共查询到20条相似文献,搜索用时 93 毫秒
1.
E SosaR Cabrera-Sierra Marina E Rincón M.T OropezaI González 《Electrochimica acta》2002,47(8):1197-1208
Non-stoichiometric iron sulfide films (FexSy) were formed electrochemically on a 1018 carbon steel/1 M (NH4)2S, 500 ppm CN− interface, using cyclic chronoamperometry for different time intervals. The films showed great stability in medium typical of the catalytic plants of PEMEX Mexico (0.1 M (NH4)2S, 10 ppm CN− as NaCN, pH 8.8). Characterization of the films by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) show two different behaviors depending on the growth time. For films grown at times <15 min, oxidation of the film was continuous, while oxidation ability for the film formed at times >15 min was lower. Film characteristics were more clearly defined by EIS experiments, as the Nyquist diagrams show depressive loops with high, real impedance values (Zr>1 kΩ cm2) for films grown at longer times. Structural characterization by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) correlated electrochemical behavior with topographical changes and chemical composition of the films formed. The abundance of sulfur and pyrrhotite is evident in the samples grown for increasing times, and is likely due to electrochemical/chemical oxidation of iron sulfides during film growth. The sulfur-rich layer is responsible for the passive character of these films. The equivalent electrical circuit describing the EIS spectra for films formed over longer times has fewer elements than that used to model EIS spectra for films grown at shorter times. In particular, diffusion of atomic hydrogen is not apparent in sulfur-enriched films, and the charge transfer is carried out at the metal/film interface with values that are insensitive to film thickness and chemical nature. 相似文献
2.
M. A. Domínguez-Crespo A. M. Torres-Huerta S. E. Rodil S. B. Brachetti-Sibaja W. de la Cruz A. Flores-Vela 《Journal of Applied Electrochemistry》2010,40(3):639-651
X-ray photoelectron spectroscopy (XPS) was used to analyze the composition of films at different deposition parameters of
sputtered Al-Ce coatings on AA6061 aluminum alloys. By means of electrochemical impedance spectroscopy (EIS) measurements,
the protective character of these coatings was studied for 21 days of exposure in a 3.5 wt% NaCl solution and an attempt was
made to establish the relationship between film thickness and chemical composition (Al/Ce, Ce3/Ce4+ ratios) of the surface before and after the electrochemical characterization. XPS studies revealed the presence of the Alo, Al2O3, CeO2 and Ce2O3 compounds, confirming that the sputtered Al-Ce films were deposited in the metallic form and thereafter were superficially
oxidized under ambient conditions. The Al–Ce bonds were overlapped with the signal of cerium oxides. The transport phenomena
in the oxide film or controlled diffusion process are strongly dependent on the deposition parameters and exposure time in
the aggressive medium. It was also found that in the deposited samples at p4P200t300, the film was still present after 21 days of exposure, although with visible cracks and erosion areas; however, the Ce3/Ce4+ ratio almost remained constant before and after the electrochemical characterization, which explained the barrier properties
of these samples as compared with others at different deposition parameters. 相似文献
3.
A transparent passive film on electroless nickel phosphorus coating (ENPC) was obtained in a chromate (Cr3+) bath. An ENPC sample passivated in a Cr6+-containing bath was used for comparison. The corrosion properties were tested by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). SEM, XPS, and EDX were employed to analyze the chemical composition and surface morphology of the films. SEM results indicate that the passive film is too thin to be observed by SEM. The potentiodynamic polarization tests show that the corrosion currents of the two passivated samples are only about 1/25 of the un-passivated coating. The XPS analysis illustrate that the Cr6+-treated film comprises Cr, Ni and O, while the Cr3+-treated film is made up of Cr, C, O, Ni, P and N. High-resolution XPS analysis show that, both in Cr6+-treated and Cr3+-treated films, element Cr is only in the form of trivalent compounds, no hexavalent chromium existing. By XPSpeak analyzing, trivalent chromium compounds on the two treated surfaces were fitted as Cr(OH)3 and Cr2O3. However, for the Cr3+ and Cr6+ passivation routes, the Cr(OH)3 and Cr2O3 contents in passive films are widely divergent. 相似文献
4.
Isaac Adebayo Akinbulu 《Electrochimica acta》2010,55(23):7085-7093
Self-assembled monolayer (SAM) films of iron (SAM-1), cobalt (SAM-2) and manganese (SAM-3) phthalocyanine complexes, tetra-substituted with diethylaminoethanethio at the non-peripheral positions, were formed on gold electrode in dimethylformamide (DMF). Electrochemical, impedimentary and surface properties of the SAM films were investigated. Cyclic voltammetry was used to investigate the electrochemical properties of the films. Ability of the films to inhibit common faradaic processes on bare gold surface (gold oxidation, solution redox chemistry of [Fe(H2O)6]3+/[Fe(H2O)6]2+ and underpotential deposition (UDP) of copper) was investigated. Electrochemical impedance spectroscopy (EIS), using [Fe(CN)6]3−/4− redox process as a probe, offered insights into the electrical properties of the films/electrode interfaces. Surface properties of the films were probed using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The films were employed for the electrocatalytic oxidation of the pesticide, carbofuran. Electrocatalysis was evidenced from enhanced current signal and less positive oxidation potential of the pesticide on each film, relative to that observed on the bare gold electrode. Mechanism of electrocatalytic oxidation of the pesticide was studied using rotating disc electrode voltammetry. 相似文献
5.
V. Barranco 《Electrochimica acta》2004,49(12):1999-2013
The barrier properties of thin model organosilicon plasma polymers layers on iron are characterised by means of electrochemical impedance spectroscopy (EIS). Tailored thin plasma polymers of controlled morphology and chemical composition were deposited from a microwave discharge. By the analysis of the obtained impedance diagrams, the evolution of the water uptake ?, coating resistance and polymer capacitance with immersion time were monitored and the diffusion coefficients of the water through the films were calculated. The impedance data correlated well with the chemical structure and morphology of the plasma polymer films with a thickness of less than 100 nm. The composition of the films were determined by means of infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The morphology of the plasma polymer surface and the interface between the plasma polymer and the metal were characterised using atomic force microscopy (AFM). It could be shown that, at higher pressure, the film roughness increases which is probably due to the adsorption of plasma polymer nanoparticles formed in the plasma bulk and the faster film growth. This leads to voids with a size of a few tens of nanometers at the polymer/metal interface. The film roughness increases from the interface to the outer surface of the film. By lowering the pressure and thereby slowing the deposition rate, the plasma polymers perfectly imitate the substrate topography and lead to an excellent blocking of the metal surface. Moreover, the ratio of siloxane bonds to methyl-silyl groups increases which implies that the crosslink density is higher at lower deposition rate. The EIS data consistently showed higher coating resistance as well as lower interfacial capacitance values and a better stability over time for the film deposited at slower pressure. The diffusion coefficient of water in thin and ultra-thin plasma polymer films could be quantified for the smooth films. The measurements show that the quantitative evaluation of the electrochemical impedance data requires a detailed understanding of the film morphology and chemical composition. In addition, the measured diffusion coefficient of about 1.5×10−14 cm2 s−1 shows that plasma polymers can act as corrosion resistant barrier layers at polymer/metal interfaces. 相似文献
6.
Yan-Qiu Chu 《Electrochimica acta》2004,49(27):4915-4921
Spinel cobalt ferrite (CoFe2O4) thin films have been fabricated by 355 nm reactive pulsed laser deposition on stainless steel substrates. XRD and SEM analyses showed that the CoFe2O4 films exhibited a polycrystalline structure and were composed of nanoparticles with an average size of 80 nm. At 1C rate, the initial irreversible capacity of polycrystalline CoFe2O4 film electrode cycled between 0.01 and 3.0 V reached 1280 mAh/g. After 20 cycles, the reversible discharge capacities decreased and sustained about 610 mAh/g. The diffusion coefficient of Li ion for CoFe2O4 films was determined by ac impedance method, and the average value was estimated to be 1.1 × 10−13 cm2/S. Based on ex situ XRD, SEM and XPS data, the electrochemical mechanism of CoFe2O4 film with lithium upon cycling was proposed. During the first discharge, the amorphization process of CoFe2O4 film electrode is accompanied with the reduction of Co2+ and Fe3+ into metal Co and Fe, respectively, and then the reversible oxidation/reduction processes of Co, Fe and Li2O take place in the subsequent charge/discharge cycles. 相似文献
7.
Titanium dioxide (TiO2) films on glassy carbon (GC) electrode surface were prepared by the liquid phase deposition (LPD) process for different deposition
times. The morphological structure, interfacial property and electrocatalytic activity of as-prepared LPD TiO2 films on GC surface were studied by field-emission scanning electron microscopy (FE-SEM), cyclic voltammetry (CV) and electrochemical
impedance spectroscopy (EIS). The FE-SEM observation showed that the deposition time controlled the morphology of film on
GC surface. With increasing deposition time, TiO2 formed nanoparticles at the initial 5-h stage and compact thick films after 20 h. Due to the semiconducting properties of
TiO2, the LPD films inhibited the electron transfer process of [Fe(CN)6]3−/[Fe(CN)6]4− on GC by increasing the redox reaction peak potential separation of CV curve and electron transfer resistance of EIS. The
inhibition was increased with TiO2 film thickness. Nevertheless, the onset reduction potential of maleic acid decreased with increasing LPD TiO2 film thickness while the cathodic and anodic currents increased, demonstrating the useful electrocatalytic activity of LPD
TiO2 films. 相似文献
8.
Anodic films were grown potentiodynamically in different electrolytes (pH = 1-14) on a Ti-50Zr at% cast alloy, obtained by fusion in a voltaic arc under argon atmosphere. The thickness of the films was varied by changing formation potential from the open circuit potential up to about 9 V; growth was followed by 30 min stabilization at the forming potential. Films having different thicknesses were characterized by photocurrent spectroscopy (PCS) and electrochemical impedance spectroscopy (EIS). Moreover, film composition was analyzed by X-ray photoelectron spectroscopy (XPS).Regardless of the anodizing conditions, passive films on the Ti-50Zr at% alloy consist of a single layer mixed oxide phase containing both TiO2 and ZrO2 groups. However, an enrichment of Ti within the passive film, increasing with the film thickness, is detected both by PCS and XPS. This leads to concentration profiles of Ti4+ and Zr4+ ions along the thickness, and to different electronic properties of very thin films (more insulating) with respect to thicker films (more semiconducting), as revealed by the photocurrent-potential curves. 相似文献
9.
The objective of this study is to evaluate the effect of low-level hydrogen sulfide (H2S) on carbon dioxide (CO2) corrosion of carbon steel in acidic solutions, and to investigate the mechanism of iron sulfide scale formation in CO2/H2S environments. Corrosion tests were conducted using 1018 carbon steel in 1 wt.% NaCl solution (25 °C) at pH of 3 and 4, and under atmospheric pressure. The test solution was saturated with flowing gases that change with increasing time from CO2 (stage 1) to CO2/100 ppm H2S (stage 2) and back to CO2 (stage 3). Corrosion rate and behavior were investigated using linear polarization resistance (LPR) technique. Electrochemical impedance spectroscopy (EIS) and potentiodynamic tests were performed at the end of each stage. The morphology and compositions of surface corrosion products were analyzed using scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The results showed that the addition of 100 ppm H2S to CO2 induced rapid reduction in the corrosion rate at both pHs 3 and 4. This H2S inhibition effect is attributed to the formation of thin FeS film (tarnish) on the steel surface that suppressed the anodic dissolution reaction. The study results suggested that the precipitation of iron sulfide as well as iron carbonate film is possible in the acidic solutions due to the local supersaturation in regions immediately above the steel surface, and these films provide corrosion protection in the acidic solutions. 相似文献
10.
《Journal of Adhesion Science and Technology》2013,27(5):665-677
When Cu films were deposited by thermal evaporation onto stainless steel substrates at 30°C, the oxygen gas in the vacuum chamber (1.5 x 10-3 Torr) caused the adhesion of Cu films to increase from 3 to 5 MPa. Moreover, it increased further from 13 to 16 MPa when deposited at 300°C. The Cu film was not peeled off when deposited by the electron shower method and the epoxy resin failed (20 MPa), and this was independent of the addition of oxygen gas. As the chemical shift of Cu 2p3/2 was observed at the interface between the Cu film and the substrate when oxygen gas was added, it is concluded that the adhesion is mainly determined by the chemical bonding, such as CuO and Cu2O. The depth profile of Cu 2p3/2 measured by X-ray photoelectron spectroscopy (XPS) using Ar etching showed apparent thermal diffusion of Cu into the substrate. But the Ar etching rate was decreased by Cu oxides at the interface. The amount of oxides depended on the substrate temperature and the deposition method for Cu film. Therefore, the depth profile of Cu measured by XPS did not represent the thermal diffusion of Cu into the substrate correctly. When the etching rate was modified, the diffusion of Cu was almost the same for different samples deposited at the same temperature, and the effect of the thermal diffusion on the adhesion was small. The adhesion on hydrated [Cr(OH)3.0.4H2O] and hydroxide [Cr(OH)3] surfaces was lower than that on the oxide (Cr2O3) surface. In other words, the pretreatment of the substrates was very important to the adhesion. 相似文献
11.
《Ceramics International》2022,48(15):21451-21458
During the deposition of a-C:H film, defects (pinholes or discontinuities) caused by excessive stress will inevitably appear, which will reduce the corrosion resistance of the a-C:H film. In this study, top a-C:H:Si:O layers (thickness of approximately 0.3 μm) on the surface of a-C:H films were deposited on a large scale by PACVD technology using acetylene (C2H2) and/or hexamethyldisiloxane (HMDSO) as reactants, to improve the corrosion resistance of a-C:H films while ensuring the appropriate overall hardness of the films. The corrosion behaviors of the films were studied by electrochemical impedance spectroscopy (EIS) and Tafel polarization. We found that the a-C:H/a-C:H:Si:O films possess a lower electrolyte penetration rate due to their stronger capacitance characteristics. In addition, the corrosion current density of the a-C:H/a-C:H:Si:O films (10?10 A cm?2) were reduced by 2 orders of magnitude compared to the a-C:H film (10?8 A cm?2), and by 3 orders of magnitude compared to 316 stainless steel (10?7 A cm?2). The impedance results obtained by EIS were simulated using appropriate equivalent circuits, and the corresponding electrical parameters were used to further verify the electrochemical protection behavior of the top a-C:H:Si:O layer. 相似文献
12.
《Ceramics International》2021,47(24):34774-34782
SiO2 and SnO2 films were deposited using plasma-enhanced atomic layer deposition (PEALD) at low temperature (100 °C), and homogeneously mixed structure (HMS) films consisting of Si, Sn, and O were deposited through a “1st precursor dose – 2nd precursor dose – oxidation”, a new ALD process method for mixing two elements. For a deep consideration of the growth mechanism during the HMS film deposition process, density functional theory (DFT) calculations of the adsorption reactions of the precursors on the surface were conducted. The properties of the thin films such as density, atomic composition, crystallinity, surface roughness, optical transmittance and the water vapor diffusion barrier property were analyzed by XRR, XPS, XRD, AFM, UV-VIS and the electrical Ca test.By changing the dose sequence of the two precursors in the HMS process, various physical/chemical characteristics of the films could be controlled. Also, by adjusting the appropriate amount of Sn in the HMS films, the shortcomings of SnO2 were compensated by the mixed SiO2; and through this process, excellent gas diffusion barrier properties of WVTR ∼ 1.33 × 10−4 g/m2day were secured. 相似文献
13.
Sabine Szunerits Carolina Nunes Kirchner Rabah Boukherroub 《Electrochimica acta》2008,53(27):7908-7914
The paper reports on the investigation of the electrochemical behavior of a thin gold film electrode coated with silicon dioxide (SiOx) layers of increasing thickness. Stable thin films of amorphous silica (SiOx) were deposited on glass slides coated with a 5 nm adhesion layer of titanium and 50 nm of gold, using plasma-enhanced chemical vapor deposition (PECVD) technique. Scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical behavior of the interfaces. In the case of SECM, the influence of the SiOx thicknesses on the electron transfer kinetics of three redox mediators was investigated. Normalized current-distance curves (approach curves) were fitted to the theoretical model in order to find the effective heterogeneous first order rate constant (keff) at the sample. EIS was in addition used to confirm the diffusion barrier character of the SiOx interlayer. 相似文献
14.
Sahar A. Fadl-Allah Rabab M. El-Sherief Waheed A. Badawy 《Journal of Applied Electrochemistry》2008,38(10):1459-1466
Galvanostatically and potentiostatically formed surface oxide films on titanium in H2O2 free and H2O2 containing H2SO4 solutions were investigated. Conventional electrochemical techniques, electrochemical impedance spectroscopy (EIS) and scanning
electron microscopy, were used. In the absence of H2O2, the impedance response indicated a stable thin oxide film which depends on the mode of anodization of the metal. However,
in the presence of H2O2 the film characteristics were changed. A significant decrease in the corrosion resistance of the surface film was recorded.
The film characteristics were also found to be affected by the mode of oxide film growth and polarization time. The EIS results
and the impedance data fitting to equivalent circuit models have shown that the oxide film consists of two layers. The electrochemical
characteristics of the anodic films formed under different conditions have been discussed. 相似文献
15.
E. Laouini J. Douch M. Hamdani Y. Berghoute M. H. Mendonça M. I. S. Pereira R. N. Singh 《Journal of Applied Electrochemistry》2011,41(6):731-740
Spinel type CoFe2O4 thin films have been prepared, on stainless steel supports, by thermal decomposition of aqueous solutions of mixed cobalt
and iron nitrates in 1:2 molar ratio at 400 °C. The electrochemical behaviour of the CoFe2O4/1 M KOH interface was investigated by cyclic voltammetry, chronoamperometry and impedance techniques. The studies allowed
finding out the redox reactions occurring at the oxide surface. The results were compared with colloidal electrodes prepared
by alkaline precipitation of Fe(II) or Fe(III) hydrous oxi-hydroxides on platinum electrodes. In addition, it has been concluded
that the processes are diffusion-controlled and the diffusion of the hydroxide ion, through the oxide, acts as the rate-determining
step. The diffusion coefficient of OH− through the oxide film was determined using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy
techniques. 相似文献
16.
《Ceramics International》2022,48(1):137-147
Mixed phase of iron telluride based thin films consisting of nanopebbles has been grown successfully over conducting stainless steel (SS) substrate through successive ionic layer adsorption reaction (SILAR) process. Crystal structural and elemental states through XPS revealed clear indication of FeTe: Fe2TeO5 mixed phase growth and well supported through FTIR studies. Agglomeration of embedded quantum dots forming nanopebbles like surface architecture resulting in enhanced hydrophilic nature evident through contact angle and higher surface roughness by atomic force micrographs found beneficial as more electroactive surface area for electrolyte ions to interact. This helped to achieve a significant specific capacitance of 591 F/g (166 mF/cm2) @3 mV/s potential scan rate and, 107 F/g (30 mF/cm2) @0.4 mA/cm2 in NaCl electrolyte. Performed electrochemical impedance spectroscopy (EIS) studies explored clear insight of the solution and charge transfer resistances, and relaxation time constant. Iron telluride based thin film clearly demonstrates very high value of pseudo capacitive contribution than the electric double layer due to the intrinsic pseudocapacitive behavior of mixed phase. 相似文献
17.
Chems-Eddine Barchiche David Duday Patrick Choquet Henri-Noël Migeon Emmanuel Rocca 《Electrochimica acta》2009,54(24):5789-5795
In the field of corrosion protection, the research of environmentally friendly coating processes is one of the research topics. The use of gaseous atmospheric plasma, especially dielectric barrier discharge (DBD) plasma is an interesting way to rapidly form a thin protective coating. The aim of this work is to characterize the electrochemical behaviour of a SiOxCyNz film, formed from different organosilicon precursors, in neutral corrosive environment on copper. The film morphology and composition were determined by transmission electron microscopy (TEM) observations and X-ray photoelectron spectroscopy (XPS). The electrochemical behaviour of the different treated copper was studied by stationary techniques and electrochemical impedance spectroscopy (EIS). With the same plasma parameter, the kind of organosilicon precursor determines the chemical stability of the coatings in water, then their protective properties. When the SiO2-like structure contains a low carbon level, the SiOxCyNz films present a good stability in water, and acts clearly as an O2 barrier membrane. 相似文献
18.
The passive behavior of magnesium alloys ZK31, EZ33 and WE54 was studied in alkaline media (NaOH - pH 13) in the presence and absence of chloride ions. The electrochemical properties were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and capacitance measurements.X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed for the study of the chemical composition and surface morphology of the surface films, respectively.The electrochemical impedance results revealed that the film formed on the surface of the three alloys is characterized by an increasing resistance, which stabilized with time. In the absence of chloride the film resistance was identical for all the three alloys. However, in the presence of chloride, the resistance of the film formed on the EZ33 alloy dropped nearly one order of magnitude comparatively to the other alloys. Generally, in the presence of chloride there was a decrease of the conductive character of the film.The films are homogeneous and, according to the XPS results, the outer layer seemed mainly composed of Mg(OH)2 and the internal layer composed of MgO, independently of the presence of chloride. The AFM study revealed that the presence of chloride affected film morphology, namely nano-crystallites dimensions and aggregates size that increased. 相似文献
19.
《Ceramics International》2015,41(4):5758-5764
The Sm2S3 thin films with diffused nanoflakes morphology are prepared by an environment-friendly facile chemical synthesis method and used in electrochemical supercapacitors. The structural, elemental and surface morphological characterization are carried out using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and wettability techniques. The FESEM images show tree root like distribution of flakes with average flake width of about 80 nm. The film surface is lyophilic with propylene carbonate contact angle of 21°. The supercapacitive measurements are carried out through cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) techniques. The Sm2S3 film electrode exhibited a highest specific capacitance (Cs) of 213 Fg−1 at 5 mVs−1 scan rate in LiClO4-propylene carbonate electrolyte. Asymmetric nature of charge–discharge curves confirmed pseudocapacitive behavior of electrode with energy and power densities of 39.39 Whkg−1 and 4.33 kWkg−1, respectively. An equivalent series resistance of 0.44 Ωcm−2 indicated negligible ohmic losses in charge storage. An electrochemical stability of 81.47% is retained after 1000 cycles indicating that Sm2S3 is a promising candidate for supercapacitor application. 相似文献
20.
Copper anodic layers in solutions of hydroxyethylidenediphosphonic acid (HEDP), phosphoric acid, and phosphoric acid with organic and inorganic additives were analysed in situ using electrochemical impedance spectroscopy (EIS). Salt films formed in HEDP solutions were detected. No salt film was found in solutions of phosphoric acid or phosphoric acid with copper oxide, ethylene glycol and sodium tripolyphosphate as additives. Analysis of EIS data suggests that H2O molecules are the mass transport controlling species in solutions of phosphoric acid and of phosphoric acid with copper oxide, whereas Cu2+ ions are the mass transport controlling species in solutions of HEDP and of phosphoric acid with additives ethylene glycol and sodium tripolyphosphate. Very good results for electropolishing of bulk copper discs were obtained in all the above solutions, but the electropolishing of electroplated copper films on patterned silicon wafers is more challenging. In this case, good planarization was obtained only from HEDP solutions. Experimental results and theoretical analysis indicate that surface profile of anodic layers is an important factor influencing planarization of electroplated copper films on patterned silicon wafers. An electrically resistive anode film with macro surface profile can lead to planarization of the gentle surface undulations of electroplated copper films on trenched silicon wafers due to migration smoothing, diffusion smoothing, and ohmic levelling effects. 相似文献