Owing to the advantages of simple structure,low power consumption and high-density integration,memristors or memristive devices are attracting increasing attention in the fields such as next generation non-volatile me...Owing to the advantages of simple structure,low power consumption and high-density integration,memristors or memristive devices are attracting increasing attention in the fields such as next generation non-volatile memories,neuromorphic computation and data encryption.However,the deposition of memristive films often requires expensive equipment,strict vacuum conditions,high energy consumption,and extended processing times.In contrast,electrochemical anodizing can produce metal oxide films quickly(e.g.10 s) under ambient conditions.By means of the anodizing technique,oxide films,oxide nanotubes,nanowires and nanodots can be fabricated to prepare memristors.Oxide film thickness,nanostructures,defect concentrations,etc,can be varied to regulate device performances by adjusting oxidation parameters such as voltage,current and time.Thus memristors fabricated by the anodic oxidation technique can achieve high device consistency,low variation,and ultrahigh yield rate.This article provides a comprehensive review of the research progress in the field of anodic oxidation assisted fabrication of memristors.Firstly,the principle of anodic oxidation is introduced;then,different types of memristors produced by anodic oxidation and their applications are presented;finally,features and challenges of anodic oxidation for memristor production are elaborated.展开更多
Electrode materials with high desalination capacity and long-term cyclic stability are the focus of capacitive deionization(CDI) community. Understanding the causes of performance decay in traditional carbons is cruci...Electrode materials with high desalination capacity and long-term cyclic stability are the focus of capacitive deionization(CDI) community. Understanding the causes of performance decay in traditional carbons is crucial to design a high-performance material. Based on this, here, nitrogen-doped activated carbon(NAC) was prepared by pyrolyzing the blend of activated carbon powder(ACP) and melamine for the positive electrode of asymmetric CDI. By comparing the indicators changes such as conductivity, salt adsorption capacity, pH, and charge efficiency of the symmetrical ACP-ACP device to the asymmetric ACP-NAC device under different CDI cycles, as well as the changes of the electrochemical properties of anode and cathode materials after long-term operation, the reasons for the decline of the stability of the CDI performance were revealed. It was found that the carboxyl functional groups generated by the electro-oxidation of anode carbon materials make the anode zero-charge potential(E_(pzc)) shift positively,which results in the uneven distribution of potential windows of CDI units and affects the adsorption capacity. Furthermore, by understanding the electron density on C atoms surrounding the N atoms, we attribute the increased cyclic stability to the enhanced negativity of the charge of carbon atoms adjacent to quaternary-N and pyridinic-oxide-N.展开更多
To study the effect of different deposition temperatures on the optical properties of porous SiC films,single crystal Si was used as the substrate,a layer of anodic aluminum oxide(AAO)film was transferred on the Si su...To study the effect of different deposition temperatures on the optical properties of porous SiC films,single crystal Si was used as the substrate,a layer of anodic aluminum oxide(AAO)film was transferred on the Si substrate by chemical method,and then a layer of SiC was deposited on anodic aluminum oxide(AAO)template to prepare porous fluorescent SiC film by magnetron sputtering.The deposition temperature was ranged from 373 to 873 K.The thickness of the porous SiC film coated on the AAO surface was around 283 nm.It is found that the porous SiC with the deposition temperature of 873 K has the strongest photoluminescence(PL)intensity excited by 375 nm laser.The time-resolved PL spectra prove that the PL is mainly from intrinsic light emitting of SiC.With the optimized process,porous amorphous SiC film may have potential applications in the field of warm white LEDs.展开更多
Surface-enhanced Raman scattering(SERS)platform,which enables trace analyte detection,has important application prospects.By structuring/modifying the surface of the SERSsubstrate,analyte in highly diluted solutions c...Surface-enhanced Raman scattering(SERS)platform,which enables trace analyte detection,has important application prospects.By structuring/modifying the surface of the SERSsubstrate,analyte in highly diluted solutions can be concentrated into localized active areas for highly sensitive detection.However,subject to the difficulty of the fabrication process,itremains challenging to balance hot-spot construction and the concentration capacity of analyte simultaneously.Therefore,preparing SERS substrates with densely ordered hot spots andefficient concentration capacity is of great significance for highly sensitive detection.Herein,we propose an Ag and fluoroalkyl-modified hierarchical armour substrate(Ag/F-HA),which has a double-layer stacking design to combine analyte concentration with hotspot construction.The microarmour structure is fabricated by femtosecond-laser processing to serve as asuperhydrophobic and low-adhesive surface to concentrate analyte,while the anodic aluminium oxide(AAO)template creates a nanopillar array serving as dense and ordered hot spots.Under the synergistic action of hot spots and analyte concentration,Ag/F-HA achieves a detectionlimit down to 10^(-7)M doxorubicin(DOX)molecules with a RSD of 7.69%.Additionally,Ag/F-HA exhibits excellent robustness to resist external disturbances such as liquid splash or abrasion.Based on our strategy,SERS substrates with directional analyte concentrations are further explored by patterning microcone arrays with defects.This work opens a way to the realistic implementation of SERS in diverse scenarios.展开更多
The effect of the microstructure of an Al 7050-T7451 substrate on the anodic oxide formation in sulfuric acid was studied in this article. The microstructure of the substrate was assessed by optical microscope (OM) ...The effect of the microstructure of an Al 7050-T7451 substrate on the anodic oxide formation in sulfuric acid was studied in this article. The microstructure of the substrate was assessed by optical microscope (OM) and transmission electron microscope (TEM). The surface and cross-section morphologies of the oxide films were examined by scanning electron microscope (SEM). The chemical composition of intermetallic particles in the alloys and films was investigated using energy dispersive spectroscope (EDS). The roles of intermetallic phases and grain or subgrain boundaries on the oxide film formation were researched using the potentiodynamic and potentiostatic polarization technique in sulfuric acid solution. The results show that the transition of coarse intermetallic particles or grain (subgrain) boundaries at the surface of Al alloys can be characterized by potentiodynamic polarization curves. The surface and cross-section micrographs of the anodic layer seem to preserve the microstructure of the substrate. Large cavities in the anodic films are caused by the preferential dissolution of coarse AItCuMg particles and the entrance of Cu-rich remnants into the electrolyte during anodizing. The Al7Cu2Fe particles tend to be occluded in the oxide layer or lose from the oxide surface because of peripheral trenching. Small pores in the films are induced by the dissolution of precipitates in grain or subgrain boundaries. The film surface of recrystallized grain bodies is smooth and homogeneous.展开更多
Intermetallic phases were found to influence the anodic oxidation and corrosion behavior of 5A06 aluminum alloy. Scattered in- termetallic particles were examined by scanning electron microscopy (SEM) and energy dis...Intermetallic phases were found to influence the anodic oxidation and corrosion behavior of 5A06 aluminum alloy. Scattered in- termetallic particles were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) after pretreatment. The anodic film was investigated by transmission electron microscopy (TEM), and its corrosion resistance was analyzed by electrochemical impedance spectroscopy (EIS) and Tafel polarization in NaC1 solution. The results show that the size of A1-Fe-Mg-Mn particles gradually decreases with the iron content. During anodizing, these intermetallic particles are gradually dissolved, leading to the complex porosity in the anodic film beneath the particles. After anodizing, the residual particles are mainly silicon-containing phases, which are embedded in the an- odic film. Electrochemical measurements indicate that the porous anodic film layer is easily penetrated, and the barrier plays a dominant role in the overall protection. Meanwhile, self-healing behavior is observed during the long immersion time.展开更多
Anodic oxide films of the titanium alloy Ti-10V-2Fe-3Al in ammonium tartrate electrolyte without hydrofluoric acid or fluoride were fabricated. The morphology, components, and microstructure of the films were characte...Anodic oxide films of the titanium alloy Ti-10V-2Fe-3Al in ammonium tartrate electrolyte without hydrofluoric acid or fluoride were fabricated. The morphology, components, and microstructure of the films were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy. The results showed that the films were thick, uniform, and nontransparent. Such films exhibited sedimentary morphology, with a thickness of about 3 μm, and the pore diameters of the deposits ranged from several hundred nanometers to 1.5 μm. The films were mainly titanium dioxide. Some coke-like deposits, which may contain or be changed by OH, NH, C-C, C-O, and C=O groups, were doped in the films. The films were mainly amorphous with a small amount of anatase and rutile phase.展开更多
The anodic oxidation of aqueous solutions containing dimethyl phthalate (DMP) up to 125 mg/L with sodium sulfate (Na2SO4) as supporting electrolyte within the pH range 2.0-10.0 was studied using a one-compartment ...The anodic oxidation of aqueous solutions containing dimethyl phthalate (DMP) up to 125 mg/L with sodium sulfate (Na2SO4) as supporting electrolyte within the pH range 2.0-10.0 was studied using a one-compartment batch reactor employing a boron-doped diamond (BDD) as anode. Electrolyses were carded out at constant current density (1.5-4.5 mA/cm^2). Complete mineralization was always achieved owing to the great concentration of hydroxyl radical (-OH) generated at the BDD surface. The effects of pH, apparent current density and initial DMP concentration on the degradation rate of DMP, the specific charge required for its total mineralization and mineralization current efficiency were investigated systematically. The mineralization rate of DMP was found to be pH-independent and to increase with increasing applied current density. Results indicated that this electrochemical process was subjected, at least partially, to the mass transfer of organics onto the BDD surface. Kinetic analysis of the temporal change of DMP concentration during electrolysis determined by High Performance Liquid Chromatography (HPLC) revealed that DMP decay under all tested conditions followed a pseudo first-order reaction. Aromatic intermediates and generated carboxylic acids were identified by Gas Chromatography- Mass Spectrometry (GC-MS) and a general pathway for the electrochemical incineration of DMP on BDD was proposed.展开更多
Anatase titanium dioxide is an active photocatalyst, but it is difficult to immobilize on the substrate. A crystalline TiO2 porous film was prepared directly on the surface of pure titanium by anodic oxidation in this...Anatase titanium dioxide is an active photocatalyst, but it is difficult to immobilize on the substrate. A crystalline TiO2 porous film was prepared directly on the surface of pure titanium by anodic oxidation in this work. Constant voltage and constant current anodic oxidation were adopted with sulphuric acid used as the electrolyte, pure titanium as the anode and copper as the cathode. The morphology and structure of the porous film on the substrate were analyzed with the aid of Field Emission Scanning Electron Microscopy (FESEM) and X-ray Diffraction (XRD). The effects of the parameters of anodic oxidation (such as voltage, the concentration of sulphuric acid, anodization time and current density) on the aperture and the crystalline phase of the TiO2 porous film were systematically investigated. The results indicate that the increase of current density facilitates the augment of the aperture and the generation of anatase and mille. In addition, the forming mechanism of anatase and mille TiO2 porous films was discussed.展开更多
Anodic oxide films grown on titanium alloy Ti-10V-2Fe-3Al in the solution of sodium tartrate, then sealed in boiling deionised water and calcium acetate solution were observed by using field emission scanning electron...Anodic oxide films grown on titanium alloy Ti-10V-2Fe-3Al in the solution of sodium tartrate, then sealed in boiling deionised water and calcium acetate solution were observed by using field emission scanning electron microscopy (FE-SEM), and were chemically analysed by using energy dispersive spectroscopy (EDS). Corrosion behaviour was investigated in a 3.5% sodium chloride solution, using electrochemical impedance spectroscopy (EIS). The morphology of the anodic oxide films was dependent on the sealing processes. The surface sealed in calcium acetate solution presented a more homogeneous and smooth structure compared with that sealed in boiling deionised water. The corrosion resistance of the oxide films sealed in calcium acetate solution was better than that sealed in boiling deionised water.展开更多
The synthesis of Pd-Ag alloy nanowires in nanopores of porous anodic aluminum oxide (AAO) template by electrochemical deposition technique was reported. Pd-Ag alloy nanowires with 16%-25% Ag content are expected to ...The synthesis of Pd-Ag alloy nanowires in nanopores of porous anodic aluminum oxide (AAO) template by electrochemical deposition technique was reported. Pd-Ag alloy nanowires with 16%-25% Ag content are expected to serve as candidates of useful nanomaterials for the hydrogen sensors. Scanning electron microscopy (SEM) and energy dispersed X-ray spectroscopy (EDX) were employed to characterize the morphologies and compositions of the Pd-Ag nanowires. X-ray diffraction (XRD) was used to characterize the phase properties of the Pd-Ag nanowires. Pd-Ag alloy nanowire arrays with 17.28%-23.76% Ag content have been successfully fabricated by applying potentials ranging from -0.8 to -1.0 V (vs SCE). The sizes of the alloy nanowires are in agreement with the diameter of AAO nanopores. The underpotential deposition of Ag+ on Pd and Au plays an important role in producing an exceptionally high Ag content in the alloy. Alloy compositions can still be controlled by adjusting the ion concentration ratio of Pd^2+ and Ag+ and the electrodeposition processes. XRD shows that nanowires obtained are in the form of alloy of Pd and Ag.展开更多
In order to analyze the influence of the anodizing process on the thermal load of an aluminum alloy piston,dedicated temperature tests have been carried out using the Hardness Plug method and the results for the anodi...In order to analyze the influence of the anodizing process on the thermal load of an aluminum alloy piston,dedicated temperature tests have been carried out using the Hardness Plug method and the results for the anodized piston have been compared with those obtained separately for an original aluminum piston.In addition,numerical simulations have been conducted to analyze the temperature field and thermal stress distribution.Simulations and experiments show that the maximum temperature of the anodized piston is 16.36%and 5.4%smaller than that of the original piston under the condition of maximum torque and maximum power,respectively.The thermal stress of the temperature field of both pistons is within 50 Mpa,which meets the strength requirements of the material at high temperature.However,the area with significant thermal stress of the anodized piston is significantly smaller than that of the original piston.Combined with the fatigue analysis data,it can be seen that the safety factor of the anodized piston greater than 1.8 is 99.13%.Therefore,adopting the anodizing process not only reduces the piston thermal load,but also helps to extend its life and improve its reliability.展开更多
The effects of insoluble eutectic Si particles on the growth of anodic oxide films on ZL114A aluminum alloy substrates were in- vestigated by optical microscopy (OM) and scanning electron microscopy (SEM). The ano...The effects of insoluble eutectic Si particles on the growth of anodic oxide films on ZL114A aluminum alloy substrates were in- vestigated by optical microscopy (OM) and scanning electron microscopy (SEM). The anodic oxidation was performed at 25℃ and a con- stant voltage of 15 V in a solution containing 50 g/L sulfuric acid and 10 g/L adipic acid. The thickness of the formed anodic oxidation film was approximately 7.13 μm. The interpore distance and the diameters of the major pores in the porous layer of the film were within the ap- proximate ranges of 10~20 nm and 5-10 nm, respectively. Insoluble eutectic Si particles strongly influenced the morphology of the anodic oxidation films. The anodic oxidation films exhibited minimal defects and a uniform thickness on the ZL114A substrates; in contrast, when the front of the oxide oxidation films encountered eutectic Si particles, defects such as pits and non-uniform thickness were observed, and pits were observed in the films.展开更多
The aim of this work was to investigate the effects of calcination/acid-activation on the composition, structure, and photocatalytic (PC) reduction property of an anodic oxidation TiO2/Ti film catalyst. The surface ...The aim of this work was to investigate the effects of calcination/acid-activation on the composition, structure, and photocatalytic (PC) reduction property of an anodic oxidation TiO2/Ti film catalyst. The surface morphology and phase composition were examined by scanning electron microscopy and X-ray diffraction. The catalytic property of the film catalysts was evaluated through the removal rate of potassium chromate during the PC reduction process. The results showed that the film catalysts were composed of anatase and rutile TiO2 with a micro-porous surface structure. The calcination treatment increased the content of TiO2 in the film, changed the relative ratio of anatase and rutile TiO2, and decreased the size of the micro pores of the film catalysts. The removal rate of potassium chromate was related to the technique parameters of calcination/acid-activation treatment. When the anodic oxidation TiO2/Ti film catalyst was calcined at 873 K for 30 min and then acid-activated in the concentrated H2SO4 for 60 min, it presented the highest catalytic property, with the removal rate of potassium chromate of 96.3% during the PC reduction process under the experimental conditions.展开更多
Electrochromic and auto-bleaching processes at the WO2 anodic film in 0. 5 mol/L H2SO4 solution were investigated by cyclic voltammetry, a. c. impedance technique and photocurrent spectrometry. The colouration mechani...Electrochromic and auto-bleaching processes at the WO2 anodic film in 0. 5 mol/L H2SO4 solution were investigated by cyclic voltammetry, a. c. impedance technique and photocurrent spectrometry. The colouration mechanism consists of hydrogen adsorption on the WO2 surface and the transport of H atoms in the WO, lattice. The bleaching process involves at least two steps: transport of interstitial H atoms and hydrogen desorption on the W surface, resulting in interstitial H+ ions; then extration of the H+ ions driven by the external electric field. The auto-bleaching arises from the hydroxylation due to both partial interstitial H atoms and a little of water contained in the film.展开更多
A new Fe Pt nanostructure with stripe-like patterns has been prepared by direct current(DC) magnetron sputtering on anodic aluminum oxide(AAO) templates. AAO templates anodized under low voltages(7 V) demonstrat...A new Fe Pt nanostructure with stripe-like patterns has been prepared by direct current(DC) magnetron sputtering on anodic aluminum oxide(AAO) templates. AAO templates anodized under low voltages(7 V) demonstrate self-organized,maze-like patterns, different from the conventional porous structures obtained at high voltages. Fe Pt thin films deposited on such templates tend to replicate the morphology of the templates. Although there is no obvious spatial ordering, the dimensions of the Fe Pt nano-stripes are highly uniform, due to the constrained growth along the transverse direction of the AAO pattern. The magnetic properties are strongly influenced by this unique morphology. While continuous films demonstrate strong exchange coupling, the dominant interaction in Fe Pt nano-stripes with the same nominal thickness is magnetostatic. The morphology also dictates the magnetization reversal behaviors, with thin films dominated by domain nucleation; while nano-stripes incline to reverse their magnetization by spin rotation. Our work demonstrates that selforganized AAO templates can be used to control the morphology and magnetic behavior of Fe Pt materials.展开更多
Micron sized hexagon- and flower-like nanostructures of lead oxide(α-PbO2) have been synthesized by very simple and cost effective route of anodic oxidation of lead sheet. These structures were easily obtained by t...Micron sized hexagon- and flower-like nanostructures of lead oxide(α-PbO2) have been synthesized by very simple and cost effective route of anodic oxidation of lead sheet. These structures were easily obtained by the simple variation of applied voltage from 2-6 V between the electrodes. Lead sheet was used as an anode and platinum sheet served as a cathode. Anodic oxidation at 2 V resulted in the variable edge sized(1-2 μm) hexagon-like structures in the electrolyte. When the applied potential was increased to 4 V a structure of distorted hexagons consisting of some flower-like structures were obtained. Further increment of potential up to 6 V resulted in flower like structures of α-PbO2 having six petals. The diameter of the flower-like structures was 200-500 nm and the size of a petal was 100-200 nm.展开更多
Tantalum (Ta) oxide flhns with tunable structural color were fabricated easily using anodic oxidation. The structure, components, and surface valence states of the oxide films were investigated by using gazing incid...Tantalum (Ta) oxide flhns with tunable structural color were fabricated easily using anodic oxidation. The structure, components, and surface valence states of the oxide films were investigated by using gazing incidence X-ray diffractometry, X-ray photoelectron microscopy, and surface analytical techniques. Their thickness and optical properties were studied by using spectroscopic ellipsometry and total reflectance spectrum. Color was accurately defined using L*a*b* scale. The thickness of compact Ta2O5 films was linearly dependent on anodizing voltage. The film color was tunable by adjusting the anodic voltage. The difference in color appearance resulted from the interference behavior between the interfaces of air-oxide and oxide metal.展开更多
基金supported by the National Key Research and Development Program of China (Grant No.2018YFE0203802)Natural Science Foundation of Hubei Province, China (Grant No.2022CFA031)Dongguan Innovative Research Team Program (2020607101007)。
文摘Owing to the advantages of simple structure,low power consumption and high-density integration,memristors or memristive devices are attracting increasing attention in the fields such as next generation non-volatile memories,neuromorphic computation and data encryption.However,the deposition of memristive films often requires expensive equipment,strict vacuum conditions,high energy consumption,and extended processing times.In contrast,electrochemical anodizing can produce metal oxide films quickly(e.g.10 s) under ambient conditions.By means of the anodizing technique,oxide films,oxide nanotubes,nanowires and nanodots can be fabricated to prepare memristors.Oxide film thickness,nanostructures,defect concentrations,etc,can be varied to regulate device performances by adjusting oxidation parameters such as voltage,current and time.Thus memristors fabricated by the anodic oxidation technique can achieve high device consistency,low variation,and ultrahigh yield rate.This article provides a comprehensive review of the research progress in the field of anodic oxidation assisted fabrication of memristors.Firstly,the principle of anodic oxidation is introduced;then,different types of memristors produced by anodic oxidation and their applications are presented;finally,features and challenges of anodic oxidation for memristor production are elaborated.
文摘Electrode materials with high desalination capacity and long-term cyclic stability are the focus of capacitive deionization(CDI) community. Understanding the causes of performance decay in traditional carbons is crucial to design a high-performance material. Based on this, here, nitrogen-doped activated carbon(NAC) was prepared by pyrolyzing the blend of activated carbon powder(ACP) and melamine for the positive electrode of asymmetric CDI. By comparing the indicators changes such as conductivity, salt adsorption capacity, pH, and charge efficiency of the symmetrical ACP-ACP device to the asymmetric ACP-NAC device under different CDI cycles, as well as the changes of the electrochemical properties of anode and cathode materials after long-term operation, the reasons for the decline of the stability of the CDI performance were revealed. It was found that the carboxyl functional groups generated by the electro-oxidation of anode carbon materials make the anode zero-charge potential(E_(pzc)) shift positively,which results in the uneven distribution of potential windows of CDI units and affects the adsorption capacity. Furthermore, by understanding the electron density on C atoms surrounding the N atoms, we attribute the increased cyclic stability to the enhanced negativity of the charge of carbon atoms adjacent to quaternary-N and pyridinic-oxide-N.
基金Funded by the National Natural Science Foundation of China(No.11747133)the Fundamental Research Funds for the Central Universities(No.195209019)。
文摘To study the effect of different deposition temperatures on the optical properties of porous SiC films,single crystal Si was used as the substrate,a layer of anodic aluminum oxide(AAO)film was transferred on the Si substrate by chemical method,and then a layer of SiC was deposited on anodic aluminum oxide(AAO)template to prepare porous fluorescent SiC film by magnetron sputtering.The deposition temperature was ranged from 373 to 873 K.The thickness of the porous SiC film coated on the AAO surface was around 283 nm.It is found that the porous SiC with the deposition temperature of 873 K has the strongest photoluminescence(PL)intensity excited by 375 nm laser.The time-resolved PL spectra prove that the PL is mainly from intrinsic light emitting of SiC.With the optimized process,porous amorphous SiC film may have potential applications in the field of warm white LEDs.
基金National Natural Science Foundation of China(Nos.92050203,52122511,52305319,52375582)Shenzhen Fundamental Research Program(Nos.JCYJ20200109105606426,JCYJ20190808164007485)。
文摘Surface-enhanced Raman scattering(SERS)platform,which enables trace analyte detection,has important application prospects.By structuring/modifying the surface of the SERSsubstrate,analyte in highly diluted solutions can be concentrated into localized active areas for highly sensitive detection.However,subject to the difficulty of the fabrication process,itremains challenging to balance hot-spot construction and the concentration capacity of analyte simultaneously.Therefore,preparing SERS substrates with densely ordered hot spots andefficient concentration capacity is of great significance for highly sensitive detection.Herein,we propose an Ag and fluoroalkyl-modified hierarchical armour substrate(Ag/F-HA),which has a double-layer stacking design to combine analyte concentration with hotspot construction.The microarmour structure is fabricated by femtosecond-laser processing to serve as asuperhydrophobic and low-adhesive surface to concentrate analyte,while the anodic aluminium oxide(AAO)template creates a nanopillar array serving as dense and ordered hot spots.Under the synergistic action of hot spots and analyte concentration,Ag/F-HA achieves a detectionlimit down to 10^(-7)M doxorubicin(DOX)molecules with a RSD of 7.69%.Additionally,Ag/F-HA exhibits excellent robustness to resist external disturbances such as liquid splash or abrasion.Based on our strategy,SERS substrates with directional analyte concentrations are further explored by patterning microcone arrays with defects.This work opens a way to the realistic implementation of SERS in diverse scenarios.
文摘The effect of the microstructure of an Al 7050-T7451 substrate on the anodic oxide formation in sulfuric acid was studied in this article. The microstructure of the substrate was assessed by optical microscope (OM) and transmission electron microscope (TEM). The surface and cross-section morphologies of the oxide films were examined by scanning electron microscope (SEM). The chemical composition of intermetallic particles in the alloys and films was investigated using energy dispersive spectroscope (EDS). The roles of intermetallic phases and grain or subgrain boundaries on the oxide film formation were researched using the potentiodynamic and potentiostatic polarization technique in sulfuric acid solution. The results show that the transition of coarse intermetallic particles or grain (subgrain) boundaries at the surface of Al alloys can be characterized by potentiodynamic polarization curves. The surface and cross-section micrographs of the anodic layer seem to preserve the microstructure of the substrate. Large cavities in the anodic films are caused by the preferential dissolution of coarse AItCuMg particles and the entrance of Cu-rich remnants into the electrolyte during anodizing. The Al7Cu2Fe particles tend to be occluded in the oxide layer or lose from the oxide surface because of peripheral trenching. Small pores in the films are induced by the dissolution of precipitates in grain or subgrain boundaries. The film surface of recrystallized grain bodies is smooth and homogeneous.
基金financially supported by the National Natural Science Foundation of China(No.51271012)
文摘Intermetallic phases were found to influence the anodic oxidation and corrosion behavior of 5A06 aluminum alloy. Scattered in- termetallic particles were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) after pretreatment. The anodic film was investigated by transmission electron microscopy (TEM), and its corrosion resistance was analyzed by electrochemical impedance spectroscopy (EIS) and Tafel polarization in NaC1 solution. The results show that the size of A1-Fe-Mg-Mn particles gradually decreases with the iron content. During anodizing, these intermetallic particles are gradually dissolved, leading to the complex porosity in the anodic film beneath the particles. After anodizing, the residual particles are mainly silicon-containing phases, which are embedded in the an- odic film. Electrochemical measurements indicate that the porous anodic film layer is easily penetrated, and the barrier plays a dominant role in the overall protection. Meanwhile, self-healing behavior is observed during the long immersion time.
基金This work was financially supported by the Natural Science Foundation of Jiangsu Province (No. BK2004129) the Aviation Science Foundation of China (No. 04H52059).
文摘Anodic oxide films of the titanium alloy Ti-10V-2Fe-3Al in ammonium tartrate electrolyte without hydrofluoric acid or fluoride were fabricated. The morphology, components, and microstructure of the films were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy. The results showed that the films were thick, uniform, and nontransparent. Such films exhibited sedimentary morphology, with a thickness of about 3 μm, and the pore diameters of the deposits ranged from several hundred nanometers to 1.5 μm. The films were mainly titanium dioxide. Some coke-like deposits, which may contain or be changed by OH, NH, C-C, C-O, and C=O groups, were doped in the films. The films were mainly amorphous with a small amount of anatase and rutile phase.
基金supported by the National Natural Science Foundation of China (No 50778172) the Funds for Creative Research Groups of China (No 50621804)
文摘The anodic oxidation of aqueous solutions containing dimethyl phthalate (DMP) up to 125 mg/L with sodium sulfate (Na2SO4) as supporting electrolyte within the pH range 2.0-10.0 was studied using a one-compartment batch reactor employing a boron-doped diamond (BDD) as anode. Electrolyses were carded out at constant current density (1.5-4.5 mA/cm^2). Complete mineralization was always achieved owing to the great concentration of hydroxyl radical (-OH) generated at the BDD surface. The effects of pH, apparent current density and initial DMP concentration on the degradation rate of DMP, the specific charge required for its total mineralization and mineralization current efficiency were investigated systematically. The mineralization rate of DMP was found to be pH-independent and to increase with increasing applied current density. Results indicated that this electrochemical process was subjected, at least partially, to the mass transfer of organics onto the BDD surface. Kinetic analysis of the temporal change of DMP concentration during electrolysis determined by High Performance Liquid Chromatography (HPLC) revealed that DMP decay under all tested conditions followed a pseudo first-order reaction. Aromatic intermediates and generated carboxylic acids were identified by Gas Chromatography- Mass Spectrometry (GC-MS) and a general pathway for the electrochemical incineration of DMP on BDD was proposed.
文摘Anatase titanium dioxide is an active photocatalyst, but it is difficult to immobilize on the substrate. A crystalline TiO2 porous film was prepared directly on the surface of pure titanium by anodic oxidation in this work. Constant voltage and constant current anodic oxidation were adopted with sulphuric acid used as the electrolyte, pure titanium as the anode and copper as the cathode. The morphology and structure of the porous film on the substrate were analyzed with the aid of Field Emission Scanning Electron Microscopy (FESEM) and X-ray Diffraction (XRD). The effects of the parameters of anodic oxidation (such as voltage, the concentration of sulphuric acid, anodization time and current density) on the aperture and the crystalline phase of the TiO2 porous film were systematically investigated. The results indicate that the increase of current density facilitates the augment of the aperture and the generation of anatase and mille. In addition, the forming mechanism of anatase and mille TiO2 porous films was discussed.
基金Supported by the National Natural Science Foundation of China(No.51271012)
文摘Anodic oxide films grown on titanium alloy Ti-10V-2Fe-3Al in the solution of sodium tartrate, then sealed in boiling deionised water and calcium acetate solution were observed by using field emission scanning electron microscopy (FE-SEM), and were chemically analysed by using energy dispersive spectroscopy (EDS). Corrosion behaviour was investigated in a 3.5% sodium chloride solution, using electrochemical impedance spectroscopy (EIS). The morphology of the anodic oxide films was dependent on the sealing processes. The surface sealed in calcium acetate solution presented a more homogeneous and smooth structure compared with that sealed in boiling deionised water. The corrosion resistance of the oxide films sealed in calcium acetate solution was better than that sealed in boiling deionised water.
基金supported by the National Natural Science Foundation of China under Grant No.20373015the Hunan Education Office under Grant No.04C033.
文摘The synthesis of Pd-Ag alloy nanowires in nanopores of porous anodic aluminum oxide (AAO) template by electrochemical deposition technique was reported. Pd-Ag alloy nanowires with 16%-25% Ag content are expected to serve as candidates of useful nanomaterials for the hydrogen sensors. Scanning electron microscopy (SEM) and energy dispersed X-ray spectroscopy (EDX) were employed to characterize the morphologies and compositions of the Pd-Ag nanowires. X-ray diffraction (XRD) was used to characterize the phase properties of the Pd-Ag nanowires. Pd-Ag alloy nanowire arrays with 17.28%-23.76% Ag content have been successfully fabricated by applying potentials ranging from -0.8 to -1.0 V (vs SCE). The sizes of the alloy nanowires are in agreement with the diameter of AAO nanopores. The underpotential deposition of Ag+ on Pd and Au plays an important role in producing an exceptionally high Ag content in the alloy. Alloy compositions can still be controlled by adjusting the ion concentration ratio of Pd^2+ and Ag+ and the electrodeposition processes. XRD shows that nanowires obtained are in the form of alloy of Pd and Ag.
文摘In order to analyze the influence of the anodizing process on the thermal load of an aluminum alloy piston,dedicated temperature tests have been carried out using the Hardness Plug method and the results for the anodized piston have been compared with those obtained separately for an original aluminum piston.In addition,numerical simulations have been conducted to analyze the temperature field and thermal stress distribution.Simulations and experiments show that the maximum temperature of the anodized piston is 16.36%and 5.4%smaller than that of the original piston under the condition of maximum torque and maximum power,respectively.The thermal stress of the temperature field of both pistons is within 50 Mpa,which meets the strength requirements of the material at high temperature.However,the area with significant thermal stress of the anodized piston is significantly smaller than that of the original piston.Combined with the fatigue analysis data,it can be seen that the safety factor of the anodized piston greater than 1.8 is 99.13%.Therefore,adopting the anodizing process not only reduces the piston thermal load,but also helps to extend its life and improve its reliability.
基金financially supported by the National Nature Science Foundation of China (No. 21371019)the Aero Science Foundation of China (No. 2011ZE51057)
文摘The effects of insoluble eutectic Si particles on the growth of anodic oxide films on ZL114A aluminum alloy substrates were in- vestigated by optical microscopy (OM) and scanning electron microscopy (SEM). The anodic oxidation was performed at 25℃ and a con- stant voltage of 15 V in a solution containing 50 g/L sulfuric acid and 10 g/L adipic acid. The thickness of the formed anodic oxidation film was approximately 7.13 μm. The interpore distance and the diameters of the major pores in the porous layer of the film were within the ap- proximate ranges of 10~20 nm and 5-10 nm, respectively. Insoluble eutectic Si particles strongly influenced the morphology of the anodic oxidation films. The anodic oxidation films exhibited minimal defects and a uniform thickness on the ZL114A substrates; in contrast, when the front of the oxide oxidation films encountered eutectic Si particles, defects such as pits and non-uniform thickness were observed, and pits were observed in the films.
基金supported by the National High Technology Research and Development Program of China (No. 2007AA03Z337)the Harbin Special Creation Foundation for Science and Technology of Fellow in China (No. 2006RFQXG032)
文摘The aim of this work was to investigate the effects of calcination/acid-activation on the composition, structure, and photocatalytic (PC) reduction property of an anodic oxidation TiO2/Ti film catalyst. The surface morphology and phase composition were examined by scanning electron microscopy and X-ray diffraction. The catalytic property of the film catalysts was evaluated through the removal rate of potassium chromate during the PC reduction process. The results showed that the film catalysts were composed of anatase and rutile TiO2 with a micro-porous surface structure. The calcination treatment increased the content of TiO2 in the film, changed the relative ratio of anatase and rutile TiO2, and decreased the size of the micro pores of the film catalysts. The removal rate of potassium chromate was related to the technique parameters of calcination/acid-activation treatment. When the anodic oxidation TiO2/Ti film catalyst was calcined at 873 K for 30 min and then acid-activated in the concentrated H2SO4 for 60 min, it presented the highest catalytic property, with the removal rate of potassium chromate of 96.3% during the PC reduction process under the experimental conditions.
基金The project Supported by National Natural Science Foundation of China.
文摘Electrochromic and auto-bleaching processes at the WO2 anodic film in 0. 5 mol/L H2SO4 solution were investigated by cyclic voltammetry, a. c. impedance technique and photocurrent spectrometry. The colouration mechanism consists of hydrogen adsorption on the WO2 surface and the transport of H atoms in the WO, lattice. The bleaching process involves at least two steps: transport of interstitial H atoms and hydrogen desorption on the W surface, resulting in interstitial H+ ions; then extration of the H+ ions driven by the external electric field. The auto-bleaching arises from the hydroxylation due to both partial interstitial H atoms and a little of water contained in the film.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51025101,51101095,61434002,11274214,and 51301099)the Program of"One Hundred Talented People"of Shanxi Province,China
文摘A new Fe Pt nanostructure with stripe-like patterns has been prepared by direct current(DC) magnetron sputtering on anodic aluminum oxide(AAO) templates. AAO templates anodized under low voltages(7 V) demonstrate self-organized,maze-like patterns, different from the conventional porous structures obtained at high voltages. Fe Pt thin films deposited on such templates tend to replicate the morphology of the templates. Although there is no obvious spatial ordering, the dimensions of the Fe Pt nano-stripes are highly uniform, due to the constrained growth along the transverse direction of the AAO pattern. The magnetic properties are strongly influenced by this unique morphology. While continuous films demonstrate strong exchange coupling, the dominant interaction in Fe Pt nano-stripes with the same nominal thickness is magnetostatic. The morphology also dictates the magnetization reversal behaviors, with thin films dominated by domain nucleation; while nano-stripes incline to reverse their magnetization by spin rotation. Our work demonstrates that selforganized AAO templates can be used to control the morphology and magnetic behavior of Fe Pt materials.
基金financial support from USACH-Chile, Council of Scientific and Industrial Research (CSIR) and University Grant Commission (UGC) New Delhi, India
文摘Micron sized hexagon- and flower-like nanostructures of lead oxide(α-PbO2) have been synthesized by very simple and cost effective route of anodic oxidation of lead sheet. These structures were easily obtained by the simple variation of applied voltage from 2-6 V between the electrodes. Lead sheet was used as an anode and platinum sheet served as a cathode. Anodic oxidation at 2 V resulted in the variable edge sized(1-2 μm) hexagon-like structures in the electrolyte. When the applied potential was increased to 4 V a structure of distorted hexagons consisting of some flower-like structures were obtained. Further increment of potential up to 6 V resulted in flower like structures of α-PbO2 having six petals. The diameter of the flower-like structures was 200-500 nm and the size of a petal was 100-200 nm.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10974204 and 50931002)the Hundred Talent Program of the Chinese Academy of Sciences
文摘Tantalum (Ta) oxide flhns with tunable structural color were fabricated easily using anodic oxidation. The structure, components, and surface valence states of the oxide films were investigated by using gazing incidence X-ray diffractometry, X-ray photoelectron microscopy, and surface analytical techniques. Their thickness and optical properties were studied by using spectroscopic ellipsometry and total reflectance spectrum. Color was accurately defined using L*a*b* scale. The thickness of compact Ta2O5 films was linearly dependent on anodizing voltage. The film color was tunable by adjusting the anodic voltage. The difference in color appearance resulted from the interference behavior between the interfaces of air-oxide and oxide metal.