Página 3 dos resultados de 974 itens digitais encontrados em 0.009 segundos

Electrochemical and spectroscopic characterization of screen-printed gold-based electrodes modified with self-assembled monolayers and Tc85 protein

FERREIRA, A. A. P.; FUGIVARA, C. S.; BARROZO, S.; SUEGAMA, P. H.; YAMANAKA, H.; BENEDETTI, A. V.
Fonte: ELSEVIER SCIENCE SA Publicador: ELSEVIER SCIENCE SA
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.46%
This work investigates the formation of self-assembled monolayers (SAMs) of cystamine and cystamine-glutaraldehyde on a screen-printed electrode, and the immobilization of the Tc85 protein (from Trypanosoma cruzi) on these monolayers. The methods used included infrared techniques, cyclic voltammetry, and electrochemical impedance spectroscopy. The electrochemical studies were performed at pH 6.9 in 0.1 mol L(-1) phosphate buffer solution containing Fe(CN)(6)(-3/-4) redox species. The surface coverage (0) of the electrode was 0.10 (cystamine), 0.35 (cystamine-glutaraldehyde) and 0.84 (Tc85). Interpretation of electrochemical impedance spectroscopy results was based on a charge-transfer reaction involving Fe(CN)(6)(-3/-4) species at high frequencies, followed by a diffusion through the monolayers at lower frequencies. Estimates of the electrode surface coverage, active site radius, and distance between two adjacent sites assumed that charge transfer occurred at the active sites, and that there was a planar diffusion of redox species to these sites. (C) 2009 Elsevier B.V. All rights reserved.; FAPESP[05/50574-4]; CNPq[150670/2007-9]; CNPq[300728/2007-7]; FUNDUNESP[01093/05-DFP]

Synthesis, characterization and electrochemical behavior of the vanadium pentoxide/cetyl pyridinium chloride hybrid material

GUERRA, E. M.; CESTAROLLI, D. T.; SILVA, L. M. Da; OLIVEIRA, H. P.
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
76.32%
In situ and ex situ studies concerning the new hybrid material vanadium pentoxide xerogel in the presence of the cationic surfactant cetyl pyridinium chloride (V(2)O(5)/CPC) are presented. The in situ characterization studies revealed the presence of a lamellar structure for the V(2)O(5)/CPC hybrid material. The intercalation reaction was evidenced on the basis of the increase in the d-spacing as well as the displacement of the infrared bands toward lower energy levels. Electrochemical studies comprising the cyclic voltammetry and the electrochemical impedance spectroscopy techniques showed that the behavior of the hybrid material is considerably influenced by the electrolyte composition. The ion insertion/de-insertion into the V(2)O(5) xerogel structure accompanying the charge transfer process is influenced by the solid-state diffusion process modeled by using the finite-space Warburg element.; CAPES; FAPESP; CNPq

Direct Electrochemical Determination of Glyphosate at Copper Phthalocyanine/Multiwalled Carbon Nanotube Film Electrodes

MORAES, Fernando C.; MASCARO, Lucia H.; MACHADO, Sergio A. S.; BRETT, Christopher M. A.
Fonte: WILEY-V C H VERLAG GMBH Publicador: WILEY-V C H VERLAG GMBH
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
76.32%
A copper phthalocyanine/multiwalled carbon nanotube film-modified glassy carbon electrode has been used for the determination of the herbicide glyphosate (Gly) at -50 mV vs. SCE by electrochemical oxidation using differential pulse voltamtnetry (DPV). Cyclic voltammetry and electrochemical impedance spectroscopy showed that Gly is adsorbed on the metallic centre of the copper phthalocyanine molecule, with formation of Gly-copper ion complexes. An analytical method was developed using DPV in pH 7.4 phosphate buffer solution, without any pretreatment steps: Gly was determined in the concentration range of 0.83-9.90 mu mol L(-1), with detection limit 12.2 nmol L(-1) (2.02 mu g L(-1)); CNPq, Brazil[201494/2008-6]; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação para a Ciência e a Tecnologia de Portugal (FCT); Fundacao para a Ciencia e Tecnologia (FCT), Portugal[PTDC/QUI/65255/2006]; Fundacao para a Ciencia e Tecnologia (FCT), Portugal[PTDC/QUI/65732/2006]; Fundação para a Ciência e a Tecnologia de Portugal (FCT)

Estudo da influência de organo-silanos na resistência à corrosão de aço-carbono por meio de técnicas eletroquímicas. ; The study of organosilanes influence on mild steel and the corrosion resistance evaluation by electrochemical techniques.

Oliveira, Marcos Fernandes de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 04/08/2006 PT
Relevância na Pesquisa
76.35%
Na presente tese foi investigado o desempenho de camadas de organo-silanos sobre chapas de aço-carbono, similares às utilizadas na fabricação de veículos da indústria automobilística. As técnicas utilizadas neste estudo compreenderam a Espectroscopia de Impedância Eletroquímica (EIE) e a Resistência de Polarização Linear, por meio das quais foram determinadas respectivamente, as propriedades resistivas dos filmes e a redução das velocidades de corrosão do substrato. O estudo compreendeu a avaliação de diversos organo-silanos funcionais e não-funcionais, submetidos a diferentes condições experimentais. Os ensaios preliminares tiveram por finalidade selecionar aqueles com melhor desempenho como sistemas de proteção em monocamadas. A partir desta seleção e,, informações da literatura, novos ensaios foram conduzidos por meio de um Projeto Fatorial de Experimentos, combinando os silanos funcionais com melhor desempenho com outro silano não-funcional, designado como 1,2-bis(trietoxilsilil)etano (BTSE). Esta combinação teve por finalidade produzir camadas duplas de silanos para proteger o aço-carbono. As variáveis independentes estudadas foram a combinação entre as camadas de BTSE e do silano funcional, além das condições de hidrólise...

Caracterização da superfície do aço-carbono ABNT 1008 revestida com organo-silanos por meio de técnicas eletroquímicas e físico-químicas.; Characterization of the surface of steel-carbon ABNT 1008 coated with organo-silanes by means of electrochemical and physical-chemistry techniques.

Aquino, Isabella Pacifico
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 09/06/2006 PT
Relevância na Pesquisa
76.37%
O objetivo deste trabalho foi caracterizar por meio de técnicas eletroquímicas e físicoquímicas o comportamento das camadas de silano aplicadas diretamente sobre as chapas de aço-carbono ABNT 1008 pela técnica de imersão, como uma proteção contra a corrosão. O estudo compreendeu a avaliação do comportamento das monocamadas de BTSE [Bis-1,2-(trietoxisilil)etano], VS (Viniltrietoxisilano) e BTSPA [Bis-(y-trimetoxisililpropil)amina], variando as condições de cura (tempo e temperatura) e também da dupla camada de silano. A dupla camada consistiu na combinação de BTSE como primeira camada e uma segunda camada de VS ou BTSPA. A espectroscopia de impedância eletroquímica (EIS) em solução de NaCl 0,1 M possibilitou detectarem a resistência à corrosão das camadas de silano, revelando que a sua eficiência aumenta com o aumento da temperatura e do tempo de cura e também que uma dupla camada apresenta um efeito protetor mais eficiente que o das monocamadas. Assim, a dupla camada de BTSE + BTSPA forneceu o melhor resultado, comprovando que confere melhor proteção ao aço-carbono. Com a medida ângulo de contato foi possível caracterizar a hidrofobicidade da superfície metálica revestida com o filme de silano, constatando-se que as camadas de BTSE...

Estudo da corrosão localizada da liga de alumínio 7475-T761 por espectroscopia de impedância eletroquímica global e local em meio de sulfato de sódio.; Localized corrosion study of aluminum alloy 7475-T761 in sulfate medium using global and local electrochemical impedance spectroscopy.

Ferrari, Jean Vicente
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 20/07/2011 PT
Relevância na Pesquisa
66.54%
As ligas de Al utilizadas na indústria aeroespacial com finalidade estrutural apresentam microestrutura complexa devido aos tratamentos termo-mecânicos a que são submetidas visando o aumento da resistência mecânica. Estas ligas se caracterizam pela presença de um grande número de intermetálicos (IMs) em sua microestrutura, os quais possuem atividade eletroquímica diferente da matriz provocando problemas de corrosão localizada devido à formação de microcélulas galvânicas. Na última década a espectroscopia de impedância eletroquímica (LEIS) tem se estabelecido como uma poderosa técnica na elucidação de aspectos locais relacionados à corrosão, e também tem servido para estudos de aspectos teóricos referentes à distribuição de potencial e corrente na superfície de eletrodos e suas correlações com a reatividade superficial. Esta técnica se baseia na análise de diferentes impedâncias locais obtidas por meio de um bi-eletrodo posicionado nas proximidades do eletrodo de trabalho. O presente trabalho visa estudar a corrosão localizada da liga de Al 7475-T761, utilizada na estrutura de asas e na fuselagem de aeronaves, em meios contendo íons sulfato por meio de espectroscopia de impedância eletroquímica global (EIS) e por LEIS...

Electrochemical behaviour of heat-treated Al-Zn-Mg alloys in chloride solutions containing sulphate

Moreira, A. H.; Benedetti, A. V.; Sumodjo, PTA; Garrido, J. A.; Cabot, P. L.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 2823-2831
ENG
Relevância na Pesquisa
76.39%
The electrochemical corrosion and passivation of Al-5Zn-1.7Mg-0.23Cu-0.053Nb alloys, submitted to different heat treatments (cold-rolled, annealed, quenched and aged, and quenched in two steps and aged), in sulphate-containing chloride solutions, has been studied by means of cyclic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). The cyclic polarization curves showed that sulphate addition to the chloride solution produced a poor reproducible shift of the breakdown potential to more positive potentials. The repassivation potentials, much more reproducible, and practically separating the passive from the pitting potential region, were slightly displaced in the negative direction with that addition. When the alloys were potentiodynamically polarized in the passive potential region, sulphate was incorporated in the oxide film, thus precluding chloride ingress. In addition, Zn depletion was favoured, whereas Mg losses were avoided. Different equivalent circuits corresponding to different alloys and potentials in the passive and pitting regions were employed to account for the electrochemical processes taking place in each condition. This work shows that sulphate makes these alloys more sensitive to corrosion...

Avaliação dos filmes oxidos crescidos anodicamente na liga Ti-6Al-7Nb, pela tecnica de impedancia eletroquimica, para aplicação como biomaterial; Evaluation of anodic oxide films in Ti-6Al-7Nb alloy, through electrochemical impedance technique, to be applied as biomaterial

Kenji Kawakami
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 30/08/1996 PT
Relevância na Pesquisa
76.29%
Não informado; In this work is developped a procedure for evaluation of oxides films properties. Through Electrochemical Impedance Spectroscopy, by obtaining from Bode diagrams a capacitance and dissipation coefficient. It is proposed a mathematical model for the metal-oxide-eletrolute system description based on na equivalent circuit. The oxide films properties are evaluated by fitting procedure. The technique . is applied to Ti-6AI-7Nb anodized alloys, used as a substitute for Ti-6AI-4Valloy, in surgical aplications. The results show the possibility of film properties evaluation from direct analysis of Bode diagrams

Relaxation time distribution analysis of a polymer electrolyte fuel cell stack from its impedance response

Lopes, Vitor V.; Silva, R. A.; Novais, Augusto Q.; Rangel, C. M.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em 10/11/2011 ENG
Relevância na Pesquisa
76.29%
Electrochemical impedance spectroscopy (EIS) is an analysis technique that is commonly used as a base diagnostics technique for the in-situ analysis of the kinetic and transport properties of proton exchange membrane (PEM) fuel cells. This work proposes to use the distribution of relaxation times (DRT) as a complementary analysis technique for the interpretation of EIS data. For this purpose, the DRT is deduced for a modified Randles electric circuit composed of a constant phase element (CPE) connected in parallel with a resistance in series with a finite diffusion Warburg element. The experimental EIS data collected from an eight cell PEMFC with an open-air cathode was modeled through the use of two modified Randles circuit representing the fuel-cell electrodes. The analysis of the DRT allows to identify further characteristics of the individual processes that occur at both electrodes, while also being instrumental in detecting the effect on the fuel cell performance of some operating conditions, namely hydrogen flow-rate and current.

Oxide loading effect on the electrochemical performance of LaNiO3 coatings in alkaline media

Soares, C. O.; Silva, R. A.; Carvalho, M. D.; Jorge, M. E. Melo; Gomes, A.; Rangel, C. M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2013 ENG
Relevância na Pesquisa
76.32%
LaNiO3 film electrodes were prepared by brush painting using nickel-foam supports in order to increase its surface area available for electrochemical reactions. Loadings varying between 20 and 140 mg cm-2 were tested. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to evaluate the coatings roughness (Rf) and morphology (f) factors, complemented by optical microscopy observations. The values obtained from the two methods are in excellent agreement. The Rf values, ranging from 848 ± 50 to 4260 ± 60, are within the highest in the open literature. A simulation, of the effect of the oxide loading on the coatings Rf values, was performed using just the experimental values of the roughness factors for oxide free foam and pelleted electrodes. It was found that the increase of oxide loading causes a quasi linear increase of the electrodes active surface area. Simulated values were in excellent agreement with the experimental roughness factors and pore resistances obtained by CV and EIS. The electrodes were tested for oxygen evolution.

Characterization and electrochemical behaviour of nanostructured calcium samarium manganite electrodes fabricated by RF-Magnetron Sputtering

Barrocas, B.; Sério, S.; Rovisco, A.; Nunes, Y.; Sá, A. I. Correia de; Pereira, M. I. da Silva; Jorge, M. E. Melo
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2014 ENG
Relevância na Pesquisa
76.28%
Ca1-xSmxMnO3(0 . x . 0.4) films were successfully fabricated on Indium Tin Oxide (ITO) coated quartzglass substrates by radio frequency magnetron sputtering technique (RF- magnetron sputtering) fromcompacted nanosized powder targets, and subsequent annealing at 800.C in air, for 6 h. X-ray diffrac-tion shows a pure typical perovskite phase for x . 0.1. Scanning electron microscopy and atomic forcemicroscopy revealed that the films surface is dense, with low roughness, depending on the Sm content, even though a few cracks were observed. Crystallite size was found to decrease with the Sm content. Theelectrodes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The oxide electrode fs capacitance was estimated using both techniques and the corresponding roughness factors evaluated. The values obtained from the two methods show a good agreement. A com-parison between the voltammetric data and those referred in the literature allowed finding out that theredox reaction occurring at the electrode surface involves the pair Mn4+/Mn3+. EIS measurements con-firm the voltammetric data and they also give additional information about the film porosity and the charge transfer resistance. This last parameter is associated with the oxidation and reduction of the pairMn3+/Mn4+and after normalized by the roughness factor shows an increase with samarium content.

Comparative study between the electrochemical behavior of TiN, TiCxNy and CrN hard coatings by using microscopy and electrochemical techniques

Senna,L.F.; Achete,C.A.; Simão,R.A.; Hirsch,T.
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2001 EN
Relevância na Pesquisa
76.37%
Hard thin TiN, TiCxNy and CrN films deposited by Physical Vapor Deposition (PVD) techniques onto steel substrates were immersed in an aggressive environment and evaluated by Atomic Force Microscopy (AFM) and Electrochemical Impedance Spectroscopy (EIS). The mechanical and electrochemical behavior, as well as the microstructure of TiCxNy depended directly on the contents of carbon and nitrogen in the coating. The best results were obtained with stoichiometric coatings that are presented in this work. Although a small amount of pinholes could be observed, the electrochemical performance of TiN film was poorer than the stoichiometric TiCxNy coating. However, the CrN films showed the highest initial and residual corrosion resistance values, probably due to their dense structure.

Plasmonic-Based Electrochemical Impedance Spectroscopy: Application to Molecular Binding

Lu, Jin; Wang, Wei; Wang, Shaopeng; Shan, Xiaonan; Li, Jinghong; Tao, Nongjian
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
66.48%
Plasmonic-based electrochemical impedance spectroscopy (P-EIS) is developed to investigate molecular binding on surfaces. Its basic principle relies on the sensitive dependence of surface plasmon resonance (SPR) signal on surface charge density, which is modulated by applying an AC potential to a SPR chip surface. The AC component of the SPR response gives the electrochemical impedance, and the DC component provides the conventional SPR detection. The plasmonic-based impedance measured over a range of frequency is in quantitative agreement with the conventional electrochemical impedance. Compared to the conventional SPR detection, P-EIS is sensitive to molecular binding taking place on the chip surface, and less sensitive to bulk refractive index changes or non-specific binding. Moreover, this new approach allows for simultaneous SPR and surface impedance analysis of molecular binding processes.

Electrochemical Impedance Spectroscopy Investigation on the Clinical Lifetime of ProTaper Rotary File System

Penta, Virgil; Pirvu, Cristian; Demetrescu, Ioana
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
66.5%
The main objective of the current paper is to show that electrochemical impedance spectroscopy (EIS) could be a method for evaluating and predicting of ProTaper rotary file system clinical lifespan. This particular aspect of everyday use of the endodontic files is of great importance in each dental practice and has profound clinical implications. The method used for quantification resides in the electrochemical impedance spectroscopy theory and has in its main focus the characteristics of the surface titanium oxide layer. This electrochemical technique has been adapted successfully to identify the quality of the Ni-Ti files oxide layer. The modification of this protective layer induces changes in corrosion behavior of the alloy modifying the impedance value of the file. In order to assess the method, 14 ProTaper sets utilized on different patients in a dental clinic have been submitted for testing using EIS. The information obtained in regard to the surface oxide layer has offered an indication of use and proves that the said layer evolves with each clinical application. The novelty of this research is related to an electrochemical technique successfully adapted for Ni-Ti file investigation and correlation with surface and clinical aspects.

Effect of conductivity and frequency on detection of heterogeneities in solid/liquid interfaces using local electrochemical impedance Theoretical and experimental study

Montoya, Rodrigo; García-Galván, Federico R.; Jiménez Morales, Antonia; Galván Sierra, Juan Carlos
Fonte: Elsevier Publicador: Elsevier
Tipo: info:eu-repo/semantics/acceptedVersion; info:eu-repo/semantics/article Formato: application/pdf
Publicado em 01/02/2012 ENG
Relevância na Pesquisa
76.26%
This short communication demonstrates, by solving the Laplace equation with proper boundary conditions (BC) using finite element method (FEM), that it is not possible to establish a correlation between what happens in the electrolyte near an active boundary and what really occurs at the actual boundary if adequate ranges of electrolyte conductivity and input AC signal frequency are not selected, especially when inhomogeneities approximated by Neumann BC are present. Experimental evidence obtained by local electrochemical impedance mapping (LEIM) supports the theoretical results.; This work has been supported by the Ministry of Science and Inno-vationofSpain(MAT2006-04486andIPT-020000-2010-0001Projects)

The effect of hydrogen peroxide on the electrochemical behaviour of Ti-13Nb-13Zr alloy in Hanks' solution

Assis,Sérgio Luiz de; Costa,Isolda
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2006 EN
Relevância na Pesquisa
76.35%
Titanium alloys are largely used for biomedical applications mainly due to their high corrosion resistance resulting from the protective oxide film formed on their surface. The literature, however, has pointed out discrepancies between in vitro tests and in vivo tests. These discrepancies have been ascribed to hydrogen peroxide (H2O2) generated by inflammatory reactions. In this investigation the electrochemical behaviour of a Ti-13Nb-13Zr alloy, which was developed as material for implants, has been evaluated in Hanks' solution, with and without H2O2. The evolution of the electrochemical behavior was monitored by electrochemical impedance spectroscopy (EIS) and the results were fitted to an equivalent circuit that simulates an oxide film as a duplex layer structure composed of an inner barrier layer and an outer porous layer. In the solution without H2O2, the oxide film was very stable during the whole test period. On the other hand, in the solution with H2O2, the EIS results varied significantly, indicating a progressive decrease in the barrier layer resistance until 35 days which was followed by the restoration of the barrier layer protective characteristics against corrosion, either due to its growth or to its self-healing after partial consumption of the oxidant agent. The oxide film formed on the Ti alloy samples after 125 days of immersion in Hanks' solution...

Electrochemical impedance spectroscopy modeling using the dis-tribution of relaxation times and error analysis for fuel cells

Lopes, Vitor V.; Rangel, C. M.; Novais, Augusto Q.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 ENG
Relevância na Pesquisa
76.21%
This paper proposes a new approach to determine the distribution of relaxation times (DRT) directly from the electro-chemical impedance spectroscopy (EIS) data, i.e. without the use of an equivalent electrical circuit model. The method uses a generalized fractional-order Laguerre basis to represent EIS where both the parameters of the basis and their co-efficients are estimated by solving a nonconvex minimization problem. Furthermore, the DRT confidence region is de-termined to assess the accuracy and precision of the DRT estimate. The approach is applied to analyze the dominant dynamic properties of an open-cathode hydrogen fuel-cell under different current and air-flow conditions. Results showed that the estimated DRT closely reconstructs EIS data even when there is a higher variance at smaller relaxation times.

Morphological and Electrochemical Analysis of a Self-Assembled Monolayer of 3-Mercaptopropionic Acid on Gold Electrode; Análise Morfológica e Eletroquímica de uma Monocamada do Ácido 3-Mercaptopropiônico sobre Eletrodo de Ouro

Cleverson S. Santos; Universidade Estadual de Ponta Grossa; Rosana Mosanha; Universidade Estadual de Ponta Grossa; Luis Fernando Marchesi; Universidade Tecnológica Federal do Paraná; Christiana A. Pessôa; Universidade Estadual de Ponta Grossa
Fonte: Revista Virtual de Química Publicador: Revista Virtual de Química
Tipo: ; Formato: binary/octet-stream
Publicado em 18/09/2015 PT
Relevância na Pesquisa
76.28%
This paper investigates the morphology of a polycrystalline gold electrode modified with a monolayer of 3-MPA (Au/MPA) constructed in different immersion times and thiol concentrations, using the techniques of electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). It was verified that both surface roughness as the capacitance of the Au/MPA are dependent on the concentration and the organization of the 3-MPA molecules adsorbed on the gold electrode surface. Voltammetric results demonstrated that the coverage is dependent on the immersion time and concentration of the 3-MPA solution. These results are in agreement with the EIS results which showed the increased in charge transfer resistance (Rct) as a function of the immersion time, due to increase of the electron transfer block caused by the monolayer. However, the Rct increased until 180 min. and higher immersion times did not show significant variations in resistance. DOI: 10.5935/1984-6835.20150095; Este artigo investiga a morfologia do eletrodo de ouro policristalino modificado com monocamada do 3-MPA (Au/MPA) construído em diferentes tempos de imersão e concentrações do tiol, utilizando as técnicas de espectroscopia de impedância eletroquímica (EIE) e microscopia de força atômica. Verificou-se que tanto a rugosidade da superfície...

Evaluation of Corrosion Behavior of Copper in Chloride Media Using Electrochemical Impedance Spectroscopy (EIS)

Nagiub,A.M.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2005 EN
Relevância na Pesquisa
76.39%
The corrosion behavior of pure copper rotating cylinder electrode (RCE) exposed to 3% NaCl or artificial seawater prepared as Vätäänen nine salt solution (VNSS) has been studied using electrochemical impedance spectroscopy (EIS) and polarization techniques. EIS experiments for copper RCE were carried out at different rotation rate from 0 rpm to 1600 rpm. Polarization resistance (Rp) values were obtained from both EIS and polarization experiments. Excellent agreement between impedance and polarization data is observed. RCE experiments demonstrated that Ecorr and corrosion rate for copper depend linearly on rotation speed r0.7. The results obtained showed that EIS is a powerful electrochemical method to follow the change of corrosion mechanisms.

Inhibitor for the corrosion of mild steel in H2SO4

Patel,Niketan S.; Jauhari,Smita; Mehta,Girishkumar N.
Fonte: South African Journal of Chemistry Publicador: South African Journal of Chemistry
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
Relevância na Pesquisa
66.52%
An extract of Terminalia chebula fruits was investigated as a corrosion inhibitor of mild steel in 0.5 M H2SO4 by means of conventional mass loss, electrochemical polarization, electrochemical impedance spectroscopy and scanning electron microscopy. The mass loss results showed that the extract of Terminalia chebula is an excellent corrosion inhibitor, electrochemical polarization data revealed the mixed mode of inhibition and the results of electrochemical impedance spectroscopy showed that the change in the impedance parameters, charge transfer resistance and double layer capacitance with the change in concentration of the extract is due to the adsorption of active molecules leading to the formation of a protective layer on the surface of mild steel. Scanning electron microscopic studies provided confirmatory evidence of an improved surface condition, due to adsorption, for corrosion protection.