Submitted by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-03-28T13:17:32Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação_ Jennifer S. Fonseca.pdf: 5044644 bytes, checksum: 0cf098fc158bb9034a0275f3fdc8b0d0 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-03-28T13:18:14Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação_ Jennifer S. Fonseca.pdf: 5044644 bytes, checksum: 0cf098fc158bb9034a0275f3fdc8b0d0 (MD5) / Made available in DSpace on 2018-03-28T13:18:15Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação_ Jennifer S. Fonseca.pdf: 5044644 bytes, checksum: 0cf098fc158bb9034a0275f3fdc8b0d0 (MD5) Previous issue date: 2017-06-30 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Microbial fuel cells (MFC) are electrochemical devices that exploit the ability of some species of microorganisms to use electrodes as final acceptors of electrons in their metabolism. The interest in this technology is associated with the possibility of using different compounds, including domestic and industrial effluents, in the generation of electric energy. In this context, the study of MFC that use residual frying oils (RFO) as substrate gains attention by bringing an alternative both from an environmental and an energetic point of view. The objective of this work was to model the best conditions for the simultaneous degradation of these RFO and electric current generation of a microbial fuel cell inoculated with Shewanella putrefaciens. For this purpose, a factorial and central compound planning (CCP) design was used, in which microbial metabolism was studied under the effects of pH, temperature, medium agitation, oil concentration and time. The experimental data were obtained in a two-chamber MFC, an anode and a cathode, separated by a proton exchange membrane. The anode was inoculated with S. putrefaciens under anaerobic conditions and fed with RFO, while the cathode was fed with tap water and salinized tap water. In the anode, an electrode was used as a graphite cloth with a polypropylene mesh and an aluminum heatsink on the cathode. Both were connected externally by an electrical resistance. During the operation of the system, the anode compartment was operated in batch mode. The results show that in less than two days of operation the current generation had reached a stable value, proving the exoelectrogenic capacity of the bacteria. It was observed that S. putrefaciens did not develop a biofilm on the surface of the electrodes with samples from the University Restaurant (UR), but adhered to the electrode with domestic oil as a substrate, demonstrating a direct mechanism of extracellular electron transfer to establish the electrical contact with The electrode. In general, the mathematical modeling of the degradation of the oils for the simultaneous generation of electric current was possible, requiring further studies of the chemical composition of the oils for the evaluation of the efficiency of the MFC with the chemical parameters, since it was only possible to analyze from the point of electrical parameters. In addition, it was possible to verify that the amount of bacterial colonies does not interfere in the generation of tension, being this one generated of stable form with small cellular concentrations. / Células combustíveis microbianas (CCM) são dispositivos eletroquímicos que exploram a habilidade de algumas espécies de micro-organismos utilizarem eletrodos como aceptores finais de elétrons em seu metabolismo. O interesse nesta tecnologia está associado à possibilidade de empregar diferentes compostos, inclusive efluentes domésticos e industriais, na geração de energia elétrica. Neste contexto, o estudo de CCM que usem óleos de fritura residuais (OFR) como substrato ganha atenção por trazer uma alternativa tanto do ponto de vista ambiental quanto energético. Assim o objetivo deste trabalho foi modelar as melhores condições para a simultânea degradação destes OFR e geração de corrente elétrica de uma célula combustível microbiana inoculada com Shewanella putrefaciens. Para tal fim foi empregado um planejamento fatorial e planejamento de composto central (PCC), no qual o metabolismo microbiano foi estudado sob os efeitos de pH, temperatura, agitação do meio, concentração do óleo e tempo. Os dados experimentais foram obtidos em uma CCM de dois compartimentos, um ânodo e um cátodo, separados por uma membrana de troca de prótons. O ânodo foi inoculado com S. putrefaciens em condições de anaerobiose e alimentado com OFR, enquanto, o cátodo foi alimentado com água da torneira e água da torneira salinizado. No ânodo, foi empregado como eletrodo pano de grafite imobilizado com tela de polipropileno e no cátodo um dissipador de calor de alumínio. Ambos estavam conectados externamente por uma resistência elétrica. Durante a operação do sistema, o compartimento do ânodo foi operado em regime de batelada. Os resultados ilustram que em menos de dois dias de operação a geração de corrente elétrica já havia atingido um valor estável, comprovando a capacidade exoeletrogênica da bactéria. Observou-se que a S. putrefaciens pouco desenvolveu biofilme na superfície dos eletrodos com amostras do óleo do Restaurante Universitário (RU), mas aderiu ao eletrodo tendo óleo doméstico como substrato, demonstrando um mecanismo direto de transferência eletrônica extracelular para estabelecer o contato elétrico com o eletrodo. De maneira geral, a modelagem matemática da degradação dos óleos para simultânea geração de corrente elétrica foi possível, necessitando de maiores estudos da composição química dos óleos para a avaliação da eficiência da CCM com os parâmetros químicos, uma vez que só foi possível analisar do ponto de vista dos parâmetros elétricos. Além disso, foi possível verificar que a quantidade de colônias bacterianas não interfere na geração de tensão, sendo este gerado de forma estável com pequenas concentrações celulares.

Orientador: Prof. Dr. Caetano Rodrigues Miranda / Tese (doutorado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, 2015. / In this thesis, we explore computational materials science for energy technologies. More specifically, a multiscale computational methodology ranging from atomistic to mesoscopic methods was used to investigate the potential use of nanostructured materials for applications in: (i) hydrogen and fuel cells, (ii) rechargeable batteries, and (iii) oil recovery techniques. First principles simulations based on the Density Functional Theory were successfully employed to characterize and propose nanomaterials for hydrogen production and storage, fuel cells, and battery technologies. It was possible to understand fundamental properties that are essential to further development in these technologies, e. g. structural, electronic, catalytic and kinetic properties. The structural, energetic and electronic properties of layered metallic nanofilms of Pd, Pt and Au as catalysts for hydrogen and fuel cell applications were investigated. We have shown that Pd and Pt nanofilms are interesting systems, with improved catalytic activity for hydrogen, oxygen and ethanol. The evaluation of the electronic structure of such nanofilms shows the existence of a linear correlation between the d-band center and adsorption energies. The determination of such trends represents a significative contribution to the design of new and improved catalysts, since it is a valuable tool to predict the catalytic activity of nanofilms. Significant breakthroughs were also obtained when applying first principles calculations to battery technologies. The adsorption and di.usion properties of Li and Mg were investigated in transition metal dichalcogenide inorganic nanotubes. A high ion mobility is observed at the surface of MoS2 and WS2 nanotubes, which support the potential application of the use of such systems as additive electrode materials for high-rate battery applications. By using classical molecular dynamics calculations, the structural and di.usion properties of organic electrolytes could be determined and may help in the development of rechargeable batteries. Our simulations have demonstrated that mixture of ethylene carbonate and ethylmethyl carbonate present better di.usion properties as electrolyte in lithium ion batteries, since it is possible to obtain a good degree of dissociation associated to a good ionic conductivity. xvi Abstract In order to extent the nanoscale e.ects to the microscale, we also successfully propose a hierarchical computational protocol that combines molecular dynamics and mesoscopic lattice Boltzmann calculations. The e.ects of dispersed functionalized SiO2 nanoparticles in brine to the oil recovery process in a covered clay pore structure is explored. Molecular dynamics simulations have shown that the addition of functionalized nanoparticles to the brine solution reduces the interfacial tension between oil and brine. Followed by an increase of the contact angle. By mapping these results into lattice Boltzmann parameters, the oil displacement process in hydrophilic pore models was investigated. Our simulations indicate that the observed changes in the interfacial tension and wettability by the inclusion of SiO2 nanoparticles indeed improve the oil recovery process in a microscale, and seems to be a good alternative as injection fluids for enhanced oil recovery techniques. Thus, our proposed hierarchical computational protocol that combines molecular dynamics and lattice Boltzmann method simulations can be a versatile tool to investigate the e.ects of the interfacial tension and wetting properties on fluid behavior at both nano and micro scales. Although it is clear that the search and development of new advanced materials continues to be a key factor in energy technologies, the present thesis represent a significant contribution to understand the fundamental phenomena underlying hydrogen production and storage, fuel cells, batteries, and fossil fuel applications.

Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-06-06T20:07:41Z No. of bitstreams: 1 RaffaelPinto.pdf: 7905766 bytes, checksum: 7f7997961e840698d9d936cdea00b602 (MD5) / Made available in DSpace on 2017-06-06T20:07:41Z (GMT). No. of bitstreams: 1 RaffaelPinto.pdf: 7905766 bytes, checksum: 7f7997961e840698d9d936cdea00b602 (MD5) Previous issue date: 2008-05-21 / Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão (FAPEMA) / In this work have been investigated the dielectric and vibrational properties of the ORMOSIL membranes based on PDMS and TEOS doped with MDS using the Di erential Scanning Calorimetry (DSC), impedance, Raman and infrareds spectroscopy technics. Such membranes are hybrid organic-inorganic materials with potential application in PEMFC (Proton Exchange Membrane Fuel Cell) and were doped with concentrations 0%(Pure Membrane), 5%, 10%, 20% e 30% of MDS. The thermal measurements were performed in the range from room temperature and 550 oC. The results showed that, after the MDS inclusion, the membranes absorb water. Besides, then thermal stability of the membranes decreased with the MDS inclusion. The dielectrics measurements were performed in temperature range of 313K-373K. The results showed that room temperature conductivity increases linearly with the frequency, until 353K, suggesting a hopping conduction and leaving this linear behavior above 353K. Besides, it was observed that conductivity doesn't increases linearly with MDS concentration, but increases until maximal value for 20% MDS concentration and decreases again for 30% MDS concentration de ning a synergetic e ect, which probably is associate with con gurational arrange of microcristallites MDS. Another feature of that membranes is a relaxation process visible in the electrical module graphics which appear just in doped membranes, being however, due to the MDS. The vibrational properties of hybrids membranes were obtained through Raman scattering and infrared. The results con rmed the presence of Si¡O¡Si, Si¡C, Si¡OH, C2H5, Si¡CH3, CH3, CH2, C¡H, S=O and S¡O groups. Where the S=O and S¡O groups are presents just in MDS compound. Consequently, their respective peaks appear only in the doped membrane spectra. / Neste trabalho foram investigadas as propriedades térmicas, dielétricas e vibracionais das membranas de ORMOSIL baseadas em PDMS e TEOS dopadas com MDS através das técnicas de calorimetria diferencial de varredura, espectroscopias de impedância, Raman e infravermelho. Essas membranas são materiais híbridos orgânico-inorgânico com grande potencialidade de aplicação em células combustíveis do tipo PEM (Proton Exchange Membrane) e foram dopadas nas concentrações de 0%(Pura), 5%, 10%, 20% e 30% de MDS. As medidas térmicas foram realizadas entre a temperatura ambiente e 500 oC e mostraram que as membranas passam a absorver água quando o MDS é inserido. Mostraram também que as membranas têm sua estabilidade térmica reduzida quando o MDS é inserido. As medidas dielétricas foram realizadas no intervalo de temperatura entre 40 e 100oC. Os resultados mostraram que a condutividade à temperatura ambiente aumenta de maneira praticamente linear com a freqüência, mantendo-se assim até 80±C sugerindo uma condução por hopping e deixando de ter esse comportamento linear para temperaturas acima de 80±C. Observou-se também que a condutividade não aumenta linearmente com a concentração de MDS, mas atinge um valor máximo para a membrana com 20% de MDS e diminui novamente para a membrana com 30% de MDS caracterizando assim um efeito sinergético, que provavelmente está associado ao arranjo configuracional dos microcristalitos do MDS. Uma outra característica interessante dessas membranas, é um processo de relaxação visível nos grá cos do módulo elétrico o qual consta apenas nas membranas dopadas, sendo portanto, característico do MDS. As propriedades vibracionais desses materiais híbridos foram determinadas através de medidas do espalhamento Raman. Os resultados da espectroscopia Raman e infravermelho confirmaram a presença dos grupos Si¡O¡Si, Si¡C, Si¡OH, C2H5, Si¡CH3, CH3, CH2, C¡H, S=O e S¡O. Onde estes dois últimos estão presentes somente no MDS e, por essa razão, seus respectivos picos só se apresentaram no espectro das membranas dopadas.