The effect of adding a non-ionic surfactant to disperse oxide particles on the electrochemical pe... more The effect of adding a non-ionic surfactant to disperse oxide particles on the electrochemical performance of PAni/LiMnNiO4 composites is evaluated by using cyclic voltammetry (CV), impedance measurements and constant-current charge/discharge cycling techniques. Three surfactants based on ethoxylated (EO) and propoxylated (PO) lauryl alcohols (3EO/6PO, L306; 4EO/5PO, L405; and 6EO/3PO, L603) were investigated. For comparative purposes, the oxide and polyaniline were prepared by sol–gel and chemical methods and were also investigated for their physical and electrochemical performances. By galvanostatic charge–discharge tests, the PAni/LiMnNiO4 L306 composite showed a better electrochemical performance than each single component and other composites (PAni/LiMnNiO4 L405 and PAni/LiMnNiO4 L603). The electrical conductivity of this composite reached 21.7 S cm−1, and an initial discharge capacity of 198 mAh g−1 was obtained. After 21 cycles, the retention capacity was 91%. These results i...
One way to obtain orientation of polymer chains is to grow them inside a structurally organized h... more One way to obtain orientation of polymer chains is to grow them inside a structurally organized host framework. In this work we report on the preparation of nanocomposites by encapsulating polyaniline in three different hosts: (a) Tin IV 2-carboxyethyl phosphonate (lamellar host), (b) porous glass (Vycor - Corning 7930) and (c) sol-gel silica. The hosts and respective composites were characterized by X-Ray Diffractommetry, Cyclic Voltammetry and Scanning and Transmission Electron Microscopy. Each organized host determined the growth of the conductive polymer and the results obtained confirm the enhanced molecular order of polyaniline chains. Keywords: Conducting polymers; Composites; Template synthesis. Preparação de polímeros condutores em sistemas organizados Resumo Uma maneira de obtenção de cadeias poliméricas orientadas consiste na síntese do polímero no interior de hospedeiros organizados estruturalmente. Neste trabalho reportamos a preparação de nanocompósitos por meio do enc...
Dentre muitas fibras naturais de interesse tecnológico, o resíduo de madeira substitui com vantag... more Dentre muitas fibras naturais de interesse tecnológico, o resíduo de madeira substitui com vantagens as cargas e reforços tradicionalmente empregados em compostos e compósitos poliméricos, particularmente os de origem mineral, tais como talco, CaCO3 e fibra de vidro. A tecnologia dos chamados Wood-Plastic Composites (WPC´s) envolve conceitos de compatibilidade e processabilidade e apresenta grandes desafios tecnológicos para a formulação e estabilização da mistura devido a baixa estabilidade térmica da celulose. Muitos dos avanços tecnológicos em WPC?s dependem de uma análise criteriosa das características físicas de seus componentes e das condições de processamento do sistema, particularmente aspectos relacionados a sua compatibilização. No presente trabalho são apresentados estudos sobre a reatividade do polipropileno modificado com anidrido maleico (PP-MAH) utilizado como compatibilizante em compósitos termoplásticos de polipropileno com farinha de madeira. A influência da carga ...
The composite SnP-C/Fe/PAni was obtained as a powder by polymerization of aniline in the interlay... more The composite SnP-C/Fe/PAni was obtained as a powder by polymerization of aniline in the interlayer space of the host tin (IV) 2-carboxyethylphosphonate (SnP-C). The photoelectrochemical behavior of the composite was investigated as a function of applied potential, polyaniline concentration and direction of the polychromatic irradiation. The stability of the device using a liquid electrolyte was also determined. The photoelectrochemical response is sensitive to the oxidation state of the polymer. Depending on the potential applied to the electrode we observe cathodic or anodic photocurrents.
Photoelectrochemistry is based on interfacial electron transfer, where one of the phases is the e... more Photoelectrochemistry is based on interfacial electron transfer, where one of the phases is the excited state of a semiconductor. We used the a.c. impedance technique in order to investigate these interface processes. Polyaniline films galvanostatically grown on platinum electrodes showed variation of photocurrent responses with d.c. bias with two maxima, 0.4 and 0.7 V, and a minimum at 0.65 V.
Lithium manganese oxide powders were prepared via combustion reaction. Structural characterizatio... more Lithium manganese oxide powders were prepared via combustion reaction. Structural characterization of the powder using X-ray diffraction and scanning electron microscopy confirmed the formation of a LiMn2O4 nanosized powder. LiMn2O4 films were prepared by spin coating using 80 wt% of oxide, 15 wt% of polyaniline (PAni) as an electronic conductor and 5 wt% of polyvinylidene (PVDF) as a binder in
Water drop contact-angle measurements were used to monitor the organic contamination cleaning pro... more Water drop contact-angle measurements were used to monitor the organic contamination cleaning process of InP crystals by refluxing in a sequence of solvents. A single reflux in methanol reduces the contact angle by the same amount as a solvent sequence. MOCVD confirms the cleanliness of the InP crystals treated by a single reflux in methanol.
A new methodology that combines the sol–gel method and a template approach is used to synthesize ... more A new methodology that combines the sol–gel method and a template approach is used to synthesize porous LiNi1−xCoxO2 films. Conventional films are obtained through the sol–gel method. The films are used to evaluate the influence of this new methodology on the electrochemical performance. It was observed, from X-ray diffraction analysis on the conventional film that a further increase in the
The effect of adding a non-ionic surfactant to disperse oxide particles on the electrochemical pe... more The effect of adding a non-ionic surfactant to disperse oxide particles on the electrochemical performance of PAni/LiMnNiO4 composites is evaluated by using cyclic voltammetry (CV), impedance measurements and constant-current charge/discharge cycling techniques. Three surfactants based on ethoxylated (EO) and propoxylated (PO) lauryl alcohols (3EO/6PO, L306; 4EO/5PO, L405; and 6EO/3PO, L603) were investigated. For comparative purposes, the oxide and polyaniline were prepared by sol–gel and chemical methods and were also investigated for their physical and electrochemical performances. By galvanostatic charge–discharge tests, the PAni/LiMnNiO4 L306 composite showed a better electrochemical performance than each single component and other composites (PAni/LiMnNiO4 L405 and PAni/LiMnNiO4 L603). The electrical conductivity of this composite reached 21.7 S cm−1, and an initial discharge capacity of 198 mAh g−1 was obtained. After 21 cycles, the retention capacity was 91%. These results i...
One way to obtain orientation of polymer chains is to grow them inside a structurally organized h... more One way to obtain orientation of polymer chains is to grow them inside a structurally organized host framework. In this work we report on the preparation of nanocomposites by encapsulating polyaniline in three different hosts: (a) Tin IV 2-carboxyethyl phosphonate (lamellar host), (b) porous glass (Vycor - Corning 7930) and (c) sol-gel silica. The hosts and respective composites were characterized by X-Ray Diffractommetry, Cyclic Voltammetry and Scanning and Transmission Electron Microscopy. Each organized host determined the growth of the conductive polymer and the results obtained confirm the enhanced molecular order of polyaniline chains. Keywords: Conducting polymers; Composites; Template synthesis. Preparação de polímeros condutores em sistemas organizados Resumo Uma maneira de obtenção de cadeias poliméricas orientadas consiste na síntese do polímero no interior de hospedeiros organizados estruturalmente. Neste trabalho reportamos a preparação de nanocompósitos por meio do enc...
Dentre muitas fibras naturais de interesse tecnológico, o resíduo de madeira substitui com vantag... more Dentre muitas fibras naturais de interesse tecnológico, o resíduo de madeira substitui com vantagens as cargas e reforços tradicionalmente empregados em compostos e compósitos poliméricos, particularmente os de origem mineral, tais como talco, CaCO3 e fibra de vidro. A tecnologia dos chamados Wood-Plastic Composites (WPC´s) envolve conceitos de compatibilidade e processabilidade e apresenta grandes desafios tecnológicos para a formulação e estabilização da mistura devido a baixa estabilidade térmica da celulose. Muitos dos avanços tecnológicos em WPC?s dependem de uma análise criteriosa das características físicas de seus componentes e das condições de processamento do sistema, particularmente aspectos relacionados a sua compatibilização. No presente trabalho são apresentados estudos sobre a reatividade do polipropileno modificado com anidrido maleico (PP-MAH) utilizado como compatibilizante em compósitos termoplásticos de polipropileno com farinha de madeira. A influência da carga ...
The composite SnP-C/Fe/PAni was obtained as a powder by polymerization of aniline in the interlay... more The composite SnP-C/Fe/PAni was obtained as a powder by polymerization of aniline in the interlayer space of the host tin (IV) 2-carboxyethylphosphonate (SnP-C). The photoelectrochemical behavior of the composite was investigated as a function of applied potential, polyaniline concentration and direction of the polychromatic irradiation. The stability of the device using a liquid electrolyte was also determined. The photoelectrochemical response is sensitive to the oxidation state of the polymer. Depending on the potential applied to the electrode we observe cathodic or anodic photocurrents.
Photoelectrochemistry is based on interfacial electron transfer, where one of the phases is the e... more Photoelectrochemistry is based on interfacial electron transfer, where one of the phases is the excited state of a semiconductor. We used the a.c. impedance technique in order to investigate these interface processes. Polyaniline films galvanostatically grown on platinum electrodes showed variation of photocurrent responses with d.c. bias with two maxima, 0.4 and 0.7 V, and a minimum at 0.65 V.
Lithium manganese oxide powders were prepared via combustion reaction. Structural characterizatio... more Lithium manganese oxide powders were prepared via combustion reaction. Structural characterization of the powder using X-ray diffraction and scanning electron microscopy confirmed the formation of a LiMn2O4 nanosized powder. LiMn2O4 films were prepared by spin coating using 80 wt% of oxide, 15 wt% of polyaniline (PAni) as an electronic conductor and 5 wt% of polyvinylidene (PVDF) as a binder in
Water drop contact-angle measurements were used to monitor the organic contamination cleaning pro... more Water drop contact-angle measurements were used to monitor the organic contamination cleaning process of InP crystals by refluxing in a sequence of solvents. A single reflux in methanol reduces the contact angle by the same amount as a solvent sequence. MOCVD confirms the cleanliness of the InP crystals treated by a single reflux in methanol.
A new methodology that combines the sol–gel method and a template approach is used to synthesize ... more A new methodology that combines the sol–gel method and a template approach is used to synthesize porous LiNi1−xCoxO2 films. Conventional films are obtained through the sol–gel method. The films are used to evaluate the influence of this new methodology on the electrochemical performance. It was observed, from X-ray diffraction analysis on the conventional film that a further increase in the
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