19 Dec 2004. / Published through the Information Bridge: DOE Scientific and Technical Information. "IS-T 1983" Fei Tang. 12/19/2004. Report is also available in paper and microfiche from NTIS.

19 Dec 2004. / Published through the Information Bridge: DOE Scientific and Technical Information. "IS-T 1993" Ning Yang. 12/19/2004. Report is also available in paper and microfiche from NTIS.

L’utilisation croissante de systèmes électroniques miniaturisés induit une forte demande en microsources d’énergie performantes, telles que les microbatteries au lithium. En vue d’améliorer les propriétés de l’électrolyte, nous avons étudié les propriétés électriques et thermomécaniques d’électrolytes solides de type borate de lithium. Une corrélation entre la conductivité ionique et le coefficient de dilatation thermique (CTE) a été mise en évidence pour différentes compositions de verres massifs. A partir des résultats de CTE obtenus, un modèle de prédiction basé sur les travaux de Appen permettant la détermination de ce dernier en fonction de la composition chimique a été développé. Dans un second temps, différentes techniques de préparation de cibles denses nitrurées ont été mises en œuvre afin d’abaisser le CTE de la cible et ainsi permettre son utilisation sur une plus longue durée. Par ailleurs, l’utilisation d’une cible nitrurée a également été envisagée pour augmenter la teneur en azote dans les couches minces. Finalement, des couches minces d’électrolyte de différentes compositions ont été préparées par pulvérisation cathodique (sous plasma d’argon ou d’azote pur) et ont fait l’objet d’une caractérisation chimique, structurale, électrique et thermomécanique. Le rôle bénéfique de l’azote sur la conductivité ionique des couches minces a ainsi pu être confirmé. / The growing use of miniaturized electronic devices results in a strong demand in high-performance energy microsources, such as lithium microbatteries. In order to improve electrolyte properties, we have studied the electrical and thermomechanical properties of bulk electrolyte based on lithium borate glasses. A correlation between ionic conductivity and thermal expansion coefficient has been evidenced for bulk materials. Further to CTE results, a predicting model based on studies leaded by Appen allowing a determination of CTE as a function of the chemical composition has been developed. In a second time, different preparation techniques of dense nitrated targets have been implemented in order to decrease their CTE and to allow their use for a longer period. Otherwise, nitrated targets have also been considered to increase the nitrogen content in thin films. Finally, electrolyte thin films of different compositions have been prepared by rf magnetron sputtering (under pure argon or nitrogen gas) and have been chemically, structurally, electrically and thermomecanically characterized. The favorable influence of nitrogen on the ionic conductivity of thin films has been confirmed.

Ce travail de thèse porte sur l’étude et la réalisation de micro-capteurs dédiés à la mesure de vitesse angulaire par des principes basés sur des échanges thermiques. Deux types de gyromètres ont été développés dont la principale différence est liée au principe qui permet la mise en mouvement du gaz : convection forcée pour l’un et expansion thermique pour l’autre. Le principe est basé sur la modification par la force de Coriolis des échanges thermiques dans un fluide chauffé localement lorsque le dispositif est soumis à une vitesse de rotation. L’utilisation d’un fluide comme masse sismique est en rupture avec les concepts de gyromètres dits traditionnels. Cet avantage a pour conséquence la possibilité d’une utilisation dans des conditions environnementales sévères telles que de fortes accélérations (> 10 000 g) et de fortes vibrations. Les objectifs de ce travail consistent à étudier, à développer et à caractériser ces deux types de gyromètres. Pour cela, des études numériques ont été menées afin de mieux appréhender les phénomènes physiques et thermiques mis en jeu dans la cavité. On a pu aussi étudier l’effet des paramètres thermo-physiques du fluide, des différentes dimensions géométriques et de la vitesse d’écoulement du gaz sur la sensibilité et l’étendue de mesure. Par ailleurs, des prototypes des deux types de gyromètres ont été réalisés puis caractérisés. Les résultats sont très encourageants et les principes validés, mais leur confrontation avec ceux de la simulation montre que des améliorations sont à apporter sur le modèle numérique. / This PhD thesis deals with both study and fabrication of micro-sensors dedicated to the measurement of angular velocity, these devices are based on heat exchanges. Two types of gyroscopes have been developed, one using a jet of gas being deflected by the rotation, the other one using thermal expansion of a gas. Under rotation, heat transfers in a locally heated fluid is modified by the Coriolis force and induces a change in temperature distribution. Using a fluid as seismic mass enhances performances in terms shock (> 10 000g) and vibration resistances compared with standard mechanical gyroscopes.The aim of this work has been to study, develop and characterize these two gyroscopes. For this purpose, numerical studies have been carried out in order to improve our understanding of physical and thermal phenomena involved in the device. Effects of thermo-physical parameters, sensor size and gas flow velocity on both sensitivity and measuring range were analyzed.On the other hand, prototypes of both gyroscopes were manufactured and characterized. The proof of concept has been validated and encouraging results have been found. Comparison of measure and simulation have shown that improvements have to be made on the numerical model.

Made available in DSpace on 2014-06-11T19:32:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-05-19Bitstream added on 2014-06-13T19:21:56Z : No. of bitstreams: 1 cabanasnavarro_f_dr_rcla.pdf: 4430700 bytes, checksum: a93015794da4e288862dea20ef0e01d3 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Considerando um conjunto de 21 tipos de rochas utilizadas como revestimento e subdivididas em quatro conjuntos por afinidade da composição mineral (rochas carbonáticas, quartzosas, feldspáticas e quartzo-feldspáticas) foram realizados ensaios tecnológicos para a determinação do coeficiente de dilatação térmica linear e da resistência à compressão uniaxial, bem como a anisotropia dessas propriedades. Os dados tecnológicos obtidos foram correlacionados com informações petrográficas qualitativas e quantitativas referentes à composição mineral, variações texturais e estruturais determinadas em seções ortogonais entre si a partir de um sistema de referência (xyz) baseado na foliação e lineação macroscopicamente visíveis. A análise integrada dos dados utilizando estatística convencional e multivariada procurou apontar as variáveis petrográficas mais relevantes para as duas propriedades tecnológicas enfocadas e suas respectivas anisotropias. A dilatação térmica e sua anisotropia são influenciadas principalmente pela composição mineral e pela orientação preferencial dos minerais embora as microfissuras desempenhem papel importante em alguns casos. A tensão de compressão mostra sua variabilidade e anisotropia influenciadas pela granulação média, tipos de contatos minerais predominantes e padrões de microfissuras mais ou menos definidos por influência da foliação presente. Constatou-se que no conjunto analisado a presença da foliação não implica necessariamente em anisotropia das duas propriedades estudadas. / The anisotropy of thermal expansion coefficient and compressive tensile strength were determined for 21 commercially used stones gathered in four set according the main mineral composition named carbonatic, quartz-rich, feldspar-rich and quartz-feldspar-rich rocks. Using a coordinate reference system (xyz) based on the macroscopic visible foliation and lineation the samples were submitted to normalized laboratorial analyses for determination of the both technological properties and the petrographical features such as mineral composition, texture and fabric. Additionally was carried out measurements of weathered area and microcrack quantification by image analysis and texture quantification by U-stage methods. In order to understand the relationship between the anisotropy measured and petrographical data it was applied traditional and multivariate statistical analysis. The results pointed to the great significance of mineral composition and the crystallographic preferred orientation for thermal expansion and respective anisotropy, especially to monomineralic and/or foliated rocks, in spite of some cases microcracks play this role. The compressive strength is mainly controlled by a complex interaction between grain size distribution, grain boundary and microcrack patterns related or not to foliation.

Made available in DSpace on 2016-12-08T17:19:39Z (GMT). No. of bitstreams: 1 Resumo.pdf: 35261 bytes, checksum: 5c14dd5939481fe398edfb044903a091 (MD5) Previous issue date: 2011-07-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This paper presents a study on the linear thermal expansion of foundry sands used as aggregates in foundry cores with resin phenolic-urethane/Cold Box. The work examines the correlation between thermal expansion of the sand and hot deformation tendency of the core during the casting process. The hot deformation tendency has important technological significance, because it affects the dimensional quality of the casting. It was tested three silica sands, one chromite sand, two types of based aluminum silicates sands and two types of blended minerals. The sands were characterized for particle size distribution, loss on ignition, AFS clay content, density, permeability, pH, acid demand, specific surface area, coefficient of angularity, chemical analysis, XRD, shape and surface of the grains and linear thermal expansion. The dilatometer test was done with loose unbonded sands. The sand was placed into an alumina sample holder and inserted into the dilatometer. The hot deformation tendency of the core was performed with two tests: first, using an experimental iron casting and second a hot distortion laboratory test, in which the test specimen was subjected to heating by a flame. It was verified that the hot deformation tendency is directly correlated to the thermal expansion of the sand. The higher the thermal expansion of the sand used to make cores the more susceptible it is to hot deformation. / O presente trabalho apresenta um estudo sobre a influência da expansão térmica linear das areias de fundição utilizadas para a confecção de machos com resina fenólicauretânica/ Cold Box sobre a tendência à deformação a quente dos machos durante o processo de fundição das peças. A tendência à deformação a quente dos machos tem grande importância tecnológica, porque isto afeta diretamente a qualidade dimensional das peças fundidas. Foram ensaiadas três areias de sílica, uma areia de cromita, duas areias à base de silicato de alumínio, dois compostos de minerais. As areias foram caracterizadas quanto à distribuição granulométrica, perda ao fogo, teor de argila AFS, densidades solta e relativa, permeabilidade, pH, demanda ácida, superfície específica, coeficiente de angularidade, análise química, difratometria de raios-X, formato e superfície dos grãos e expansão térmica linear. O ensaio de dilatometria das areias foi realizado em corpos de provas não ligados com aglomerantes, ou seja, a areia foi acondicionada em um porta-amostra de alumina e este foi inserido no dilatômetro. Foram executados dois ensaios de tendência à deformação a quente dos machos: o ensaio de corpo de prova fundido e o ensaio de distorção a quente em laboratório, onde o corpo de prova (macho) é submetido a um aquecimento por chama. Verificou-se que a tendência à deformação a quente dos machos tem correlação direta com a expansão térmica da areia. Quanto maior a expansão térmica da areia utilizada para a confecção do macho mais suscetível ele estará à deformação a quente.

Orientadores: Elizabete Jordão, Vanderley de Vasconcelos / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-08T15:54:28Z (GMT). No. of bitstreams: 1 Dias_MarcioSoares_D.pdf: 4467183 bytes, checksum: 0454257feb5bb8587142baa338c5666a (MD5) Previous issue date: 2007 / Resumo: A dependência com a temperatura das propriedades térmicas dos materiais faz com que a análise do transiente térmico em varetas combustíveis de reatores nucleares seja não-linear. Tradicionalmente, métodos de diferenças finitas ou de elementos finitos são utilizados para resolver este problema. A remoção efetiva do calor gerado nas varetas combustíveis constitui uma das considerações primárias no projeto de reatores nucleares. Os fabricantes de combustíveis nucleares e as geradoras de energia elétrica de fonte nuclear devem demonstrar a segurança do reator através da análise dos resultados de situações transientes diversas. Estes transientes podem ocorrer tanto em operação normal, quanto em situações de acidentes e devem ser analisados para assegurar que a vareta combustível manterá sua integridade para todas estas condições. A equação de transferência de calor para o combustível é não-linear. Esta equação não-linear de diferenciais parciais pode ser convertida em uma forma linear por meio da transformação baseada nas propriedades térmicas. Este trabalho apresenta a análise teórica aplicada no desenvolvimento de um modelo analítico, aqui chamado de variacionais relativos e direcionado para a modelagem de propriedades térmicas de materiais cerâmicos de aplicação nuclear, em particular o dióxido de urânio, UO2, e o óxido de alumínio, Al2O3. As propriedades térmicas modeladas são aquelas envolvidas no processo de condução de calor em materiais cristalinos: expansão térmica, calor específico, condutividade térmica e as suas formas integrais. No processo de avaliação de dados foram utilizados cerca de 5500 medidas de propriedades físicas e térmicas disponíveis na literatura aberta. Com base neste desenvolvimento é estabelecida a relação linear entre a variação de entalpia e a integral de condutividade térmica do UO2. Esta relação permite resolver, analiticamente, as distribuições espacial e temporal de temperaturas no combustível nuclear para as condições de estado estacionário e de transiente. A solução encontrada aplica-se igualmente outros sistemas onde o balanço de energia seja determinado pelo equilíbrio entre calor armazenado e calor transportado. A modelagem analítica desenvolvida amplia as possibilidades de avaliação crítica da consistência de propriedades térmicas e físicas dos materiais / Abstract: The temperature dependence of the material thermal properties makes the transient thermal analysis of reactor fuel pins to be non-linear. Traditionally, finite difference or finite element methods have been used to solve this problem. Effective heat removal from the fuel pins of a nuclear reactor poses one of the primary considerations in reactor design. Nuclear fuel vendors and nuclear electricity utilities must demonstrate the safety of the reactor by thorough examination of the outcome of various transient situations. These transient effects may occur in normal operation as well as in accident situations and must be analysed to insure the fuel pin maintains its integrity. The governing heat transfer equation for the fuel is non-linear. This non-linear, partial differential equation can be recast into a linear form by introducing a transformation based on material property. This work presents the theoretical analyses to develop a analytical model, here named model of relative variationals, for modelling of thermal properties of nuclear ceramic materials, in matter uranium dioxide, UO2, and aluminium oxide, Al2O3. The modeled thermal properties are those involved in the process of heat transport in crystalline materials: thermal expansion, specific heat, thermal conductivity and their integral forms. In the data evaluation process were used about 5500 measures of physical and thermal properties available in the open literature. Based on this development, the linear relationship has been established between the UO2 enthalpy and thermal conductivity integral. This relationship enables the heat conduction equation to be solved analytically for steady state and transient conditions. The solution is also applied in other systems where the balance of energy is determined by the equilibrium between stored heat and transported heat. The developed analytical modelling enlarges the possibilities for critical evaluation of the thermal and physical properties of the materials / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química

O presente trabalho, realizado junto ao Grupo de Novos Materiais e Dispositivos (GNMD), no Laboratório de Microeletrônica do Departamento de Sistemas Eletrônicos da Escola Politécnica da USP, visou determinar algumas das propriedades termo-mecânicas de materiais depositados pela técnica de plasma enhanced chemical vapor deposition (PECVD) que são importantes para o desenvolvimento de sistemas microeletromecânicos (MEMS). O módulo de elasticidade, a tensão mecânica residual, o coeficiente de expansão térmica e a condutividade térmica de filmes finos de carbeto de silício amorfo hidrogenado (a-SiC:H) e de oxinitreto de silício (SiOxNy) foram estudados. Medidas de nanoindentação e ressonância de cantilevers foram utilizadas para a obtenção do módulo de elasticidade e os resultados obtidos foram similares (75 e 91 GPa) pelos dois métodos e compatíveis com valores encontrados na literatura. Além disso, obteve-se o módulo de elasticidade de filmes de cromo (285 GPa). A tensão mecânica residual dos filmes utilizados neste trabalho foi medida através da curvatura do substrato induzida pela deposição dos filmes e pela deformação de cantilevers. O valor médio da tensão mecânica, obtido pela curvatura do substrato, variou de -69 MPa até -1750 MPa, mostrando grande dependência das condições de deposição dos filmes. O método que utiliza a deformação de cantilevers possibilitou a obtenção do gradiente de tensão mecânica, que também mostrou uma dependência das condições de deposição, sendo sempre o a-SiC:H quase estequiométrico o menos tensionado. O coeficiente de expansão térmica foi medido utilizando a técnica do gradiente de temperatura e o valor obtido foi similar a valores reportados na literatura para o carbeto de silício cristalino. Para um a-SiC:H quase estequiométrico foi obtido um coeficiente de expansão térmica de 3,41 m/oC, enquanto para um a-SiC:H rico em carbono o valor foi de 4,36 m/oC. Também foi verificado que a variação da resistência do cromo em função da temperatura é pequena, não permitindo sua utilização como sensor de temperatura e inviabilizando a obtenção da condutividade térmica dos filmes estudados. Além disso, foram apresentados trabalhos promissores, mostrando o potencial dos materiais estudados para o desenvolvimento de MEMS. Nesses trabalhos, demonstrou-se a viabilidade de integrar microestruturas atuadas termicamente e guias de onda ópticos, utilizando os materiais estudados neste trabalho. Foram fabricados chaves ópticas, portas lógicas ópticas, fontes de luz integradas e acoplamento das fontes de luz com guias de onda. / This work, realized at the New Materials and Devices Group (GNMD) at the Microelectronics Laboratory of the Department of Electronic Systems of the Polytechnic School of the University of São Paulo, focused at the determination of thermo-mechanical properties of materials deposited by plasma enhanced chemical vapor deposition (PECVD) that are important for the development of microelectromechanical systems (MEMS). The Youngs modulus, the residual stress, the coefficient of thermal expansion and the thermal conductivity of amorphous hydrogenated silicon carbide (a-SiC:H) and silicon oxynitride (SiOxNy) thin films were studied. Nanoindentation and the resonance of cantilevers were used to obtain the Youngs modulus. The results were similar (75 and 91 GPa) with both methods and compatible with literature values. Further, the Youngs modulus of chromium films was also obtained (285 GPa). The residual stress of thin films was obtained through the substrate curvature induced by the film deposition and through the deformation of cantilever beams. The residual stress, obtained through the substrate curvature, varied between -69 MPa and -1750 MPa, showing great dependence on the deposition conditions of these materials. The deformation of cantilevers allowed the determination of the stress gradient and it was also affected by the deposition conditions. In all stress measurements the near stoichiometry a-SiC:H film was less stressed. The coefficient of thermal expansion was measured using the temperature gradient technique and the obtain values were similar to those reported in the literature for crystalline silicon carbide. For a near stoichiometry a-SiC:H film, a value of 3.41 m/oC was obtained, while a carbon rich film showed a thermal expansion coefficient of 4.36 m/oC. It was also verified that the variation of the chromium resistance as a function of temperature is small. This did not allow the utilization of chromium as a temperature sensor, which prevented the obtention of the thermal conductivity of the studied films. Also, some promising works were presented, showing potential applications of the studied materials for the development of MEMS. In these works, the viability of integration of thermal actuated microstructures and optical waveguides was demonstrated. In these works, optical switches, optical logic gates, integrated light sources and coupling of integrated light sources with optical waveguides were presented.

This thesis aims at investigating size dependence of properties of nanostructures from the point of view of a general scaling theory that smoothly connects properties of the bulk to that of nanostructures. Two different examples of a ``static'' and a ``dynamic'' property are considered in this study. The first example studied is of size dependence of coefficient of thermal expansion (CTE) which a static property of nanostructures. The CTE of nanobars and nanoslabs is studied using equilibrium molecular dynamics and dynamical matrix formulation in an electrically insulating medium. It is found that the fractional change in CTE from the bulk value scales inversely with the size of the nanostructures, thus, showing a simple description in terms of a scaling theory. In the second part, electron transport in carbon nanotube field effect transistors (CNTFETs) is studied using Landauer formalism. A CNTFET involves transport through a 1-d ballistic carbon nanotube channel with Schottky barriers (SB) at contacts which determines the transport characteristics. The CNT is modeled as a 1-d semiconductor having only two bands separated by an energy gap which depends inversely on tube diameter. After the contact is made, a self-consistent potential appears due to charge transfer between CNT and metal, which is calculated by solving Poisson equation. The electron transmission across the barriers is calculated using WKB approximation. Current and conductance are calculated using Landauer-Buttiker formula. Diameter dependence of properties like, conductance, threshold voltage, VON, etc. is calculated. It is found that there is no simple scaling for a property for small values of diameter. The scaling form is, however, found to be valid for larger diameters. Also, other calculated device characteristics are in close agreement with experiments. The model presented in this thesis is the first detailed study illustrating the applicability of the scaling approach to the properties of nanostructures. The static properties show scaling behavior, while ``dynamic'' properties derived from electronic response do not.

Les contraintes environnementales ont amené les constructeurs et équipementiers automobiles à développer de nouveaux types de transmission aux contraintes d'encombrement axial importantes. Pour la première fois, ce travail se concentre sur la caractérisation et l'identification du comportement sous sollicitations thermiques et mécaniques de la garniture d'embrayage, un matériau composite complexe. Les sollicitations de traction ont été réalisées à différentes températures et fréquences sur des échantillons prélevés dans le disque ou le disque complet. Nous avons ainsi identifié les caractéristiques élastiques et viscoélastiques en fonction de la température ainsi que les mécanismes d'endommagement. La dilatation thermique de la garniture a été observée sur les disques complets. Ainsi, grâce à l'utilisation de la stéréo-corrélation couplée avec des méthodes d'identification inverse nous avons pu décrire le couplage entre l'hétérogénéité du matériau et l'effet de la structure annulaire. Enfin au travers de cycles thermiques lents et homogènes, l'étude présente l'évolution du coefficient d'expansion thermique et de la tenue mécanique du matériau. / The clutch facing is an annular shaped continuous fiber composite which transmits the rotary motion from the engine to the wheels. In use it is submitted to thermal and mechanical loadings which can cause changes in the dimensions. New clutch technologies call for a better control of these changes. For the first time, this thesis was dedicated to the understanding of the dimensional stability of the clutch facing. Tensile tests were carried out under different temperature and for different frequencies on small cut specimens or on the entire annular disc. We were then able to identify the elastic and viscoelastic properties as well as the damage mechanisms until failure. The thermal expansion was measured on the entire disc as well. Thanks to digital image stereo correlation and reverse identification methods we were able to describe the coupling between the material's heterogeneities and its annular shape. Finally, this thesis presents the evolution of the material properties after homogeneous thermal cycling.