Oxide films hinder diffusion and resist external forces,which determines the flame ignition mechanism of magnesium alloys.The effects of the continuity,compactness and mechanical properties of oxide films on the ignit...Oxide films hinder diffusion and resist external forces,which determines the flame ignition mechanism of magnesium alloys.The effects of the continuity,compactness and mechanical properties of oxide films on the ignition mechanism were analyzed,by investigating the flame ignition behaviors of AZ80(ZM5),EZ30K(ZM6)and WE43 Mg alloys.The results show that the rupture of the oxide films caused by liquid gravity was the key to causing ignition.According to thermodynamic calculations,compared with Mg,Al cannot be preferentially oxidized;while Nd can be preferentially oxidized through significant enrichment,resulting in a discontinuous Nd_(2)O_(3)inner layer in the ZM6 alloy;in contrast,Y has a strong preferential oxidation ability,which gives the WE43 alloy a continuous Y_(2)O_(3)inner layer and self-healing ability.In addition,the oxide film of the ZM5 alloy is loose and has poor mechanical properties,so it cannot effec-tively hinder diffusion and resist liquid gravity.Differently,the oxide films of the ZM6 and WE43 alloys are dense and have better mechanical properties,leading to higher ignition temperatures and longer igni-tion times.In addition,a criterion was proposed to predict the ignition time based on the law of energy conservation,and it was simplified to predict the ignition temperature.The errors between the predicted and measured values are within 11%.展开更多
Nano-scale chemical inhomogeneity in surface oxide films formed on a V-and N-containing martensite stainless steel and tempering heating induced changes are investigated by a combination of synchrotron-based hard X-ra...Nano-scale chemical inhomogeneity in surface oxide films formed on a V-and N-containing martensite stainless steel and tempering heating induced changes are investigated by a combination of synchrotron-based hard X-ray Photoelectron emission spectroscopy(HAXPES)and microscopy(HAXPEEM)as well as microscopic X-ray absorption spectroscopy(μ-XAS)techniques.The results reveal the inhomogeneity in the oxide films on the micron-sized Cr_(2)N-and VN-type particles,while the inhomogeneity on the martensite matrix phase exists due to localised formation of nano-sized tempering nitride particles at 600℃.The oxide film formed on Cr_(2)N-type particles is rich in Cr_(2)O_(3) compared with that on the martensite matrix and VN-type particles.With the increase of tempering temperature,Cr_(2)O_(3) formation is faster for the oxidation of Cr in the martensite matrix than the oxidation of Cr nitride-rich particles.展开更多
The oxide films of 316L and T91 exposed to 350-500℃ steam were investigated using transmission electron microscopy(TEM).Independent of the exposure temperature,a triplex oxide structure with outer magnetite,inner Cr-...The oxide films of 316L and T91 exposed to 350-500℃ steam were investigated using transmission electron microscopy(TEM).Independent of the exposure temperature,a triplex oxide structure with outer magnetite,inner Cr-rich(Fe_(1.4)Cr_(1.6)O_(4)),and Ni-rich layer formed on 316L,while only a duplex layer with outer magnetite and inner Cr-rich(Fe_(2.2)Cr_(0.8)O_(4))layer formed on T91.As the fast channels for oxidant and the obstacles for solid-state diffusion,nanopores are distributed evenly in the Cr-rich inner layer and are more abundant in 316L than in T91.The oxidation behavior of the materials was understood based on the microscopic characteristics of the oxide films.展开更多
A study was conducted to develop low-friction, wear-resistant surfaces on high temperature alloys for the temperature range from 26℃ to 900℃. The approach investigated consists of modifying the naturally occurring o...A study was conducted to develop low-friction, wear-resistant surfaces on high temperature alloys for the temperature range from 26℃ to 900℃. The approach investigated consists of modifying the naturally occurring oxide film in order to improve its tribological properties. Improvement is needed at low temperatures where the oxide film, previously formed at high temperature, spalls due to stresses induced by sliding. Experiments with Ti, W and Ta additions show a beneficial effect when added to Ni and Ni-base alloys. Low friction can be maintained down to 100℃ from 900℃. For unalloyed Ni friction and surface damage increases at 400℃ to 500℃. Two new alloys were perpared based on the beneficial results of binary alloys and ZrO2 diffusion in Ni.Low friction at temperature above 500℃ and reasonable values (0.32~0.42) at low temperature are obtained.展开更多
Nano cerium oxide films were applied on AA7020-T6 aluminum alloy and the effects of acetic acid concentration on the microstructure and electrochemical properties of the coated samples were investigated by using scann...Nano cerium oxide films were applied on AA7020-T6 aluminum alloy and the effects of acetic acid concentration on the microstructure and electrochemical properties of the coated samples were investigated by using scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and potentiodynamic polarization methods. It has been found that by increasing the acetic acid/CeCl3·7H2O molar ratio, high uniform and crack-free films with well-developed grains were obtained and grain sizes of the films decreased. Elimination of cracks and decreasing grain size of the nano cerium oxide films caused corrosion resistance to increase.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
Porous anodic oxide films were fabricated galvanostatically on titanium alloy Ti-10V-2Fe-3Al in ammonium tartrate solution with different anodizing time.Scanning electron microscopy(SEM) and field emission scanning el...Porous anodic oxide films were fabricated galvanostatically on titanium alloy Ti-10V-2Fe-3Al in ammonium tartrate solution with different anodizing time.Scanning electron microscopy(SEM) and field emission scanning electron microscopy(FE-SEM) were used to investigate the morphology evolution of the anodic oxide film.It is shown that above the breakdown voltage,oxygen is generated with the occurrence of drums morphology.These drums grow and extrude,which yields the compression stress.Subsequently,microcracks are generated.With continuous anodizing,porous oxides form at the microcracks.Those oxides grow and connect to each other,finally replace the microcrack morphology.The depth profile of the anodic oxide film formed at 1 800 s was examined by Auger electron spectroscopy(AES).It is found that the film is divided into three layers according to the molar fractions of elements.The outer layer is incorporated by carbon,which may come from electrolyte solution.The thickness of the outer layer is approximately 0.2-0.3 μm.The molar fractions of elements in the intermediate layer are extraordinarily stable,while those in the inner layer vary significantly with sputtering depth.The thicknesses of the intermediate layer and the inner layer are 2 μm and 1.0-1.5 μm,respectively.Moreover,the growth mechanism of porous anodic oxide films in neutral tartrate solution was proposed.展开更多
The chemical stripping method of titanium alloy oxide films was studied. An environment friendly solution hydrogen peroxide and sodium hydroxide without hydrofluoric acid or fluoride were used to strip the oxide films...The chemical stripping method of titanium alloy oxide films was studied. An environment friendly solution hydrogen peroxide and sodium hydroxide without hydrofluoric acid or fluoride were used to strip the oxide films. The morphologies of the surface and cross-section of the oxide films before and after the films stripping were characterized by using scanning electron microscopy （SEM）. The microstructure and chemical compositions of the oxide films before and after the films stripping were investigated by using Raman spectroscopy （Raman） and X-ray photoelectron spectroscopy （XPS）. It was shown that the thickness of the oxide film was in the range of 5-6 μm. The oxide films were stripped for 2 to 8 min in the solution. Moreover, the effect of the stripping time on the efficiency of the film stripping was investigated, and the optimum stripping time was between 6-8 min. When the stripping solution completely dissolved the whole film, the α/β microstructure of the titanium alloy Ti-10V-2Fe-3Al was partly revealed. The stripping mechanism was discussed in terms of the dissolution of film delamination. The hydrogen peroxide had a significant effect on the dissolution of the titanium alloy anodic oxide film. The feasibility of the dissolution reaction also was evaluated.展开更多
In this work, we focus on the optical super-resolution effect induced by strong nonlinear saturation absorption(NSA) of graphene oxide(GO) membranes. The third-order optical nonlinearities are characterized by the can...In this work, we focus on the optical super-resolution effect induced by strong nonlinear saturation absorption(NSA) of graphene oxide(GO) membranes. The third-order optical nonlinearities are characterized by the canonical Z-scan technique under femtosecond laser(wavelength: 800 nm, pulse width: 100 fs) excitation. Through controlling the applied femtosecond laser energy, NSA of the GO films can be tuned continuously. The GO film is placed at the focal plane as a unique amplitude filter to improve the resolution of the focused field. A multi-layer system model is proposed to present the generation of a deep sub-wavelength spot associated with the nonlinearity of GO films. Moreover, the parameter conditions to achieve the best resolution(~λ/6) are determined entirely. The demonstrated results here are useful for high density optical recoding and storage, nanolithography, and super-resolution optical imaging.展开更多
The oxidation properties of Fe-20Cr, Fe-20Cr-0.2Dy and Fe-20Cr-lDy alloys were studied using gravimetric and electrochemical techniques. The high-temperature oxide films of Dy-doped Fe-20Cr alloys were prepared in air...The oxidation properties of Fe-20Cr, Fe-20Cr-0.2Dy and Fe-20Cr-lDy alloys were studied using gravimetric and electrochemical techniques. The high-temperature oxide films of Dy-doped Fe-20Cr alloys were prepared in air at 900 ℃for 24, 48 and 100 h, respectively. The electrochemical experiment was performed by a three-electrode electrochemical cell and in 0.1 mol/L Na2SO4 aqueous solution. Proper models were built for describing electrochemical impedance spectroscopy of the different oxide layers and the spectra were interpreted in terms of a two-layer model of the films. The results revealed that the oxide films of Dy-doped Fe-20Cr alloys became compacter than that of undoped alloys and retained their good protective ability for a relatively long time. With increasing content of Dy, the protection of the oxide films slightly decreased. Mott-Schottky curves indicated that all the oxides were n-type semi-conductors, and the Nd value of oxide film on Fe-20Cr was much larger than that of Dy-doped Fe-20Cr alloys. The results of kinetic curves and SEM were in agreement with electrochemical impedance spectroscopy and Mott-Schottky data.展开更多
Oxide films formed on the surfaces of Fe-based bulk metallic glasses in the temperature range between 373 K and 573 K were characterized and their effects on the corrosion behaviors were investigated by microstructura...Oxide films formed on the surfaces of Fe-based bulk metallic glasses in the temperature range between 373 K and 573 K were characterized and their effects on the corrosion behaviors were investigated by microstructural and electrochemical analysis. The oxide film formed at 573 K is iron-rich oxide and it exhibits an n-type semiconductor at a higher potential than 0.35 V and a p-type semiconductor at a lower potential than 0.35 V. Capacitance measurements show that the donor density decreases with the increase in oxidation temperature, while the thickness of the space charge layer increases with the oxidation temperature rising. The result of immersion tests shows that the mass loss rate increases with the oxidation temperature rising. Therefore, the correlation between microstructure and corrosion resistance needs to be proposed because the corrosion resistance is deteriorated with the development of the oxide films.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 so-called“Oxide/Metal/Oxide sandwich”method is one of the technique used to investigate the dynamic oxidation of metals which happens during the casting process.In this study,characteristics of the oxide films f...The so-called“Oxide/Metal/Oxide sandwich”method is one of the technique used to investigate the dynamic oxidation of metals which happens during the casting process.In this study,characteristics of the oxide films formed on the molten magnesium in dynamic conditions have been investigated using the aforementioned method.The air bubbles were released into the cast sample at the pressure of 0.2 atm through a quartz tube of 1 mm internal diameter.The interface of two adjacent entrapped bubbles is considered as the Oxide/Metal/Oxide(OMO)sandwich.The sandwiches were characterized by the aid of the optical and scanning electron microscopy and also X-Ray diffraction analyses.Two different approaches,including measuring the width of the folds formed on the oxide films and the edge of the sandwiches,were used to estimate the thickness of the films.The thicknesses were estimated to be in the range of 200 to 800 nm.The features such as fold,wrinkle,and crack were observed on the OMO sandwiches.On the microscopic scale,the oxide films were rough and porous.This is attributed to the non-protective behavior of oxide films.The XRD patterns indicated that the oxide films formed on the pure molten magnesium in dynamic conditions are crystallized MgO.展开更多
Tin oxide（SnO2） and fluorine doped tin oxide（FTO） films were prepared on glass substrates by sol-gel spin-coating using SnCl4 and NH4F precursors.Fluorine doping concentration was fixed at 4 at%and 20 at%by contro...Tin oxide（SnO2） and fluorine doped tin oxide（FTO） films were prepared on glass substrates by sol-gel spin-coating using SnCl4 and NH4F precursors.Fluorine doping concentration was fixed at 4 at%and 20 at%by controlling precursor sol composition.Films exhibited the tetragonal rutile-type crystal structure regardless of fluorine concentration.Uniform and highly transparent FTO films,with more than 85%of optical transmittance,were obtained by annealing at 600℃.Florine doping of films was verified by analyzing the valence band region obtained by XPS.It was found that the fluorine doping affects the shape of valence band of SnO2 films.In addition,it was observed that the band gap of SnO2 is reduced as well as the Fermi level is upward shifted by the effect of fluorine doping.展开更多
Nucleation of Fe-rich intermetallic phases on α-Al2O3 oxide films was analyzed in five experimental Al-Fe-Mn-Si alloys. In an attempt to verify the role of α-Al2O3 films in nucleating Fe-rich intermetallics, experim...Nucleation of Fe-rich intermetallic phases on α-Al2O3 oxide films was analyzed in five experimental Al-Fe-Mn-Si alloys. In an attempt to verify the role of α-Al2O3 films in nucleating Fe-rich intermetallics, experiments have been conducted under conditions where formed in situ oxide films were present. Some Fe-rich intermetallics are observed to be related with the oxide films in the microstructure, the present results are in accordance with some research that suggest that the Fe-rich intermetallic phases nucleate upon the oxide films. The intermetallic phases and α-Al2O3 films were unambiguously identified with the help of complementary techniques such as thermal analysis, SEM/EDS and X-ray diffraction.展开更多
This paper describes effects of 40 kHz ultrasound on the oxide films of stainless steel in sulphate electrolytes so as to determine the transmitted power and to characterize mass transfer and peak current density on t...This paper describes effects of 40 kHz ultrasound on the oxide films of stainless steel in sulphate electrolytes so as to determine the transmitted power and to characterize mass transfer and peak current density on the electrode surface. Emphasis was mainly laid on electrochemical oxidations and peeling mechanism of oxide films in sonicated sulphate solutions （0.5 and 1.0 mol/L）. Polarization voltammetry, current response traces and SEM analysis were carded out in order to provide full information as to oxide films surface. Results shows that the rate of electrochemical oxidation, the shape of polarization curves and the surface micrographs in sonicated sulphate electrolytes are different from those obtained without introduction of ultrasound. It is concluded that ultrasound can change the electro-chemical behavior of oxide films by its cavitaion effects, which would produce transient mechanical impulsive force and enhance electrochemical reactions.展开更多
Irradiation makes structural materials of nuclear reactors degraded and failed.However,the damage process of materials induced by irradiation is not fully elucidated,mostly because the charged particles only bombarded...Irradiation makes structural materials of nuclear reactors degraded and failed.However,the damage process of materials induced by irradiation is not fully elucidated,mostly because the charged particles only bombarded the surface of the materials(within a few microns).In this work,we investigated the effects of surface irradiation on the indirect irradiation region of the(Al0.3Cr0.2Fe0.2Ni0.3)3O4 high entropy oxide(HEO)films in detail by plasma surface interaction.The results show that the damage induced by surface irradiation significantly extends to the indirect irradiation region of HEO film where the helium bubbles,dislocations,phase transformation,and the nickel oxide segregation were observed.展开更多
Vanadium oxide films were grown by atomic layer deposition using the tetrakis[ethylmethylamino] vanadium as the vanadium precursor and H2O as the oxide source. The effect of the source temperature on the quality of va...Vanadium oxide films were grown by atomic layer deposition using the tetrakis[ethylmethylamino] vanadium as the vanadium precursor and H2O as the oxide source. The effect of the source temperature on the quality of vanadium oxide films and valence state was investigated. The crystallinity, surface morphology, film thickness, and photoelectric properties of the films were characterized by x-ray diffraction, atomic force microscope, scanning electron microscope, I–V characteristics curves, and UV–visible spectrophotometer. By varying the source temperature, the content of V6O11, VO2, and V6O13 in the vanadium oxide film increased, that is, as the temperature increased, the average oxidation state generally decreased to a lower value, which is attributed to the rising of the vapor pressure and the change of the ionization degree for organometallics. Meanwhile, the root-mean-square roughness decreased and the metal–insulator transition temperature reduced. Our study is great significance for the fabrication of vanadium oxide films by atomic layer deposition.展开更多
Pulsed reactive sputtering is a novel process used to deposit some compound films, which are not deposited by traditional D.C. reactive sputtering easily. In this paper some experimental results about the deposition o...Pulsed reactive sputtering is a novel process used to deposit some compound films, which are not deposited by traditional D.C. reactive sputtering easily. In this paper some experimental results about the deposition of Al oxide films by pulsed reactive sputtering are presented. The hysteresis phenomenon of the sputtering voltage and deposition rate with the change of oxygen flow during sputtering process are discussed.展开更多
CO2 and O2 were employed as reactive gases to fabricate carbon-doped titanium oxide films using DC reactive magnetron sputtering. Microstructure, composition and optical band gap of the films were investigated by X-ra...CO2 and O2 were employed as reactive gases to fabricate carbon-doped titanium oxide films using DC reactive magnetron sputtering. Microstructure, composition and optical band gap of the films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and UV-visible spectrophotometer, respectively. The results showed that carbon-doped titanium monoxide films （C-TiO） with a carbon concentration of 5.8 at.% were obtained in an AffCO2 mixed atmosphere. However, carbon-doped futile and anatase （C-TiO2） with a carbon concentration of about 1.4 at.% were obtained in an Ar/CO2/O2 mixed atmosphere. The optical band gaps of C-TiO and C-TiO2 were about 2.6 and 2.9 eV, respectively. Both of them were narrower than that of pure TiO2 films. Films with narrowed optical band gap energy are promising in promoting their photo-catalytic activity.展开更多
基金supported by the National Key Research and Development Program of China(No.2021YFB3501002)the National Science and Technology Major Project(No.J2019-Ⅷ-0003-0165)the National Natural Science Foundation of China(No.52301059).
文摘Oxide films hinder diffusion and resist external forces,which determines the flame ignition mechanism of magnesium alloys.The effects of the continuity,compactness and mechanical properties of oxide films on the ignition mechanism were analyzed,by investigating the flame ignition behaviors of AZ80(ZM5),EZ30K(ZM6)and WE43 Mg alloys.The results show that the rupture of the oxide films caused by liquid gravity was the key to causing ignition.According to thermodynamic calculations,compared with Mg,Al cannot be preferentially oxidized;while Nd can be preferentially oxidized through significant enrichment,resulting in a discontinuous Nd_(2)O_(3)inner layer in the ZM6 alloy;in contrast,Y has a strong preferential oxidation ability,which gives the WE43 alloy a continuous Y_(2)O_(3)inner layer and self-healing ability.In addition,the oxide film of the ZM5 alloy is loose and has poor mechanical properties,so it cannot effec-tively hinder diffusion and resist liquid gravity.Differently,the oxide films of the ZM6 and WE43 alloys are dense and have better mechanical properties,leading to higher ignition temperatures and longer igni-tion times.In addition,a criterion was proposed to predict the ignition time based on the law of energy conservation,and it was simplified to predict the ignition temperature.The errors between the predicted and measured values are within 11%.
基金supported by the Vinnova(project number 2020-03778)supported by the Swedish Research Council(Vetenskapsradet,project number 2021-04157).
文摘Nano-scale chemical inhomogeneity in surface oxide films formed on a V-and N-containing martensite stainless steel and tempering heating induced changes are investigated by a combination of synchrotron-based hard X-ray Photoelectron emission spectroscopy(HAXPES)and microscopy(HAXPEEM)as well as microscopic X-ray absorption spectroscopy(μ-XAS)techniques.The results reveal the inhomogeneity in the oxide films on the micron-sized Cr_(2)N-and VN-type particles,while the inhomogeneity on the martensite matrix phase exists due to localised formation of nano-sized tempering nitride particles at 600℃.The oxide film formed on Cr_(2)N-type particles is rich in Cr_(2)O_(3) compared with that on the martensite matrix and VN-type particles.With the increase of tempering temperature,Cr_(2)O_(3) formation is faster for the oxidation of Cr in the martensite matrix than the oxidation of Cr nitride-rich particles.
基金supported by the National Natural Science Foundation of China(Nos.12005269 and U1832206).
文摘The oxide films of 316L and T91 exposed to 350-500℃ steam were investigated using transmission electron microscopy(TEM).Independent of the exposure temperature,a triplex oxide structure with outer magnetite,inner Cr-rich(Fe_(1.4)Cr_(1.6)O_(4)),and Ni-rich layer formed on 316L,while only a duplex layer with outer magnetite and inner Cr-rich(Fe_(2.2)Cr_(0.8)O_(4))layer formed on T91.As the fast channels for oxidant and the obstacles for solid-state diffusion,nanopores are distributed evenly in the Cr-rich inner layer and are more abundant in 316L than in T91.The oxidation behavior of the materials was understood based on the microscopic characteristics of the oxide films.
文摘A study was conducted to develop low-friction, wear-resistant surfaces on high temperature alloys for the temperature range from 26℃ to 900℃. The approach investigated consists of modifying the naturally occurring oxide film in order to improve its tribological properties. Improvement is needed at low temperatures where the oxide film, previously formed at high temperature, spalls due to stresses induced by sliding. Experiments with Ti, W and Ta additions show a beneficial effect when added to Ni and Ni-base alloys. Low friction can be maintained down to 100℃ from 900℃. For unalloyed Ni friction and surface damage increases at 400℃ to 500℃. Two new alloys were perpared based on the beneficial results of binary alloys and ZrO2 diffusion in Ni.Low friction at temperature above 500℃ and reasonable values (0.32~0.42) at low temperature are obtained.
文摘Nano cerium oxide films were applied on AA7020-T6 aluminum alloy and the effects of acetic acid concentration on the microstructure and electrochemical properties of the coated samples were investigated by using scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and potentiodynamic polarization methods. It has been found that by increasing the acetic acid/CeCl3·7H2O molar ratio, high uniform and crack-free films with well-developed grains were obtained and grain sizes of the films decreased. Elimination of cracks and decreasing grain size of the nano cerium oxide films caused corrosion resistance to increase.
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Project(50571003) supported by the National Natural Science Foundation of China
文摘Porous anodic oxide films were fabricated galvanostatically on titanium alloy Ti-10V-2Fe-3Al in ammonium tartrate solution with different anodizing time.Scanning electron microscopy(SEM) and field emission scanning electron microscopy(FE-SEM) were used to investigate the morphology evolution of the anodic oxide film.It is shown that above the breakdown voltage,oxygen is generated with the occurrence of drums morphology.These drums grow and extrude,which yields the compression stress.Subsequently,microcracks are generated.With continuous anodizing,porous oxides form at the microcracks.Those oxides grow and connect to each other,finally replace the microcrack morphology.The depth profile of the anodic oxide film formed at 1 800 s was examined by Auger electron spectroscopy(AES).It is found that the film is divided into three layers according to the molar fractions of elements.The outer layer is incorporated by carbon,which may come from electrolyte solution.The thickness of the outer layer is approximately 0.2-0.3 μm.The molar fractions of elements in the intermediate layer are extraordinarily stable,while those in the inner layer vary significantly with sputtering depth.The thicknesses of the intermediate layer and the inner layer are 2 μm and 1.0-1.5 μm,respectively.Moreover,the growth mechanism of porous anodic oxide films in neutral tartrate solution was proposed.
基金Funded by the National Natural Science Foundation of China(No. 51171011)
文摘The chemical stripping method of titanium alloy oxide films was studied. An environment friendly solution hydrogen peroxide and sodium hydroxide without hydrofluoric acid or fluoride were used to strip the oxide films. The morphologies of the surface and cross-section of the oxide films before and after the films stripping were characterized by using scanning electron microscopy （SEM）. The microstructure and chemical compositions of the oxide films before and after the films stripping were investigated by using Raman spectroscopy （Raman） and X-ray photoelectron spectroscopy （XPS）. It was shown that the thickness of the oxide film was in the range of 5-6 μm. The oxide films were stripped for 2 to 8 min in the solution. Moreover, the effect of the stripping time on the efficiency of the film stripping was investigated, and the optimum stripping time was between 6-8 min. When the stripping solution completely dissolved the whole film, the α/β microstructure of the titanium alloy Ti-10V-2Fe-3Al was partly revealed. The stripping mechanism was discussed in terms of the dissolution of film delamination. The hydrogen peroxide had a significant effect on the dissolution of the titanium alloy anodic oxide film. The feasibility of the dissolution reaction also was evaluated.
基金supported by the National Natural Science Foundation of China(Nos.61575139,51602213 and 11604236)the Young Science Foundation of Taiyuan University of Technology(No.2015QN066)
文摘In this work, we focus on the optical super-resolution effect induced by strong nonlinear saturation absorption(NSA) of graphene oxide(GO) membranes. The third-order optical nonlinearities are characterized by the canonical Z-scan technique under femtosecond laser(wavelength: 800 nm, pulse width: 100 fs) excitation. Through controlling the applied femtosecond laser energy, NSA of the GO films can be tuned continuously. The GO film is placed at the focal plane as a unique amplitude filter to improve the resolution of the focused field. A multi-layer system model is proposed to present the generation of a deep sub-wavelength spot associated with the nonlinearity of GO films. Moreover, the parameter conditions to achieve the best resolution(~λ/6) are determined entirely. The demonstrated results here are useful for high density optical recoding and storage, nanolithography, and super-resolution optical imaging.
基金supported by the National Natural Science Foundation of China (51201073)Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘The oxidation properties of Fe-20Cr, Fe-20Cr-0.2Dy and Fe-20Cr-lDy alloys were studied using gravimetric and electrochemical techniques. The high-temperature oxide films of Dy-doped Fe-20Cr alloys were prepared in air at 900 ℃for 24, 48 and 100 h, respectively. The electrochemical experiment was performed by a three-electrode electrochemical cell and in 0.1 mol/L Na2SO4 aqueous solution. Proper models were built for describing electrochemical impedance spectroscopy of the different oxide layers and the spectra were interpreted in terms of a two-layer model of the films. The results revealed that the oxide films of Dy-doped Fe-20Cr alloys became compacter than that of undoped alloys and retained their good protective ability for a relatively long time. With increasing content of Dy, the protection of the oxide films slightly decreased. Mott-Schottky curves indicated that all the oxides were n-type semi-conductors, and the Nd value of oxide film on Fe-20Cr was much larger than that of Dy-doped Fe-20Cr alloys. The results of kinetic curves and SEM were in agreement with electrochemical impedance spectroscopy and Mott-Schottky data.
基金supported by the National Natural Science Foundation of China (No.51165038)the Doctoral Startup Fund of Nanchang Hangkong University (No.EA201103238)the Korean Ministry of Commerce, Industry and Energy through the project entitled as "The Development of Structural Metallic Materials and Parts with Super Strength and High Performance"
文摘Oxide films formed on the surfaces of Fe-based bulk metallic glasses in the temperature range between 373 K and 573 K were characterized and their effects on the corrosion behaviors were investigated by microstructural and electrochemical analysis. The oxide film formed at 573 K is iron-rich oxide and it exhibits an n-type semiconductor at a higher potential than 0.35 V and a p-type semiconductor at a lower potential than 0.35 V. Capacitance measurements show that the donor density decreases with the increase in oxidation temperature, while the thickness of the space charge layer increases with the oxidation temperature rising. The result of immersion tests shows that the mass loss rate increases with the oxidation temperature rising. Therefore, the correlation between microstructure and corrosion resistance needs to be proposed because the corrosion resistance is deteriorated with the development of the oxide films.
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.
文摘The so-called“Oxide/Metal/Oxide sandwich”method is one of the technique used to investigate the dynamic oxidation of metals which happens during the casting process.In this study,characteristics of the oxide films formed on the molten magnesium in dynamic conditions have been investigated using the aforementioned method.The air bubbles were released into the cast sample at the pressure of 0.2 atm through a quartz tube of 1 mm internal diameter.The interface of two adjacent entrapped bubbles is considered as the Oxide/Metal/Oxide(OMO)sandwich.The sandwiches were characterized by the aid of the optical and scanning electron microscopy and also X-Ray diffraction analyses.Two different approaches,including measuring the width of the folds formed on the oxide films and the edge of the sandwiches,were used to estimate the thickness of the films.The thicknesses were estimated to be in the range of 200 to 800 nm.The features such as fold,wrinkle,and crack were observed on the OMO sandwiches.On the microscopic scale,the oxide films were rough and porous.This is attributed to the non-protective behavior of oxide films.The XRD patterns indicated that the oxide films formed on the pure molten magnesium in dynamic conditions are crystallized MgO.
文摘Tin oxide（SnO2） and fluorine doped tin oxide（FTO） films were prepared on glass substrates by sol-gel spin-coating using SnCl4 and NH4F precursors.Fluorine doping concentration was fixed at 4 at%and 20 at%by controlling precursor sol composition.Films exhibited the tetragonal rutile-type crystal structure regardless of fluorine concentration.Uniform and highly transparent FTO films,with more than 85%of optical transmittance,were obtained by annealing at 600℃.Florine doping of films was verified by analyzing the valence band region obtained by XPS.It was found that the fluorine doping affects the shape of valence band of SnO2 films.In addition,it was observed that the band gap of SnO2 is reduced as well as the Fermi level is upward shifted by the effect of fluorine doping.
基金the National Council for Science and Technology of Mexico(Conacyt)for the financial support provided to carry out this work(Project No.149030).
文摘Nucleation of Fe-rich intermetallic phases on α-Al2O3 oxide films was analyzed in five experimental Al-Fe-Mn-Si alloys. In an attempt to verify the role of α-Al2O3 films in nucleating Fe-rich intermetallics, experiments have been conducted under conditions where formed in situ oxide films were present. Some Fe-rich intermetallics are observed to be related with the oxide films in the microstructure, the present results are in accordance with some research that suggest that the Fe-rich intermetallic phases nucleate upon the oxide films. The intermetallic phases and α-Al2O3 films were unambiguously identified with the help of complementary techniques such as thermal analysis, SEM/EDS and X-ray diffraction.
文摘This paper describes effects of 40 kHz ultrasound on the oxide films of stainless steel in sulphate electrolytes so as to determine the transmitted power and to characterize mass transfer and peak current density on the electrode surface. Emphasis was mainly laid on electrochemical oxidations and peeling mechanism of oxide films in sonicated sulphate solutions （0.5 and 1.0 mol/L）. Polarization voltammetry, current response traces and SEM analysis were carded out in order to provide full information as to oxide films surface. Results shows that the rate of electrochemical oxidation, the shape of polarization curves and the surface micrographs in sonicated sulphate electrolytes are different from those obtained without introduction of ultrasound. It is concluded that ultrasound can change the electro-chemical behavior of oxide films by its cavitaion effects, which would produce transient mechanical impulsive force and enhance electrochemical reactions.
基金National Key Research and Development Program of China(Grant No.2017YFB0405702)the National Natural Science Foundation of China(Grant No.11775150).
文摘Irradiation makes structural materials of nuclear reactors degraded and failed.However,the damage process of materials induced by irradiation is not fully elucidated,mostly because the charged particles only bombarded the surface of the materials(within a few microns).In this work,we investigated the effects of surface irradiation on the indirect irradiation region of the(Al0.3Cr0.2Fe0.2Ni0.3)3O4 high entropy oxide(HEO)films in detail by plasma surface interaction.The results show that the damage induced by surface irradiation significantly extends to the indirect irradiation region of HEO film where the helium bubbles,dislocations,phase transformation,and the nickel oxide segregation were observed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674038,61674021,61704011,and 61904017)the Developing Project of Science and Technology of Jilin Province,China(Grant Nos.20170520118JH and 20160520027JH)the Youth Foundation of Changchun University of Science and Technology(Grant No.XQNJJ-2018-18).
文摘Vanadium oxide films were grown by atomic layer deposition using the tetrakis[ethylmethylamino] vanadium as the vanadium precursor and H2O as the oxide source. The effect of the source temperature on the quality of vanadium oxide films and valence state was investigated. The crystallinity, surface morphology, film thickness, and photoelectric properties of the films were characterized by x-ray diffraction, atomic force microscope, scanning electron microscope, I–V characteristics curves, and UV–visible spectrophotometer. By varying the source temperature, the content of V6O11, VO2, and V6O13 in the vanadium oxide film increased, that is, as the temperature increased, the average oxidation state generally decreased to a lower value, which is attributed to the rising of the vapor pressure and the change of the ionization degree for organometallics. Meanwhile, the root-mean-square roughness decreased and the metal–insulator transition temperature reduced. Our study is great significance for the fabrication of vanadium oxide films by atomic layer deposition.
文摘Pulsed reactive sputtering is a novel process used to deposit some compound films, which are not deposited by traditional D.C. reactive sputtering easily. In this paper some experimental results about the deposition of Al oxide films by pulsed reactive sputtering are presented. The hysteresis phenomenon of the sputtering voltage and deposition rate with the change of oxygen flow during sputtering process are discussed.
基金supported by the National Natural Science Foundation of China (Nos.81171462 and 51062002)the Sichuan Youth Science & Technology Foundation for Distinguished Young Scholars (No.2012JQ0001)the Fundamental Research Funds for the Central Universities (Nos.SWJTU11CX078 and SWJTU12ZT08)
文摘CO2 and O2 were employed as reactive gases to fabricate carbon-doped titanium oxide films using DC reactive magnetron sputtering. Microstructure, composition and optical band gap of the films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and UV-visible spectrophotometer, respectively. The results showed that carbon-doped titanium monoxide films （C-TiO） with a carbon concentration of 5.8 at.% were obtained in an AffCO2 mixed atmosphere. However, carbon-doped futile and anatase （C-TiO2） with a carbon concentration of about 1.4 at.% were obtained in an Ar/CO2/O2 mixed atmosphere. The optical band gaps of C-TiO and C-TiO2 were about 2.6 and 2.9 eV, respectively. Both of them were narrower than that of pure TiO2 films. Films with narrowed optical band gap energy are promising in promoting their photo-catalytic activity.
