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‣ Interaction of BSA protein with copper evaluated by electrochemical impedance spectroscopy and quartz crystal microbalance

Pinto, Edilson M.; Soares, David M.; Brett, Christopher M. A.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
Português
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The interaction of bovine serum albumin (BSA) protein with copper in phosphate buffer solution has been studied by a combination of electrochemical impedance spectroscopy (EIS) close to the open circuit potential, with simultaneous monitoring by the electrochemical quartz crystal microbalance (EQCM), in order to throw light on BSA adsorption. Copper films were electroplated onto gold quartz crystals and mounted in the EQCM. Experiments were conducted in the presence and absence of dissolved oxygen and of BSA and the results show the influence of O2 on the protein/metal interaction and also show specific interactions between BSA and copper. The good reproducibility obtained in these experiments suggests future application to other systems and which should lead to a better understanding of the use of such types of protein as corrosion inhibitors.; http://www.sciencedirect.com/science/article/B6TG0-4RSYCCD-5/1/a45edf5c4389350ee3577b6142716862

‣ Estudos de Sinterização e de Envelhecimento Térmico de Cerâmicas de Zircônia - Ítria por Espectroscopia de Impedância; Sintering and Thermal Ageing Studies of Zirconia - Yttria Ceramics by Impedance Spectroscopy

Florio, Daniel Zanetti de
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 24/08/1998 Português
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Eletrólitos sólidos cerâmicos de ZrO2:8% mol Y2O3 foram preparados com pós de três origens: pó comercial fabricado pela Nissan (Japão), pó obtido por coprecipitação dos hidróxidos no IPEN e pó obtido por mistura de óxidos (utilizando-se ZrO2 produzido na Usina de Zircônio do IPEN e Y2O3 (USA) de pureza superior a 99,9%). Esses materiais de partida foram analisados pelas seguintes técnicas: fluorescência de raios X para a determinação dos teores de ítrio, difração de raios X para a determinação das fases, sedimentação para a determinação da distribuição do tamanho de partículas, adsorsão gasosa (BET) para a determinação da área de superfície específica e microscopia eletrônica de transmissão para a determinação do tamanho médio de partícula. Amostras compactadas foram analisadas por dilatometria para avaliar os estágios de sinterização. As amostras sinterizadas foram caracterizadas por difração de raios X para análise de fases e microscopia eletrônica de varredura para análise da morfologia dos grãos. Análises por espectroscopia de impedância foram feitas para acompanhar o envelhecimento térmico dos eletrólitos sólidos de zircônia-ítria a 600 ºC, temperatura de trabalho do sensor permanente de oxigênio...

‣ "Estudo da eletro-oxidação de monóxido de carbono sobre eletrocatalisadores suportados por espectroscopia de impedância eletroquímica"; Study of carbon monoxide electro-oxidation on supported electrocatalysts by electrochemical impedance spectroscopy

Ciapina, Eduardo Gonçalves
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 16/02/2006 Português
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O presente trabalho estudou comparativamente, do ponto de vista fundamental, a reação de eletro-oxidação de monóxido de carbono (CO) em meio ácido, sobre Pt75Sn25/C, Pt65Ru35/C e Pt/C através da Espectroscopia de Impedância Eletroquímica. Os materiais foram preparados por redução com ácido fórmico e caracterizados fisicamente por EDX e DRX de alta intensidade e eletroquimicamente por voltametria. Previamente aos estudos de Impedância, foram realizados estudos potenciodinâmicos da reação de eletro-oxidação de CO adsorvido (?Stripping de CO?) e a oxidação de CO em uma solução saturada de CO. Para os materiais Pt65Ru35/C e Pt/C, estes estudos mostraram que há um deslocamento de potencial do inicio da oxidação para valores mais positivos quando CO está presente em solução se comparado a oxidação (stripping) de CO, devido a competição de sítios de adsorção entre moléculas de CO e H2O, responsáveis pela reação. Por outro lado, no material bimetálico Pt75Sn25/C a presença de CO em solução não influenciou de maneira significativa o potencial de inicio da oxidação, confirmando a ausência de adsorção competitiva neste material. A curva de polarização em estado estacionário revelou que, dentre os 3 materiais estudados...

‣ Utilization of electrochemical impedance spectroscopy for monitoring bornite (CU5FeS4) oxidation by Acidithiobacillus ferrooxidans

Bevilaqua, Denise; Acciari, Heloisa Andréa; Arena, Fabiana A.; Benedetti, Assis V.; Fugivara, Cecilio S.; Tremiliosi Filho, Germano; Garcia Junior, Oswaldo
Fonte: Pergamon-Elsevier B.V. Ltd Publicador: Pergamon-Elsevier B.V. Ltd
Tipo: Artigo de Revista Científica Formato: 254-262
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); In this work, the monitoring of the bacterial and chemical dissolution of bornite was evaluated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS); the mineral surface was examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The analysis of CV results allowed attributing the different peaks observed in both direct and reverse potential scanning to the oxidation of bornite to a secondary covellite and its reduction via different non stoichiometric copper sulphides intermediaries. EIS data for bornite were obtained in control medium up to 78 h of immersion, when a cellular suspension of A. ferrooxidans was added and the experiments continued up to a 192 h of test. The EIS response was different when bacteria were added in the beginning of the test or after some hours of immersion in acid solution. The experiments were performed in different cell configurations and a model of the electrode/electrolyte interface. The correspondent equivalent electrical circuit was used to fit impedance spectra for all studied conditions. A common equivalent circuit used for corrosion processes where anodic (degradation of the mineral) and cathodic (oxygen reduction) reactions occur in parallel...

‣ Electrochemical impedance spectroscopy as a tool to estimate thickness in PB films

Gimenez-Romero, D.; Bueno, P. R.; Castano, C.; Gabrielli, C.; Perrot, H.; Garcia-Jareno, J. J.; Vicente, F.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 371-374
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The analysis of the faradaic impedance of electroactive films provides a characteristic point from which it is possible to estimate the thickness of thin films. Thus, electrochemical impedance spectroscopy was used in this paper as a fast and easy technique to estimate this thickness. The proposed method was checked on PB films. (c) 2006 Elsevier B.V. All rights reserved.

‣ Oxidative dissolution of chalcopyrite by Acidithiobacillus ferrooxidans analyzed by electrochemical impedance spectroscopy and atomic force microscopy

Bevilaqua, D.; Diez-Perez, I; Fugivara, C. S.; Sanz, F.; Benedetti, A. V.; Garcia, O.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 79-84
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The microbiological leaching of chalcopyrite (CuFeS2) is of great interest because of its potential application to many CuFeS2-rich ore materials. However, the efficiency of the microbiological process is very limited because this mineral is one of the most refractory to bacterial attack. Knowledge of bacterial role during chalcopyrite oxidation is very important in order to improve the efficiency of bioleaching operation. The oxidative dissolution of a massive chalcopyrite electrode by Acidithiobacillus ferrooxidans was evaluated by electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). A massive chalcopyrite electrode was utilized in a Tait-type electrochemical cell in acid medium for different immersion times in the presence or absence of bacterium. The differences observed in the impedance diagrams were correlated with the adhesion process of bacteria on the mineral surface. (C) 2004 Elsevier B.V. All rights reserved.

‣ Impedance spectroscopy analysis of TiO(2) thin film gas sensors obtained from water-based anatase colloids

Ponce, M. A.; Parra, R.; Savu, R.; Joanni, E.; Bueno, P. R.; Cilense, M.; Varela, José Arana; Castro, M. S.
Fonte: Elsevier B.V. Sa Publicador: Elsevier B.V. Sa
Tipo: Artigo de Revista Científica Formato: 447-452
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); In this work impedance spectroscopy technique was employed in order to characterize the gas-sensing behavior of undoped titanium dioxide(TiO(2)) polycrystalline thin films. The electrical measurements were performed in a sensor-testing chamber that allows independent control of temperature, pressure, gas composition and flow rate. Frequency measurements, in the range from 40 Hz to 110 MHz,were performed in order to evaluate the gas sensor response of the samples as a function of temperature (50-350 degrees C) and surrounding atmosphere (vacuum Or air at atmospheric pressure). Impedance spectroscopy is a very useful and important technique clue to the possibility of using this method for discriminating between grain boundary capacitance (C(gb)) and grain boundary resistance (R(gb)) contributions. Therefore, a simple model taking into account variations in the intergranular potential barriers is proposed in this work. (C) 2009 Elsevier B.V. All rights reserved.

‣ Using the electrochemical impedance spectroscopy to characterize carbon steel in biodiesel medium

Akita, A. H.; Fugivara, C. S.; Aoki, I. V.; Benedetti, A. V.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 71-77
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Electrochemical impedance spectroscopy measurements using two carbon steel electrodes in soybean biodiesel medium, produced by methylic route, were performed in an electrochemical cell that allows positioning the two electrodes face-to-face. To retain the biodiesel between the electrodes and prevent its leakage a porous membrane soaked in biodiesel was used. The amplitude of the AC potential and the area of the electrodes were varied. The linearity between disturbance and response signals was observed for tests when the amplitude of the AC potential was lower than 1500 mV (rms). The electrical resistance of biodiesel dominates the global response and carbon steel presents low corrosion, which is observed only at low frequency, and was confirmed by chemical tests performed in the membrane. In conclusion the electrical resistance of biodiesel can be estimated using electrochemical impedance spectroscopy with two electrodes set up. ©The Electrochemical Society.

‣ PERFORMANCE EVALUATION OF GENE EXPRESSION PROGRAMMING IN IMPEDANCE SPECTROSCOPY FOR SENSOR MODELLING

Ramos, Pedro M.; Janeiro, Fernando M.
Fonte: IMEKO World Congress Publicador: IMEKO World Congress
Tipo: Aula
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This paper describes the recent improvements in the use of gene expression programming and genetic algorithms in impedance spectroscopy, namely in sensor modelling. Insight is given in the inner workings of the gene expression programming while highlighting the proposed improvements. The performance of the improved algorithm is also analyzed. It is further validated by the successful application to measurements of a real sensor.

‣ Gene expression programming for automatic circuit model identification in impedance spectroscopy: Performance evaluation

Ramos, Pedro M.; Janeiro, Fernando M.
Fonte: Measurement Publicador: Measurement
Tipo: Artigo de Revista Científica
Português
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Circuit/model identification is applied to impedance spectroscopy when there is no prior knowledge of the inner workings of the sensor or process under analysis. This paper presents a performance assessment of gene expression programming for automatic circuit model identification in impedance spectroscopy. The main objective of this work is to improve gene expression programming specific implementation details, with pre-embedding knowledge regarding circuit simplification rules, in order to improve its performance for circuit identification in impedance spectroscopy. Three different versions of gene expression programming are presented, discussed and analyzed. Insight is given into the inner workings of gene expression programming while highlighting the proposed changes in the three versions. The performance of the improved algorithm is analyzed through numerical simulated impedance data. It is further validated by the successful application to measurements of a real sensor along with a study of its performance on measured data.

‣ Assessing cell polarity reversal degradation phenomena in PEM Fuel Cells by electrochemical impedance spectroscopy

Travassos, Maria Antónia; Lopes, Vitor V.; 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 12/12/2011 Português
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The mechanisms of fuel cell degradation are multiple and not well understood. Irreversible changes in the kinetic and/or transport properties of the cell are fostered by thermal, chemical and mechanical issues which constrain stability, power and fuel cell lifetime. Within the in-situ diagnostics methods and tools available, in-situ electrochemical impedance spectroscopy (EIS) is within the most promising to better understand and categorize changes during fuel cell ageing. In this work, the degradation phenomena caused by cell polarity reversal due to fuel starvation of an open cathode 16 MEA (membrane-electrode assembly) –low power PEM fuel cell (15 W nominal power) is reported using EIS as a base technique. A frequency response analyzer from Solartron Model 1250 was used connected to an electrochemical interface also from Solartron, Model 1286. The range of covered frequencies spans from 37000 Hz to 0.01Hz. Hydrogen is supplied from a metallic hydride small reactor with a capacity of 50 NL H2 at a pressure of 0.2 bar. Measuring the potential of individual cells, while the fuel cell is on load, was found instrumental in assessing the “state of health” of cells at fixed current. Location of affected cells, those farthest away from hydrogen entry in the stack...

‣ Bioelectrical impedance spectroscopy for the assessment of body fluid volumes of term neonates

Ferreira,D.M.; Souza,M.N.
Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/11/2004 Português
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The assessment of fluid volume in neonates by a noninvasive, inexpensive, and fast method can contribute significantly to increase the quality of neonatal care. The objective of the present study was to calibrate an acquisition system and software to estimate the bioelectrical impedance parameters obtained by a method of bioelectrical impedance spectroscopy based on step response and to develop specific equations for the neonatal population to determine body fluid compartments. Bioelectric impedance measurements were performed by a laboratory homemade instrument. The volumes were estimated in a clinical study on 30 full-term neonates at four different times during the first month of life. During the first 24 hours of life the total body water, extracellular water and intracellular water were 2.09 ± 0.25, 1.20 ± 0.19, and 0.90 ± 0.25 liters, respectively. By the 48th hour they were 1.87 ± 0.27, 1.08 ± 0.17, and 0.79 ± 0.21 liters, respectively. On the 10th day they were 2.02 ± 0.25, 1.29 ± 0.21, and 0.72 ± 0.14 liters, respectively, and after 1 month they were 2.34 ± 0.27, 1.62 ± 0.20, and 0.72 ± 0.13 liters, respectively. The behavior of the estimated volume was correlated with neonatal body weight changes, leading to a better interpretation of such changes. In conclusion...

‣ Electrochemical impedance spectroscopy of dodecylsulphate doped polypyrrole films in the dark and under illumination

Martini,Milena; Matencio,Tullio; Alonso-Vante,Nicolás; De Paoli,Marco-Aurélio
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2000 Português
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The morphology, thickness, oxidation and illumination effects in dodecylsulphate doped polypyrrole films can be qualitatively observed by EIS and consist in variations of interfacial and bulk resistances and capacitances of a proposed equivalent circuit. The circuit well with the measured spectra of films obtained with 190 mC cm-2 of synthesis charge density. For thinner films the calculated values observed by electrochemical impedance spectroscopy (EIS) deviate probably due to the absence of diffusion effects. The oxidation of the films diminishes the total impedance over the entire frequency range. The morphology effects are also observed in the entire spectra. The illumination effects are reversible and are observed as expected only in the reduced form of the polymer. The illumination reduces the internal resistance and the space-charge capacitance and increases the charge transfer resistance and the double layer capacitance.

‣ Characterization of Bi4Ge3O12 single crystal by impedance spectroscopy

Macedo,Zélia Soares; Martinez,André Luiz; Hernandes,Antonio Carlos
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2003 Português
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Bi4Ge3O12 (bismuth germanate - BGO) single crystals were produced by the Czochralski technique and their electrical and dielectric properties were investigated by impedance spectroscopy. The isothermal ac measurements were performed for temperatures from room temperature up to 750 °C, but only the data taken above 500 °C presented a complete semicircle in the complex impedance diagrams. Experimental data were fitted to a parallel RC equivalent circuit, and the electrical conductivity was obtained from the resistivity values. Conductivity values from 5.4 × 10(9) to 4.3 × 10-7 S/cm were found in the temperature range of 500 to 750 °C. This electrical conductivity is thermally activated, following the Arrhenius law with an apparent activation energy of (1.41 ± 0.04) eV. The dielectric properties of BGO single crystal were also studied for the same temperature interval. Permittivity values of 20 ± 2 for frequencies higher than 10³ Hz and a low-frequency dispersion were observed. Both electric and dielectric behavior of BGO are typical of systems in which the conduction mechanism dominates the dielectric response.

‣ Impedance spectroscopy study of nanopore arrays for biosensing applications

Kant, K.; Kurkuri, M.; Yu, J.; Shapter, J.G.; Priest, C.; Losic, D.
Fonte: American Scientific Publishers Publicador: American Scientific Publishers
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
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Molecular or ion transport through a single nanopore or nanopore array is a key process in a number of applications including: molecular separation, biosensing, energy storage, nanofluidics and nanoelectronics. In this study, the electrochemical and electrical properties of nanopore arrays were investigated by electrochemical impedance spectroscopy (EIS), to explore their capability towards the development of improved nanopore biosensing devices. Anodic aluminum oxide (AAO) nanopore arrays with square patterns were fabricated by a photolithographic technique for use as a biosensing platform. To demonstrate the potential capability of these nanoporous arrays for biosensing applications, their internal surfaces were functionalized with a self-assembled monolayer of phosphonic acid; followed by covalent bonding with the model binding molecule streptavidin. The sensing performance of the prepared sensing device was characterized by EIS using different concentrations of biotin as probe molecule. The changes in impedance signal in response to the specific binding of biotin molecules to the streptavidin inside nanopores were monitored and explored depending on pore morphology. The results obtained for this system exhibit a high level of sensitivity and selectivity...

‣ The influence of nanopore dimensions on the electrochemical properties of nanopore arrays studied by impedance spectroscopy

Kant, K.; Priest, C.; Shapter, J.G.; Losic, D.
Fonte: MDPI AG Publicador: MDPI AG
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
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The understanding of the electrochemical properties of nanopores is the key factor for better understanding their performance and applications for nanopore-based sensing devices. In this study, the influence of pore dimensions of nanoporous alumina (NPA) membranes prepared by an anodization process and their electrochemical properties as a sensing platform using impedance spectroscopy was explored. NPA with four different pore diameters (25 nm, 45 nm and 65 nm) and lengths (5 μm to 20 μm) was used and their electrochemical properties were explored using different concentration of electrolyte solution (NaCl) ranging from 1 to 100 μM. Our results show that the impedance and resistance of nanopores are influenced by the concentration and ion species of electrolytes, while the capacitance is independent of them. It was found that nanopore diameters also have a significant influence on impedance due to changes in the thickness of the double layer inside the pores.; Krishna Kant, Craig Priest, Joe G. Shapter, and Dusan Losic

‣ Evaluation of the dielectric properties of biodiesel fuels produced from different vegetable oil feedstocks through electrochemical impedance spectroscopy

M'Peko, Jean Claude; Reis, Diany L. S.; Souza, José E.; Caires, Anderson R. L.
Fonte: Elsevier; London Publicador: Elsevier; London
Tipo: Artigo de Revista Científica
Português
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Biodiesel fuels were prepared from different vegetable oil sources (canola, soybean, sunflower, and corn) and studied through electrochemical impedance spectroscopy. The dielectric constant from these biofuels evidenced no important dependence on feedstock, suggesting basically no change in fuels' polarity from varying the raw materials. In a different way, huge variations of the electrical resistivity and relaxation frequency were found when comparing among the studied biodiesels. Our findings demonstrate that these variations are closely associated with changes in the biodiesel viscosity, which is known to modulate charge mobility and was feedstock dependent. Accordingly, the impedance spectroscopy is here revealed to be a sensitive, alternative and reliable analytical approach for distinguishing among different feedstock-related biodiesels and monitoring certain biofuels' properties, like viscosity and interrelated parameters, usually connected with fatty acid structural profiles in biodiesel fuels.; FAPESP; FUNDECT; CNPq

‣ Uso da espectroscopia por impedância para a medição da fração volumétrica de água em emulsões de água e óleo = : The use of impedance spectroscopy for the water concentration measurement in water and oil emulsions; The use of impedance spectroscopy for the water concentration measurement in water and oil emulsions

Matheus Puttinati Casari
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 24/02/2014 Português
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A concentração volumétrica de água na produção de óleo cru é um parâmetro constantemente monitorado para acompanhar as sempre inconstantes propriedades do reservatório assim com para razões de otimização; resumindo, o que é importante é o volume de óleo na produção. A medição da concentração volumétrica de água é geralmente feita em bancada (colhendo uma amostra da produção e analisando-a em um laboratório) ou por sensores que monitoram a concentração em tempo real. Uma das técnicas utilizadas para a medição online da concentração de água é a espectroscopia por impedância. De fato, propriedades dielétricas e condutivas formam a impedância elétrica da solução. Na presente análise foram considerados os dois tipos básicos de emulsão: água em óleo (A/O) e óleo em água (O/A). O objetivo deste trabalho foi comparar a concentração de água medida com a predição do modelo matemático baseado nas medições das propriedades dielétricas e condutivas da solução. As emulsões de água e óleo foram sintetizadas em condições de laboratório. A concentração de água variou entre 13,1% à 41,1% em volume para as emulsões A/O e de 50% à 60% em volume para as emulsões O/A à temperaturas de 25°C à 62°C e salinidade da água de 0 (água deionizada)...

‣ Degradation characteristics of hydroxyapatite coatings on orthopedic TiAlV in simulated physiological media investigated by electrochemical impedance spectroscopy

Souto, R. M.; Laz, Maria M.; Reis, R. L.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /10/2003 Português
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This paper concentrates on the degradation characteristics of hydroxyapatite (HA) coatings on orthopaedic Ti-6Al-4V alloy while immersed in Ringer's salt solution, which were investigated by electrochemical impedance spectroscopy. Electrochemical impedance spectroscopy measurements were used to in situ characterize the electrochemical behavior of the passivated alloy covered with HA during aging in Ringer's solution. Comparison of the electrochemical data for the coated material with that for the uncoated metal substrate was also performed. The characteristic feature that describes the electrochemical behavior of the coated material is the coexistence of large areas of the coating itself with pores where the substrate is exposed to the aggressive media. The interpretation of results was thus performed in terms of a two-layer model of the film, in which the precipitation of hydrated oxide or phosphate compounds seals the pores left by the ceramic coating. The blocking effect due to salt precipitation inside the pores produces an enhancement of the resistance values, thus effectively diminishing the metal ion release in the system.; Collaborative Research Programme (Acción Integrada No. HP1995-0092 and HP1996-0109) between Spain and Portugal.

‣ Preliminary studies of PVC membranes based on 1-furoyl-3-phenylthiourea by impedance spectroscopy

Arias de Fuentes,O; Jimenez,C; Bratov,A
Fonte: Sociedad Mexicana de Física Publicador: Sociedad Mexicana de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2006 Português
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The results obtained from characterization studies of sensor membranes by impedance spectroscopy are presented in this work. The PVC membrane used contained tris(2-ethylhexyl)phosphate as a plasticizer and 1-furoyl-3-phenylthiourea as an ionophore for lead ions. To perform this study, a special cell was designed by the authors. This made it possible to study the behavior of the electrical membrane characteristics with the lead concentrations in the solution. In all cases, the shape of the impedance spectra obtained showed a clear semicircle at high frequencies. This semicircle is associated with the bulk properties of the membranes. It was not possible to resolve another semicircle corresponding to the charge transfer at the interface. For this reason our study focussed on the bulk membrane electric characteristics. Both the dependence of the membrane resistance on the solution lead ion concentration and its behavior in time are reported.