After a few remarks about the history of diffusion in solids we remind the reader to some basics of diffusion such as tracer diffusion, interdiffusion, high- diffusivity paths, and basic diffusion mechanism in solids. We then summarize self-diffusion in cubic, hexagonal metals and metals with phase transformations. Then we summarize diffusion of substitutional impurities (solutes) in metals and remind the reader to the phenomena of slow solute diffusion in aluminium and of fast solute diffusion in polyvalent metals. We finish the part on solute diffusion with some remarks on interstitial impurities We start the part on intermetallic alloys by reminding the reader to some of the more frequent structures. We consider examples of the influence of order-disorder transformation on diffusion. We then discuss diffusion in cubic B2-structured phases and in B2-, L12 - and DO 3- intermetallics, We then discuss uniaxial L1 0 -intermetallics and C11 b-structured molybdenum disilicide. We finish with some remarks diffusion in the cubic Laves phase Co2 Nb.:1. Introduction – some historical remarks 2. Some basics 2.1 Tracer diffusion 2.2 Interdiffusion 2.2.2 The ‘random alloy’ approximation for interdiffusion 2.2.1 Boltzmann-Matano method 2.3 High-diffusivity paths in solids 2.4 Diffusion mechanisms in solids 3. Self-diffusion in metals 3.1 Cubic metals 3.2 Uniaxial metals 3.3 Metals with phase transitions 4, Impurity diffusion in metals 4.1 Diffusion of substitutional impurities 4.2 Slow impurity diffusion in aluminium 4.3 Fast impurity diffusion in polyvalent metals 4.4 Diffusion of fast diffusing interstitial impurities and of hydrogen 5. Diffusion in Intermetallics 5.1 Some structures of intermetallics 5.2 Influence of order-disorder transitions on diffusionThis work is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/1 5.3 Diffusion in B2 phases and B2-intermetallics 5.4 Diffusion in L12-intermetallics 5.5 Diffusion in DO3-intermetallics 5.5 Diffusion in L10-intermetallics 5.6 Diffusion in C11b-structured molybdenum disilicide 5.6 Diffusion in the Laves phase Co 2Nb

Made available in DSpace on 2014-06-11T19:25:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-03-01Bitstream added on 2014-06-13T18:28:55Z : No. of bitstreams: 1 saggioro_bz_me_rcla.pdf: 2011105 bytes, checksum: 3a55198b06d17033aac4826618ba3503 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Superfícies de vidro plano comercial (flotado) e de vidros sintetizados no laboratório com diferentes concentrações em massa de SnO2 foram expostos aos vapores resultantes da decomposição de KNO3 fundido a uma temperatura um pouco abaixo da temperatura de transição vítrea. Medidas de EDS mostram um aumento da concentração dos íons K+ na superfície com o aumento do tempo de exposição aos vapores. Alguns destes íons migraram para o interior dos vidros, conforme mostram as medidas do perfil de concentração. Os coeficientes de difusão foram determinados utilizando a técnica de Bolztzman-Matano. Esta mudança na concentração de K+ provocou modificações estruturais na superfície, alterando algumas de suas propriedades físico-químicas. Espectros de reflexão no infravermelho foram realizadas nestas amostras e mostraram que as alterações mais pronunciadas ocorreram na banda em tono de 950 cm-1. A dureza Vickers aumenta com o tempo de exposição. O índice de refração foi determinado pelos métodos de Brewster e refratometria Abbe. Constatou-se que quanto maior o tempo de exposição aos vapores, maior o valor do índice de refração das amostras. Foi verificado se esta nova técnica de troca iônica, isto é, por exposição a vapores, é propicia na preparação de dispositivos baseados em guias de ondas planares, utilizando a técnica de acoplamento de prisma. Vidros sintetizados também foram submetidos a testes de dilatometria com o intuito de determinar a temperatura de transição vítrea e calcular o coeficiente de expansão térmica. Medidas de densidade foram realizadas utilizando o principio de Arquimedes. Há diversas evidências experimentais que o estanho incorporado à estrutura vítrea atua como cátion formador de vidros, e que inibe a difusão iônica. / Surfaces of commercial plane glass (floated) and glasses synthesized in laboratory with different concentrations of SnO2 were exposed to vapors resulting from the decomposition of molten KNO3 at temperatures somewhat below the glass transitions. EDS measurements show an increase of the K+ concentration at the surfaces during the time of exposition to the vapors. Some of these ions migrate into the near surface layers of the samples, according to the measured concentration profiles. Diffusion coefficients were determined using the Bolztzman-Matano technique. The changes in concentration promote structural modifications at the surfaces, changing some of the physico-chemical properties of the glasses. Reflectance spectra in the infrared were carried out in these samples and one observe that the most pronounced change occurred around 950 cm-1. The Vickers hardness increases with the exposition time. The refractive index was determined by Brewster method and by Abbe refractometry. The longer the time of exposition to the vapors, the higher was the refractive index of the samples. This new technique of ionic exchange, that is, the exposition to vapors, was tested to verify if it is appropriate to prepare planar waveguide devices, and the coupling prism method was employed. Synthesized glasses were also subjected to dilatometric tests in order to determine the glass transition temperature, Tg, and the average thermal expansion coefficient, a. Density measurements were performed using Archimedes principle. There are several experimental evidences that tin is incorporated in the glass structure as a glass former cation, and it hinders ionic diffusion.

Orientador: Ervino Carlos Ziemath / Banca: Dimas Roberto Vollet / Banca: Eduardo Bellini Ferreira / Resumo: Superfícies de vidro plano comercial (flotado) e de vidros sintetizados no laboratório com diferentes concentrações em massa de SnO2 foram expostos aos "vapores" resultantes da decomposição de KNO3 fundido a uma temperatura um pouco abaixo da temperatura de transição vítrea. Medidas de EDS mostram um aumento da concentração dos íons K+ na superfície com o aumento do tempo de exposição aos vapores. Alguns destes íons migraram para o interior dos vidros, conforme mostram as medidas do perfil de concentração. Os coeficientes de difusão foram determinados utilizando a técnica de Bolztzman-Matano. Esta mudança na concentração de K+ provocou modificações estruturais na superfície, alterando algumas de suas propriedades físico-químicas. Espectros de reflexão no infravermelho foram realizadas nestas amostras e mostraram que as alterações mais pronunciadas ocorreram na banda em tono de 950 cm-1. A dureza Vickers aumenta com o tempo de exposição. O índice de refração foi determinado pelos métodos de Brewster e refratometria Abbe. Constatou-se que quanto maior o tempo de exposição aos vapores, maior o valor do índice de refração das amostras. Foi verificado se esta nova técnica de troca iônica, isto é, por exposição a vapores, é propicia na preparação de dispositivos baseados em guias de ondas planares, utilizando a técnica de acoplamento de prisma. Vidros sintetizados também foram submetidos a testes de dilatometria com o intuito de determinar a temperatura de transição vítrea e calcular o coeficiente de expansão térmica. Medidas de densidade foram realizadas utilizando o principio de Arquimedes. Há diversas evidências experimentais que o estanho incorporado à estrutura vítrea atua como cátion formador de vidros, e que inibe a difusão iônica. / Abstract: Surfaces of commercial plane glass (floated) and glasses synthesized in laboratory with different concentrations of SnO2 were exposed to "vapors" resulting from the decomposition of molten KNO3 at temperatures somewhat below the glass transitions. EDS measurements show an increase of the K+ concentration at the surfaces during the time of exposition to the vapors. Some of these ions migrate into the near surface layers of the samples, according to the measured concentration profiles. Diffusion coefficients were determined using the Bolztzman-Matano technique. The changes in concentration promote structural modifications at the surfaces, changing some of the physico-chemical properties of the glasses. Reflectance spectra in the infrared were carried out in these samples and one observe that the most pronounced change occurred around 950 cm-1. The Vickers hardness increases with the exposition time. The refractive index was determined by Brewster method and by Abbe refractometry. The longer the time of exposition to the vapors, the higher was the refractive index of the samples. This new technique of ionic exchange, that is, the exposition to vapors, was tested to verify if it is appropriate to prepare planar waveguide devices, and the coupling prism method was employed. Synthesized glasses were also subjected to dilatometric tests in order to determine the glass transition temperature, Tg, and the average thermal expansion coefficient, a. Density measurements were performed using Archimedes principle. There are several experimental evidences that tin is incorporated in the glass structure as a glass former cation, and it hinders ionic diffusion. / Mestre

Dans la course à la miniaturisation des dispositifs de la microélectronique, les alliages SiGe sont des matériaux remarquables pour poursuivre l'amélioration des performances des composants de type CMOS, le Silicium atteignant aujourd'hui ses limites physiques. En effet, une méthode originale pour appliquer une contrainte de compression uniaxiale au canal de conduction Silicium, afin d'augmenter la mobilité des trous des transistors pMOS, consiste à remplacer le Silicium dans les régions Source et Drain par des couches SiGe pseudomorphiques. L'utilisation de sources solides sacrificielles de Germanium peut être une solution pour la fabrication de telles structures. Dans ce travail, nous avons ainsi étudié l'interdiffusion Ge-Si, induite par recuit thermique à haute température, à partir d'hétérostructures Ge/Si dont la couche de Germanium est déposée par CVD. Le développement de la méthodologie SIMS MCs2+, que nous réalisons dans cette thèse, assure la caractérisation chimique de couches graduelles Si1-xGex dans la gamme complète de concentrations (0 d x d 1). Nous montrons que l'interdiffusion Ge-Si est fortement dépendante de la composition en Germanium mais également des défauts structuraux formés aux interfaces Ge-Si. Nous avons alors développé un modèle qui permet de reproduire fidèlement les profils expérimentaux. L'effet du dopage Bore tend à réduire légèrement l'interdiffusivité. Finalement, nous montrons que l'utilisation de couches de Germanium polycristallin est prometteuse pour la fabrication de couches graduelles Si1-xGex. En effet, elle permet de réduire la densité de défauts structuraux initialement présents dans les films monocristallins.

Magnesium, being lightweight, offers potential to be developed into extensive structural applications. The transportation segment has particular interest in Mg and Mg alloy for applications where reduced vehicle weight is proportional to increased fuel efficiency. Aluminum and zinc are two of the most common alloying elements in commercial Mg alloys. They improve the physical properties of Mg through solid solution strengthening and precipitation hardening. Diffusion plays a key role in the kinetics of and microstructural development during solidification and heat treatment. However, there is limited diffusion data available for Mg and Mg alloys. In particular, because Al is monoisotopic, tracer diffusion data is not available. Interdiffusion of Mg solid solution with Zn also does not exist in literature. The diffusional interaction of Al and Zn in Mg solid solution at temperatures ranging from 623 – 723K was examined using solid-to-solid diffusion couple method. The objective of this thesis is two-fold: first, is the examination of interdiffusion in the Mg solid solution phase of the binary Mg-Al and Mg-Zn systems; second, is to explore non-conventional analytical methods to determine impurity diffusion coefficients. The quality of diffusion bonding was examined by optical microscopy and scanning electron microscopy with X-ray energy dispersive spectroscopy, and concentration profiles were determined using electron probe microanalysis with pure standards and ZAF matrix correction. Analytical methods of concentration profiles based on Boltzmann-Matano analysis for binary alloys are presented along with compositional dependent interdiffusion coefficients. As the iv concentration of Al or Zn approaches the dilute ends, an analytical approach based on the Hall method was employed to estimate the impurity diffusion coefficients. Zinc was observed to diffuse faster than Al, and in fact, the impurity diffusion coefficient of Al was smaller than the self-diffusion coefficient of Mg. In the Mg solid solution with Al, interdiffusion coefficients increased by an order of magnitude with an increase in Al concentration. Activation energy and pre-exponential factor for the average effective interdiffusion coefficient in Mg solid solution with Al was determined to be 186.8 KJ/mole and 7.69 x 10-1 m2/sec. On the other hand, in the Mg solid solution with Zn, interdiffusion coefficients did not vary significantly as a function of Zn concentration. Activation energy and pre-exponential factor for the average effective interdiffusion coefficient in Mg solid solution with Zn was determined to be 129.5 KJ/mole and 2.67 x 10-4 m2/sec. Impurity diffusion coefficients of Al in Mg was determined to have activation energy and pre-exponential factor of 144.1 KJ/mole and 1.61 x 10-4 m2/sec. Impurity diffusion coefficients of Zn in Mg was determined to have activation energy and preexponential factor of 109.8 KJ/mole and 1.03 x 10-5 m2/sec. Temperature and compositiondependence of interdiffusion coefficients and impurity diffusion coefficients are examined with respect to reported values in literature, thermodynamic factor, Φ, diffusion mechanisms in hexagonal close packed structure, and experimental uncertainty