2012 IEEE International Symposium on Electrical Insulation (ISEI), June 10-13, 2012, Ritz Carlton Hotel, San Juan, PR, USA

Computational quantum mechanics in the frame work of density functional theory (DFT) was used to investigate the effect of chemical impurities on high field conduction in polyethylene (PE). The impurity states in the band gap caused by common chemical impurities were characterized in terms of their “depth”, i.e. energy relative to their relevant band edge (valence band or conduction band), and in terms of the extent to which their wavefunctions were localized to a single polymer chain or extended across chains. It was found that impurity states can affect high field phenomena by providing “traps” for carriers, the depths of which were computed from first principle in agreement with estimates in literature. Since the square of the wavefunction is proportional to the spatial electron probability density, transfer of charge between chains requires wavefunctions which are extended across chains. Impurity states which are extended between chains can facilitate the inherently limited interchain charge transfer in PE, as the DFT study of iodine doped PE revealed. The introduction of iodine into PE increases conductivity by several orders of magnitude, increases hole mobility to a much greater extent than electron mobility, and decreases the activation energy of conduction from about 1 eV to about 0.8 eV. These characteristics were explained in terms of the impurity states introduced by iodine and wavefunctions of those states. Understanding the effect of iodine on conduction in PE provided a basis for understanding the effect of common chemical impurities on conduction therein. In particular, carbonyl and vinyl impurities create states which should promote hole mobility in a manner very similar to that caused by iodine. It was demonstrated that in the context of high field conduction in PE, besides the traditional focus on the depth of impurity states, it is important to study the spatial features of the states wavefunctions which are neither discussed nor accounted for in present models.

Computational quantum mechanics in the frame work of density functional theory (DFT) was used to investigate the effect of chemical impurities on high field conduction in polyethylene (PE). The impurity states in the band gap caused by common chemical impurities were characterized in terms of their “depth”, i.e. energy relative to their relevant band edge (valence band or conduction band), and in terms of the extent to which their wavefunctions were localized to a single polymer chain or extended across chains. It was found that impurity states can affect high field phenomena by providing “traps” for carriers, the depths of which were computed from first principle in agreement with estimates in literature. Since the square of the wavefunction is proportional to the spatial electron probability density, transfer of charge between chains requires wavefunctions which are extended across chains. Impurity states which are extended between chains can facilitate the inherently limited interchain charge transfer in PE, as the DFT study of iodine doped PE revealed. The introduction of iodine into PE increases conductivity by several orders of magnitude, increases hole mobility to a much greater extent than electron mobility, and decreases the activation energy of conduction from about 1 eV to about 0.8 eV. These characteristics were explained in terms of the impurity states introduced by iodine and wavefunctions of those states. Understanding the effect of iodine on conduction in PE provided a basis for understanding the effect of common chemical impurities on conduction therein. In particular, carbonyl and vinyl impurities create states which should promote hole mobility in a manner very similar to that caused by iodine. It was demonstrated that in the context of high field conduction in PE, besides the traditional focus on the depth of impurity states, it is important to study the spatial features of the states wavefunctions which are neither discussed nor accounted for in present models.

Thesis (M.S.)--University of Alabama at Birmingham, 2009. / Title from PDF t.p. (viewed July 21, 2010). Includes bibliographical references (p. 70-72).

Submitted by MAICON CARLONE DA SILVA null (maicon.carlone@gmail.com) on 2017-05-23T16:56:49Z No. of bitstreams: 1 Dissertação - Maicon Carlone da Silva .pdf: 5898245 bytes, checksum: dcaea8b738bb0b5c8699c89bc40d8b7a (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-05-23T18:30:12Z (GMT) No. of bitstreams: 1 silva_mc_me_bauru.pdf: 5898245 bytes, checksum: dcaea8b738bb0b5c8699c89bc40d8b7a (MD5) / Made available in DSpace on 2017-05-23T18:30:12Z (GMT). No. of bitstreams: 1 silva_mc_me_bauru.pdf: 5898245 bytes, checksum: dcaea8b738bb0b5c8699c89bc40d8b7a (MD5) Previous issue date: 2017-04-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Compostos do tipo Ca1-xRxB6 (onde R representa o elemento de terra rara) tem sido estudados durantes os últimos anos principalmente no que se refere as suas características magnéticas e de transporte, porem elas ainda são controversas. Em particular a técnica de Ressonância Magnética tem sido usada para estudar compostos de Ca1-xEuxB6 (EPR) para diversas concentrações de Eu, o qual sugere a existência de uma transição metal isolante quando mudamos a concentração de Eu. Neste trabalho deveremos analisar teoricamente os espectros experimentais deste composto, em função da concentração deste elemento de terra rara. Os espectros de EPR foram simulados usando o modelo de Plefka para diversos valores de concentração x em Ca1-xEuxB6 monocristalino, isto é, 7%, 10%, 15%, 30%, 60% e 100%, visando elucidar a evolução das fases isolantes e semimetálicas, além do colapso do espectro com o aumento da concentração da impureza magnética. Tendo em vista que formas de linha simétricas são características de matrizes isolantes e assimétricas de matrizes metálicas, focaremos o nosso estudo na assimetria dos espectros de EPR. Para procurar pelo conjunto de parâmetros que melhor ajusta o espectro teórico ao experimental utilizamos o método de Simulated Annealing (SA), onde minimizamos a diferencia média quadrática entre os espectros. Ao longo deste trabalho foram reproduzidos as principais características dos espectros experimentais. Também obtivemos parâmetros importantes como o de Campo Cristalino, valor de g, parâmetros de troca da interação Eu-Eu e o parâmetro de assimetria do espectro de absorção. Conseguimos mostrar que ao aumentar a concentração o espectro evolui de uma forma Lorentziana para Dysoniana, mostrando a existência da transição metal-isolante. / Compounds of the type Ca1-xRxB6 (where R represents the element of rare earth) have been studied during the last years mainly as regards their magnetic and transport characteristics, but they are still controversial. In particular the Magnetic Resonance technique has been used to study compounds of Ca1-xEuxB6 (EPR) for several concentrations of Eu, which suggests the existence of an insulating metal transition when we change the concentration of Eu. In this work we will theoretically analyze the spectra Experimental results of this compound, depending on the concentration of this element of rare earth. In the present case, the EPR fine structure spectra were simulated using the Plefka model for various values of concentration (x) in monocrystalline Ca1-xEuxB6, that is, 7%, 10%, 15%, 30%, 60% and 100%, aiming to elucidate the evolution of the insulating and semi-metallic phases, besides the collapse of the spectrum with the increase of the concentration of magnetic impurities. Considering that symmetrical line shapes are characteristic of insulating and asymmetric matrices of metal matrices, we will focus our study on the asymmetry of RPE spectra. To find for the set of parameters that best adjusts the theoretical spectrum to the experimental, we used the Simulated Annealing (SA) method, where we minimize the mean square difference between the spectra. Throughout this work the main characteristics of the experimental spectra were reproduced. We also obtained important parameters such as the Crystalline Field, g value, Eu-Eu interaction exchange parameters and the asymmetry parameter of the absorption spectrum. We show that by increasing the concentration the spectrum evolves from a Lorentzian to Dysonian form, showing the existence of the metal-insulating transition.

Made available in DSpace on 2014-06-11T19:29:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-12-18Bitstream added on 2014-06-13T18:39:08Z : No. of bitstreams: 1 moretti_jp_me_bauru.pdf: 623430 bytes, checksum: 8a8b037467da86497bd4f13030b6c3d1 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os defletores de calor automotivos são constituídos de uma carcaça de aço aluminizado que envolve um isolante térmico, fisicamente bastante semelhante ao papel, entrentanto com uma composição elevada de partes inorgânicas, chegando a cerca de 80% do material seco. Esses materiais são utilizados para a proteção de vários componentes fundamentais nos veículos presentes em locais de temperaturas extremamentes elevadas, tais como o bloco do motor e o sistema de exaustão de gases. Essa proteção garantes a integridade de peças vitais sensíveis ao calor, como por exemplo, os circuitos eletro-eletrônicos. Neste trabalho, recortes do elemento defletor de calor foram reciclados em sistema manual e em escala industrial e propriedades como espessura, densidade, compreensibilidade, retorno, teor de cinzas, efetividade da deflexão de calor, além da análise por termogravimetria e microscopia eletrônica de varredura com acoplamento de sistema de energia dispersiva (EDS) foram realizados. Os produtos reciclados demonstraram resultados positivos quanto aos ensaios de deflexão de calor, teor de cinzas, ensaio termogravimétrica e visualmente dos espectros de energia dispersiva, indicando a manutenção da composição geral do material após os processos de reciclagem realizados. Os resultados dos ensaios físicos, como espessura, densidade, resistência à tração após quatro horas a sem graus Celsius, resistência à tração após 22 horas a 200 graus Celsius, compreessibilidade e retorno, compressibilidade e retorno após 22 horas a 200 graus Celsius, apontaram variações de acordo com a prensagem exercida no material, indicando a necessidade de melhorias nos processos de reciclagem utilizados / The automotive heat shields are made of an aluminized steel housing that surrounds a thermal insulator, physically quite similar to paper, though with a composition of inorganic parts high, reaching about 80% of dry material. These materials are used to protect several key components in vehicles sites present in extremely high temperatures, such as the engine block and the exhaust gas system. This protetion ensures the integrity of vital parts sensitive to heat, such as electric and electronic circuits. In this paper, clippings element baffe heat were recycled in manual in industrial scale and properties such as thickness, density, compressibility, recovery, ignition loss, effectiveness of heat deflection, and thermogravimetric analysis and scanning electron microscopy with coupling energy dispersive system (EDS) were performed. The recycled product showed positive results regarding heat deflection tests, ash content, thermogravimetric test and visually energy dispersive spectra, indicating maintaining the overall composition of the material after recycling processes performed. The results of the physical tests such as thickness, density, tensile strengh after four hours at one hundred degrees Celsius tensile strength after twenty-two hours to two hundred degrees Celsius, and recovery, compressibility, compressibility and recovery after twenty-two hours to two hundred degrees Celsius, showed variations according to the press exerted on the material, pointing to the need for improvements in recycling processes used

Orientador: Sandro Donnini Mancini / Banca: Jane Maria Faulstich de Paiva / Banca: Maria Lucia Pereira Antunes / Resumo: Os defletores de calor automotivos são constituídos de uma carcaça de aço aluminizado que envolve um isolante térmico, fisicamente bastante semelhante ao papel, entrentanto com uma composição elevada de partes inorgânicas, chegando a cerca de 80% do material seco. Esses materiais são utilizados para a proteção de vários componentes fundamentais nos veículos presentes em locais de temperaturas extremamentes elevadas, tais como o bloco do motor e o sistema de exaustão de gases. Essa proteção garantes a integridade de peças vitais sensíveis ao calor, como por exemplo, os circuitos eletro-eletrônicos. Neste trabalho, recortes do elemento defletor de calor foram reciclados em sistema manual e em escala industrial e propriedades como espessura, densidade, compreensibilidade, retorno, teor de cinzas, efetividade da deflexão de calor, além da análise por termogravimetria e microscopia eletrônica de varredura com acoplamento de sistema de energia dispersiva (EDS) foram realizados. Os produtos reciclados demonstraram resultados positivos quanto aos ensaios de deflexão de calor, teor de cinzas, ensaio termogravimétrica e visualmente dos espectros de energia dispersiva, indicando a manutenção da composição geral do material após os processos de reciclagem realizados. Os resultados dos ensaios físicos, como espessura, densidade, resistência à tração após quatro horas a sem graus Celsius, resistência à tração após 22 horas a 200 graus Celsius, compreessibilidade e retorno, compressibilidade e retorno após 22 horas a 200 graus Celsius, apontaram variações de acordo com a prensagem exercida no material, indicando a necessidade de melhorias nos processos de reciclagem utilizados / Abstract: The automotive heat shields are made of an aluminized steel housing that surrounds a thermal insulator, physically quite similar to paper, though with a composition of inorganic parts high, reaching about 80% of dry material. These materials are used to protect several key components in vehicles sites present in extremely high temperatures, such as the engine block and the exhaust gas system. This protetion ensures the integrity of vital parts sensitive to heat, such as electric and electronic circuits. In this paper, clippings element baffe heat were recycled in manual in industrial scale and properties such as thickness, density, compressibility, recovery, ignition loss, effectiveness of heat deflection, and thermogravimetric analysis and scanning electron microscopy with coupling energy dispersive system (EDS) were performed. The recycled product showed positive results regarding heat deflection tests, ash content, thermogravimetric test and visually energy dispersive spectra, indicating maintaining the overall composition of the material after recycling processes performed. The results of the physical tests such as thickness, density, tensile strengh after four hours at one hundred degrees Celsius tensile strength after twenty-two hours to two hundred degrees Celsius, and recovery, compressibility, compressibility and recovery after twenty-two hours to two hundred degrees Celsius, showed variations according to the press exerted on the material, pointing to the need for improvements in recycling processes used / Mestre

CAPES / Com o avanço da miniaturização de componentes e dispositivos eletrônicos ocorrida nos últimos anos, a utilização de materiais dielétricos e a necessidade de informações precisas sobre o comportamento dielétrico apresentado por estes materiais aumentou consideravelmente. Neste trabalho é apresentado inicialmente as motivações para o estudo do comportamento dielétrico e da modelagem da função resposta dielétrica. A partir da teoria proposta por Debye e identificando suas peculiaridades, são exploradas algumas extensões deste modelo e analisada a interpretação da função resposta proposta por estes. Muitos modelos assumiam a existência de múltiplas interações envolvendo os dipolos com o meio dielétrico, as quais contribuíam para a dinâmica do comportamento dielétrico, somente mais tarde é que estas múltiplas interações ganharam uma conexão entre a resposta dielétrica observada com as propriedades intrínsecas do material. Por meio do modelo proposto por Dissado e Hill e assumindo dados experimentais disponíveis na literatura para alguns materiais, foi testada a validade da função resposta resultante do modelo, na qual veri cou-se a capacidade da mesma em ajustar as curvas para as componentes real e imaginária da permissividade para uma grande variedade de materiais dielétricos. A partir das simulações e análises realizadas, ficou evidente a dependência do comportamento dielétrico com a temperatura, fato este que deverá ser abordado em trabalhos futuros. / With the improvement of miniaturization of electronic components and devices occurred in recent years, the use of dielectric materials and the need for accurate information about the dielectric behavior displayed by these materials has increased considerably. In this work is initially presented the motivations for the study of dielectric behavior and the modeling of the dielectric response function. From the theory proposed by Debye and identifying its peculiarities, are exploited some extensions of this model and analyzed the interpretation of response function proposed by these. Many models used to assume the existence of multiple interactions involving the dipoles with the dielectric medium, which contributed to the dynamics of the dielectric behavior, only later the multiple interactions won a connection between the dielectric response observed with the intrinsic properties of the materials. Through the model proposed by Dissado and Hill and assuming experimental data available in bibliography for some materials, was tested the validity of the response function resulting from the model, in which was veri ed the ability of the same to adjust the curves for the real and imaginary components of permittivity to a wide variety of dielectric materials. From the simulations and analyzes performed, was evident the dependence of dielectric behavior with temperature, a fact that should be discussed in future works.

The topic of this publication is a comparison of insulated sandwich panels and materials of organic origin - wood based materials. There were compared insulative properties, lifetime and finacial costs of these materials.

Neste trabalho obtivemos curvas de corrente induzida por raios-x no teflon FEP que apresentou as seguintes características: a) Inicialmente a corrente subiu, atingindo um máximo em torno dos 10s; b) Decaiu lentamente durante aproximadamente meia-hora, e; c) Atingiu um estado estacionário daí por diante. Ao se desligar a radiação, registrou-se a componente atrasada desta corrente. Usamos amostras de 25&#956m de espessura e área irradiada foi de 12,5cm2 ; o campo aplicado da ordem de 104V/cm e taxa de exposição da ordem de 102 R/S. Verificamos que depois de completada de uma medida da corrente induzida num amostra, esta não voltava a se repetir se realizada depois algumas horas; a corrente então não apresentava um máximo, indo diretamente ao valor estacionário; porém se recuperava com o tempo, repetindo a primeira medida depois de algumas semanas. Para mostrar que esta subida e descida da corrente induzida, não era devido a um efeito de campo, realizamos uma medida onde aplicamos o campo intermitente por curtos períodos de tempo, enquanto a amostra era irradiada. O resultado se mostrou igual aos realizados com tensão aplicada permanentemente. Estudamos ainda a dependência da condutividade induzida com a taxa de exposição e com o campo. Finalmente construímos um modelo teórico para o material que permitiu a obtenção de parâmetros do mesmo concordantes com o esperado. Acrescentamos a este trabalho uma curva que mostra o efeito da variação da temperatura sobre uma medida longa da absorção dielétrica. / In this work we measured X-ray indeuced currents in teflon FEP wich show the following features: a) At the beginning the current increases and reaches a maximum at about 10s; b) It decays slowly during 30 minutes, when a steady state is reached slowly during 30 minutes, when a steady state is reached the delayed conductvity was also measured. The sample were 25&#956m thick and the irradiated área was 12,5cm2; the applied field was of the order of 104 V/cm and the dose rate of the order of 102 R/S. It was observed that a new measurement of the induced conductivity does not duplicate the first one, but after a few hours it come backs to the original one. In order to show that the increase and the deacrease of the current is not caused by na electric field effect we realized a measurement where we polled the sample intermitently while it was irradiated. The current thus obtained had about the same values of the first measuments, when the voltage was applied all the time during the measurement. We also measured the absorption current f a teflon sample wich shows after some days the effect of its variation due the variation of the ambiental temperature.