(XRD). The binding forces of the MAO, MAO+GO and MAO+GO+SDBS three coatings were measured by a scratch tester. The mechanical property of the three coatings was analyzed using the nano-indentation technique. The corrosion resistance of the coatings was tested by the electrochemical system in 3.5% NaCl solution. The photocatalytic activity of the prepared samples was evaluated by determining the degradation of methylene blue(MB) solution. The results showed that compared to the MAO coating, the morphologies and phase compositions of MAO+GO and MAO+GO+SDBS composite coatings were significantly different. These two composite coatings all had superior photocatalytic activity. Especially, the MAO+GO composite coating still had enhanced binding force and excellent corrosion resistance. Furthermore, the relationship between the microstructure and the properties of these three MAO coatings was analyzed.
基金supported by the Natural Science Foundation of Guangxi Zhuang(2022JJD120011)the National Natural Science Foundation of China(22479031,22162004)the Project for Enhancing Young and Middle-aged Teacher's Research Basis Ability in Colleges of Guangxi(2025KY0040).
文摘NiMo catalyst exhibits excellent catalytic performance in the electrooxidation of 5-hydroxymethylfurfural(HMF)to produce high-value 2,5-furandicarboxylic acid(FDCA).Although metallic nickel is known to undergo reconstruction into high-valent species during the reaction,the dynamic evolution of molybdenum components in NiMo catalyst and their mechanistic roles in catalytic reaction remain unclear.In this study,the structural evolution of NiMo alloy during HMF electrooxidation is systematically investigated.Operando analyses reveal that under anodic polarization,molybdenum undergoes oxidative dissolution in the form of MoO_(4)^(2-),concurrently driving the generation of high-valent Ni^(3+)species.Meanwhile,the dissolved MoO_(4)^(2-)re-adsorbs on the catalyst surface,forming a unique interfacial structure with Ni^(3+).Electrochemical results demonstrate that this surface structure facilitates a synergistic effect between the MoO_(4)^(2-)and high-valent Ni^(3+),enhancing the adsorption and activation of HMF molecules.Therefore,the NiMo alloy exhibits excellent catalytic performance,with a high FDCA selectivity of 99.0%.This study provides new insights into the relationship between the catalyst reconstruction process and enhancement of catalytic performance.
文摘BACKGROUND Gastric cancer(GC)is a type of cancer which causes high cancer-related mortality.Surgical operation and systematic chemical therapies are primary choices for the treatment of GC patients with advanced stages,however,the 5-year overall survival is only around 30%.AIM To investigate the role of mesenchymal stem cell(MSC)-derived long non-coding RNAs(lncRNA)NKILA in fatty acid oxidation and chemoresistance in GC cells,mediated through the miR-485-5p/STAT3 pathway.METHODS GC cell lines(AGS and MKN45)were co-cultured with human bone marrowderived MSCs were cultured.The MSC identity was confirmed by flow cytometry(CD73,CD90,CD105>95%positive,CD34,CD45 negative).Co-culture of GC cells and MSCs was performed in Transwell plates,where MSCs were placed in the upper chamber and GC cells in the lower chamber for 72 hours.For transfections,pcDNA-NKILA vectors,shSTAT3,and miR-485-5p mimics were utilized.Colony formation,apoptosis assays(Annexin V/PI staining),sphere formation,and flow cytometry were performed to evaluate cell proliferation,stemness,and chemoresistance.qPCR was used to analyze gene expression(Sox2,Oct4,CD133,LIN28,NKILA),and Western blotting assessed protein levels of stemness markers.Luciferase reporter assays were conducted to confirm miR-485-5p/STAT3 interactions,and biotin-labeled RNA pulldown was used to assess RNA-protein binding.Fatty acid oxidation was evaluated using a CPT1 activity assay andβ-oxidation rate detection.ATP levels were measured to assess the energetic status of GC cells.Clinical GC tissue samples were collected from patients at our hospital for validation.RESULTS MSCs were found to enhance the stemness and chemoresistance of GC cells.Co-culturing MKN45 and AGS cells with MSCs significantly increased sphere-forming ability and the expression of key cancer stem cell markers(SOX2,Oct4,LIN28,CD133),indicating that MSCs promote stem-like properties.Flow cytometry confirmed an enrichment of CD44+and CD133+subpopulations in MSC-treated GC cells.Additionally,MSC co-culture reduced chemotherapy-induced apoptosis and enhanced cell proliferation,suggesting a protective role in chemotherapy resistance.MSC-derived lncRNA NKILA further promoted stemness and chemoresistance,enhancing expression of stem cell markers and protecting cells from oxaliplatin and 5-FU-induced apoptosis.MSC co-culture also induced fatty acid oxidation in GC cells,as shown by increased CPT1 activity,β-oxidation rates,and ATP levels.NKILA mediated these effects by upregulating STAT3,which was confirmed to regulate fatty acid oxidation and chemoresistance.NKILA’s interaction with miR-485-5p further promoted STAT3 expression and fatty acid oxidation,reinforcing its role in maintaining stemness and enhancing chemoresistance.CONCLUSION MSCs enhance the stemness and chemoresistance of GC cells by secreting lncRNA NKILA,which promotes fatty acid oxidation through STAT3 activation.NKILA modulates the miR-485-5p/STAT3 axis,thereby increasing energy metabolism and supporting cancer stem cell properties.Targeting NKILA or the miR-485-5p/STAT3 pathway offers potential therapeutic strategies to overcome chemoresistance in GC.
基金National Natural Science Foundation of China(No.11675031) for their support of this research
文摘The feasibility of the formation of a liquid plasma catalysis system through micro arc oxidation（MAO） under AC power with titanium-aluminum alloy electrodes was investigated.In the decolorization of organic dyeing wastewater simulated with Rhodamine B,Ti-Al alloy electrodes were superior over Ti electrodes and Al electrodes.The optimal molar percentage of Ti in alloy electrodes was 70%and the optimal decolorization rate was up to 88.9%if the additive suitable for Al was added into the solution to be treated.The decolorization rates were the same in the case of the alloy-alloy electrodes and alloy-Al electrodes.The proportion of the effects of plasma,TiO2 catalyzer during MAO and H2O2 after MAO in decolorization has been obtained.With the catalysis of TiO2 formed on the electrodes,the reaction rate was improved by a maximum of 95%and the decolorization rate was improved by a maximum of 71.6%.Based on the spectral analysis,the plasma catalysis mechanism has been studied.
文摘Magnesium and its alloys have been used in many industries, but they are reactive and require protection against aggressive environments. In this study, oxide coatings were applied on AZ91D magnesium alloy using micro-arc oxidation （MAO） process. Then, in order to seal the pores of the MAO coatings, the samples were immersed in cerium bath for different times. The surface morphologies and compositions of the coatings were analyzed by scanning electron microscopy （SEM） and X-ray energy dispersive spectroscopy （EDS）, respectively. The corrosion behavior of the coatings was investigated with electrochemical impedance spectroscopy （EIS） and potentiodynamic polarization tests in 3.5 wt.% NaCl solution. The amount of the porosity of the coating was measured by electrochemical method. It was found that the sealing treatments by immersion in cerium bath successfully sealed the pores of the MAO coatings. The results of the corrosion tests showed that the MAO coating which was sealed in Ce bath for 10 min enhanced the corrosion resistance of the substrate significantly. Furthermore, this coating had the lowest amount of the porosity among the coatings.
基金supported by the National Natural Science Foundation of China(Nos.51671063,51771060 and51871068)the Key Laboratory of Lightweight and high strength structural materials of Jiangxi Province(No.20171BCD40003)+4 种基金the Research Fund for the Doctoral Program of Higher Education(No.20132304110006)Heilongjiang Province Natural Science Foundation(No.ZD2017010)the Fundamental Research Funds for the Central Universities(No.HEUCFG201834)the Harbin City Application Technology Research and Development Project(Nos.2015RQXXJ001 and 2017RAQXJ032)the Science and Technology Innovation Project(No.009-031-001)
文摘Calcium phosphate(CaP) coatings were prepared on Mg–8Li–2Ca magnesium alloy by micro-arc oxidation(MAO) in an alkaline Na_3PO_4–Ca[C_3H_7O_6P] base solution at the different applied voltages. Scanning electron microscope and X-ray diffraction were employed to characterize the microstructure and phase composition of the coatings, respectively. The corrosion resistance of the coatings was assessed by potential dynamic polarization curves, electrochemical impedance spectroscopy and hydrogen evolution experiment in simulated body fluids solution. The friction and wear properties were evaluated by friction and wear testing machine. The results demonstrate that the coating surface is porous and mainly composed of MgO, Ca_5(PO_4)_3(OH) and CaH_2P_2O_5. With the increase in voltage, the corrosion resistance and wear resistance of the MAO coating are both enhanced. The corrosion current density of the MAO coating decreases about two orders of the magnitude compared to the substrate. Additionally, wear and corrosion mechanisms are discussed.
文摘Ceramic coatings were prepared on AZ91 D Mg alloy by micro-arc oxidation （MAO） in aluminate electrolytes, with Al2O3 nano-additive suspending at different concentrations. Effects of nano-additive concentration on the structure, phase composition, hardness and anti-corrosion property of the MAO coatings were analyzed by scanning electron microscopy, X-ray diffraction, micro-hardness test and electrochemical method, respectively. The results revealed that Al2O3 nano-particles were mostly incorporated into ceramic coating chemically, transferred into MgAl2O4, rather than being trapped mechanically during MAO process. With the increase of Al2O3 concentration, the voltage-time response, content of MgAl2O4, hardness and anti-corrosion property increased. However, when the concentration varied from 10 g/L to 15 g/L, these behaviors and properties changed only a little. This result indicated that, after the concentration of Al2O3 nano-additive reaching 10 g/L, the incorporation of Al2O3 nano-particles turned into a saturation state, due to the complex process during MAO treatment. Therefore, 10 g/L might be a proper concentration for MAO coating to incorporate Al2O3 nano-particles,
基金supported by the Ministry of Education of the People's Republic of China (Contract No. 210051)
文摘To improve the surface corrosion resistance of the alumina films fabricated by micro-arc oxidation （MAO）,Al2O3 coatings at different current densities （5,7 and 10 A/dm 2） were produced on aluminum alloys by adding SiC nano-particles into electrolyte during MAO process.The morphology and phase composition of the coatings were investigated by scanning electron microscopy （SEM） and X-ray diffraction （XRD）,respectively.Furthermore,the corrosion performance of the coatings was evaluated via a three-electrode system in a 3.5 wt pct NaCl solution.From the obtained morphology of alumina coatings,it was believed that the Al2O3 coatings embedded with SiC nano-particles were formed.The electrochemical impedance spectroscopy （EIS） plots and potentiodynamic polarization plots of the Al2O3 coatings with and without SiC nano-particles at different current densities reveal that the Al2O3 coatings with SiC nano-particles formed at 10 A/dm 2 showed the better corrosion resistance than the other coatings produced at 5 and 7 A/dm 2.
基金supported by the Shanghai Science and Technology R&D Fund(Nos.0952nm04400,07JC14057 and 08ZR1421600)the National Basic Research Fund(No. 2005CB623901)the National Natural Science Foundation of China(Nos.30700170,30973041 and 81271959)
文摘Micro-arc oxidized Cu-incorporated TiO2 coatings （Cu-TiO2） were prepared in the Ca, P, Cu-containing electrolyte to obtain an implant material with superior biological activity and antibacterial property. The surface topography, phase, and element composition of the TiO2 and Cu-TiO2 coatings were characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and energy-dispersive X-ray spectrometry （EDS）, respectively. Staphylococcus aureus （S. aureus） was selected to evaluate the antibacterial property of the Cu-TiO2 coatings, whereas osteoblastic MG63 cells were cultured on the coatings to investigate the biological activity. The obtained results demonstrated that Cu element was successfully incorporated into the porous nano-structured TiO2 coatings, which did not alter apparently the surface topography and phase composition of the coatings as compared to the Cu-free TiO2 coatings. Moreover, the antibacterial studies suggested that the Cu-incorporated TiO2 coatings could significantly inhibit the adhesion of S. aureus. In addition, the in vitro biological evaluation displayed that the adhesion, proliferation and differentiation of MG63 cells on the Cu-incorporated coatings were enhanced as compared to those on the Cu-free coatings and Ti plates. In conclusion, the innovative Cu-incorporated nano-structured TiO2 coatings on Ti substrate with excellent antibacterial property and biological activity are promising candidates for orthopedic implant.
基金Jilin Provincial Science & Technology Department for supporting this research under contract number 20080505
文摘To improve the surface wear resistance of the ceramic coating fabricated by micro-arc oxidation （MAO） on AZ91D magnesium alloy,ceramic coatings embedded with SiC nano-particles at different current frequency （500 Hz,700 Hz,and 900 Hz） were produced during the MAO process.The morphology and phase composition of the coatings were investigated by scanning electron microscopy （SEM）,field emission scanning electron microscopy （FESEM）,and X-ray diffraction （XRD）.The surface roughness of the coatings was characterized by confocal laser scanning microscopy （CLSM）.Simultaneously,the tribological properties of the composite coatings were evaluated by using a universal materials tester （UMT）.The results shows that the wear resistance of the ceramic coatings with SiC nano-particles was improved significantly compared to the ceramic coatings without SiC nano-particles.Furthermore,the composite coating formed at current frequency 900 Hz showed the better wear resistance than the others.
基金financially supported by the Postdoctoral Science Research Developmental Foundation of Heilongjiang Province (No. LBH-Q12004)the Education Department Foundation from Heilongjiang Province (No.11521575)the Science and Technology Project of Mudanjiang, Heilongjiang Province, China (No.G2012g0008)
文摘Compound ceramic coatings with the main crystalline of Al_2TiO_5（in the as-prepared coating without treatment） were prepared in situ on the surface Ti-6Al-4V alloy by means of pulsed bipolar micro-arc oxidation in Na AlO_2 solution. For the purpose of studying the antioxidation properties of the samples, the coated samples treated in argon and the as-coated samples were calcined in air at 1000 °C. And the related characteristics were investigated by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and X-ray fluorescence（XRF） spectroscopy, respectively. The results show that, when it was calcined in air for 1 h, Al_2TiO_5in the as-prepared coating decomposed and transformed into α-Al_2O_3 and rutile TiO_2.However, after almost 4 h in argon, Al_2TiO_5in the asprepared coating decomposed and the final coating surface contents are completely α-Al_2O_3, and those of the middle interface are mainly Al_2O_3 and Ti_2O_3. The morphologies of the coatings after calcination in argon and air are different.High-temperature oxidation occurred violently in the alloy substrate without coatings. Furthermore, the weight gain curves of the as-prepared samples and the coated samples treated in argon both show a parabolic shape.
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...
文摘Micro-arc oxidation(MAO)coatings were fabricated on AZ31 magnesium alloy and the effect of Na2CO3 on the energy consumption was studied.The results show that the concentration of Na2CO3 has a critical effect on the discharge behavior of MAO process.With increasing the Na2CO3 concentration in the electrolyte,the arcing voltage and working voltage decrease.A proper concentration is needed to achieve the highest growth rate of the coatings and the lowest energy consumption per unit coating volume.The addition of Na2CO3 decreases the arcing and working voltage of MAO discharge.It is attributed to that the Na2CO3 leads to much more micropores due to the decomposition of MgCO3 to produce more gas.
基金This work was financially supported bythe Doctoral Foundation ofYanshan University(B41)theScience and Technology Foundation ofYanshan University(YDJJ0169).
文摘In order to prepare ornamental and anti-corrosive coating on aluminum alloys, preparation technology of black micro-arc ceramic coatings on Al alloys in silicate based electrolyte was studied. The influence of content of Na2WO4 and combination additive in solution on the performance of black ceramic coatings was studied; the anticorrosion performances of black ceramic coatings were evaluated through whole-immersion test and electrochemical method in 3.5% NaCl solution at different pH value; SEM and XRD were used to analyze the surface morphology and phase constitutes of the black ceramic coatings. Experimental results indicated that, without combination additives, with the increasing of Na2WO4 content in the electrolyte, ceramic coating became darker and thicker, but the color was not black; after adding combination additive, the coating turned to be black; the black ceramic coating was multi-hole form in surface. There was a small quantity of tungsten existing in the black ceramic coating beside α-Al2O3 phase and β-Al2O3 phase. And aluminum alloy with black ceramic coating exhibited excellent anti-corrosion property in acid, basic and neutral 3.5% NaCl solution.
