An isothermal calorimeter controlled by the Peltier effect has been designed and constructed in order to investigate reaction rates in solventwater mixtures. Because a thermal method was used a constant temperature environment was essential and this was achieved by using a water bath controlled to + 0.0010C. This callorinieter has been used to study the alkaline hydrolysis of methyl acetate in dimethylsulphoxide, and tetrahydrofuran - water mixtures at 15, 25 and 35 [degrees]C. The results of other investigations on similar reactions have been reviewed and an attempt has been made to correlate the electrostatic theories of Laidler and Eyring, and Amis and jaffe with these results. Finally, because it appears that specific solvent interactions play a major part in the reaction rates the role of water in the reaction mechanism has been examined. A mechanistic explanation has been proposed in order to correlate the rate of reaction with the composition of water-solvent mixtures which justifies the Laidler and Eyring treatment of solvent effects on ion-molecule reactions. / Bradford University

<p>Energy harvesting is an interesting topic for today since we face running out of energy source, a serious problem in the world. Thermoelectric devices are a good candidate. They can convert heat (i.e. temperature gradient) to electricity. This result leads us to use them to harvest waste heat from engines or in power plants to generate electricity. Moreover, thermoelectric devices also perform cooling by applied voltage to device. This process is clean, which means that no greenhouse gases are emitted during the process. However, the converting efficiency of thermoelectrics are very low compare to a home refrigerator. The thermoelectric figure of merit (ZT_m) is a number which defines the converting efficiency of thermoelectric materials and devices. ZT_m is defined by Seebeck coefficient, electrical conductivity and thermal conductivity. To improve the converting efficiency, nanolaminated materials are good candidate.</p><p> </p><p>This thesis studies TiN/ScN artificial nanolaminates, or superlattices were grown by reactive dc magnetron sputtering from Ti and Sc targets. For TiN/ScN superlattice, X-ray diffraction (XRD) and reciprocal space map (RSM) show that we can obtain single crystal TiN/ScN superlattice. X-ray reflectivity (XRR) shows the superlattice films have a rough surface, supported by transmission electron microscopy (TEM). Also, TiN/ScN superlattices grew by TiN as starting layer has better crystalline quality than ScN as starting layer. The electrical measurement shows that our superlattice films are conductive films.</p><p> </p><p>Ca-Co-O system for inherently nanolaminated materials were grown by reactive rf magnetron sputtering from Ca/Co alloy target. The XRD shows we maybe get the [Ca₂CoO₃]_xCoO₂ phase, so far. The energy dispersive X-ray spectroscopy (EDX) reported that our films have Al conmination. We also discovered unexpected behavior when the film grown at high temperature showed larger thickness instead of thinner, which would have been expected due to possible Ca evaporation. The Ca-Co-O system requires further studies.</p>

Energy harvesting is an interesting topic for today since we face running out of energy source, a serious problem in the world. Thermoelectric devices are a good candidate. They can convert heat (i.e. temperature gradient) to electricity. This result leads us to use them to harvest waste heat from engines or in power plants to generate electricity. Moreover, thermoelectric devices also perform cooling by applied voltage to device. This process is clean, which means that no greenhouse gases are emitted during the process. However, the converting efficiency of thermoelectrics are very low compare to a home refrigerator. The thermoelectric figure of merit (ZTm) is a number which defines the converting efficiency of thermoelectric materials and devices. ZTm is defined by Seebeck coefficient, electrical conductivity and thermal conductivity. To improve the converting efficiency, nanolaminated materials are good candidate.   This thesis studies TiN/ScN artificial nanolaminates, or superlattices were grown by reactive dc magnetron sputtering from Ti and Sc targets. For TiN/ScN superlattice, X-ray diffraction (XRD) and reciprocal space map (RSM) show that we can obtain single crystal TiN/ScN superlattice. X-ray reflectivity (XRR) shows the superlattice films have a rough surface, supported by transmission electron microscopy (TEM). Also, TiN/ScN superlattices grew by TiN as starting layer has better crystalline quality than ScN as starting layer. The electrical measurement shows that our superlattice films are conductive films.   Ca-Co-O system for inherently nanolaminated materials were grown by reactive rf magnetron sputtering from Ca/Co alloy target. The XRD shows we maybe get the [Ca2CoO3]xCoO2 phase, so far. The energy dispersive X-ray spectroscopy (EDX) reported that our films have Al conmination. We also discovered unexpected behavior when the film grown at high temperature showed larger thickness instead of thinner, which would have been expected due to possible Ca evaporation. The Ca-Co-O system requires further studies.

The electrical and thermal conductance and the Seebeck coefficient are calculated for one-dimensional systems, and their behavior as a function of temperature and chemical potential is investigated. It is shown that the conductances are proportional to an average of the transmission probability around the Fermi level with the average taken for the thermal conductance being over a wider range. This has the effect of creating less well-defined plateaus for thermal-conductance quantization experiments. For weak non-linearities, the charge and entropy currents across a quantum point contact are expanded as a series in powers of the applied bias voltage and the temperature difference. After that, the expansions of the Seebeck voltage in temperature difference and the Peltier heat in current are obtained. Also, it is shown that the linear thermal conductance of a quantum point contact displays a half-plateau structure, almost flat regions appearing around half-integer multiples of the conductance quantum. This structure is investigated for the saddle-potential model.

Os materiais cerâmicos termoelétricos preparados a partir de ligas de SiGe, são utilizados em Geradores de Potência a Radioisótopos (GTR), na conversão de energia por efeitos termoelétricos. Neste trabalho de pesquisa foram estudadas as condições de preparação destas cerâmicas a partir de ligas de Silício-Germânio. Visou-se, portanto obter a melhor eficiência, pela otimização da \"Fator de Mérito\" (ou Número de loffe) , através dos processos de preparação e tratamentos térmicos da liga, e também na dopagem das cerâmicas. As ligas de silício-germânio (Si80Ge20) foram obtidas pela técnica de crescimento Czochralski, com campo elétrico aplicado (ECZ) e também por outras técnicas de fusão e solidificação, para comparação. Amostras com homogeneidade satisfatória foram quebradas e moídas para processamento cerâmico. E em seguida o pó da liga foi então dopado, misturando-se este com pó de boro amorfo e depois prensado, a fim de se obter elementos cerâmicos semicondutores tipo-p, com propriedades termoelétricas para altas temperaturas (&#8776 1000&#176C). A sinterização foi feita por três técnicas diferentes: pela técnica dos Pós Discretos ou PIES (Pulverized and Intermixed Elements of Sintering), pelo procedimento cerâmico convencional, e pela Prensagem a Quente (HotPressing), sendo esta última usada como padrão de comparação. As amostras obtidas foram analisadas e caracterizadas por técnicas convencionais de caracterização cerâmica tais como: medidas da densidade, dos tamanhos dos grãos, porosidade, área superficial, etc. e também por medidas de alguns dos parâmetros físicos que influenciam diretamente na eficiência termoelétrica tais como: coeficiente Seebeck, calor específico e parâmetro de rede, para ligas de composição nominal Si80Ge20 sem e com dopantes para semicondutores tipo-p. Uma amostra preparada pela General Electric usando a técnica de Prensagem a Quente (Hot-Pressing), foi usada como padrão de comparação. A liga obtida pela técnica ECZ apresentou boa homogeneidade. Foi encontrado que a qualidade microestrutural das cerâmicas tais como: densidade, a regularidade e a composição química dos grãos das cerâmicas depende muito da técnica de processamento. Estes elementos cerâmicos termoelétricos poderão ser usados como fonte de energia em Geradores de Potência Termoelétrica a Radioisótopos (GTR) mais especificamente na alimentação de satélites brasileiros fabricados pelo Centro Técnico Aeroespacial (CTA) junto com o Instituto de Estudos Avançados (IEAv) através da Divisão de Energia Nuclear (IEAvENU) deste Instituto, ou entre outras aplicações para fins militares e civil / Doped ceramics elements, prepared from Si-Ge alloy are used in Radioisotopic Thermoelectric Generators (GTR) for energy conversion by thermoelectrical effects. In this research the experimentais conditions to prepare thermoeletric ceramics from Silicon-Germanium alloys have been determined. The purpose was to get the best efficiency, by optimization of the \"Merit Figure\" (or \"loffe Number\'), using different preparation methods and thermal treatments of alloys, as well as the doping of these ceramics. Silicon-Gemanium alloys (Si80Ge20) have been grown by the Czochralski technique under applied eletric field (ECZ) , as well as by others fusion techniques for comparison. Afier the fusion of the alloy, samples with satisfactory homogeneity have been smashed and milled for ceramic processing. Powder of Si-Ge alloy was then heavely doped by mixing with amorphous boron powder and pressed to get type-P semiconductor thermoelectrical ceramics elements, at high temperatures (&#8776 1000 &#176C). The sintering was made by three differents techniques: PIES method (Pulverized and Intermixed Elements of Sintering), convencional ceramic processing, and Hot-Pressing sintering, for comparison. The samples have been analyzed and characterized by conventional ceramics technique such as: determination of density, grain size, porosity, surface area, etc. and measuring toa some physical parameters that affect directly the thermoelectrical efficiency such as: Seebeck coefficient, specific heat and lattice parameter to Silicon-Germanium alloys with nominal composition Si80Ge20 with or without dopings to type-P semiconductors. A sample prepared by General Electric Company using the Hot-Pressing technique was used as standard. The alloy grown by ECZ technique showed a good homogeneity. It was found that the microstructural quality of the ceramics such as: density, grains regularity and chemical composition of the ceramics depend of the ceramic processing technique. These thermoelectrical elements can be used as power supply for the Brazilian satellites made by the Centro Técnico Aeroespacial (CTA) together with the Instituto de Estudos Avançados (IEAv) through the Divisão de Engenharia Nuclear (ENU) , and among other applications for military and civil purposes

Made available in DSpace on 2014-12-17T15:14:52Z (GMT). No. of bitstreams: 1 JoseASM_TESE.pdf: 5255189 bytes, checksum: cf0724bd476902a8aa17f19022619211 (MD5) Previous issue date: 2010-12-17 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / This study will show the capability of the reactive/nonreactive sputtering (dc/rf) technique at low power for the growth of nanometric thin films from magnetic materials (FeN) and widegap semiconductors (AlN), as well as the technological application of the Peltier effect using commercial modules of bismuth telluride (Bi2Te3). Of great technological interest to the high-density magnetic recording industry, the FeN system represents one of the most important magnetic achievements; however, diversity of the phases formed makes it difficult to control its magnetic properties during production of devices. We investigated the variation in these properties using ferromagnetic resonance, MOKE and atomic force microscopy (AFM), as a function of nitrogen concentration in the reactive gas mixture. Aluminum nitride, a component of widegap semiconductors and of considerable interest to the electronic and optoelectronic industry, was grown on nanometric thin film for the first time, with good structural quality by non-reactive rf sputtering of a pure AlN target at low power (&#8776; 50W). Another finding in this study is that a long deposition time for this material may lead to film contamination by materials adsorbed into deposition chamber walls. Energy-dispersive X-ray (EDX) analysis shows that the presence of magnetic contaminants from previous depositions results in grown AlN semiconductor films exhibiting magnetoresistance with high resistivity. The Peltier effect applied to commercially available compact refrigeration cells, which are efficient for cooling small volumes, was used to manufacture a technologically innovative refrigerated mini wine cooler, for which a patent was duly registered / Neste trabalho ser? mostrado a habilidade da t?cnica de sputtering (dc/rf) reativo/n?o-reativo a baixa pot?ncia para o crescimento de filmes nanom?tricos de materiais magn?ticos (FeN) e semicondutores de gap largo (AlN) assim como a aplica??o tecnol?gica do efeito peltier por m?dulos comerciais de Telureto de Bismuto (Bi2Te3). De grande interesse tecnol?gico para ind?stria de grava??o magn?tica de altas densidades o sistema FeN apresenta um dos mais altos momentos magn?ticos, entretanto a diversidade de fases formadas torna-o ainda, de dif?cil controle as suas propriedades magn?ticas para produ??o de dispositivos. Neste trabalho foi investigado a varia??o destas propriedades por resson?ncia ferromagn?tica, MOKE e microscopia de for?a at?mica (AFM) em fun??o da concentra??o de nitrog?nio na mistura gasosa do crescimento reativo. O Nitreto de Alum?nio, enquadrado nos semicondutores de gap largo e de grande interesse na ind?stria eletr?nica e optoeletr?nica foi crescido em filmes nanom?tricos, de modo in?dito, com boa qualidade estrutural a partir de alvo puro de AlN por sputtering rf n?o-reativo a baixa pot?ncia (~50W). Outra verifica??o deste trabalho ? que o longo tempo de deposi??o para este material, pode levar a contamina??o dos filmes por materiais adsorvidos nas paredes da c?mara de deposi??o. A investiga??o por EDX mostra a presen?a de contaminantes magn?ticos, provenientes de deposi??es anteriores, leva os filmes semicondutores de AlN crescidos a apresentarem magnetoresist?ncia com resistividade alta. O efeito peltier aplicado nas c?lulas compactas de refrigera??o dispon?veis comercialmente e eficientes para resfriamento de pequenos volumes foi aplicada na cria??o de uma adega refrigerada disponibilizado para a ind?stria local como inova??o tecnol?gica com registro de patente

Os materiais cerâmicos termoelétricos preparados a partir de ligas de SiGe, são utilizados em Geradores de Potência a Radioisótopos (GTR), na conversão de energia por efeitos termoelétricos. Neste trabalho de pesquisa foram estudadas as condições de preparação destas cerâmicas a partir de ligas de Silício-Germânio. Visou-se, portanto obter a melhor eficiência, pela otimização da \"Fator de Mérito\" (ou Número de loffe) , através dos processos de preparação e tratamentos térmicos da liga, e também na dopagem das cerâmicas. As ligas de silício-germânio (Si80Ge20) foram obtidas pela técnica de crescimento Czochralski, com campo elétrico aplicado (ECZ) e também por outras técnicas de fusão e solidificação, para comparação. Amostras com homogeneidade satisfatória foram quebradas e moídas para processamento cerâmico. E em seguida o pó da liga foi então dopado, misturando-se este com pó de boro amorfo e depois prensado, a fim de se obter elementos cerâmicos semicondutores tipo-p, com propriedades termoelétricas para altas temperaturas (&#8776 1000&#176C). A sinterização foi feita por três técnicas diferentes: pela técnica dos Pós Discretos ou PIES (Pulverized and Intermixed Elements of Sintering), pelo procedimento cerâmico convencional, e pela Prensagem a Quente (HotPressing), sendo esta última usada como padrão de comparação. As amostras obtidas foram analisadas e caracterizadas por técnicas convencionais de caracterização cerâmica tais como: medidas da densidade, dos tamanhos dos grãos, porosidade, área superficial, etc. e também por medidas de alguns dos parâmetros físicos que influenciam diretamente na eficiência termoelétrica tais como: coeficiente Seebeck, calor específico e parâmetro de rede, para ligas de composição nominal Si80Ge20 sem e com dopantes para semicondutores tipo-p. Uma amostra preparada pela General Electric usando a técnica de Prensagem a Quente (Hot-Pressing), foi usada como padrão de comparação. A liga obtida pela técnica ECZ apresentou boa homogeneidade. Foi encontrado que a qualidade microestrutural das cerâmicas tais como: densidade, a regularidade e a composição química dos grãos das cerâmicas depende muito da técnica de processamento. Estes elementos cerâmicos termoelétricos poderão ser usados como fonte de energia em Geradores de Potência Termoelétrica a Radioisótopos (GTR) mais especificamente na alimentação de satélites brasileiros fabricados pelo Centro Técnico Aeroespacial (CTA) junto com o Instituto de Estudos Avançados (IEAv) através da Divisão de Energia Nuclear (IEAvENU) deste Instituto, ou entre outras aplicações para fins militares e civil / Doped ceramics elements, prepared from Si-Ge alloy are used in Radioisotopic Thermoelectric Generators (GTR) for energy conversion by thermoelectrical effects. In this research the experimentais conditions to prepare thermoeletric ceramics from Silicon-Germanium alloys have been determined. The purpose was to get the best efficiency, by optimization of the \"Merit Figure\" (or \"loffe Number\'), using different preparation methods and thermal treatments of alloys, as well as the doping of these ceramics. Silicon-Gemanium alloys (Si80Ge20) have been grown by the Czochralski technique under applied eletric field (ECZ) , as well as by others fusion techniques for comparison. Afier the fusion of the alloy, samples with satisfactory homogeneity have been smashed and milled for ceramic processing. Powder of Si-Ge alloy was then heavely doped by mixing with amorphous boron powder and pressed to get type-P semiconductor thermoelectrical ceramics elements, at high temperatures (&#8776 1000 &#176C). The sintering was made by three differents techniques: PIES method (Pulverized and Intermixed Elements of Sintering), convencional ceramic processing, and Hot-Pressing sintering, for comparison. The samples have been analyzed and characterized by conventional ceramics technique such as: determination of density, grain size, porosity, surface area, etc. and measuring toa some physical parameters that affect directly the thermoelectrical efficiency such as: Seebeck coefficient, specific heat and lattice parameter to Silicon-Germanium alloys with nominal composition Si80Ge20 with or without dopings to type-P semiconductors. A sample prepared by General Electric Company using the Hot-Pressing technique was used as standard. The alloy grown by ECZ technique showed a good homogeneity. It was found that the microstructural quality of the ceramics such as: density, grains regularity and chemical composition of the ceramics depend of the ceramic processing technique. These thermoelectrical elements can be used as power supply for the Brazilian satellites made by the Centro Técnico Aeroespacial (CTA) together with the Instituto de Estudos Avançados (IEAv) through the Divisão de Engenharia Nuclear (ENU) , and among other applications for military and civil purposes

The introduction of this paper describes three thermoeletrical effects and their properties. It also deals with thermoelectrical cells, which are using Seebeck´s and Peltrier´s effects. The paper decribes principles how the Peltier´s cells work, their mathematical model, construction and practical use. The paper shows what kinds, shapes and output we can meet at the market and which kinds of parameters regulate their selection. The paper suggests the possibility to measure characteristic behaviour and quantity during laboratories tasks and their evaluations. At the conclusion is adduced the suggestion of laboratory task together with theoretically made pilot protocol.

No description available.

Local thermal management has important implications regarding comfort, energy consumption, and electronic device performance/lifetime. While organic thermoelectrics have emerged as promising materials for flexible thermoelectric energy harvesting devices, their potential as Peltier cooling element has been largely overlooked. Here, micro-thermoelectric coolers based on doped small molecule thin-films with a fast response time (around 25 µs) which is among the fastest micro-thermoelectric coolers reported are presented. This experimental cooling performance is supported by simulation using the finite-element method for thermal transport. The results show that organic thermoelectrics offer great potential for flexible and wearable micro-thermoelectric cooling applications.