Le recyclage du combustible nucléaire passe par la production de poudres d’oxydes mixtes (U,Pu)O₂. Un des principaux procédés utilisés pour obtenir ce type de poudre comporte une étape de calcination d’oxalates mixtes qui se décomposent en oxyde. Le contrôle des propriétés physico-chimiques de la poudre au cours du traitement thermique des oxalates (étape précédant la mise en forme des pastilles combustibles) requiert une attention particulière, car celles-ci auront une conséquence directe sur l’aptitude à la compaction et au frittage.Dans ce contexte, ces travaux traitent de l’évolution des caractéristiques des poudres, et de la cinétique des différentes étapes de décomposition les influençant, lors de la calcination des oxalates mixtes U-Ce (simulant U-Pu).Une étude expérimentale détaillée sur les caractéristiques morphologiques et texturales, notamment la surface spécifique, a été menée et a permis de dresser un schéma d’évolution de la poudre lors des différentes étapes de décomposition. De plus, les variations de la teneur en carbone au cours de la calcination ont aussi été étudiées. Ce travail a permis d’identifier les étapes de décomposition d’intérêt pour le contrôle des caractéristiques des poudres lors du procédé de calcination.Enfin, ces étapes réactionnelles d’intérêt ont fait l’objet d’une étude cinétique détaillée. Celle-ci a conduit à l’identification de modèles adaptés au système d’étude qui décrivent les phénomènes physiques et chimiques ayant lieu au cours de la décomposition. / Nuclear fuel recycling process includes production of mixed oxide powder as (U,Pu)O₂. One of the most common processes actually investigated to get this kind of powder involves a calcination step of mixed oxalate which decomposes in oxide products. Physical and chemical powder characteristics during oxalate heat treatment (taking place before pellet shaping step) need a special attention. In fact, powder properties can affect directly their sintering and compaction abilities.The aim of this work deals with the powder characteristics evolution and the decomposition kinetics of steps having an effect on them, during U-Ce mixed oxalate calcination (surrogate system of U-Pu couple).A detailed experimental study of morphological and textural characteristics, especially specific surface area, has been carried out. The results have enabled to achieve a textural evolution pattern during different steps of oxalate decomposition. Moreover, carbon content variations through heat treatment process have been studied. This experimental route point out the most interesting decomposition steps impacting powder characteristics during calcination.Finally, a kinetic study of these decomposition steps has been performed. This exercise led to suitable kinetic models describing physical and chemical phenomena taking place during oxalate thermal decomposition process.

Les cinétiques de décomposition dues à la présence d'une lacune de miscibilité dans le système Fe-Cr sont généralement étudiées dans des alliages Fe-Cr massifs pour lesquels la décomposition se déroule en 3 dimensions. Nous avons étudié les cinétiques de décomposition spinodale dans des couches minces Fe-Cr. Ces couches minces comportent une oscillation de composition de Cr dont le vecteur d'onde est perpendiculaire à la surface de l'échantillon. La décomposition de l'alliage a alors pour conséquence d'augmenter l'amplitude de l'oscillation au cours d'un recuit et donc d'engendrer une décomposition selon une seule dimension. Des échantillons comportant des oscillations de différentes longueurs d'onde ont ainsi été conçus. Des recuits à 500°C sur ces échantillons ont été analysés par sonde atomique tomographique. Ces résultats ont ensuite été comparés à des simulations AKMC et en champ moyen. Des recuits à 500°C d'un échantillon comportant une oscillation de composition d'une longueur d'onde de 22nm ont montré une diminution inattendue de l'amplitude de l'oscillation. Des recuits à 500°C d'un échantillon comportant une oscillation de composition d'une longueur d'onde de 6nm ont montré plusieurs comportements de l'oscillation de composition. En effet, l'oscillation s'est amplifiée par endroits alors qu'elle s'amortie ou encore évolue peu à d'autres. La présence d'O et de joints grains dans les couches minces peuvent rendre compte de ces différents comportements. / Decomposition kinetics due to the presence of a miscibility gap in the Fe-Cr system are generally studied in Fe-Cr bulk alloys for which the decomposition occurs in three dimensions. We studied the spinodal decomposition kinetics in Fe-Cr thins films. These thin films have a Cr composition oscillation whose wave vector is perpendicular to the sample surface. The decomposition of the alloy lead an increase of the oscillation amplitude during annealing and thus generate a decomposition in a single dimension. Samples having different oscillation wavelengths have been designed. Annealing treatments at 500°C of these samples were analyzed by atom probe tomography. These results were then compared to AKMC and mean field simulations. Annealing treatments at 500°C of a sample having a composition oscillation with a 22nm wavelength showed an unexpected decrease in oscillation amplitude. Annealing treatments at 500°C of a sample having a composition oscillation with a 6nm wavelength showed several behavior of the composition oscillation. Indeed, the oscillation amplifies by places while damps or changes very little in other places. The presence of O and grain boundaries in thin films may explain these different behaviors.

The disproportionation of H₂O₂ to H₂O and molecular O₂ catalyzed by platinum nanocatalysts is technologically very important in several energy conversion technologies, such as steam propellant thrust applications and hydrogen fuel cells. However, the mechanism of H₂O₂ decomposition on platinum has been unresolved for more than 100 years and the kinetics of this reaction were poorly understood. Our goal was to quantify the effect of reaction conditions and catalyst properties on the decomposition of H₂O₂ by platinum nanocatalysts and determine the mechanism and rate-limiting step of the reaction. To this end, we have characterized two commercial platinum nanocatalysts, known as platinum black and platinum nanopowder, and studied the effect of different reaction conditions on their rates of H₂O₂ decomposition. These samples have different particle size and surface chemisorbed oxygen abundance, which were varied further by pretreating both samples at variable conditions. The rate of H₂O₂ decomposition was studied systematically as a function of H₂O₂ concentration, pH, temperature, particle size and surface chemisorbed oxygen abundance. The mechanism of H₂O₂ decomposition on platinum proceeds via two cyclic oxidation-reduction steps. Step 1 is the rate limiting step of the reaction. Step 1: Pt + H₂O₂ → H₂O + Pt(O). Step 2: Pt(O) + H₂O₂ → Pt + O₂ + H₂O. Overall: 2 H₂O₂ → O₂ + 2 H₂O. The decomposition of H₂O₂ on platinum follows 1st order kinetics in terms of H₂O₂ concentration. The effect of pH is small, yet statistically significant. The rate constant of step 2 is 13 times higher than that of step 1. Incorporation of chemisorbed oxygen at the nanocatalyst surface resulted in higher initial rate of H₂O₂ decomposition because more sites initiate their cyclic process in the faster step of the reaction. Particle size does not affect the kinetics of the reaction. This new molecular-scale understanding of the decomposition of H₂O₂ by platinum is expected to help advance many energy technologies that depend on the rate of H₂O₂ decomposition on nanocatalysts of platinum and other metals. / Ph. D. / Platinum nanomaterials are indispensable to catalyze a variety of industrial and technological processes ranging from catalytic conversion of carbon monoxide (CO), hydrocarbons, and nitrogen oxides (NO_x) in modern automobiles to energy production by hydrogen fuel cells and thrust generation in steam propellers. These technological innovations have a tremendous impact in modern society, including the areas of transportation, energy supply, soil and water quality, environmental remediation and global climate change. The decomposition of hydrogen peroxide (H₂O₂) to water (H₂O) and oxygen (O₂) on platinum nanomaterials is of particular importance because it affects the efficacy of many technological applications, such as hydrogen peroxide steam propellers and hydrogen fuel cells. However, the reaction pathway and kinetics of H₂O₂ decomposition on platinum were only partly understood. My goal was to understand how the reaction conditions and the nanocatalyst properties control the mechanism and kinetics of platinum-catalyzed hydrogen peroxide decomposition. To do that we characterized the atomic scale structural and chemical properties of two different platinum nanocatalysts, known as platinum black and platinum nanopowder and evaluated the effect of their properties in their catalytic activity. Our characterization studies were used to understand the reactivity of these two platinum nanocatalysts in the decomposition of H₂O₂, which we evaluated separately in laboratory studies. Establishing relationships between the catalyst properties and their activity, as we have done in this work for platinum nanocatalysts in the decomposition of hydrogen peroxide, has the potential to improve nanocatalyst design and performance for those applications.

Dissolved organic matter (DOM) is the largest pool of organic carbon in aquatic systems and an important component of the global carbon cycle. Large amounts of DOM are decomposed within lakes, resulting in fluxes of CO2 and CH4 to the atmosphere. Therefore, there is a considerable interest in understanding the controls of DOM decomposition in freshwaters. There is evidence that in lakes intrinsic controls related to DOM composition are of primary importance, yet our knowledge about molecular drivers of DOM degradation is limited. This thesis addresses the link between chemical composition and reactivity of lake DOM by applying an experimental approach, molecular-level DOM characterization, and kinetic modeling of DOM decay. The first study shows that photoinduced transformations and partial removal of colored aromatic components of DOM have profound effects on DOM degradation kinetics, mediated by the shifts in the relative share of rapidly and slowly degrading DOM fractions. Two following studies estimate exponential decay coefficients for each individual molecular formula identified within bulk DOM. A continuous distribution of exponential decay coefficients is found within bulk DOM, which directly corroborates the central and previously empirically untested assumption behind the reactivity continuum model of DOM decay. Further, individual decay rates are evaluated in connection to specific molecular properties. On average, highly unsaturated and phenolic compounds appear to be more persistent than compounds with higher aromatic content (plant polyphenols and polycondensed aromatics), and aliphatic compounds demonstrate the highest decay rates. The reactivity of aromatics additionally increases with increasing nominal oxidation state of carbon. Molecular analysis further indicates that increasing reactivity of DOM after UV exposure is caused by disintegration of supramolecular complexes. Study IV shows that changes in relative proportion of terrestrial versus algal DOM control degradability of DOM through seasons. Under ice, when algal-derived DOM is maximally depleted, DOM degradation potential converges to similarly low levels, regardless of lake type (productive or humic), and bacterial respiration primarily relies on terrestrial carbon. This suggests a general pattern of baseline metabolism across boreal lakes. I conclude that DOM is a dynamic reactivity continuum and a tight link exists between DOM behavior and compositional properties.

Atualmente, a participação da energia elétrica na matriz energética mundial é um assunto em evidência. O estudo do compósito isolante da barra estatórica, um dos componentes principais da máquina hidrogeradora, permite a obtenção de informações físico-químicas relevantes ao aperfeiçoamento do sistema, e também de estudos de comportamento térmico quando este é exposto à alta temperatura, por diferentes intervalos de tempo submetidos a estresses mecânicos, elétricos e/ou químicos. O sistema em estudo é o MICALASTIC®, desenvolvido pela empresa Siemens em 1960. Neste trabalho, as propriedades térmicas do compósito isolante, formado por uma fita de mica, resina epóxi (DGEBA), endurecedor (MHHPA) e acelerador naftenato de zinco (N-Zn) foram estudadas. Utilizando-se as técnicas termoanalíticas Calorimetria Exploratória Diferencial (DSC) e Termogravimetria e Termogravimetria Derivada (TG/DTG), o comportamento térmico de cada um dos materiais foi avaliado. As curvas DSC e TG/DTG também evidenciaram as possíveis interações químicas entre os componentes. Os estudos referentes à cura do material e da degradação térmica do compósito curado foram realizados. Observou-se claramente a influência da quantidade de acelerador na polimerização do sistema. A partir das curvas DSC, observou-se dois mecanismos de cura diferentes coexistentes, um com menor quantidade de N-Zn e outro com concentração maior, resultando em eventos de cura com início em temperaturas diferentes. Esse fato ainda não havia sido estudado desde a origem do sistema. Além disso, a perda de massa referente à evaporação do endurecedor no início do processo de cura foi confirmada a partir da caracterização do compósito por espectroscopia de absorção na região do infravermelho, comparando-se os espectros antes e após o fenômeno. Na prática, dois perfis de impregnação, o Homogêneo e o Heterogêneo, de barras condutoras são utilizados, e uma diferença significativa entre eles foi observada. Os estudos desenvolvidos devem ser associados a testes elétricos específicos para o melhor entendimento da relação entre a aplicação do material e suas propriedades teóricas termoanalíticas. Além disso, foi realizado o estudo cinético da decomposição térmica do compósito curado por métodos termogravimétricos, isotérmico e dinâmico. / Currently, the electric energy participation in the world energy matrix is a significant issue. The insulating composite in stator bars, which are one of the most important components in hydrogenerator machines, allows the attainment of relevant physical and chemical information to system optimization, in addition to study thermal behavior when the material is exposed to high temperatures, for different time intervals and mechanical, chemical and/or electrical stress. The studied system is MICALASTIC®, developed by Siemens Company in 1960. In this work, thermal properties of this insulating composite, composed by mica tape, epoxy resin (DGEBA), hardener (MHHPA) and zinc naphtenate (N-Zn) as accelerator, were studied. Using thermoananalytical techniques as Differential Scanning Calorimetry (DSC) and Thermogravimetry and Derivative Thermogravimetry (TG/DTG), thermal behavior of each material was evaluated. DSC and TG/DTG curves evidenced chemical interactions between components. The study relative to material curing and cured composite thermal degradation were described. It was clearly observed the N-Zn amount influence in the cure of system, and through DSC curves, it was possible to observe two distinct polymerization coexisting mechanisms, one with lower quantity of N-Zn and another one with bigger concentration, resulting in cure events starting in different temperatures. This fact has not been studied yet since the system has been originated. Besides that, the weight loss related to hardener evaporation starting with curing process was confirmed by composite characterization by FTIR spectra, before and after phenomenon. In practice, two impregnation patterns (Homogeneous and Heterogeneous) of conductive bars are used and a significant difference between them was observed. The developed studies have to be associated to electrical tests to a best understanding about material application and theoretical thermoanalytical properties. In addition, it was performed thermal decomposition of cured composite kinetic study by isothermic and dynamic thermogravimetric methods

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2018-11-29T17:41:33Z No. of bitstreams: 1 2013 - Emerson Dalla Chieza.pdf: 3379954 bytes, checksum: 59d75d0f24fddc7d958c8e981de2274a (MD5) / Made available in DSpace on 2018-11-29T17:41:33Z (GMT). No. of bitstreams: 1 2013 - Emerson Dalla Chieza.pdf: 3379954 bytes, checksum: 59d75d0f24fddc7d958c8e981de2274a (MD5) Previous issue date: 2013-10-25 / The objective of this study was to establish an organic management form of corn and Crotalaria juncea intercropping, which allows to optimize production "in situ" by fabaceae plant biomass with nitrogen input to the system, without the competition that presence of green manure can to exercise, follow to compromise the performance of cereal. Three experiments were conducted in the experimental field of Embrapa Agrobiology in Serop?dica - RJ, between of November 2010 to March 2012. The experimental design was randomized blocks with six treatments and four replications (Experiments 1 and 3) or three replicates (experiment 2). The first experiment took place between November 2010 and March 2011 and had the following treatments: T1 - C. juncea seeded seven days before corn crop and managed at 33 days after emergence (33 DAE), T2 ? C. juncea seeded at the same date of corn sowing (29 DAE), T3 - C. juncea seeded 14 days after corn sown (102 DAE), T4 - C. juncea seeded 28 days after corn sown (88 DAE), T5 and T6 - corn cropping alone. Experiment 2: T1 - C. juncea seeds seven days before the corn (43 DAE), T2 - C. juncea seeded at the same date of corn sowing (37 DAE), T3 - C. juncea seeded seven days after corn sown (74 DAE), T4 - C. juncea seeded 14 days after corn sown (67 DAE), T5 and T6 - corn cropping alone. To first and second experiments, T3, T4 and T6 had been received 70 kg ha-1 of nitrogen by castor bean pie. Treatments of the third experiment consisted: T1 and T2 - C. juncea seeded at the same date of corn sowing (30 DAE) at the single row, T3 and T4 ? corn cropping alone at the single row, T5 and T6 - C. juncea seeded at the same date of corn sowing (30 DAE) at the double rows. For T2 and T6 treatments the green manure was managed and removed from the area, and had been added castor bean pie (70 kg of N ha-1). Also T4 received castor bean pie as a N source for corn. Also in the first experiment, for T1 and T2 trataments proceeded up studies of decomposition and release of nutrients from waste C. juncea by litter bags with 8 intervals collections. For the third test is conducted studies agronomic performance of corn and nitrogen losses through ammonia volatilization to waste C. juncea, castor bean pie and cattle manure through static cameras semi open. When corn sown simultaneously, regardless of the time of sowing, C. juncea did not affect the yield of cereal, promoted the addition of nitrogen to the system able of promoting positive balances for this nutrient. When the green manure was sown 7 days before or 14 days after sowing corn in the summer period, exerted a negative influence on growth and yield of maize. The waste C. juncea showed high rates of decomposition and nutrient release, with half-life for N less than 14 days. Were found discrepant emission rates for ammonia and castor bean pie residue C. juncea, with accumulated losses of about 46 and 14 %, respectively. The arrangement in double rows corn planting did not influence the yield of cereal. The results post the consortium in corn and C. juncea sown simultaneously as a promising culture system, capable of producing corn grain above the average yield of Rio of Janeiro state. / O objetivo geral deste trabalho foi estabelecer uma forma de manejo org?nico do cons?rcio entre as culturas de milho e Crotalaria juncea, que possibilite otimizar a produ??o ?In situ? de biomassa vegetal pela fabaceae, com aporte de nitrog?nio ao sistema, sem que a presen?a do adubo verde exer?a competi??o capaz de comprometer o rendimento do cereal. Foram conduzidos tr?s experimentos no campo experimental da Embrapa Agrobiologia em Serop?dica ? RJ, entre os meses de novembro de 2010 e mar?o de 2012. O delineamento experimental utilizado foi o de blocos ao acaso, com seis tratamentos e quatro repeti??es (experimentos 1 e 3) ou tr?s repeti??es (experimento 2). O primeiro experimento ocorreu entre novembro de 2010 e mar?o de 2011 e teve os seguintes tratamentos: T1?C. juncea semeada sete dias antes da cultura do milho e manejada aos 33 dias ap?s emerg?ncia (33 DAE); T2?C. juncea semeada simult?nea ao milho (manejo aos 29 DAE); T3?C. juncea semeada 14 dias ap?s o milho (manejo aos 102 DAE) + 70 kg N ha-1; T4?C. juncea semeada 28 dias ap?s o milho (manejo aos 88 DAE) + 70 kg N ha-1; T5-milho em monocultivo e T6-milho em monocultivo + 70 kg N ha-1. Experimento 2 (abril a setembro de 2011): T1?C. juncea semeada sete dias antes da cultura do milho (manejo aos 43 DAE); T2?C. juncea semeada simult?nea ao milho (manejo aos 37 DAE); T3?C. juncea semeada sete dias ap?s o milho (manejo aos 74 DAE) + 70 kg N ha-1; T4?C. juncea semeada 14 dias ap?s o milho (manejo aos 67 DAE) + 70 kg N ha-1; T5- milho em monocultivo e T6?milho em monocultivo+ 70 kg N ha-1. Os tratamentos do 3? Experimento (novembro de 2011 a mar?o de 2012) consistiram em: T1-C. juncea semeada simult?nea ao milho em fila simples com manejo aos 30 DAE e a biomassa da C. juncea mantida na ?rea; T2?C. juncea semeada simult?nea ao milho em fila simples com manejo aos 30 DAE com remo??o da parte a?rea de C. juncea e aplica??o de 70 kg N ha-1 via torta de mamona; T3- milho monocultivo em fila simples; T4 ?milho monocultivo em fila simples + 70 kg N ha-1; T5- C. juncea semeada simult?nea ao milho em fila dupla com manejo aos 30 DAE e a biomassa da C. juncea mantida na ?rea; T6 ? C. juncea semeada simult?nea ao milho em fila dupla com remo??o da parte a?rea de C. juncea e aplica??o de 70 kg N ha-1. Para todos os experimentos, o nitrog?nio aplicado em cobertura teve como fonte a torta de mamona. Nos dois primeiros ensaios foram realizados estudos morfofisiol?gicos dos cultivos a partir da an?lise funcional do crescimento de plantas, al?m do balan?o monet?rio e balan?o aparente de nitrog?nio. Tamb?m no experimento I, para T1 e T2, procederam-se estudos de decomposi??o e libera??o de nutrientes dos res?duos de C. juncea via sacolas de decomposi??o, com 8 intervalos de coletas. Para o terceiro ensaio procederam-se estudos de desempenho agron?mico do milho, an?lise econ?mica e balan?o de nitrog?nio. Tamb?m foram feitos estudos das perdas de nitrog?nio via volatiliza??o de am?nia para res?duos de C. juncea, torta de mamona e esterco bovino, atrav?s de c?meras est?ticas semi abertas em oito intervalos de coleta. Quando semeada simultaneamente ao milho, independente da ?poca de semeadura, a C. juncea n?o comprometeu o rendimento do cereal, promoveu a adi??o de nitrog?nio ao sistema capaz de promover balan?os positivos para este nutriente. Quando o adubo verde foi semeado 7 dias antes ou 14 dias ap?s a semeadura do milho, no per?odo de ver?o, esse exerceu influ?ncia negativa no crescimento e na produ??o de gr?os do milho. Os res?duos de C. juncea apresentaram elevadas taxas de decomposi??o e libera??o de nutrientes, com tempo de meia vida para N de menos de 14 dias. Foram encontradas discrepantes taxas de emiss?o de am?nia para torta de mamona e res?duos de C. juncea, com perdas acumuladas de cerca de 46 e 14%, respectivamente. O arranjo em fileiras duplas de plantio de milho n?o influenciou no rendimento do cereal. Os resultados encontrados postam o cons?rcio em milho e C. juncea semeados simultaneamente como um promissor sistema de cultivo, capaz de proporcionar produ??o de gr?os de milho acima da m?dia produtiva do estado do Rio de Janeiro.

Jusqu’à présent, la dynamique des fractions végétales n’avait jamais été étudiée dans les estuaires macrotidaux en raison de leur faible quantité, par rapports aux fortes charges en matières en suspension fines, et du manque de protocoles d’étude et d’échantillonnage adéquats. Les débris végétaux sont toutefois à l’origine de perturbations d’activités économiques qui impliquent la filtration de larges volumes d’eau. L’objectif de cette thèse était ainsi de comprendre la dynamique d’apport et de transit de ces débris végétaux dans l’estuaire de la Gironde par la mise en oeuvre d’un suivi spatio-temporel de leur distribution et de techniques nouvelles pour un tel estuaire hyper-turbide (incubations in-situ litter-bag, caractérisation biogéochimique, identification des sources). Les résultats principaux sont la mise en évidence du contrôle du régime hydrologique sur leur distribution et la détermination des échelles de temps de leur persistance dans l’estuaire de la Gironde. / Up to now, vegetal fraction dynamics has not been studied in macrotidal estuaries, due to its low quantity in comparison to the strong charge of suspended particulate matter, and due to the lack of appropriate protocols to sample and examine it. Nevertheless, vegetal debris have been identified as a factor able to disrupt a wide range of stakeholder activities that require huge volumes of water to filter. The objective of this PhD was to understand the input and transfer dynamics of vegetal debris in the Gironde Estuary by the implementation of a spatiotemporal btrack of their distribution and by the development of new techniques for this hyper-turbide estuary (in situ litter-bag incubations, biogeochemical characterization, and identification of the sources). Mean results highlight the influence of the hydrological regime in their distribution and reveal time scales of their persistence in the Gironde Estuary.

Atualmente, a participação da energia elétrica na matriz energética mundial é um assunto em evidência. O estudo do compósito isolante da barra estatórica, um dos componentes principais da máquina hidrogeradora, permite a obtenção de informações físico-químicas relevantes ao aperfeiçoamento do sistema, e também de estudos de comportamento térmico quando este é exposto à alta temperatura, por diferentes intervalos de tempo submetidos a estresses mecânicos, elétricos e/ou químicos. O sistema em estudo é o MICALASTIC®, desenvolvido pela empresa Siemens em 1960. Neste trabalho, as propriedades térmicas do compósito isolante, formado por uma fita de mica, resina epóxi (DGEBA), endurecedor (MHHPA) e acelerador naftenato de zinco (N-Zn) foram estudadas. Utilizando-se as técnicas termoanalíticas Calorimetria Exploratória Diferencial (DSC) e Termogravimetria e Termogravimetria Derivada (TG/DTG), o comportamento térmico de cada um dos materiais foi avaliado. As curvas DSC e TG/DTG também evidenciaram as possíveis interações químicas entre os componentes. Os estudos referentes à cura do material e da degradação térmica do compósito curado foram realizados. Observou-se claramente a influência da quantidade de acelerador na polimerização do sistema. A partir das curvas DSC, observou-se dois mecanismos de cura diferentes coexistentes, um com menor quantidade de N-Zn e outro com concentração maior, resultando em eventos de cura com início em temperaturas diferentes. Esse fato ainda não havia sido estudado desde a origem do sistema. Além disso, a perda de massa referente à evaporação do endurecedor no início do processo de cura foi confirmada a partir da caracterização do compósito por espectroscopia de absorção na região do infravermelho, comparando-se os espectros antes e após o fenômeno. Na prática, dois perfis de impregnação, o Homogêneo e o Heterogêneo, de barras condutoras são utilizados, e uma diferença significativa entre eles foi observada. Os estudos desenvolvidos devem ser associados a testes elétricos específicos para o melhor entendimento da relação entre a aplicação do material e suas propriedades teóricas termoanalíticas. Além disso, foi realizado o estudo cinético da decomposição térmica do compósito curado por métodos termogravimétricos, isotérmico e dinâmico. / Currently, the electric energy participation in the world energy matrix is a significant issue. The insulating composite in stator bars, which are one of the most important components in hydrogenerator machines, allows the attainment of relevant physical and chemical information to system optimization, in addition to study thermal behavior when the material is exposed to high temperatures, for different time intervals and mechanical, chemical and/or electrical stress. The studied system is MICALASTIC®, developed by Siemens Company in 1960. In this work, thermal properties of this insulating composite, composed by mica tape, epoxy resin (DGEBA), hardener (MHHPA) and zinc naphtenate (N-Zn) as accelerator, were studied. Using thermoananalytical techniques as Differential Scanning Calorimetry (DSC) and Thermogravimetry and Derivative Thermogravimetry (TG/DTG), thermal behavior of each material was evaluated. DSC and TG/DTG curves evidenced chemical interactions between components. The study relative to material curing and cured composite thermal degradation were described. It was clearly observed the N-Zn amount influence in the cure of system, and through DSC curves, it was possible to observe two distinct polymerization coexisting mechanisms, one with lower quantity of N-Zn and another one with bigger concentration, resulting in cure events starting in different temperatures. This fact has not been studied yet since the system has been originated. Besides that, the weight loss related to hardener evaporation starting with curing process was confirmed by composite characterization by FTIR spectra, before and after phenomenon. In practice, two impregnation patterns (Homogeneous and Heterogeneous) of conductive bars are used and a significant difference between them was observed. The developed studies have to be associated to electrical tests to a best understanding about material application and theoretical thermoanalytical properties. In addition, it was performed thermal decomposition of cured composite kinetic study by isothermic and dynamic thermogravimetric methods