Certos solos não saturados ao serem umedecidos experimentaram bruscas reduções de volume, sob cargas praticamente constantes. O fenômeno é atribuído a um colapso de estrutura do solo, donde a designação de solo colapsível. Essa redução de volume pode ocorrer sob a ação do próprio peso do solo, mas é mais comum ocorrer quando o solo está sujeito a um carregamento adicional. Muitos dos problemas de recalques nas áreas urbanas e industrias na Região Sudeste do Brasil estão associados ao colapso dos solos. Deformações induzidas por umedecimento (colapso) têm sido reportados como decorrrentes de vazamentos oriundo das redes de esgoto e de abastecimento de água. Porém, pouco se sabe sobre a influência de vazamentos de diferentes efluentes químicos nesse fenômeno e em outros fenômenos eventualmente associados com a dispersão dos solos. Neste trabalho, analisa-se o comportamento colapsível de dois solos típicos do interior do Estado de São Paulo, considerando diferentes soluções como líquido inundante. Utilizaram-se substâncias orgânicas e inorgânicas com o intuito de verificar a interferência de algumas propriedades químicas destas soluções (pH, constante dielétrica, concentração e temperatura) no comportamento colapsível dos solos. Para evitar a ação dos fluídos químicos na dispersão dos solos, realizou-se o \"pinhole test\". Análises porosimétricas por intrusão de mercúrio foram utilizadas para identificar mudanças ocorridas nos poros das amostras após os ensaios edométricos. Para a análise estrutural, foram analisadas lâminas delgadas em microscópio óptico. Verificou-se que a presença de um agente dispersivo na solução tende a influenciar o potencial de colapso dos solos. A constante dielétrica, o pH e a concentração mostraram-se influentes para alguns fluídos de saturação. Os resultados dos \"pinholes tests\" revelaram que o fluxo das diferentes soluções não provocou a dispersão do solo. Ensaios de porosimetria ) por intrusão de mercúrio indicaram que as deformações por colapso resultam de uma redução do volume de macroporos. A análise das lâminas delgadas mostrou diferentes facetas dos processos ocorrentes em nível estrutural, como diminuição considerável dos poros e modificações no plasma para as amostras inundadas com as soluções defloculantes de hexametafosfato de sódio e hidróxido de sódio. / Some non saturated soils show considerable volume reduction when wetted under constant loads. The phenomenon is attributed to soil structure collapse, thus the designation collapsible soils;. Volume reduction upon wetting can arise under soil self weight, but it is more common when the soil is subjected to an additional load. Many settlement problems in urban and industrial areas in Southern Brazil are associated to soil collapse. Wetting induced strains (collapse) have been related to water and sewer leakage. However little is known about the influence of different effluent leakage from industrial plants in the phenomenon and in other related phenomenon such as soil dispersion. This work deals with the collapsible behavior of two typical soils from the state of São Paulo assessed by means of wetting both soils with different chemical solutions. Organic and inorganic solutions were applied, aiming to verify the interference of some physic-chemical properties of the solutions (pH, dielectric constant, concentration, temperature) in the collapse behavior of the soils. The soil dispersion was evaluated through pinhole tests, where the same solutions used in the collapse tests were applied in the leaching procedures. Thin sections and mercury porosimetry of the soils were used to study the soil structural features. It is shown that the dielectric constant and the pH tends to influence the collapse potential of the soils when some solutions are concerned. Mercury intrusion tests have revealed that collapse deformations are related to macropores volume reduction. Thin sections have shown some features of the occurring processes on a structural levei, such as pore reductions and changes in fine matrix for the soil samples soaked with sodium hexametaphosphate and sodium hydroxide solution.

Devido aos diversos efeitos causados pela presença de \'SO IND.2\' em gases liberados na atmosfera, considerável atenção tem sido dada às técnicas para remoção deste poluente proveniente do processo de combustão. Neste trabalho apresenta-se um estudo relacionado com a determinação das melhores condições de granulometria e temperatura no processo de sorção de \'SO IND.2\' por um calcário dolomítico, denominado DP, e um calcário calcítico, denominado ICB, empregando-se a termogravimetria e porosimetria de adsorção de nitrogênio. Foram estudadas cinco faixas de granulometria média (385, 460, 545, 650 e 775 µm) e temperatura (variando de 745 a 920 ºC) para cada calcário. Com a aplicação do planejamento experimental, obtiveram-se superfícies de resposta com pontos de máximo indicando as melhores condições para cada calcário. Para o calcário DP, as maiores conversões (52%) foram obtidas na temperatura de calcinação de 850ºC e granulometria de 545 µm e as menores conversões foram obtidas para temperaturas acima de 900ºC e abaixo de 780ºC. Para o calcário ICB, as melhores condições foram obtidas em temperatura de 815ºC e 274 µm (conversão de 36,7%). Estabelecendo-se uma correlação entre a superfície de resposta e os parâmetros da estrutura física, os calcários, na condição de máxima conversão, apresentaram maior distribuição de poros na região de 20 a 110 A, indicando que a quantidade de poros menores pode ser um fator importante na reatividade do calcário. Pelos resultados apresentados na porosimetria, ambos os calcários apresentaram a média de diâmetro de poros próxima a 0,01 µm, indicando que o processo de difusão deveria seguir a Lei de Fick. No entanto, para calcário ICB observou-se o maior desenvolvimento de microporos, indicando que o mecanismo de difusão deste calcário possivelmente segue a Lei de Knudsen, justificando as menores conversões pelo rápido bloqueio dos poros, que impedem que as camadas mais internas sejam atingidas. Por meio das imagens obtidas por MEV, observou-se que a superfície do calcário ICB sulfatado apresentou uma camada mais fechada e compactada do que o calcário DP. / Due to various effects caused by the presence of \'SO IND.2\' in gases released into the atmosphere, considerable attention has been given to techniques of removal of this pollutant from the combustion processes. This dissertation reports on studies related to the determination of the optimum conditions of temperature and particle size in \'SO IND.2\' sorption by a dolomite, called DP and a calcite, called ICB. Five ranges of granulometry (385, 460, 545, 650 e 775 µm) and temperature (from 745 to 920ºC) were studie for each limestone. The application of experimental design resulted in a response surface with maximum values of temperature and particle size. For DP, the highest conversions (52%) were obtained at 850ºC and particle size of 545 µm and the lowest conversions were obtained at temperatures over 900ºC and below 780ºC. For ICB, the best conditions were obtained at 815ºC and 274 µm (36.7% conversion). The correlation between response surface and physical structure parameters showed that the amount of small pores is an important factor in the reactivity of the sorbents. For both DP and ICB, the average of pore size is close to 0.01 µm, indicating that the diffusion mechanism should follow the Fick law. However, in limestone ICB a further development of micropores was observed, allowing concluding that the diffusion mechanism possibly follows Knudsen law, which justifies the lowest conversions by quick pore blockage, consequently making the inner layers inaccessible. These assumptions were evidenced by the scanning electron microscopy (SEM), in which a compacted and closed layer was showed on ICB sulfated surface.

Certos solos não saturados ao serem umedecidos experimentaram bruscas reduções de volume, sob cargas praticamente constantes. O fenômeno é atribuído a um colapso de estrutura do solo, donde a designação de solo colapsível. Essa redução de volume pode ocorrer sob a ação do próprio peso do solo, mas é mais comum ocorrer quando o solo está sujeito a um carregamento adicional. Muitos dos problemas de recalques nas áreas urbanas e industrias na Região Sudeste do Brasil estão associados ao colapso dos solos. Deformações induzidas por umedecimento (colapso) têm sido reportados como decorrrentes de vazamentos oriundo das redes de esgoto e de abastecimento de água. Porém, pouco se sabe sobre a influência de vazamentos de diferentes efluentes químicos nesse fenômeno e em outros fenômenos eventualmente associados com a dispersão dos solos. Neste trabalho, analisa-se o comportamento colapsível de dois solos típicos do interior do Estado de São Paulo, considerando diferentes soluções como líquido inundante. Utilizaram-se substâncias orgânicas e inorgânicas com o intuito de verificar a interferência de algumas propriedades químicas destas soluções (pH, constante dielétrica, concentração e temperatura) no comportamento colapsível dos solos. Para evitar a ação dos fluídos químicos na dispersão dos solos, realizou-se o \"pinhole test\". Análises porosimétricas por intrusão de mercúrio foram utilizadas para identificar mudanças ocorridas nos poros das amostras após os ensaios edométricos. Para a análise estrutural, foram analisadas lâminas delgadas em microscópio óptico. Verificou-se que a presença de um agente dispersivo na solução tende a influenciar o potencial de colapso dos solos. A constante dielétrica, o pH e a concentração mostraram-se influentes para alguns fluídos de saturação. Os resultados dos \"pinholes tests\" revelaram que o fluxo das diferentes soluções não provocou a dispersão do solo. Ensaios de porosimetria ) por intrusão de mercúrio indicaram que as deformações por colapso resultam de uma redução do volume de macroporos. A análise das lâminas delgadas mostrou diferentes facetas dos processos ocorrentes em nível estrutural, como diminuição considerável dos poros e modificações no plasma para as amostras inundadas com as soluções defloculantes de hexametafosfato de sódio e hidróxido de sódio. / Some non saturated soils show considerable volume reduction when wetted under constant loads. The phenomenon is attributed to soil structure collapse, thus the designation collapsible soils;. Volume reduction upon wetting can arise under soil self weight, but it is more common when the soil is subjected to an additional load. Many settlement problems in urban and industrial areas in Southern Brazil are associated to soil collapse. Wetting induced strains (collapse) have been related to water and sewer leakage. However little is known about the influence of different effluent leakage from industrial plants in the phenomenon and in other related phenomenon such as soil dispersion. This work deals with the collapsible behavior of two typical soils from the state of São Paulo assessed by means of wetting both soils with different chemical solutions. Organic and inorganic solutions were applied, aiming to verify the interference of some physic-chemical properties of the solutions (pH, dielectric constant, concentration, temperature) in the collapse behavior of the soils. The soil dispersion was evaluated through pinhole tests, where the same solutions used in the collapse tests were applied in the leaching procedures. Thin sections and mercury porosimetry of the soils were used to study the soil structural features. It is shown that the dielectric constant and the pH tends to influence the collapse potential of the soils when some solutions are concerned. Mercury intrusion tests have revealed that collapse deformations are related to macropores volume reduction. Thin sections have shown some features of the occurring processes on a structural levei, such as pore reductions and changes in fine matrix for the soil samples soaked with sodium hexametaphosphate and sodium hydroxide solution.

Mesoporous silica materials containing microporous cavities provided by covalently bound ¦Â-cyclodextrin (CD ICS) were synthesized by co-condensation of a ¦Â-CD functionalized triethoxy silane (CD ICL) with tetraethyl orthosilicate (TEOS) by using neutral amine surfactants as structure directing agents (SDA). CD ICL was prepared by reacting ¦Â-CD with 3-isocyanatopropyltriethoxysilane. IR spectroscopy of CD ICL showed complete disappearance of isocyanato group at 2270 cm-1. 1H NMR results indicate an average of four isocyanate linkers covalently attached to random hydroxyl substituents of each molecule of ¦Â-CD. <p> Nine different CD ICS materials were synthesized using dodecylamine, tetradecylamine or hexadecylamine with ¦Â-CD (2, 4, and 6 mol %) with respect to TEOS. The incorporation of ¦Â-CD within the mesoporous framework was supported by IR, Raman, MALDI TOF MS, solid state 13C NMR CP-MAS and TGA results. Small angle X-ray diffraction results showed a peak at 2¦È ¡Ö 2.20, supporting the presence of an ordered silica mesostructure framework. For materials with same CD loading, the surface area and pore volume doubled as the surfactant from dodecylamine to hexadecylamine. However, as the CD loading increased from 2% to 6%, the surface area decreases by a factor of ~ 1.5. <p>MALDI TOF mass spectrometry showed two peaks at m/z 1157 a.m.u. and 1173 a.m.u. for [¦Â-CD + Na]+ and [¦Â-CD + K]+ respectively due to desorption of ¦Â-CD from the walls of the silica matrix. The 13C NMR CP MAS results showed 13C signals in the region ¦Ä=60-110 ppm due to the nuclei of ¦Â-CD. CD ICS materials were found to be effective as a sorbent in both gas and aqueous phases, respectively. The sorption capacity (mmol/g) of p-nitrophenol increased from 61% to 84% with an increase of CD loading from 2% to 6% and as the alkyl chain length of the SDA increases from dodecylamine to hexadecylamine. The adsorption isotherm of CH3Cl in the gas phase and that of p-nitrophenol in the aqueous phase at ambient temperature adopts a multilayer model of adsorption.

Mesoporous silica materials containing microporous cavities provided by covalently bound ¦Â-cyclodextrin (CD ICS) were synthesized by co-condensation of a ¦Â-CD functionalized triethoxy silane (CD ICL) with tetraethyl orthosilicate (TEOS) by using neutral amine surfactants as structure directing agents (SDA). CD ICL was prepared by reacting ¦Â-CD with 3-isocyanatopropyltriethoxysilane. IR spectroscopy of CD ICL showed complete disappearance of isocyanato group at 2270 cm-1. 1H NMR results indicate an average of four isocyanate linkers covalently attached to random hydroxyl substituents of each molecule of ¦Â-CD. <p> Nine different CD ICS materials were synthesized using dodecylamine, tetradecylamine or hexadecylamine with ¦Â-CD (2, 4, and 6 mol %) with respect to TEOS. The incorporation of ¦Â-CD within the mesoporous framework was supported by IR, Raman, MALDI TOF MS, solid state 13C NMR CP-MAS and TGA results. Small angle X-ray diffraction results showed a peak at 2¦È ¡Ö 2.20, supporting the presence of an ordered silica mesostructure framework. For materials with same CD loading, the surface area and pore volume doubled as the surfactant from dodecylamine to hexadecylamine. However, as the CD loading increased from 2% to 6%, the surface area decreases by a factor of ~ 1.5. <p>MALDI TOF mass spectrometry showed two peaks at m/z 1157 a.m.u. and 1173 a.m.u. for [¦Â-CD + Na]+ and [¦Â-CD + K]+ respectively due to desorption of ¦Â-CD from the walls of the silica matrix. The 13C NMR CP MAS results showed 13C signals in the region ¦Ä=60-110 ppm due to the nuclei of ¦Â-CD. CD ICS materials were found to be effective as a sorbent in both gas and aqueous phases, respectively. The sorption capacity (mmol/g) of p-nitrophenol increased from 61% to 84% with an increase of CD loading from 2% to 6% and as the alkyl chain length of the SDA increases from dodecylamine to hexadecylamine. The adsorption isotherm of CH3Cl in the gas phase and that of p-nitrophenol in the aqueous phase at ambient temperature adopts a multilayer model of adsorption.

Des résines polymères mésoporeuses ont été préparées à partir d’un série de diamide (BHPBn) comme porogènes. Ces composés s’auto-assemblent dans les solvants non polaires pour former des nanotubes d’un diamètre peu polydisperse et d’une dizaine de nm. Ces tubes sont formés dans un mélange monomère/réticulant et la suspension qui en résulte est photopolymérisée pour donner une résine contenant les tubes. Ces derniers sont extraits avec un solvant dissociant pour donner des pores. On obtient des résines avec des pores de 37 à 51 nm, selon le porogène, ainsi qu’on l’a mesuré par MET et par adsorption de N2. Ces diamètres des pores ne sont pas corrélés à ceux de BHPBn et toujours supérieur.Ces résines ont été fonctionalisées avec des carboxylates, des esters du N-hydroxysuccinimide ou d’époxydes. Des lipases ont été liées au résines par ces fonctions avec des taux de 69 mg par g de résine époxide et de 60 mg/g de résine COOSu. Les enzymes liées ont une activité de moins de 1 % de celle des enzymes libres, ce qui peut être expliqué par une dénaturation des enzymes sur la surface des pores qui est hydrophobe. / Mesoporous polymeric resins have been prepared with a series of diamides (BHPBn) as porogens. These compounds self-assemble in non-polar solvents into nanotubes with monodisperse diameters ranging from 21 to 34 nm. The tubes are formed in mixtures of monmers/crosslinkers, and the resulting suspension is photopolymerized to yield a resin embedding the tubes. The later are removed from the resin by leaching it with a dissociating solvent, yielding pores. One obtains resins with pore sizes comprised between 37 and 51 nm, depending on the porogen, as measured by TEM or by N2 adsorption. The pore sizes of the corresponding resin were not correlated to those of the starting porogen and always higher. The resins were successfully functionalized with carboxylic acids, N-hydroxysuccinimde esters (COOSu), or epoxide. Enzymes were attached to the resins via those functions, with rates of 69 mg per g of resin for epoxide resins and 60 mg/g for COOSu resins. The activity of the enzymes attached on the resins was measured and found less than 1 % of the activity of the free enzyme, which may be explained by a denaturation of the enzyme due to the hydrophobic nature of the pore surface.

Dans cette thèse, le problème de l'infiltration de bio-adhésifs résineux dans la dentine a été abordé par le biais de deux études, expérimentale et numérique. L'originalité de ces travaux réside dans le fait que l'échelle à laquelle nous nous sommes placés est nanoscopique. En effet, c'est l'infiltration d'un réseau de fibres de collagène de diamètre de l'ordre de 80nm qui pilote l'adhésion des composites résineux à la dentine. Une étude MEB a été menée pour confirmer et compléter la connaissance actuelle du milieu poreux. Cependant un paramètre manque dans la perspective d'une modélisation géométrique du réseau : la porosité n'est pas connue. Une étude complémentaire du substrat par porosimétrie à intrusion de mercure a donc été menée. La porosité volumique de la dentine déminéralisée est estimée à 55%. Deux tailles de pores sont révélées : la première correspond aux tubules et canalicules (autour de 1micron) et la seconde aux espaces interfibrillaires (autour de 50nm) jamais encore caractérisés de manière volumique. Cette étude permet aussi une investigation méthodologique. La lyophilisation, technique de séchage peu utilisée en odontologie, est évaluée et comparée à la technique de séchage utilisant l'HMDS. La lyophilisation semble être une technique de séchage fiable et convient parfaitement aux essais de porosimétrie. La modélisation géométrique du réseau fibreux est ensuite réalisée : les fibres sont considérées comme des zones à viscosité élevée. Cette modélisation est validée par comparaison des écoulements entre une fibre modélisée implicitement et une autre modélisée plus classiquement. L'orientation des fibres n'étant pas connue quantitativement, il a été choisi de construire trois types de réseau, le plus proche de la réalité (à la vue des images MEB) étant le réseau où les fibres sont disposées aléatoirement. Sa perméabilité a été estimée et validée par comparaison avec différentes études de réseaux fibreux ou non. Enfin, l'avancée du front est abordée de manière dynamique. Les équations d'avancée du front sont mises en place. Les équations de Navier Stokes sont couplées avec une méthode level set : l'interface correspondant au front d'infiltration n'est pas maillé (tout comme les fibres) mais correspond à une isovaleur d'une certaine fonction. Un attention particulière est portée aux conditions aux limites au niveau de la ligne triple et par le biais d'un terme ajouté à la formulation variationnelle, l'angle de contact est fixé. Ici, la principale difficulté est la prise ne compte des fibres qui ont été définies de manière implicite. Cette fois, les fibres sont uniquement le lieu de l'application de la condition aux limites fixant l'angle de contact et ne sont plus des zones de viscosité élevée car cela bloquerait le front. Le problème est résolu pour différentes géométries de réseaux fibreux. Tout d'abord, l'influence de certains paramètres sur des réseaux simples est sondée puis l'infiltration du modèle géométrique complet (réseau fibreux et tubules) est réalisée. Une conclusion cruciale pour les praticiens est mis en avant : augmenter le temps d'infiltration de la résine n'améliore pas l'infiltration. La simulation d'un essai de porosimétrie permet de distinguer deux tailles de pores distinctes et nécessite un ajustement car un décalage en pression par rapport à la courbe expérimentale est observée. L'outil construit permet une approche pédagogique de l'essai de porosimétrie et, après ajustement, pourra permettre la validation de diverses géométries. / In dentin restoration, collagen fiber network infiltration is an issue. In this thesis, an experimental study is lead prior to numerical modelling. Demineralized dentin porosity is a key parameter in dentin bonding that will in?uence the hybrid layer quality. Its characterization could be helpful to improve the monomers in?ltration. So, the objectives of the experimental study were to assess demineralized dentin porosity and quantify the different porous features distribution within the material using mercury intrusion porosimetry (MIP) technique. We compared hexamethyldisilazane (HMDS) drying and lyophilization (LYO) (freeze-drying) in sample preparation. The results showed two types of pores corresponding either to tubules and microbranches or to inter-?brillar spaces created by demineralization. Global porosity varied from 59% (HMDS-dried samples) to 70% (freeze-dried samples). Lyophilization drying technique seems to lead to less shrinkage than HMDS drying. FESEM revealed that collagen ?bers of demineralized lyophilized samples are less melted together than in the HMDS-dried samples. Using our experimental data , we have constructed a relevant numerical geometrical model of the network. The specificity of our model is that the fibers are taken into account implicitly using a regularized Heaviside function. This function is either used to set the viscosity or to localize the contact line where capillary forces are applied. A level set technique with respect to fluid infiltration front tracking in five fiber networks using the level set method and Navier-Stokes equations with capillary terms is used to point out efficient critical infiltration parameters. A variational formulation which can be implemented in FEM is proposed both for the infiltration front and the contact line. Because of lack of knowledge on fiber orientation, different configurations were tested through permeability assessment of the whole network. Fiber orientation, interfibrillar space and contact angle influence were investigated. Then a network representing the dentinal porous substrate is infiltrated by a wetting fluid and we came to a useful conclusion : increasing infiltration time will not improve the quality of the bonding. In order to link the numerical and experimental studies, infiltration curves of mercury into the porous network are compared. We used a non-wetting fluid (mercury) to invade the numerical porous network to model the porosimetry test. As mercury do not invade the porous network naturally, an incremental pressure is applied to force it to penetrate the porous medium. The simulation is qualitatively satisfying and enables to point out the porosimetry test limitations in a pedagogical way. Thanks to the simulation, we can see the mercury invading pore spaces: big pores are penetrated first and then small pores (which obviously cannot be seen during the experimental process). Quantitatively, two sizes of pore are detected and their contributions to total porosity are satisfying. Nevertheless, the pore size values have to be ajusted. To conclude, this thesis contributed to the characterization of demineralized dentin. The numerical modeling allows us to point out influencing parameters during capillary infiltration of a fibrous network and to illustrate the porosimetry test process an its limitations. An interesting tool to confirm a geometrical model has been built. The tools that have been built can easily been used to other porous structures.

O presente trabalho teve como objetivo a implementação de técnicas de Ressonância Magnética Nuclear (RMN) para o estudo de meios porosos em geral, com potenciais aplicações no estudo de rochas, ossos, polímeros e materiais cerâmicos porosos. Devido à heterogeneidade e à complexidade desses meios, torna-se importante correlacionar variados parâmetros físicos que contenham informações tanto sobre a dinâmica molecular quanto sobre a estrutura físico-química dos poros e dos fluidos que os permeiam. Utilizando técnicas de RMN, é possível investigar esses parâmetros através da medida dos coeficientes de difusão e dos tempos de relaxação longitudinal e transversal dos fluidos presentes nos poros, que apresentam diferentes estados dinâmicos, variando desde um líquido isotrópico até um líquido com alta viscosidade ou organizado devido à sua interação com a superfície dos poros ou com partículas presentes nos fluidos. Para isso, foram empregadas técnicas de RMN baseadas especialmente em medidas de tempos de relaxação transversal que, quando adequadamente combinadas, permitem a construção de mapas bidimensionais que correlacionam propriedades da dinâmica molecular de fluidos saturantes nessas amostras em instantes diferentes do experimento, provendo informações sobre as dimensões e escalas temporais envolvidas na dinâmica dos fluidos saturantes dos meios porosos. Esses mapas foram obtidos a partir de dados experimentais obtidos com rochas petrolíferas saturadas com água via algoritmos de inversão da transformada de Laplace bidimensional. Este trabalho foi realizado utilizando a infraestrutura existente nos laboratórios de RMN do IFSC, sendo grande parte do hardware e software desenvolvidos durante o projeto de doutorado. Foi desenvolvido um programa para processamento da transformada inversa de Laplace de dados unidimensionais, sendo este utilizado para o estudo de propriedades de adesão de pastilhas de gesso quando submetidas a diferentes pressões. Além disso, foram desenvolvidos modelos computacionais para simular essas propriedades relacionadas aos experimentos utilizados para o estudo dos meios porosos. Parte deste trabalho contou com a realização de dos estudos na Victoria University of Wellington em colaboração com o professor Paul T. Callaghan através do Programa de Doutorado e Estágio no Exterior (PDEE) da CAPES. / This study aimed to implement Nuclear Magnetic Resonance (NMR) for the study of porous media in general, with potential applications in the study of rocks, bones, porous polymers and ceramics. Due to the heterogeneity and complexity of these media, it becomes important to correlate various physical parameters that contain information about both the molecular dynamics on the structure and physical chemistry of pore fluid and the permeate. Using NMR techniques, it is possible to investigate these parameters by measuring diffusion coefficients, transverse and longitudinal relaxation times of fluids within the pores, which have different dynamical states, ranging from an isotropic liquid to a liquid with high viscosity or organized due to its interaction with the surface of the pores or particles suspended in fluid. For this, we employed NMR techniques based especially on measurements of transverse relaxation times, which when properly combined, allow the construction of two-dimensional maps that correlate properties of the molecular dynamics of fluids saturating these samples at different times of the experiment, providing information on dimensions and time scales involved in the dynamics of fluids saturating the porous media. These maps were obtained from experimental data on water-saturated oil rocks via inversion of two-dimensional Laplace transform. This work was performed using the existing infrastructure in the IFSC NMR laboratories and much of the hardware and software was developed during the doctoral project. We developed a program for processing the one-dimensional inverse Laplace transform data, which was used for studying the adhesion properties of gypsum pellets when subjected to different pressures. Additionally, we developed computational models to simulate physical-chemical properties related to the experiments used for the studies of fluids within porous media. Part of this work included studies performed in Victoria University of Wellington in collaboration with Professor Paul T. Callaghan through the Programa de Doutorado e Estágio no Exterior (PDEE) from CAPES.

Devido aos diversos efeitos causados pela presença de \'SO IND.2\' em gases liberados na atmosfera, considerável atenção tem sido dada às técnicas para remoção deste poluente proveniente do processo de combustão. Neste trabalho apresenta-se um estudo relacionado com a determinação das melhores condições de granulometria e temperatura no processo de sorção de \'SO IND.2\' por um calcário dolomítico, denominado DP, e um calcário calcítico, denominado ICB, empregando-se a termogravimetria e porosimetria de adsorção de nitrogênio. Foram estudadas cinco faixas de granulometria média (385, 460, 545, 650 e 775 µm) e temperatura (variando de 745 a 920 ºC) para cada calcário. Com a aplicação do planejamento experimental, obtiveram-se superfícies de resposta com pontos de máximo indicando as melhores condições para cada calcário. Para o calcário DP, as maiores conversões (52%) foram obtidas na temperatura de calcinação de 850ºC e granulometria de 545 µm e as menores conversões foram obtidas para temperaturas acima de 900ºC e abaixo de 780ºC. Para o calcário ICB, as melhores condições foram obtidas em temperatura de 815ºC e 274 µm (conversão de 36,7%). Estabelecendo-se uma correlação entre a superfície de resposta e os parâmetros da estrutura física, os calcários, na condição de máxima conversão, apresentaram maior distribuição de poros na região de 20 a 110 A, indicando que a quantidade de poros menores pode ser um fator importante na reatividade do calcário. Pelos resultados apresentados na porosimetria, ambos os calcários apresentaram a média de diâmetro de poros próxima a 0,01 µm, indicando que o processo de difusão deveria seguir a Lei de Fick. No entanto, para calcário ICB observou-se o maior desenvolvimento de microporos, indicando que o mecanismo de difusão deste calcário possivelmente segue a Lei de Knudsen, justificando as menores conversões pelo rápido bloqueio dos poros, que impedem que as camadas mais internas sejam atingidas. Por meio das imagens obtidas por MEV, observou-se que a superfície do calcário ICB sulfatado apresentou uma camada mais fechada e compactada do que o calcário DP. / Due to various effects caused by the presence of \'SO IND.2\' in gases released into the atmosphere, considerable attention has been given to techniques of removal of this pollutant from the combustion processes. This dissertation reports on studies related to the determination of the optimum conditions of temperature and particle size in \'SO IND.2\' sorption by a dolomite, called DP and a calcite, called ICB. Five ranges of granulometry (385, 460, 545, 650 e 775 µm) and temperature (from 745 to 920ºC) were studie for each limestone. The application of experimental design resulted in a response surface with maximum values of temperature and particle size. For DP, the highest conversions (52%) were obtained at 850ºC and particle size of 545 µm and the lowest conversions were obtained at temperatures over 900ºC and below 780ºC. For ICB, the best conditions were obtained at 815ºC and 274 µm (36.7% conversion). The correlation between response surface and physical structure parameters showed that the amount of small pores is an important factor in the reactivity of the sorbents. For both DP and ICB, the average of pore size is close to 0.01 µm, indicating that the diffusion mechanism should follow the Fick law. However, in limestone ICB a further development of micropores was observed, allowing concluding that the diffusion mechanism possibly follows Knudsen law, which justifies the lowest conversions by quick pore blockage, consequently making the inner layers inaccessible. These assumptions were evidenced by the scanning electron microscopy (SEM), in which a compacted and closed layer was showed on ICB sulfated surface.

L'objectif de cette recherche est d’analyser l’apparition et la propagation des fissures de dessiccation et de mieux comprendre la relation entre les comportements macroscopique et microscopique de cinq argiles, une kaolinite, une montmorillonite et trois mélanges de kaolinite et montmorillonite. A l'échelle macroscopique, la méthode est basée sur (1) la mesure de la teneur en eau, de l’indice des vides et du degré de saturation en fonction de la succion au cours du séchage, qui permet de préciser la relation entre le retrait et la désaturation et met en évidence les phases caractéristiques du comportement; (2) des mesures de teneur en eau et des déformations globales dans les tests de dessiccation libre afin d'étudier leur homogénéité ; (3) la détermination des déformations et des déplacements locaux pendant le séchage avec les logiciels VIC-2D et VIC-3D ; (4) une étude classique des paramètres des fissures ; (5) des essais de traction pour déterminer les propriétés des argiles impliquées dans la formation de fissures . A l'échelle microscopique, l'étude est basée sur une analyse approfondie de la microstructure en utilisant en particulier le microscope électronique à balayage, couplé à une méthode adaptée pour l'identification des orientations préférentielles des particules. Cette étude microscopique est complétée par l'analyse de porosimétrie au mercure, une méthode qui permet de quantifier l'espace poral et de caractériser l’indice des vides local. Outre les recherches sur les sols argileux, les effets de la décompression et de la succion sur la formation des fissures dans une roche argileuse ont été analysés également. La relation entre les changements macroscopiques, les changements dans la microstructure et de la porosité a été étudiées. Lors des essais de dessiccation libre, les déformations et les déplacements sont obtenus avec Vic-2D. Les zones de l’échantillon où les fissures apparaissent sont identifiées ainsi que l’évolution des déformations et des déplacements avant l’apparition des fissures. A la fin du séchage, les fissures forment une sorte de réseau, où des bifurcation peuvent être observées dans certains cas. Deux modes de fissuration sont détectés pendant les essais : le mode de traction et le mode de déchirement. Lorsqu’une fissure est causée par des tractions, la direction de propagation suit la direction perpendiculaire à l’extension maximale. S’il y a des distorsions à proximité de la fissure, alors sa direction change. Au début du séchage, les déplacements et les déformations sur le bord sont plus importants que dans les autres parties du modèle. Au voisinage des fissures, les déplacements et les déformations deviennent plus grands que dans les autres parties. Dans la plus grande partie du modèle, les déformations principales sont essentiellement longitudinales et transversales. Pour un matériau donné, la résistance à la traction augmente lorsque la teneur en eau diminue. Le tracé des résultats en fonction de l’indice de liquidité permet de mettre en évidence l’effet de la minéralogie sur la résistance à la traction. Au même indice de liquidité, la contrainte maximale de traction diminue lorsque le pourcentage de monmorillonite augmente. L’effet de la succion sur la résistance à la traction semble qualitativement similaire à ce qui est observé dans le cas de la résistance à la compression simple : on observe que la résistance à la traction est une fonction linéaire du logarithme de la succion. L’analyse au MEB de quatre suspensions soumises à plusieurs succions met en évidence l’isotropie globale de la microstructure, avec une orientation aléatoire des particules, tandis qu’une analyse plus fine révèle que la microstructure peut présenter localement une certaine anisotropie. / The objective of this research is to analyze the appearance and propagation of cracks related to desiccation and to provide a better understanding of the relation between the macroscopic and microscopic behavior of five clays, a kaolinite, a montmorillonite and three mixtures of kaolinite and montmorillonite. At the macroscopic scale, the method is based on (1) measurements of water content, void ratio and degree of saturation versus suction during drying, which allows to specify the relationship between shrinkage and desaturation and highlights the characteristic phases of behavior; (2) measurements of water contents and global deformations in free desiccation tests in order to study their homogeneity; (3) the determination of the local deformations and displacements during drying using the softwares VIC-2D and VIC-3D; (4) a classical study of the parameters of cracks; (5) traction tests in order to identify the tensile properties of the clays involved in the formation of cracks. At the microscopic scale, the study is based on a thorough microstructure analysis using in particular scanning electron microscope, coupled to an adapted method for the identification of preferential orientations of particles. This microscopic study is complemented by mercury intrusion porosimetry analysis, a method which allows to quantify the poral space and to characterize the local void ratio. In addition to the research on clay soils, the effects of decompression and suction on the formation of cracks in a clay rock were analyzed too. The relationship between macroscopic changes and the changes in the microstructure and porosity was investigated. During free desiccation tests, two-dimensional strains and displacements maps are obtained with Vic-2D. The zones of the sample where cracks appear are identified as well as the evolution of strains and displacements before the appearance of cracks. At the end of desiccation, the cracks form a kind of network. Bifurcation of cracks can be observed in some cases. Two modes of cracks are detected during the tests: traction mode and tearing mode. When a crack is caused by traction, the propagation direction follows the direction perpendicular to maximum extension. If there are shear strains in the vicinity of the crack, then its direction changes. In the early time of desiccation, the displacements and strains on the boundaries are larger than those in the other parts of the model. In the vicinity of cracks, displacements and strains are relatively larger than those in the other parts. In most parts of the model, the principal strains are mainly longitudinal and transversal. For a given material, tensile strength increases when water content decreases. Plotting the results versus the liquidity index allows highlighting the effect of mineralogy on tensile strength. At the same liquidity index, the maximum tensile stress decreases when the montmorillonite content increases. The effect of suction on tensile strength seems qualitatively similar to what is observed in the case of unconfined compression strength with tensile strength being a linear function of the logarithm of suction. Analysis with SEM of four slurries submitted to several suctions highlights the global isotropy of the microfabric, with a random orientation of the particles, while a finer analysis reveals that the fabric may present locally some anisotropy.