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Estudo de eletrodegrada??o de poluentes emergentes em c?lulas eletroqu?micas do tipo eletr?lito polim?rico s?lidoCastro J?nior, Jos? Geraldo Mendes 29 August 2017 (has links)
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Previous issue date: 2017 / Eletrodos de di?xido de chumbo (PbO2) suportados sobre tecido de carbono e tela de a?o
inoxid?vel foram utilizados na degrada??o eletroqu?mica dos f?rmacos paracetamol (PCT) e
dipirona (DPN), utilizando-se uma c?lula eletroqu?mica do tipo eletr?lito polim?rico s?lido
(EPS) munida de eletrodos perme?veis a fluidos (EPFs). Todos os estudos foram conduzidos
na condi??o de batelada empregando-se a ?gua livre de eletr?litos. Os estudos eletroqu?micos
de degrada??o dos f?rmacos foram conduzidos em fun??o da densidade de corrente aparente
(jap) (ex., 5, 10, 20, 100, 150 e 200 mA cm-2) e da concentra??o inicial (ex., 10, 30 e 50 mg L 1).
As amostras tratadas foram analisadas pelas t?cnicas de espectrofotometria na regi?o do UVVis,
cromatografia l?quida de alta efici?ncia (CLAE) e demanda qu?mica de oxig?nio (DQO).
Verificou-se para os diferentes casos envolvendo as baixas densidades de corrente que a
remo??o das bandas de absor??o no UV-Vis, a remo??o da concentra??o dos f?rmacos (CLAE)
e a redu??o da DQO (grau de mineraliza??o) n?o foram significativos. Contrariamente, no caso
das elevadas densidades de corrente evidenciou-se uma significante melhora na degrada??o dos
f?rmacos em decorr?ncia da atua??o do oz?nio gerado eletroquimicamente. Os melhores
resultados foram obtidos para baixas concentra??es dos f?rmacos. Redu??es superiores a 95 %
de DQO para o PCT e superiores a 75 % para a DPN foram obtidas. Eletrodos de PbO2 dopados
com n?quel (ex., Ni-PbO2) suportados sobre tecido de carbono e tela de a?o inoxid?vel foram
confeccionados e caracterizados. A an?lise de microscopia eletr?nica de varredura (MEV)
revelou o aparecimento de defeitos superficiais, com a varia??o da concentra??o nominal do Ni
no banho eletrol?tico utilizado no preparo do eletrodo por eletrodeposi??o. An?lises de
difratometria de raios-X (DRX) corroboraram os resultados de MEV revelando, em alguns
casos, picos mais alargados e de menor intensidade (ex., redu??o no tamanho m?dio dos
cristalitos) com a varia??o da concentra??o nominal do Ni, indicando assim uma interfer?ncia
no processo de eletrodeposi??o do PbO2. Curvas de polariza??o em condi??es quaseestacion?rias
foram obtidas para o processo eletr?dico da rea??o de desprendimento de oxig?nio
(RDO) sendo verificado que n?o houve influ?ncia significativa do dopante sobre esta rea??o, a
qual ocorre em paralelo ao processo de degrada??o oxidativa dos f?rmacos. Verificou-se que a
produ??o de oz?nio foi ligeiramente favorecida em algumas concentra??es do dopante e em
altas densidades de corrente. No entanto, n?o foi verificada influ?ncia significativa sobre o grau
de mineraliza??o dos f?rmacos PCT e DPN mediante uso de eletrodos dopados com Ni. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Qu?mica, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2017. / Lead dioxide (PbO2) electrodes supported on carbon cloth and stainless-steel mesh substrates
were used in the electrochemical degradation of the drugs paracetamol (PCT) and dipyrone
(DPN), using a solid polymer electrolyte electrochemical cell (SPE) having fluid-permeable
electrodes (FPEs). All studies were conducted in batch condition using the electrolyte-free
water. The electrochemical degradation of the drugs was accomplished as a function of the
apparent current density (ex., 5, 10, 20, 100, 150 and 200 mA cm-2) and the initial concentration
(ex., 10, 30 and 50 mg L-1). The treated samples were analyzed using the UV-Vis
spectrophotometry technique, the high-performance liquid chromatography (HPLC), as well as
the chemical oxygen demand (COD). For the different cases involving the application of low
current density values, it was not verified significant changes accounting for the removal of the
UV-Vis absorption band, the drug concentration (HPLC), and the COD decrease (ex., the
degree of mineralization). In contrast, in the case of high current densities, a significant
improvement in the degradation of the drugs was evidenced as a result of the influence of the
electrochemically generated ozone. The best findings were obtained for low drug
concentrations. Reductions of above 95% COD for PCT and above 75% for DPN were
obtained. Nickel-doped PbO2 electrodes (ex., Ni-PbO2) supported on carbon cloth and stainlesssteel
mesh were fabricated and characterized. Scanning electron microscopy (SEM) revealed
the appearance of surface defects with a reduction in crystal size with the different Ni
concentration in the electrolytic bath used to prepare the electrode by electrodeposition. X-ray
diffraction (XRD) analyzes corroborated with the SEM results revealing the formation of
broader peaks with lower intensity, in some cases, (ex., reduction in the average crystallite size)
with the variation of the nominal dopant concentration in the electrolytic bath, thus indicating
an interference in the electrodeposition process for PbO2. Quasi-stationary polarization curves
were obtained for the electrode process of the oxygen evolution reaction (OER) and it was
verified that there was no significant influence of the dopant on this reaction, which occurs in
parallel to the process comprising the oxidative degradation of the drugs. It was found that the
ozone generation was slightly favored in some concentrations of the dopant and in higher
current densities. However, no significant influence was verified on the degree of
mineralization of PCT and DPN by the use of Ni-PbO2 electrodes.
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Gas-sensitive holographic sensorsMartínez Hurtado, Juan Leonardo January 2013 (has links)
Holographic sensors are photonic layered structures contained in analyte sensitive lms that upon illumination produce monochromatic reflections (λ). The present work reports the fabrication of oxygen and ammonia sensors in Nafi on membranes and hydrocarbon and volatile organic compound sensors in poly(dimethylsiloxane) (PDMS) films. A holographic recording technique was developed to suit these materials consisting of the in situ formation of nanoparticles of 18nm average diameter and their subsequent ordered ablation with a 300mJ laser. The wavelength of the monochromatic reflections depends principally on the refractive index of the resulting layers (n) and the separation between them (Λ). Changes in these parameters are generated by the analyte-sensor interactions and their magnitude can be correlated to the analyte concentration. The strength of these interactions is determined by the thermodynamic properties of the analytes, such as the cohesive energy density (δ^2), and this, was coupled with a photonic model for the prediction of the holographic response. After exposure to different concentrations of the analytes, the kinetics of the responses were determined and the lowest detection limits (LDL) established as follows: Hydrocarbons in PDMS holograms 1% (v/v) in 3s for a range of concentrations from 0-100%; ammonia in Nafi on holograms 0.16% in 100s in the 0-12.5% range; the LDL for oxygen sensing could not be determined although the response was recorded down to 12.5% and up to 100% in 100s. Holographic sensors show competitive responses comparable to commercially available gas sensors for biomedical diagnostics and industrial process monitoring because of their facile fabrication and their shared sensing platform allowing multiplexing.
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Investigation of bipyridilium and Prussian blue systems for their potential application in electrochromic devicesDillingham, J. L. January 1999 (has links)
No description available.
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Electro-catalysis of Oxygen Reduction on Platinum-Bismuth Alloy Nanoparticles and a Study of Nafion Ionomer ImpactFang, Junchuan 05 October 2021 (has links)
No description available.
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ENGINEERED INTERACTION BETWEEN PERFLUORINATED SULFONIC-ACID IONOMER (NAFION®) AND ELASTIN-LIKE PEPTIDES THROUGH PEPTIDE LENGTH AND GUEST RESIDUEKim, ChulOong 28 August 2019 (has links)
No description available.
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Multiscale Modeling of Water and Proton Diffusion in Self-Assembled Polymer Electrolyte MembranesNeimark, Alexander V., Vishnyakov, Aleksey, Lee, Ming-Tsung 14 September 2018 (has links)
No description available.
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Synthesis of the Diazonium (Perfluoroalkyl) Benzenesulfonimide Monomer From Nafion Monomer for Proton Exchange Membrane Fuel CellsMei, Hua, D'Andrea, Dan, Nguyen, Tuyet Trinh, Nworie, Chima 01 January 2014 (has links)
One diazonium (perfluoroalkyl) benzenesulfonimide monomer, perfluoro-3, 6-dioxa-4-methyl-7-octene benzenesulfonyl imide, has been synthesized from Nafion monomer for the first time. With trifluorovinyl ether and diazonium precursors, the partially-fluorinated diazonium PFSI monomer can be polymerized and will provide chemically bonding with carbon electrode in proton exchange membrane fuel cells. A systematic study of the synthesis and characterization of this diazonium PFSI monomer has been conducted by varying reaction conditions. The optimized synthesis method has been established in the lab.
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Two New Diazonium Bis(perfluoroalkyl)arylsulfonyl Imide Zwitterionic Monomers from Perfluoro(3-oxa-4-pentene)sulfonyl Fluoride for Proton Exchange Membrane Fuel CellsMei, Hua, Ibrahim, Faisal 01 January 2017 (has links)
Two new bis(perfluoroalkyl)arylsulfonyl imide monomers, which contain the aryl diazonium moiety and intramolecular zwitterionic fragment, have been designed and prepared for the first time from perfluoro(3-oxa-4-pentene)sulfonyl fluoride. As promising monomer candidates for high-performance proton exchange membrane fuel cell electrolytes, these two monomers have furnished perfluorinated electrolytes that include the polymers from perfluorinated sulfonic acid or perfluorinated sulfonimide monomers. The synthesis strategies and NMR analysis are summarized and discussed in details.
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Controlling methanol and water diffusion in Nafion via amine treatmentKludský, Miroslav, Vopička, Ondřej, Matějka, Pavel, Hovorka, Štěpán, Friess, Karel 12 July 2022 (has links)
No description available.
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Gold Nanoshells: Synthesis and Applications to In Situ SERSZeng, Jianbo 11 March 2013 (has links)
No description available.
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