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Propiedades eléctricas en membranas de complejos electrolitos poliméricos PVA-O...
Arbey Villegas,Edgar; Humberto Castillo,José; Bueno,Paulo RobertoElectrolitos poliméricos conductores de iones de litio, basados en alcohol de polivinilo (PVA-OH) complejado con la sal Li2SO4 y diferentes relaciones de porcentaje en peso de plastificante PEG400 fueron preparados por la técnica de solución utilizando agua desionizada como disolvente. El estudio FTIR confirma la formación del complejo polímero-sal. Las curvas de descomposición térmica obtenidas por termogravim...
Determinação dos parâmetros cinéticos e termodinâmicos da adsorção de L-cisteín...
Santos,Adriano dos; Silva,Josiel José da; Bueno,Paulo Roberto; Watanabe,Ailton MassaitiThis article discusses the adsorption kinetics of a L-cysteine monolayer onto a gold surface by means of information obtained through the QCM technique. The results indicate that the adsorption process is rapid and follows the Langmuir isotherm, in which adsorption and desorption are considered. From these measurements the following parameter values were obtained: k d = (4.2 ± 0.4) x 10-3 s-1, k a = 75 ± 6 M-1 ...
Microstructural and nonohmic properties of ZnO.Pr6O11 CoO polycrystalline system
Ramírez,Miguel Angel; Fernández,José Francisco; Frutos,José de; Bueno,Paulo Roberto; Longo,Elson; Varela,José AranaThe microstructure and electrical properties of varistors composed of (95-x) ZnO + x Pr6O11 + 5 CoO (ZPC), (x = 0.1, 0.5 and 1.0) and sintered at 1300 and 1350 °C, were investigated. According to X-ray diffraction, several phases (ZnO, Pr2O3 and Pr2CoO4) are present when x = 1.0. Using Scanning Electron Microscopy, all of these compositions contain precipitates. These phases are important regarding the developm...
Grain size effect on the electrical response of SnO2 thin and thick film gas se...
Savu,Raluca; Ponce,Miguel Adolfo; Joanni,Ednan; Bueno,Paulo Roberto; Castro,Miriam; Cilense,Mario; Varela,José Arana; Longo,ElsonPorous nano and micro crystalline tin oxide films were deposited by RF Magnetron Sputtering and doctor blade techniques, respectively. Electrical resistance and impedance spectroscopy measurements, as a function of temperature and atmosphere, were performed in order to determine the influence of the microstructure and working conditions over the electrical response of the sensors. The conductivity of all sample...
Dielectric behaviour of CaCu3Ti4O12-epoxy composites
Ramajo,Leandro Alfredo; Ramírez,Miguel Angel; Bueno,Paulo Roberto; Reboredo,María Marta; Castro,Miriam SusanaThe dielectric behavior of composite materials (epoxy resin - barium titanate and epoxy - CCTO) was analysed as a function of ceramic amount. Composites were prepared by mixing the components and pouring them into suitable moulds. In some compositions, the matrix was reduced by tetrahydrofuran (THF) incorporation. Samples containing various amounts of ceramic filler were examined by TG/DTA and scanning electron...
Electronic ceramics based on polycrystalline SnO2, TiO2 and (Sn xTi1-x)O2 solid...
Bueno,Paulo Roberto; Varela,José AranaIn the present text we discuss on electronic properties arising from polycrystalline semiconductor ceramics of SnO2, TiO2 and (Sn xTi1-x)O2 solid solution rutile-type structure. This is intended to be a short overview of the most recent papers in this area. One of the most important content discussed in this text is based on sinterability of these polycrystalline ceramics, which depends on the target applicatio...
Evaluation of rare earth oxides doping SnO2.(Co1/4,Mn3/4)O-based varistor system
Dibb,Alessandro; Cilense,Mario; Bueno,Paulo Roberto; Maniette,Yves; Varela,José Arana; Longo,ElsonThe present paper aims to verify the inuence of rare earth oxide such as lanthanum (La2O3) and neodymium (Nd2O3) doping SnO2 + 0.25%CoO + 0.75%MnO2 + 0.05%Ta2O5 system. The analysis focus on microstructural inuence on electrical properties. Microstructural analysis were made by using Transmission Electron Microscopy (TEM) at different regions of the samples. From such analysis it was found that La2O3 and Nd2O3 ...
Nonohmic behavior of SnO2.MnO2-based ceramics
Orlandi,Marcelo O.; Bueno,Paulo Roberto; Leite,Edson Roberto; Longo,ElsonThe present paper describes the nonohmic behavior of the SnO2.MnO-based system and analyzes the influence of the sintering time and the Nb2O5 concentration on this system's electrical properties. A nonlinear coefficient of ~7 was obtained for a 0.2 mol%-doped Nb2O5 composition, which is comparable to other values reported in the literature for the ternary SnO2-based systems. A recent barrier formation model pro...