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Synthesis and electrochemical properties of vanadyl phosphate di-hydrate/polyaniline derivatives hybrid films

ZAMPRONIO, Elaine C.; FERREIRA, Joao Paulo L.; OLIVEIRA, Herenilton P.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.13%
Vanadyl phosphate and its hybrid compounds have proven to undergo electrochemical intercalation and de-intercalation of lithium ions, which enables its use as cathode material for Li ion rechargeable batteries. In this context, vanadyl phosphate di-hydrate/polyaniline derivatives hybrid films were synthesized via the exfoliation and reconstruction approach in order to evaluate their potential use as cathode in ion lithium batteries. X-ray diffraction patterns indicate that the lamellar structure of the inorganic matrix is maintained, consistent with the topotactic process. In the scanning electron micrographs, hybrid films exhibit rough surface consisting of warped and cracked crystallites, quite different from vanadyl phosphate di-hydrate square platelets crystallites. Electrochemical evaluation using cyclic voltammetry and charge-discharge galvanostatic techniques shows small differences between the charge and the discharge curves, indicating an irreversibility of the hybrid systems. (C) 2009 Elsevier B.V. All rights reserved.; FAPESP[05/58934-2]; CNPq[484137/2006-9]

Polyazomethine with vinylene and phenantridine moieties in the main chain: Synthesis, characterization, opto(electrical) properties and theoretical calculations

Iwan, Agnieszka; Guimarães, Jeconias Rocha; Santos, Maria Cristina dos; Schab-Balcerzak, Ewa; Krompiec, Michal; Palewicz, Marcin; Sikora, Andrzej
Fonte: SAGE PUBLICATIONS LTD; LONDON Publicador: SAGE PUBLICATIONS LTD; LONDON
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.07%
The opto(electrical) properties and theoretical calculations of polyazomethine with vinylene and phenantridine moieties in the main chain were investigated in the present study. 2,5-Bis(hexyloxy)-1,4-bis[(2,5-bis(hexyloxy)-4-formyl-phenylenevinylene]benzene was polymerized in solution with 3,8-diamino-6-phenylphenanthridine (PAZ-PV-Ph). The temperatures of 5% weight loss (T-5%) of the polyazomethine was observed at 356 degrees C in nitrogen. Electrochemical properties of thin film of the polymer were studied by differential pulse voltammetry. The HOMO level of the PAZ-PV-Ph was at -4.97 eV. The energy band gap (E-g) was detected of approximately similar to 1.9 eV. Energy band gap (E-gopt) was additionally calculated from absorption spectrum and absorption coefficient alpha. The absorption UV-vis spectra of polyazomethine recorded in solution showed a blue shift in comparison with the solid state. HOMO-LUMO levels and E-g were additionally calculated theoretically by density functional theory and molecular simulations of PAZ-PV-Ph are presented. Current density-voltage (J-U) measurements were performed on ITO/PAZ-PV-Ph/Al, ITO/TiO2/PAZ-PV-Ph/Al and ITO/PEDOT/PAZ-PV-Ph:TiO2/Al devices in the dark and during irradiation with light (under illumination of 1000 W m(-2)). The polymer was tested using AFM technique and roughness (R-a...

Atributos mineralógicos e eletroquímicos, adsorção e dessorção de sulfato em solos paulistas.; Mineralogical and electrochemical properties, sulfate adsorption and desorption in soils from São Paulo state.

Alves, Marcelo Eduardo
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 09/04/2002 PT
Relevância na Pesquisa
46.38%
O presente trabalho teve como objetivo principal avaliar as relações entre a composição mineralógica de solos representativos do Estado de São Paulo e alguns de seus atributos eletroquímicos como o ponto de efeito salino nulo (PESN) e a capacidade de troca aniônica (CTA). Especial atenção foi dada também à quantificação de cargas negativas de caráter permanente e à contrastação dos resultados com a composição mineralógica da fração argila, a qual foi avaliada de forma qualitativa e semiquantitativa. Além dos atributos eletroquímicos supracitados, a adsorção e a dessorção de sulfato, principal forma inorgânica de enxofre presente nos solos sob condições aeróbicas, foram estudadas visando-se à determinação de índices representativos desses fenômenos e à associação dos mesmos com atributos mineralógicos, químicos e eletroquímicos dos solos. Em uma primeira etapa, amostras coletadas em camadas subsuperficiais de quinze solos localizados em diferentes regiões do Estado de São Paulo foram submetidas à uma intensa caracterização mineralógica, química e eletroquímica. Além dessas avaliações, as amostras foram utilizadas como adsorvedores em estudos de adsorção e dessorção de sulfato. Em um momento posterior e por meio do tratamento estatístico dos dados...

Obtenção, caracterização e estudos das propriedades de compósitos formados por xerogéis de pentóxido de vanádio e óxido de tungstênio; Preparation, structural and electrochemical properties of V2O5-WO3 xerogel composite

Bolsoni, Aline Turini
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 29/08/2007 PT
Relevância na Pesquisa
46.29%
O xerogel de pentóxido de vanádio possui estrutura bi-dimensional que viabiliza a intercalação de diferentes espécies como íons, compostos orgânicos e espécies poliméricas. E, quando associeado a outros óxidos de metais transição, tais como, WO3 e MoO3 apresenta uma importância em reações de catálise, pois estes óxidos atuam como promotores em reações como, por exemplo, a redução catalítica seletiva do NOx a NH3 e a oxidação de hidrocarbonetos. Além disso, estes óxidos melhoram as propriedades eletroquímicas e eletrocrômicas, favorecendo assim sua utilização em células fotoquímicas, células para conversão de energia solar e cátodos de baterias e lítio. Dentre estes óxidos, o óxido de tungstênio hidratado foi escolhido não somente por favorecer a dissociação ácida das moléculas, mas também por apresentar uma estrutura lamelar que favorece reações de intercalação sem afetar significativamente sua estrutura original. Neste contexto, o xerogel de óxido misto V2O5/WO3 foi sintetizado e suas propriedades eletroquímicas bem como sua capacidade de intercalação foi investigada. em relação ao comportamento eletroquímico, a melhor resposta foi obtida para o óxido misto com menor concentração de WO3...

Synthesis, optical and electrochemical properties of perylenes dyes for solar cells applications

Torres, Erica; Sequeira, S.; Berberan-Santos, M. N.; Brites, Maria João
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2014 ENG
Relevância na Pesquisa
66.29%
Perylene monoimides or monoanhydrides are being intensively investigated as sensitizers in DSSCs. Keeping only one acceptor group, i.e. imide or anhydride, and introducing a donor group in the 9-position (such as diarylamine) proved to be important in order to obtain a favorable orbital partitioning strength and dipole moment of perylene compounds for DSSCs [1]. One way to control optical and electrochemical properties of perylenes dyes is achieved by functionalizing periand bay positions of perylene core with different substituents. In a simplified view, the peri groups coarsely tune the spectroscopic and electrochemical properties whereas the bay functional groups provide an additional fine tuning [2,3]. Here we report the design and synthesis of new perylene dyes (Figure 1) comprising: (1) a 4-alkoxyphenylamino moiety in the 9-position as a strong donating group, (2) a cyanoacrylic acid as electron acceptor and anchoring group and (3) a triple bond as short and rigid linker between perylene core and the acceptor group [4]. The photophysical properties (i.e. absorption and emission spectra, absorption extinction coefficients, fluorescence quantum yields and lifetime measurements) and electrochemical properties of the new perylene dyes were investigated and all results will be presented and discussed.

Synthesis, photophysical and electrochemical properties of perylene dyes

Torres, Erica; Berberan-Santos, M. N.; Brites, Maria João
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2015 ENG
Relevância na Pesquisa
66.12%
Perylene dyes comprising: (i) 4-alkoxyphenylamino moiety in the 9-position as a strong donating group, (ii) cyanoacrylic acid as electron acceptor and anchoring group and (iii) a triple bond as short and rigid linker between perylene core and the acceptor group have been successfully synthesized. Their photophysical (i.e. absorption and emission spectra, molar extinction coefficients, fluorescence quantum yields and lifetime measurements) and electrochemical properties were investigated. The dyes display intense absorption in the visible exhibit high molar absorption coefficients making them good light harvesting materials for ss-DSCs.

Influence of the preparation procedure on the electrochemical properties of Pani(DMcT-Cu ion)/carbon fiber composites

Canobre,Sheila C.; Biaggio,Sonia R.; Rocha-Filho,Romeu C.; Bocchi,Nerilso
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2003 EN
Relevância na Pesquisa
46.21%
The electrochemical properties of Pani(DMcT-Cu ion)/carbon fiber composites, obtained by electrochemical means, are analysed as a function of the preparation procedure and the different copper salts (CuCl2.2H2O or CuSO4) used as source of Cu2+ ions to be incorporated into the Pani(DMcT)/carbon fiber composite. The composites were prepared according to two procedures: by adding the copper salt directly to the electrolyte during the polyaniline electrosynthesis (procedure A), or by allowing the copper ion to be physically adsorbed onto the carbon fiber prior to the polymer electroformation (procedure B). The electrochemical stability, electrical properties and morphology of the composites were analysed by cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy, respectively.

Influences of heat treatment on the structure and electrochemical properties of Mg0.9Ti0.1Ni hydrogen storage alloys

Huang,HongXia; Huang,KeLong; Liu,SuQin; Chen,DongYang; Zhuang,ShuXin
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
Relevância na Pesquisa
66.21%
In the present study, the effects of heat treatment on the structures and electrochemical properties of Mg0.9Ti0.1Ni hydrogen storage alloys have been investigated in detail. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses showed that the samples exhibited a predominantly amorphous structure. Electrochemical investigations revealed that heat treatment can improve the maximum discharge capacity and cyclic stability of the alloy electrodes. For Mg0.9Ti0.1Ni alloy prepare by ball milling, the value of Cmax was only 229.9 mAh g-1, however, the value reached 331.9 mAh g-1 after heat treatment at 873K for 8 h and then milling. The cycle voltammetry, electrochemical impedance spectroscopy and potentiodynamic polarization indicated that heat treatment not only increased the discharge capacity but also improved the charge/discharge kinetics of Mg0.9Ti0.1Ni alloy.

Effect of fluorination treatment on electrochemical properties of M1Ni3.5Co0.6Mn0.4Al0.5 hydrogen storage alloy

Huang,Hongxia; Huang,Kelong
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/2012 EN
Relevância na Pesquisa
66.17%
The influence of surface treatment by solutions of NH4F, LiF and LiF containing KBH4 on the structure and electrochemical properties of the M1Ni3.5Co0.6Mn0.4Al0.5 hydrogen storage alloy (in which M1 denotes mischmetal) is investigated. The fluorination treatment improves the electrochemical performances of the M1Ni3.5Co0.6Mn0.4Al0.5 alloy. The maximum discharge capacity (Cmax) increases from 314.8 to 325.7 (NH4F), 326.5 (LiF) and 316.4 mAh g-1 (LiF+KBH4). After 60 cycles, the capacity retention rate increases from 83.5 to 84.8% (NH4F), 89.5% (LiF) and 93.9% (LiF+KBH4). The results of the linear polarization and anodic polarization reveal that the exchange current density (I0) and the limiting current density (I L) increase after fluorination treatment, indicating an improvement of the kinetics of the hydrogen absorption/desorption.

Influence of the microstructure on the electrochemical properties of Al-Cr-N coatings deposited by co-sputtering method from a Cr-Al binary target

Quintero,Oscar Mauricio Sánchez; Chaparro,Willian Aperador; Ipaz,Leonid; Barco,Jaime Eduardo Sánchez; Beltrán,Francisco Espinoza; Zambrano,Gustavo
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2013 EN
Relevância na Pesquisa
66.21%
In the present paper, aluminum chromium nitride (Al-Cr-N) films were deposited onto AISI H13 steel substrates by a reactive d.c magnetron co-sputtering system in an atmosphere of Ar/N2 (90/10) gas mixture from a binary target composed of chromium (99.95%) and aluminum (99.99%). Different powers (40, 50, 60, and 70 W) were applied to the target, in order to study the effect of this parameter and the sputtering yield of binary target, on the microstructure and the electrochemical properties of the Al-Cr-N coatings. The corrosion behavior in 3.5 wt. (%) NaCl solution was investigated by electrochemical corrosion tests (Tafel polarization curves and Electrochemical Impedance Spectroscopy (EIS)), and the chemical composition, microstructure and the absorption bands by means of Energy Dispersive X-ray Spectroscopy (EDX), X-ray diffractometry (XRD) and Fourier Transform Infrared Spectroscopy (FTIR), respectively. EIS results showed that the Al-Cr-N coating deposited at 40 W, exhibited the lower porosity and the highest polarization resistance, and subsequently, when the power applied to the binary target increased, the corrosion rate and the porosity increase.

The electrochemical properties of four dental casting suprastructure alloys coupled with titanium implants

Tuna,Suleyman Hakan; Pekmez,Nuran Ozcicek; Keyf,Filiz; Canli,Fulya
Fonte: Faculdade De Odontologia De Bauru - USP Publicador: Faculdade De Odontologia De Bauru - USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2009 EN
Relevância na Pesquisa
56.17%
OBJECTIVES: As the choice of suprastructure alloy to be combined with titanium for the oral cavity is still a much debated issue, the aim of this study was to investigate the electrochemical interaction of the suprastructure/implant couples under the determined experiment conditions. MATERIAL AND METHODS: The potentiodynamic polarization curves and open-circuit potentials (OCP) of four UCLA type suprastructures coupled with straight Swiss Plus implant fixtures were taken in Afnor type artificial saliva solution at 37°C. The concentration of ions leached into artificial saliva solutions was estimated with ICP-MS. SEM images of the margins of suprastructure/implant couples were obtained before and after the electrochemical tests. RESULTS: The OCP value of titanium became passive at the most negative potential. The lowest difference between the initial and constant OCP value was exhibited by the Au based suprastructure. Suprastructures made greater contributions to the potentiodynamic polarization curves of the implant/suprastructure couples. According to the ICP-MS results, Pd based and Au based couples dissolved less than Co-Ni based and Co-Cr based couples. CONCLUSIONS: Within the conditions this study, it may be concluded that the titanium implant forms a stable passive oxide layer in artificial saliva exposed to open air and does not affect the corrosion properties of the suprastructures. Pd based and Au based couples have been found to be more corrosion-resistant than base alloy couples.

Structural characterization and electrochemical properties of Co3O4 anode materials synthesized by a hydrothermal method

Shin, Chorong; Manuel, James; Kim, Dul-Sun; Ryu, Ho-Suk; Ahn, Hyo-Jun; Ahn, Jou-Hyeon
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 09/01/2012 EN
Relevância na Pesquisa
46.24%
Cobalt oxide [Co3O4] anode materials were synthesized by a simple hydrothermal process, and the reaction conditions were optimized to provide good electrochemical properties. The effect of various synthetic reaction and heat treatment conditions on the structure and electrochemical properties of Co3O4 powder was also studied. Physical characterizations of Co3O4 are investigated by X-ray diffraction, scanning electron microscopy, and Brunauer-Emmett-Teller [BET] method. The BET surface area decreased with values at 131.8 m2/g, 76.1 m2/g, and 55.2 m2/g with the increasing calcination temperature at 200°C, 300°C, and 400°C, respectively. The Co3O4 particle calcinated at 200°C for 3 h has a higher surface area and uniform particle size distribution which may result in better sites to accommodate Li+ and electrical contact and to give a good electrochemical property. The cell composed of Super P as a carbon conductor shows better electrochemical properties than that composed of acetylene black. Among the samples prepared under different reaction conditions, Co3O4 prepared at 200°C for 10 h showed a better cycling performance than the other samples. It gave an initial discharge capacity of 1,330 mAh/g, decreased to 779 mAh/g after 10 cycles...

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 EN
Relevância na Pesquisa
56.24%
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

Influence of ammonia and water sorption on the chemical and electrochemical properties of polyacrylic acid and its derivates; Einfluss von Wasser- und Ammoniaksorption auf die chemischen und elektrochemischen Eigenschaften von Polyacrylsäure und deren Derivaten

Hörter, Melanie
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
Relevância na Pesquisa
46.24%
The main achievement of this research work is the elaboration of a phenomenological model that describes water vapour and ammonia gas sorption into polyacrylic acid (PAA) films and explains the associated changes of their chemical and electrochemical properties; it was successfully confronted with experimental results either gathered during the author’s work or previously published. By allowing a deeper understanding of sensing, the model will help further developments of PAA as a material for gas sensing applications. Additionally, as discussed in the opening chapter, the knowledge gained for PAA layers can be transferred to other polymer systems making PAA an interesting gas sorption model system for such materials. The phenomenological model is based on several types of experiments because the varied influences of the sorption processes cannot be observed with one single method only. First type of experiments, already published in literature, had been performed by using chemomechanical sensors as quartz microbalances and electrochemical sensors as resistance measurements and Kelvin Probe set-ups. With the same types of devices the mass uptake upon water vapour and ammonia sorption and the potential change determined in the Kelvin Probe set-up were systematically measured in this work. From these experiments important information about sorption induced changes of the polymer bulk and at the polymer/electrode interface was obtained. To complete the picture of the sorption process...

Influência do grau de redução do óxido de grafeno eletroquimicamente reduzido nas suas propriedades eletroquímicas; Influence of the extent of reduction of the electrochemically reduced graphene oxide on its electrochemical properties

Maiuí Nagáo Lindqquer de Camargo
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 10/02/2015 PT
Relevância na Pesquisa
56.24%
Este trabalho visa demonstrar como o grau de redução do óxido de grafeno eletroquimicamente reduzido (ERGO) pode ser modulado dependendo das condições experimentais utilizadas para se fazer a redução eletroquímica, e como ele influencia nas propriedades eletroquímicas do material final. Esta influência pôde ser constatada por medidas eletroquímicas, de espectroscopia Raman e de fotoelétrons excitados por raios-X (XPS). Através de experimentos eletroquímicos feitos na presença da sonda de ferri/ferrocianeto de potássio, foi possível demonstrar que os eletrodos de ouro modificados com os ERGOs com maiores graus de redução se comportam eletroquimicamente de maneira similar ao não modificado, e portanto, a redução dos grupos oxigenados da superfície do material é importante para que essa similaridade seja atingida. No entanto, essa sonda não permite monitorar o balanço entre grupos oxidados e reduzidos e para fazer isso, foi escolhida uma sonda eletroativa sensível aos grupos oxigenados. Análises feitas na presença de β-nicotinamida adenina dinucleotídeo (NADH) demonstraram que grupos funcionais oxigenados essenciais para a oxidação dessa espécie estavam diminuindo na superfície do material com o aumento do grau de redução deste. Os espectros de Raman e de XPS também confirmaram essa informação. Além disso...

Electrochemical properties of titanium nitride nerve stimulation electrodes: an in vitro and in vivo study

Meijs, Suzan; Fjorback, Morten; Jensen, Carina; Sørensen, Søren; Rechendorff, Kristian; Rijkhoff, Nico J. M.
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 04/08/2015 EN
Relevância na Pesquisa
46.31%
The in vivo electrochemical behavior of titanium nitride (TiN) nerve stimulation electrodes was compared to their in vitro behavior for a period of 90 days. Ten electrodes were implanted in two Göttingen minipigs. Four of these were used for electrical stimulation and electrochemical measurements. Five electrodes were kept in Ringer's solution at 37.5°C, of which four were used for electrical stimulation and electrochemical measurements. The voltage transients measured in vivo were 13 times greater than in vitro at implantation and they continued to increase with time. The electrochemical properties in vivo and the tissue resistance (Rtissue) followed a similar trend with time. There was no consistent significant difference between the electrochemical properties of the in vivo and in vitro electrodes after the implanted period. The differences between the in vivo and in vitro electrodes during the implanted period show that the evaluation of electrochemical performance of implantable stimulation electrodes cannot be substituted with in vitro measurements. After the implanted period, however, the performance of the in vivo and in vitro electrodes in saline was similar. In addition, the changes observed over time during the post-implantation period regarding the electrochemical properties of the in vivo electrodes and Rtissue were similar...

Specific ion effects on the electrochemical properties of cytochrome c

Medda, Lucca; Salis, Andrea; Magner, Edmond
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: info:eu-repo/semantics/article; all_ul_research; ul_published_reviewed
ENG
Relevância na Pesquisa
46.21%
peer-reviewed; The range of salts used as supporting electrolytes in electrochemical studies of redox proteins and enzymes varies widely, with the choice of an electrolyte relying on the assumption that the electrolyte used does not affect the electrochemical properties of the proteins and enzymes under investigation. Examination of the electrochemical properties of the redox protein cytochrome c (cyt c) at a 4,4'-bipyridyl modified gold electrode demonstrates that both the redox potential (E-o') and the faradaic current are influenced by the nature of the electrolyte used, in a manner explained primarily by Hofmeister effects. The faradaic peak currents display an atypical trend on switching from kosmotropic to chaotropic anions, with a maximum current observed in the presence of Cl-. For a series of cations, the peak current increased in the sequence: Li+ (0.34 mu A) Br- (0.35 mu A) > ClO4- (0.35 mu A) > SCN- (0.31 mu A) > F- (0.30 mu A). E-o' decreased by a total of 24 mV across the series F- > Cl- > Br- > ClO4- > SCN- whereas no specific ion effect on E-o' was observed for cations. Factorisation of E-o' into its enthalpic and entropic components showed that while no specific trends were observed, large changes in Delta H-o' and Delta S-o' occurred with individual ions. The effect of anions on the faradaic peak current can be qualitatively explained by considering Collins' empirical rule of 'matching water affinities'. The effect of cations cannot be explained by this rule. However...

Conducting organic polymers with electroactive dopants. Synthesis and electrochemical properties of hexacyanoferrate-doped polypyrrole

Torres-Gómez, G.; Gómez-Romero, P.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 579917 bytes; image/jpeg
ENG
Relevância na Pesquisa
66.21%
8 pages, 7 figures, 1 table.-- Printed version published Dec 4, 1998.-- Full-text version available Open Access at: http://www.cienciateca.com/PPyHCF_Synt_Met_98_98_95.pdf; A systematic study of the synthesis of heacyanoferrate-doped polypyrrole (PPy/HCF) is reported. In addition to the electrochemical growth of films, we report three different modifications of a novel chemical synthesis for the preparation of bulk powdered materials by oxidative polymerization of pyrrole by the acid derivative of HCF. The effect of temperature and duration of the reaction, doping level and aging of the materials obtained on their conductivity has been systematically studied. Higher conductivities are obtained for materials prepared at lower temperatures (0°C). This is associated to a higher content of the doping HCF anion for these lower temperature materials. With time the conductivity of all samples decreases proportionally to the corresponding initial values. Finally, we report the electrochemical properties of these hybrid materials, the cyclic voltammograms of chemical and electrochemical derivatives and their intercalation behavior, which shows a deintercalation of the electroactive HCF anion in aqueous electrolytes but not in organic (propylene carbonate...

Morphological, structural and electrochemical properties of lithium iron phosphates synthesized by Spray Pyrolysis

Martín Hernández, María Isabel; Gómez, L. S.; Meatza, I. de; Bengoechea, M.; Cantero, I.; Rabanal, M. Eugenia
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 1403281 bytes; application/pdf
ENG
Relevância na Pesquisa
56.12%
Article in Press, Accepted Manuscript.; In the field of materials for Lithium ion batteries, the lithium iron phosphate LiFePO4 has been proven for use as a positive electrode due to its good resistance to thermal degradation and overcharge, safety and low cost. The use of nanostructured materials would improve its efficiency. This work shows the results of the synthesis of nanostructured materials with functional properties for Lithium batteries through aerosol techniques. The Spray Pyrolysis method allows synthesizing nanostructured particles with spherical geometry, not agglomerates, with narrow distribution of particle size and homogeneous composition in respect to a precursor solution. Experimental techniques were focused on the morphological (SEM and TEM), structural (XRD and HRTEM-SAED), chemical (EDS) and electrochemical characterization.; The authors gratefully appreciate the financial support of the Ministry for Education and Science of Spain in the project “Advanced materials for Lithium batteries through alternative synthesis” (PIROLION project-PROFIT 2007-2008), MAT2007-64486-C07-05 (FEDER) and the Juan de la Cierva program JCI-2005-1892-13 (M.I. Martín). We thank I. Boyano for helpful discussions and A. Lago for experimental aid. The assistance in TEM characterization of the Electron Microscopy and Citometry Center...

The electrochemical properties of four dental casting suprastructure alloys coupled with titanium implants

Tuna, Suleyman Hakan; Pekmez, Nuran Ozcicek; Keyf, Filiz; Canli, Fulya
Fonte: Universidade de São Paulo. Faculdade de Odontologia de Bauru Publicador: Universidade de São Paulo. Faculdade de Odontologia de Bauru
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; Formato: application/pdf
Publicado em 01/10/2009 ENG
Relevância na Pesquisa
56.17%
OBJECTIVES: As the choice of suprastructure alloy to be combined with titanium for the oral cavity is still a much debated issue, the aim of this study was to investigate the electrochemical interaction of the suprastructure/implant couples under the determined experiment conditions. MATERIAL AND METHODS: The potentiodynamic polarization curves and open-circuit potentials (OCP) of four UCLA type suprastructures coupled with straight Swiss Plus implant fixtures were taken in Afnor type artificial saliva solution at 37°C. The concentration of ions leached into artificial saliva solutions was estimated with ICP-MS. SEM images of the margins of suprastructure/implant couples were obtained before and after the electrochemical tests. RESULTS: The OCP value of titanium became passive at the most negative potential. The lowest difference between the initial and constant OCP value was exhibited by the Au based suprastructure. Suprastructures made greater contributions to the potentiodynamic polarization curves of the implant/suprastructure couples. According to the ICP-MS results, Pd based and Au based couples dissolved less than Co-Ni based and Co-Cr based couples. CONCLUSIONS: Within the conditions this study, it may be concluded that the titanium implant forms a stable passive oxide layer in artificial saliva exposed to open air and does not affect the corrosion properties of the suprastructures. Pd based and Au based couples have been found to be more corrosion-resistant than base alloy couples.