As part of the effort to increase the reliability of the MMT Observatory (MMTO) 6.5m Primary Mirror Coating System, the specified filament has changed from a configuration in which the aluminum charge is hand wound around a tungsten filament to a configuration in which the aluminum is integrally wound with the tungsten at the time of filament manufacture. In the MMTO configuration, this filament consists of the three strands of tungsten wire and one strand of aluminum wire. In preparation of a full system test utilizing two hundred filaments fired simultaneously, an extensive testing program was undertaken to characterize these filaments using a four filament configuration in the MMTO small coating chamber (0.5m) and then a forty filament configuration in the University of Arizona Steward Observatory coating chamber (2m). The testing using the smaller coating chambers has shown these filaments provide very predicable coatings from test to test, and with the proper heating profile, these filaments greatly reduce the likelihood of aluminum drips. The initial filament design was modified during the course of testing by shortening the unwound filament length to closer match the aluminum load required in the MMTO coating chamber. This change increased the aluminum deposition rates without increasing the power delivered of the filament power supplies (commercial welders). Filament power levels measured at the vacuum chamber feedthroughs, currents, and deposition rates from multiple coating tests, including a full system test, are presented.

Ventaneiras são componentes críticos para a operação de altos fornos, soprando ar quente para o interior dos mesmos. São peças de cobre refrigeradas a água para resistir ao ambiente de trabalho com temperaturas extremamente elevadas e geralmente apresentam revestimentos superficiais para aumento de resistência contra abrasão/corrosão. O presente trabalho tem como objetivo estudar o processo de revestimento de cobre e de liga à base de níquel por alumínio via PCDC a fim de entender os efeitos das variáveis de processo nas características do revestimento formado e obter camadas de revestimento equivalentes ao que vem sendo utilizado recentemente com bons resultados em operação na indústria. Uma série de ensaios são preparados utilizando-se os substratos de cobre e liga Inconel 625 e são variados alguns parâmetros de processo como a liga máster utilizada (Al e/ou liga Fe-Al), o sal haleto ativador do processo (NH4Cl ou NaF), condição in ou out of pack, proporção entre alumina e liga máster, temperatura e tempo de processo. É realizada a caracterização dos substratos previamente e após passar pelo processo de aluminização. Também é feita uma análise de amostra tomada como referência revestida por empresa externa especializada em aluminização via PCDC, além da caracterização de todas as amostras ensaiadas. A caracterização das amostras consiste na análise microestrutural identificando as fases presentes nos revestimentos formados, morfologia das camadas, espessuras, e propriedade de dureza. As análises são realizadas através de microscópio ótico, MEV, técnicas de EDS e difração de raios X e microdurômetro. Ao final das análises, é possível identificar conjuntos de parâmetros de processo que conduzem à formação de revestimento similar ao que está sendo utilizado na indústria. Além disso, é possível entender o efeito das variáveis de processo nas características das camadas formadas sobre os substratos. / Tuyeres are critical components for blast furnace operation, blowing hot air to the interior of the furnace. They are made of copper and are water cooled in order to resist extremely high operation temperatures. Aiming to improve reliability and lifetime of the tuyeres, different types of coatings (metallic hard facings, ceramic and diffusion coatings) have been developed over the years to enhance surface resistance of the pieces. The objective of the present work is to study the process of coating copper and nickel alloy by aluminum via pack cementation diffusion coating (PCDC) in order to understand the effect of each process parameter in the features of the coating formed and to obtain coating layers similar to what has been used with good results in the industry. Several experiments are prepared for coating the substrates made of copper and Inconel 625 and some parameters are varied such as the master alloy (Al and/or Fe-Al), the activator salt (NH4Cl or NaF), the condition in or out of pack, the alumina/master alloy ratio, temperature and time of the process. It is performed analysis of the substrates previous and after the aluminization process. A sample coated in an external company specialized in aluminization process is also analyzed and taken as a reference. In addition, all the experiment samples with different process conditions are studied. The analysis consist in microstructural evaluation identifying phases formed, thickness of the coating layers and hardness measurements and are performed with the use of optical microscope, SEM, EDS techniques, X-ray diffraction technique and micro durometer. At the end of the analysis, it is possible to identify sets of process parameters that can lead to the formation of coating layers similar to what has been used with success in the industry. Furthermore, it is possible to understand the effect of the process variables in the features of the coating layers.

Le Sud du Brésil est une région où l'agriculture est très intensive et la pression sur les sols est beaucoup plus importante que dans la région amazonienne. Ainsi, il est nécessaire de développer des études qui relient le développement du sol avec son matériau source respectif, en détaillant les transformations dans la zone de transition sol-roche et ses implications pour les activités environnementales et humaines. Dans ce contexte, ce travail vise à: (i) caractériser les aspects minéralogique, pédochimique et géochimiquedes profils d'altération développés en l'absence d'action humaine ou avec une intervention minimale; (ii) caractériser qualitativement et semi-quantitativement les minéraux primaires et les minéraux pedogenic dans les sols insérés dans les régions importantes de l'écosystème du Rio Grande do Sul; et (iii) évaluer l'impact des différentes intensités de pâturage sur la minéralogie d’un Oxisol sous système intégré de production soja-élevage dans le sud du Brésil. Cette étude concerce des sols du Rio Grande do Sul dont le climat subtropical (températures moyennes annuelles ~17°C, précipitations moyennes annuelles ~1800 mm/an) favorise l’accumulation de matiére organique ainsi que la formation de minéraux argileux 2:1. Les indices d'altération (Weathering Intensity Scale - WIS et Chemical Index of Alteration - CIA) établis à partir de la composition chimique des profils d'altération permettent de classer les profils selon leur degré d’altération qui correspond également à des compositions minéralogiques différentes (smectite, smectite + kaolinite, kaolinite). L'étude a montré que des sols formés à partir de la même roche ont des différences importantes liées aux différences climatiques et de relief. Finalement, après 12 ans de culture des sols avec un système intégré culture-élevage, les surfaces non pâturées présentent une proportions moins important de minéraux 2:1. D'autre part, les surfaces sous pâturage intensif et pâturage modéré présentent un comportement similaire attribué à une aluminisation plus élevée de la couche interfoliaire de minéraux 2:1. L'aluminisation plus élevée sous gestion intensive et modérée peut fixer une partie de l'aluminium dans la phase solide du sol, ce qui pourrait le rendre moins disponible pour les plantes et diminuer sa phytotoxicité. / O sul do Brasil é uma região com uma agricultura muito intensa e com grande pressão de uso do solo, consideravelmente mais intenso do que na região da Amazônia. Assim, é necessário desenvolver estudos que relacionem o desenvolvimento do solo com seu respectivo material de origem, detalhando as transformações na zona de transição solo-rocha e suas implicações para as atividades ambientais e humanas. Neste contexto, este trabalho tem como objetivo: (i) caracterizar os aspectos mineralógicos, pedoquimicos e geoquimicos dos perfis de alteração desenvolvidos na ausência ou mínima ação humana; (ii) caracterizar qualitativa e semi-quantitativamente os minerais primários e os minerais pedogênicos em solos inseridos em regiões ecossistêmicas importantes do Rio Grande do Sul; e (iii) avaliar o impacto de diferentes intensidades de pastejo na mineralogia de um Latossolo, sob sistema de produção integrada soja-bovinos de corte no sul do Brasil.Este estudo foi realizado em solos do Rio Grande do Sul, onde o clima subtropical (temperatura média anual ~ 17°C, precipitação anual média de 1800mm/ano) favorece o acúmulo de matéria orgânica ea ocorrência de argilominerais 2:1.Os índices de intemperismo (Weathering Intensity Scale - WIS e Chemical Index of Alteration - CIA), considerando a composição mineralógica dos perfis de alteração, indicaram a seguinte sequência crescente do grau de intemperismo: esmectita < caulinita - esmectita < caulinita. O estudo mostrou diferenças importantes nos solos, mesmo entre aqueles formados a partir do mesmo material de origem, devido às diferenças climáticas e de relevo. Por fim, após 12 anos sob um sistema integrado de produção de soja-bovinos de corte, as áreas não pastejadas apresentaram menor intensidade para os argilominerais 2:1. Por outro lado, as áreas sob pastejo intensivo e pastejo moderado apresentaram comportamento semelhante, devido à maior aluminização da entrecamada dos argilominerais 2:1. A maior aluminização sob pastejo intensivo e moderado pode ser um dreno de alumínio na fase sólida do solo, tornando-o menos disponível para as plantas e diminuindo sua fitotoxicidade. / The Southern Brazil is a region with a very intensive agriculture and the pressure on soil use is considerably more intense than in the Amazonian region. Thus, it is necessary to develop studies that relate the soil development with its respective source material, detailing the transformations in the soil-rock transition zone and its implications for the environmental and human activities. In this context, this work aims to: (i) characterize the mineralogical and pedochemical alterations and geochemical evolution the profiles of the alteration developed in the absence, or the minimal human action; (ii) characterize both qualitatively and semi-quantitatively the primary and pedogenic minerals present in soils of important ecosystems in Rio Grande do Sul; And (iii) evaluate the effect of grazing intensities on the mineralogy of an Oxisol, in an integrated soybean-cattle beef production system of southern Brazil. This study concerns soils of Rio Grande do Sul, where the subtropical climate (mean annual temperature ~17°C, mean annual precipitation 1800mm/yr) favored the accumulation of organic matter and occurrence of 2:1 clay minerals. The indexes of weathering (Weathering Intensity Scale - WIS and Chemical Index of Alteration - CIA), considering the mineralogical composition of the alteration profiles, indicated the following increasing sequence of the degree of weathering: smectite composition <kaolinite-smectite composition <kaolinite composition. The study showed that the soils have important differences, even between those formed from the same material of origin, due to climatic differences and relief. Lastly, after 12 years under an integrated soybean–beef cattle production system, the ungrazed areas presented lower intensity of 2:1 minerals. On the other hand, areas under intensive grazing and moderate grazing presented similar behaviour due to the higher aluminization of the interlayer of 2:1 minerals. The higher aluminization under intensive and moderate grazing managements may be a drain on aluminum in the soil solid phase, making it less available to plants and decreasing its phytotoxicity.

Le Sud du Brésil est une région où l'agriculture est très intensive et la pression sur les sols est beaucoup plus importante que dans la région amazonienne. Ainsi, il est nécessaire de développer des études qui relient le développement du sol avec son matériau source respectif, en détaillant les transformations dans la zone de transition sol-roche et ses implications pour les activités environnementales et humaines. Dans ce contexte, ce travail vise à: (i) caractériser les aspects minéralogique, pédochimique et géochimiquedes profils d'altération développés en l'absence d'action humaine ou avec une intervention minimale; (ii) caractériser qualitativement et semi-quantitativement les minéraux primaires et les minéraux pedogenic dans les sols insérés dans les régions importantes de l'écosystème du Rio Grande do Sul; et (iii) évaluer l'impact des différentes intensités de pâturage sur la minéralogie d’un Oxisol sous système intégré de production soja-élevage dans le sud du Brésil. Cette étude concerce des sols du Rio Grande do Sul dont le climat subtropical (températures moyennes annuelles ~17°C, précipitations moyennes annuelles ~1800 mm/an) favorise l’accumulation de matiére organique ainsi que la formation de minéraux argileux 2:1. Les indices d'altération (Weathering Intensity Scale - WIS et Chemical Index of Alteration - CIA) établis à partir de la composition chimique des profils d'altération permettent de classer les profils selon leur degré d’altération qui correspond également à des compositions minéralogiques différentes (smectite, smectite + kaolinite, kaolinite). L'étude a montré que des sols formés à partir de la même roche ont des différences importantes liées aux différences climatiques et de relief. Finalement, après 12 ans de culture des sols avec un système intégré culture-élevage, les surfaces non pâturées présentent une proportions moins important de minéraux 2:1. D'autre part, les surfaces sous pâturage intensif et pâturage modéré présentent un comportement similaire attribué à une aluminisation plus élevée de la couche interfoliaire de minéraux 2:1. L'aluminisation plus élevée sous gestion intensive et modérée peut fixer une partie de l'aluminium dans la phase solide du sol, ce qui pourrait le rendre moins disponible pour les plantes et diminuer sa phytotoxicité. / O sul do Brasil é uma região com uma agricultura muito intensa e com grande pressão de uso do solo, consideravelmente mais intenso do que na região da Amazônia. Assim, é necessário desenvolver estudos que relacionem o desenvolvimento do solo com seu respectivo material de origem, detalhando as transformações na zona de transição solo-rocha e suas implicações para as atividades ambientais e humanas. Neste contexto, este trabalho tem como objetivo: (i) caracterizar os aspectos mineralógicos, pedoquimicos e geoquimicos dos perfis de alteração desenvolvidos na ausência ou mínima ação humana; (ii) caracterizar qualitativa e semi-quantitativamente os minerais primários e os minerais pedogênicos em solos inseridos em regiões ecossistêmicas importantes do Rio Grande do Sul; e (iii) avaliar o impacto de diferentes intensidades de pastejo na mineralogia de um Latossolo, sob sistema de produção integrada soja-bovinos de corte no sul do Brasil.Este estudo foi realizado em solos do Rio Grande do Sul, onde o clima subtropical (temperatura média anual ~ 17°C, precipitação anual média de 1800mm/ano) favorece o acúmulo de matéria orgânica ea ocorrência de argilominerais 2:1.Os índices de intemperismo (Weathering Intensity Scale - WIS e Chemical Index of Alteration - CIA), considerando a composição mineralógica dos perfis de alteração, indicaram a seguinte sequência crescente do grau de intemperismo: esmectita < caulinita - esmectita < caulinita. O estudo mostrou diferenças importantes nos solos, mesmo entre aqueles formados a partir do mesmo material de origem, devido às diferenças climáticas e de relevo. Por fim, após 12 anos sob um sistema integrado de produção de soja-bovinos de corte, as áreas não pastejadas apresentaram menor intensidade para os argilominerais 2:1. Por outro lado, as áreas sob pastejo intensivo e pastejo moderado apresentaram comportamento semelhante, devido à maior aluminização da entrecamada dos argilominerais 2:1. A maior aluminização sob pastejo intensivo e moderado pode ser um dreno de alumínio na fase sólida do solo, tornando-o menos disponível para as plantas e diminuindo sua fitotoxicidade. / The Southern Brazil is a region with a very intensive agriculture and the pressure on soil use is considerably more intense than in the Amazonian region. Thus, it is necessary to develop studies that relate the soil development with its respective source material, detailing the transformations in the soil-rock transition zone and its implications for the environmental and human activities. In this context, this work aims to: (i) characterize the mineralogical and pedochemical alterations and geochemical evolution the profiles of the alteration developed in the absence, or the minimal human action; (ii) characterize both qualitatively and semi-quantitatively the primary and pedogenic minerals present in soils of important ecosystems in Rio Grande do Sul; And (iii) evaluate the effect of grazing intensities on the mineralogy of an Oxisol, in an integrated soybean-cattle beef production system of southern Brazil. This study concerns soils of Rio Grande do Sul, where the subtropical climate (mean annual temperature ~17°C, mean annual precipitation 1800mm/yr) favored the accumulation of organic matter and occurrence of 2:1 clay minerals. The indexes of weathering (Weathering Intensity Scale - WIS and Chemical Index of Alteration - CIA), considering the mineralogical composition of the alteration profiles, indicated the following increasing sequence of the degree of weathering: smectite composition <kaolinite-smectite composition <kaolinite composition. The study showed that the soils have important differences, even between those formed from the same material of origin, due to climatic differences and relief. Lastly, after 12 years under an integrated soybean–beef cattle production system, the ungrazed areas presented lower intensity of 2:1 minerals. On the other hand, areas under intensive grazing and moderate grazing presented similar behaviour due to the higher aluminization of the interlayer of 2:1 minerals. The higher aluminization under intensive and moderate grazing managements may be a drain on aluminum in the soil solid phase, making it less available to plants and decreasing its phytotoxicity.

Le Sud du Brésil est une région où l'agriculture est très intensive et la pression sur les sols est beaucoup plus importante que dans la région amazonienne. Ainsi, il est nécessaire de développer des études qui relient le développement du sol avec son matériau source respectif, en détaillant les transformations dans la zone de transition sol-roche et ses implications pour les activités environnementales et humaines. Dans ce contexte, ce travail vise à: (i) caractériser les aspects minéralogique, pédochimique et géochimiquedes profils d'altération développés en l'absence d'action humaine ou avec une intervention minimale; (ii) caractériser qualitativement et semi-quantitativement les minéraux primaires et les minéraux pedogenic dans les sols insérés dans les régions importantes de l'écosystème du Rio Grande do Sul; et (iii) évaluer l'impact des différentes intensités de pâturage sur la minéralogie d’un Oxisol sous système intégré de production soja-élevage dans le sud du Brésil. Cette étude concerce des sols du Rio Grande do Sul dont le climat subtropical (températures moyennes annuelles ~17°C, précipitations moyennes annuelles ~1800 mm/an) favorise l’accumulation de matiére organique ainsi que la formation de minéraux argileux 2:1. Les indices d'altération (Weathering Intensity Scale - WIS et Chemical Index of Alteration - CIA) établis à partir de la composition chimique des profils d'altération permettent de classer les profils selon leur degré d’altération qui correspond également à des compositions minéralogiques différentes (smectite, smectite + kaolinite, kaolinite). L'étude a montré que des sols formés à partir de la même roche ont des différences importantes liées aux différences climatiques et de relief. Finalement, après 12 ans de culture des sols avec un système intégré culture-élevage, les surfaces non pâturées présentent une proportions moins important de minéraux 2:1. D'autre part, les surfaces sous pâturage intensif et pâturage modéré présentent un comportement similaire attribué à une aluminisation plus élevée de la couche interfoliaire de minéraux 2:1. L'aluminisation plus élevée sous gestion intensive et modérée peut fixer une partie de l'aluminium dans la phase solide du sol, ce qui pourrait le rendre moins disponible pour les plantes et diminuer sa phytotoxicité. / O sul do Brasil é uma região com uma agricultura muito intensa e com grande pressão de uso do solo, consideravelmente mais intenso do que na região da Amazônia. Assim, é necessário desenvolver estudos que relacionem o desenvolvimento do solo com seu respectivo material de origem, detalhando as transformações na zona de transição solo-rocha e suas implicações para as atividades ambientais e humanas. Neste contexto, este trabalho tem como objetivo: (i) caracterizar os aspectos mineralógicos, pedoquimicos e geoquimicos dos perfis de alteração desenvolvidos na ausência ou mínima ação humana; (ii) caracterizar qualitativa e semi-quantitativamente os minerais primários e os minerais pedogênicos em solos inseridos em regiões ecossistêmicas importantes do Rio Grande do Sul; e (iii) avaliar o impacto de diferentes intensidades de pastejo na mineralogia de um Latossolo, sob sistema de produção integrada soja-bovinos de corte no sul do Brasil.Este estudo foi realizado em solos do Rio Grande do Sul, onde o clima subtropical (temperatura média anual ~ 17°C, precipitação anual média de 1800mm/ano) favorece o acúmulo de matéria orgânica ea ocorrência de argilominerais 2:1.Os índices de intemperismo (Weathering Intensity Scale - WIS e Chemical Index of Alteration - CIA), considerando a composição mineralógica dos perfis de alteração, indicaram a seguinte sequência crescente do grau de intemperismo: esmectita < caulinita - esmectita < caulinita. O estudo mostrou diferenças importantes nos solos, mesmo entre aqueles formados a partir do mesmo material de origem, devido às diferenças climáticas e de relevo. Por fim, após 12 anos sob um sistema integrado de produção de soja-bovinos de corte, as áreas não pastejadas apresentaram menor intensidade para os argilominerais 2:1. Por outro lado, as áreas sob pastejo intensivo e pastejo moderado apresentaram comportamento semelhante, devido à maior aluminização da entrecamada dos argilominerais 2:1. A maior aluminização sob pastejo intensivo e moderado pode ser um dreno de alumínio na fase sólida do solo, tornando-o menos disponível para as plantas e diminuindo sua fitotoxicidade. / The Southern Brazil is a region with a very intensive agriculture and the pressure on soil use is considerably more intense than in the Amazonian region. Thus, it is necessary to develop studies that relate the soil development with its respective source material, detailing the transformations in the soil-rock transition zone and its implications for the environmental and human activities. In this context, this work aims to: (i) characterize the mineralogical and pedochemical alterations and geochemical evolution the profiles of the alteration developed in the absence, or the minimal human action; (ii) characterize both qualitatively and semi-quantitatively the primary and pedogenic minerals present in soils of important ecosystems in Rio Grande do Sul; And (iii) evaluate the effect of grazing intensities on the mineralogy of an Oxisol, in an integrated soybean-cattle beef production system of southern Brazil. This study concerns soils of Rio Grande do Sul, where the subtropical climate (mean annual temperature ~17°C, mean annual precipitation 1800mm/yr) favored the accumulation of organic matter and occurrence of 2:1 clay minerals. The indexes of weathering (Weathering Intensity Scale - WIS and Chemical Index of Alteration - CIA), considering the mineralogical composition of the alteration profiles, indicated the following increasing sequence of the degree of weathering: smectite composition <kaolinite-smectite composition <kaolinite composition. The study showed that the soils have important differences, even between those formed from the same material of origin, due to climatic differences and relief. Lastly, after 12 years under an integrated soybean–beef cattle production system, the ungrazed areas presented lower intensity of 2:1 minerals. On the other hand, areas under intensive grazing and moderate grazing presented similar behaviour due to the higher aluminization of the interlayer of 2:1 minerals. The higher aluminization under intensive and moderate grazing managements may be a drain on aluminum in the soil solid phase, making it less available to plants and decreasing its phytotoxicity.

Le Sud du Brésil est une région où l'agriculture est très intensive et la pression sur les sols est beaucoup plus importante que dans la région amazonienne. Ainsi, il est important d'étudier les processus d'altération des roches qui constituent des étapes clés du développement des sols et de leurs fonctions environnementales.Dans ce contexte, ce travail vise à : (i) caractériser la morphologie, les propriétés physiques et chimiques de profils d'altération développés en l'absence ou avec une intervention humaine minimale : (ii) établir les évolutions géochimiques et minéralogiques des sols dans un environnement subtropical ; et (iii) évaluer l'impact des actions anthropiques sur la minéralogie des horizons de surface. Cette étude concerne des sols du Rio Grande do Sul dont le climat subtropical (T ~17°C et P ~1800 mm/an) favorise l'accumulation de matière organique ainsi que la formation de minéraux argileux 2:1 en faible proportion. Les indices d'altération (Weathering Intensity Scale – WIS, Chemical Index of Alteration - CIA) permettent de classer les profils selon leur degré d'altération et de leur composition minéralogique différente (smectite, smectite + kaolinite, kaolinite). Dans la dernière partie les résultats montrent qu'après 12 ans de culture des sols avec un système intégré culture-élevage les surfaces non pâturées présentent une proportion moins importante de minéraux 2:1. Les surfaces sous pâturage intensif et modéré présentent une aluminisation plus élevée de la couche interfoliaire des minéraux 2:1. La fixation d'une partie de l'aluminium dans la phase solide du sol, ce qui pourrait le rendre moins disponible pour les plantes et diminuer sa phytotoxicité. / Southern Brazil is a region with a very intensive agriculture and the pressure on soil is considerably more intense than in the Amazonian region. Thus, it is necessary to study weathering processes as they control soil development and their environmental functions.In this context, this work aims to: (i) characterize the morphological, physical and chemical properties of weathering profiles developed in the absence, or with minimal human action; (ii) establish the geochemical and mineralogical evolution of soils in a subtropical environment; and (iii) assess the impact of anthropogenic actions on on the mineralogy of surface horizons. This study concerns soils of Rio Grande do Sul where the subtropical climate (T ~17°C and P ~1800mm/yr) favored the accumulation of organic matter and occurrence of 2:1 clay minerals in low proportion. The weathering indices (Weathering Intensity Scale - WIS and Chemical Index of Alteration - CIA) make it possible to classify the profiles according to their weathering intensity and their different mineralogical compositions (smectite, smectite + kaolinite, kaolinite).In the last chapter, the results show that after 12 years of cultivation under an integrated soybean–beef cattle production system, the ungrazed areas presented lower proportion of 2:1 minerals. The areas under intensive grazing and moderate grazing presented higher aluminization of the interlayer of 2:1 minerals. The higher aluminization under intensive and moderate grazing managements may be a drain of aluminum in the soil solid phase and possibly making it less available to plants and decreasing its phytotoxicity. / O sul do Brasil é uma região com uma agricultura muito intensa e com grande pressão de uso do solo, consideravelmente mais intenso do que na região da Amazônia. Assim, é necessário desenvolver estudos que relacionem o desenvolvimento do solo com seu respectivo material de origem, detalhando as transformações na zona de transição solo-rocha e suas implicações para as atividades ambientais e humanas. Neste contexto, este trabalho tem como objetivo: (i) caracterizar os aspectos mineralógicos, pedoquimicos e geoquimicos dos perfis de alteração desenvolvidos na ausência ou mínima ação humana; (ii) caracterizar qualitativa e semi-quantitativamente os minerais primários e os minerais pedogênicos em solos inseridos em regiões ecossistêmicas importantes do Rio Grande do Sul; e (iii) avaliar o impacto de diferentes intensidades de pastejo na mineralogia de um Latossolo, sob sistema de produção integrada soja-bovinos de corte no sul do Brasil. Este estudo foi realizado em solos do Rio Grande do Sul, onde o clima subtropical (temperatura média anual ~ 17°C, precipitação anual média de 1800mm/ano) favorece o acúmulo de matéria orgânica ea ocorrência de argilominerais 2:1.Os índices de intemperismo (Weathering Intensity Scale - WIS e Chemical Index of Alteration - CIA), considerando a composição mineralógica dos perfis de alteração, indicaram a seguinte sequência crescente do grau de intemperismo: esmectita < caulinita - esmectita < caulinita. O estudo mostrou diferenças importantes nos solos, mesmo entre aqueles formados a partir do mesmo material de origem, devido às diferenças climáticas e de relevo. Por fim, após 12 anos sob um sistema integrado de produção de soja-bovinos de corte, as áreas não pastejadas apresentaram menor intensidade para os argilominerais 2:1. Por outro lado, as áreas sob pastejo intensivo e pastejo moderado apresentaram comportamento semelhante, devido à maior aluminização da entrecamada dos argilominerais 2:1. A maior aluminização sob pastejo intensivo e moderado pode ser um dreno de alumínio na fase sólida do solo, tornando-o menos disponível para as plantas e diminuindo sua fitotoxicidade.

Le processus d'aluminisation dans les sols acides, conduit à la formation de minéraux argileux hydroxy-alumineux (HIMs). La fixation d'aluminium dans l'espace interfoliaire diminue la réactivité des feuillets expansibles (feuillets HI). La caractérisation des HIMs issus d'un Alocrisol a été réalisée par modélisation des diffractogrammes de rayons X (raies 00l) de la fraction <2 µm et de ses sous-fractions (<0.05, 0.05-0.1, 0.1-0.2 et 0.2-2 µm). Cette étude a montré que les HIMs sont des minéraux interstratifiés à deux ou trois types de feuillets (HI, illites et/ou expansibles). La proportion relative de feuillets HI par rapport à celle des feuillets expansibles diminue avec la taille des particules. La persistance de feuillets illitiques a été observée dans la fraction fine (<0.05 µm). Afin de tester l’effet de la taille des particules sur l'aluminisation, des expériences d'auto-aluminisation de vermiculites saturées K ou Ca séparées en trois fractions (0.1-0.2, 1 2 et 10-20 µm) ont été tentées. Toutes montrent l'importance du couple taille-cation interfoliaire sur le contrôle de l'échange et de la dissolution qui sont les processus de premier ordre pour l'aluminisation. C'est dans les expériences mettant en jeu les K vermiculites que la compétition entre ces deux processus conduit à la formation de minéraux interstratifiés aluminisés à trois composantes similaires à ceux identifiés dans les sols. L'effet de la taille des particules se marque par la persistance de feuillets illitiques comme cela avait été observé dans les fractions infra-micrométriques des sols. La compétition entre échange et dissolution sont donc très probablement le moteur des évolutions minérales dans les sols. / The aluminization process of clay minerals in acidic soils, leads to the formation of hydroxyl interlayered minerals (HIMs). It decreases the reactivity of the clay fraction by the fixation of aluminium in the interlayer space of expandable layers (HI). The characterization of HIMs from an Alocrisol was investigated through X-Ray Diffraction profile modeling (00l reflections) of the <2 µm size fraction and its sub-fractions (<0.05, 0.05-0.1, 0.1-0.2 and 0.2-2 µm). The results obtained highlight the mixed layer structure of HIMs which is composed of two or three different layers (HI, illites and/or expendables). The relative proportion of HI layers compared to that of expandable ones decreases with the particle size. In addition, the persistence of illite layers has been observed in the <0.05 µm size fraction. Auto aluminization experiments of K-or Ca- vermiculite separated in three-sized fraction (0.1-0.2, 1-2 and 10-20 µm) have been conducted in order to test the influence of the particle size on the aluminization process. These experiments exhibit the key role played both by the interlayer cation and the particle size on the cationic exchange and the crystal dissolution. The competition between of ion-exchange reactions and that of mineral dissolution on the K-vermiculite experiment, leads to the formation of 3 component MLMs (HI, illite and expandable) similar to those found in acidic soils. A similar effect of particle size leading to the persistence of illite layers was observed between the experiment products and the infra-micrometric particles of soils. Consequently, it is highly probable that both cation exchange and dissolution are the main processes governing the mineral evolutions in soils.

Les minéraux argileux gonflants sont omniprésents dans tous les compartiments de la surface de la Terre et notamment dans les sols. La structure lamellaire de ces minéraux et leur faible taille leur confèrent une forte réactivité notamment vis à vis des polluants et nutriments qui sont présents dans les eaux porales des sols. Dans ce cadre, cette thèse vise à contribuer à une meilleure compréhension des interactions entre des minéraux argileux gonflants et des cations nutritifs (calcium, strontium) et/ou d'intérêt environnemental (césium). Dans les sols, ces minéraux possèdent de larges distributions de taille et de cristallochimie (charge des feuillets). Par conséquent, pour mieux comprendre le rôle de chacun de ces paramètres sur la réactivité de ces particules naturelles, nous avons travaillé avec des « systèmes modèles », représentatifs des particules argileuses des sols : des particules de vermiculite triées en taille et des saponites synthétiques avec des charges de feuillets contrôlées. Les résultats d'adsorption des cations étudiés (Cs, Sr) en compétition avec les cations majeurs des eaux naturelles (Na, Ca) ont été obtenus en couplant l'analyse chimique des solutions et la modélisation des réflexions 00ℓ des diffractogrammes de rayons X afin d'obtenir la distribution de cations entre les différents sites d'adsorption (interfoliaire vs externes). Une telle approche et l'utilisation des « systèmes modèles » nous ont permis d'obtenir des paramètres quantitatifs décrivant la réactivité des minéraux argileux gonflants des sols. Ces paramètres pourront être pris en compte dans les codes de transport prédisant la migration des cations dans les sols. / The swelling clay minerals are ubiquitous in all areas of the surface of the Earth, particularly in soils. The lamellar structure of these minerals and their small size are at the origin of their high reactivity in particular with respect to pollutants and nutrients that are present in soil pore water. In this context, our work aims to contribute to a better understanding of the interactions between swelling clay minerals and cations of nutritive (calcium) and/or environmental interest (cesium, strontium). In soils, swelling clay minerals have broad size distribution and can have a varied crystal chemistry. Therefore, to better understand the role of each of these parameters on the reactivity of the natural particles, we worked with "model systems", which are yet representative of the swelling clay particles encountered in soil environment. Different particle size fractions of vermiculite and different synthetic saponites characterised by well-controlled layer charge were used as "model systems". Results concerning ion-exchange isotherms for Cs and Sr, in competition with major cations of natural waters (Na, Ca), were obtained by combining chemical analyses and 00ℓ reflection modelling of X-ray diffractograms in order to assess the cation distribution between the different adsorption sites (interlayer vs external) located on swelling clay minerals. Such approach and the use of ‘model systems’ have allowed us to obtain quantitative parameters describing the reactivity of soil swelling clay mineral particles, and should be considered in reactive transport codes devoted to predict the migration of nutritive and polluted cations in soil environments.

Masters thesis deals with formation of diffusion barrier coatings by means of powder mixtures chemical vapor deposition. Its theoretical part is focused on the problems with diffusion barriers formation, where predominantly three most commonly used methods are introduced, i.e. CVD from powder mixtures, active gasses and slurries. The experimental part of master thesis deals with the formation of nickel-aluminide diffusion barriers on Inconel 713LC superalloy substrate, where was for aluminization used six different powder mixtures at the temperature of 800 °C and dwell of 0, 2 and 5 hours.