Many of the wastes associated with the nuclear fuel cycle are toxic to the biosphere; advancing the use of high resolution spectroscopy applied to these materials will provide the chemical speciation of the interaction between nuclear waste and geological material, improving confidence in a permanent disposal method and informing clean-up operations. Luminescence spectroscopy of uranyl(VI) is a well-established technique for the molecular speciation of uranium-mineral interactions. This work explores the use of both micro- and macroscopic luminescence spectroscopy to expose uranyl(VI) speciative heterogeneity in a range of minerals which have been exposed to uranyl(VI) salt solutions. A comprehensive review of the available literature on the interaction of uranyl(VI) with a range of geological media is assessed and compared. The review finds considerable ambiguity in the speciation of uranyl(VI) at the mineral water interface. A database reporting the multi parametric luminescence properties of uranyl(VI) with silica gel, quartz, bayerite, boehmite, muscovite, kaolinite and montmorillonite (SWy-2 and STx-1b) is presented and discussed. Although some of the results are consistent with previously reported values, many newly identified species are reported and their identification speculated. Parallel factor analysis is used to deconvolute the excitationemission matrix of uranyl(VI) sorbed to silica gel between pH 3 and pH 10. The results are used to identify the spectroscopic properties of complexes >(SiO)2UO2 and >(SiO)2UO2OH and thus new complexation coefficients (log(K)) for their formation with the silica gel surface are determined, log(K1) = 9.22 ± 0.02 and log(K2) = 3.45 ± 0.01, respectively. The investigation also provides insight into the fundamental properties of uranyl(VI) excitation pathways, which are not yet fully understood. Confocal microscopy and phosphorescent lifetime image mapping (PLIM) is used to expose the sub-micron heterogeneity of uranyl(VI) sorption complexation across mineral surfaces of silica gel, bayerite and montmorillonite (STx-1b). The results suggest that changes in the uranyl(VI) lifetime can be used to observe and understand submicron changes in uranyl(VI) complexation at hitherto unknown temporal resolution.

Orientador: Maria Isabel Felisberti / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-09-27T12:44:40Z (GMT). No. of bitstreams: 1 Contar_LiviaBarbosa_M.pdf: 1831028 bytes, checksum: 9dc6aca0cd0794c653af2498ac17227d (MD5) Previous issue date: 2013 / Resumo: A incorporação de cargas em matrizes poliméricas, visando o desenvolvimento de compósitos e nanocompósitos poliméricos, tem sido foco de intensos estudos e apresentado interesse crescente na área industrial nos últimos anos em função do acréscimo conferido às suas propriedades mecânicas, térmicas e elétricas, dependendo da natureza da carga, e também devido à simplicidade, rapidez e baixo custo na obtenção destes materiais. A associação de cargas de diferentes naturezas em uma mesma matriz polimérica, além de conferir múltiplas funcionalidades ao material, pode contribuir com propriedades sinérgicas, antagônicas ou meramente aditivas. Neste trabalho, foram preparados em diferentes concentrações, compósitos binários de poliamida 6 (PA 6) com argila organicamente modificada, Cloisite® 30 B (C30B) e PA 6 com grafite puro, bem como compósitos ternários de PA 6, argila C30B e grafite, através da mistura mecânica no estado fundido, utilizando extrusora de duas roscas cônicas co-rotacionais, com o objetivo de desenvolver materiais com elevado desempenho mecânico e térmico. Corpos de prova moldados por injeção foram submetidos a ensaios para determinação de suas propriedades mecânicas (ensaios de tração e de resistência ao impacto), térmicas (DMA, TGA e DSC), morfológicas (SEM e TEM) e estruturais (XRD). Tanto os nanocompósitos de PA 6 e argila C30B, quanto os compósitos de PA 6 e grafite, apresentaram maior resistência à tração do que a PA 6 pura, assim como ocorreu com os compósitos ternários. Porém, nestes últimos, foram observados os maiores ganhos na rigidez do material, devido ao efeito co-reforçante de ambas as cargas e suas prováveis interações mútuas que favorecem a dispersão na matriz. As análises morfológicas das misturas binárias e ternárias revelaram a formação de estruturas esfoliadas e de agregados, no caso da argila, enquanto que no caso da grafite apenas se observou partículas correspondentes a agregados de multilaminas de grafeno, mesmo nos sistemas ternários. Apesar disso, contatou-se que a presença da grafite nos nanocompósitos ternários proporciona um aumento da extensão de delaminação da argila. A grafite atua como agente nucleante para a cristalização da poliamida, sem alterar a forma cristalina, no caso a forma 'alfa'. Enquanto que a argila induz a formação da fase 'gama'. / Abstract: The incorporation of fillers in polymeric matrices in order to develop polymer composites and nanocomposites has been highlighted in many works and has showed increasing interest in industrial area in the last years because of enhaced mechanical, thermal and electrical properties, depending on the filler nature, and also because of simplicity, velocity and low costs in the preparation of these materials. The association of different fillers in the same polymeric matrix, beyond multiple functionalities attributed to the material, can also contribute to synergistic, antagonistic or additive properties. In this work, binary composites of polyamide 6 (PA 6) with organic modified clay, Cloisite® 30 B (C30B), and PA 6 with pristine graphite, were prepared in different concentrations as well as ternary composites of PA 6, clay and graphite, through mechanical mixture in the molten state, using a conical co-rotational twin-screw extruder, in order to develop materials with enhaced mechanical and thermal properties. The materials were injection molded to investigate their mechanical (Tensile properties, Izod Impact resistance), thermal (DMA, TGA and DSC), morphological (SEM and TEM) and structural (XRD) properties. Both binary composites, PA 6 with C30B clay and PA 6 with graphite, showed higher tensile properties in relation to pure PA 6, and the same happened with ternary composites. But in these last one the highest gain in the material stiffness was observed, because of the co-reinforcement effect of both fillers and their mutual interations that favoured fillers dispersion. The morphological analysis of binary and ternary systems have revealed the formation of exfoliated structures and aggregates, in the case of the clay, while in the graphite case only particles refered to aggregates of graphene multi-platelets were observed even in the ternary systems. Nevertheless, it was detected that the presence of graphite in the ternary composites promotes an increase in the exfoliation degree of the organoclay. Thermal studies showed that the graphite acts as a nucleating agent for the crystallization of polyamide, without change in the crystalline 'alpha' phase, while the organoclay promotes the 'gama' phase / Mestrado / Físico-Química / Mestra em Química

Neste trabalho foi realizado um estudo das interações entre os fungicidas (carbendazim e fuberidazole) e as partículas de argilas SWy-1, SHCa-1 e SYn-1 em suspensão aquosa. Foram determinados através de isotermas de adsorção, espectrofometria de absorção no UV, de emissão de fluorescência e difratometria de raios -X. Os resultados experimentais envolvendo a adsorção foram bem ajustados pelas isotermas de Langmuir, Freundlich e Dubinin-Radushkevich os quais indicam haver alta afinidade entre os fungicidas e as argilas. A capacidade de adsorção foi maior na argila SWy-1 comparada às argilas SHCa-1 e SYn-1, sendo estas ultimas com capacidade de adsorção similares. Foi observada a adsorção dos fungicidas carbendazim e fuberidazole à região interlamelar das partículas de argila, onde ocorre a protonação da molécula dos fungicidas, tornando-a mais estável. Medidas espectrofotométricas, na região do UV, foram efetuadas em função do tempo durante 24 horas. Pela análise dos resultados obtidos, foi possível propor um mecanismo geral para explicar as mudanças espectrais que ocorrem durante a adsorção dos fungicidas nas partículas das argilas em suspensão aquosa. Os resultados de espectrofotometria de absorção no UV do fuberidazole adsorvido nas partículas das argilas e as isotermas de adsorção indicaram que existe uma correlação entre a saturação das argilas e a saturação dos sítios ácidos no processo de adsorção. A intensidade de emissão aumentou significativamente quando o carbendazim foi adsorvido nas argilas SHCa-1 e SYn-1. No entanto, com o fuberidazole observou-se uma diminuição da fluorescência. Nenhuma emissão da fluorescência dos fungicidas carbendazim e fuberidazole adsorvidos nas partículas da argila SWy-1 foi observada devido ao alto teor de ferro. A fotodegradação do carbendazim foi significativamente acelerada quando foi adsorvido nas partículas das argilas. Foi possível observar o aparecimento de novas bandas nos espectros de absorção e de emissão dos fotoprodutos formados na argila que não foram reportados na literatura. / In the present work, studies on the interaction between the fungicides (carbendazim and fuberidazole) and clay particles in aqueous suspension. It has been studied by isotherm adsorption, UV spectroscopy, emission of fluorescence and X-Ray. The results were fitted according the Langmuir, Freundlich and Dubinin- Radushkevich isotherms indicating a high affinity between the fungicide and the clay surfaces. The adsorption capacity in the SWy-1 clay was higher than the SHCa-1 and SYn-1 clays, being these last clays with same adsorption capacity between them. The fungicides can be adsorbed as neutral molecules in the external surfaces as well can be protonated in the interlamellar region of the clay particles. Spectrofothometric measurements in the UV region were taken after different time intervals. A mechanism for the adsorption of fungicides molecules on the clay particles was perceived, leading to a better understanding of the adsorption of this compound on clays. The data obtained by the absorption spectrophotometry in the UV region of the fuberidazole adsorbed in the particle clays and its adsorption isotherms indicated the correlation between the saturation of the clays and the saturation of the acid sites in the adsorption process. When carbendazim was adsorbed on the SHCa-1 and SYn-1 clay particles, the emission intensity increased significantly. However with the fuberidazole was decreased. The emission spectra showed bands attributed to both neutral adsorbed and protonated forms of the fungicides. The emission of the fungicides molecules adsorbed on the particles of SWy-1 clays was almost totally quenched due to the high load of iron. The carbendazim photodegradation process was significantly accelerated when carbendazim was adsorbed on the clay particles compared to the aqueous phase. It was possible to determine the absorption and emission spectra of photoproducts formed on the clay particles, which were not detected in other studies reported in the literature.

Neste estudo, investigaram-se mudanças nas propriedades coloidais de uma esmectita pilarizada com polihidroxicátion de alumínio. A solução pilarizante foi preparada mediante gotejamento de solução NaOH 0,4 mol L-1 em solução de AlCl3.6H2O 0,2 mol L-1, a qual foi adicionada à suspensão de argila de 1% m/m. Para avaliar mudanças nas propriedades das argilas, recorreu-se às técnicas de titulação potenciométrica descontínua, análise química total, DRX, FTIR, CTC e isotermas de adsorção/dessorção de N2. Além disso, foram realizados ensaios de adsorção de Cu2+ para avaliar a capacidade de remoção do metal de soluções aquosas pelas argilas pilarizadas e gerar informações relacionadas à interação entre adsorvente e adsorbato. Naturalmente, a argila apresentou espaçamento basal de 1,26 nm, ao passo que as pilarizadas apresentaram valores de 1,78 nm (500 oC) e 1,80 nm (350 oC). Dados da análise química total mostraram se tratar de uma montmorillonita com altos teores de Fe3+, e confirmou o aumento nos teores de Al3+ na estrutura da argila após pilarização. Os valores de área superficial específica e volume de microporos foram maiores para as argilas pilarizadas, enquanto que a CTC foi maior para a argila natural. A titulação potenciométrica mostrou modificação nas curvas de titulação com o processo de pilarização, em que nas argilas pilarizadas surgiram novos sítios de reação. Dentre as equações de adsorção aplicadas, Langmuir, Freundlich e Temkin, a primeira apresentou valores de r2 das equações linearizadas maior para todas as argilas e menor desvio médio (?g%) para argila natural, ao passo que a equação de Temkin mostrou valores de ?g(%) menores para as argilas pilarizadas. Parâmetros termodinâmicos confirmaram que a reação de adsorção de Cu2+ é espontânea para todas as argilas, principalmente para as argilas pilarizadas. Além disso, cálculos baseados em equações de Dubinin-Radushkevich evidenciam que a ligação é fraca entre metal e argila, caracterizando reações de fisissorção. / In this study, an Al-pillared smectite was synthesized and changes in its colloidal properties were investigated. The pillaring solution was prepared adding dropwise adequate volume of NaOH 0,4M to AlCl3.6H2O 0,2M solution. Then, the pillaring solution was added to a 1% w/w clay slurry with constant stirring. Potentiometric titration, chemical analysis, XRD, FTIR, CEC and N2 sorption/dessoption isotherms analysis were done to characterize the changes in clay properties. Moreover, adsorption experiments were carried out in order to evaluate the capacity of the pillared clays to remove Cu2+ from aqueous solution and to characterize the interaction between adsorbent and adsorbate. The natural clay has a basal spacing of 1.26 nm whereas the pillared clays reached 1.78 nm (500 oC) and 1.80 nm (350 oC) after calcination. Chemical analysis revealed that the montmorillonite used has high content of Fe3+ and the increase in the Al3+ amount in the structure of the pillared clays after pillaring process. The surface area and micropore volume were higher for the pillared clays and the CEC was higher for the natural clay. The pillaring process changed the potentiometric titration curves, wherein the pillared clays exhibited new reactive site. Experimental data were fit to Langmuir, Freundlich and Temkin adsorption equations, being the the first one the best (highest r2 value) for all the clays and lower standard deviation (?g%) for the natural clay. On the other hand, Temkin equation exhibited ?g% value lower for the pillared clays. Thermodynamics parameters demonstrate that the Cu2+ adsorption process is spontaneous for all the clays, but with higher values for the pillared materials. In addition, application of the Dubinin-Radushkevich equation revealed that the bond between the metal and the clay are weak, characterizing a physisorption.

Os argilominerais são empregados na área farmacêutica e cosmética tanto como excipientes quanto ingredientes ativos. Esses compostos inorgânicos são inertes quimicamente, apresentam estruturas definidas e alta estabilidade térmica, o que contribui para o uso nessas áreas. Atualmente a indústria farmacêutica busca modificações no sistema de entrega de drogas (melhorias no tempo, local e taxa de liberação), objetivando um aumento na estabilidade das drogas e a prevenção e diminuição de efeitos colaterais. Nesse sentido, surge a necessidade de desenvolver novas formulações farmacêuticas, novos métodos de preparação e novos materiais. Considerando o fato dos argilominerais incorporarem espécies diversas entre suas lamelas, é interessante explorar a possibilidade de uso dessas matrizes inorgânicas como carregadores de espécies bioativas. O principal objetivo do presente trabalho foi preparar e caracterizar argilas de uso farmacêutico e/ou cosmético intercaladas com espécies que apresentam potencial terapêutico. Para tanto, usou-se duas argilas esmectitas naturais do tipo montmorilonita (Cloisita Sódica e Veegum HS) e uma esmectita sintética do tipo hectorita (Laponita RD). Os aminoácidos L-lisina, L-arginina e L-ornitina, e o dipeptídeo L-carnosina foram imobilizados em argilas catiônicas, por meio de reação de troca iônica. Na preparação dos materiais híbridos, alguns parâmetros experimentais foram avaliados: concentração hidrogeniônica (pH) da suspensão de reação, proporção argila/aminoácido e tempo de reação. As argilas precursoras e os materiais híbridos obtidos foram caracterizados por difratometria de raios X, espectroscopia vibracional na região do infravermelho e Raman, análise termogravimétrica acoplada à espectrometria de massas e análise química de carbono. Os valores de distância interlamelar (d(001)) dos materiais sugerem que a cadeia carbônica das espécies orgânicas se orienta paralelamente em relação às lamelas de baixa densidade de carga dos argilominerais. Nos espectros vibracionais na região do infravermelho há predominância das bandas características da estrutura inorgânica, mas as bandas entre 1800 e 1400 cm-1 relativas aos grupos funcionais do aminoácido permitem inferir sobre o seu grau de protonação no material híbrido. A acidez de Brönsted gerada pela polarização das moléculas de água associadas à argila foi observada para as montmorilonitas empregadas neste estudo. Amostras preparadas em suspensões nas quais o valor do pH era maior que o valor da primeira constante ácida (pKa1) dos aminoácidos apresentam bandas atribuídas ao estiramento C=O de grupo carboxilato protonado. Os espectros Raman foram obtidos apenas para a argila sintética, uma vez que as naturais apresentam luminescência. O espectro Raman da L-carnosina imobilizada em Laponita indica a presença preponderante da espécie zwitteriônica; o deslocamento das bandas atribuídas aos grupos amida e carboxílico do dipeptídeo para região de menor energia sugere a formação de ligações de hidrogênio com os grupos silanol da Laponita. Os resultados de análise termogravimétrica acoplada à espectrometria de massas dos materiais híbridos são distintos daqueles observados para os aminoácidos livres. A temperatura de início de decomposição das espécies orgânicas não é praticamente modificada após imobilização nas argilas, mas os processos térmicos se estendem até regiões de maior temperatura, evidenciando a influência da estrutura inorgânica sobre a decomposição térmica dos aminoácidos. Através dos dados de quantidade de carbono e de água nas amostras, calculou-se a concentração de aminoácidos nos materiais híbridos (massa de aminoácido / 100 gramas de material). As maiores concentrações de aminoácido (entre seis e oito por cento) foram observadas para as amostras de Cloisita e Veegum HS, isoladas em condições nas quais predomina a interação eletrostática entre as lamelas e os aminoácidos com carga positiva. Nas condições experimentais empregadas neste trabalho não foi observada a saturação das argilas com os aminoácidos, ou seja, as cargas das lamelas não foram totalmente neutralizadas pelos íons orgânicos. / Clay minerals are used as excipients or active ingredients in the pharmaceutical and cosmetic fields. These inorganic compounds are chemically inert, have defined structures and high thermal stability, which make them useful for these areas. Currently the pharmaceutical industry seeks modifications in the drug delivery systems (improvements in the time, place and rate of release), aiming an increase in the stability of the drugs and also the prevention and reduction of side effects. In this way, it is a need to develop new pharmaceutical formulations, new preparation methods and new materials. Considering the fact that clay minerals incorporate various species between their layers, it is interesting to explore the possibility of using these inorganic matrices as carriers of bioactive species. The main aim of this work was to prepare and characterize clays of pharmaceutical and/or cosmetic usage intercalated with species of therapeutic potential. Two natural smectite clays of montmorillonite type (Sodium Cloisite and Veegum HS) and one synthetic smectite of hectorite type (Laponita RD) were employed. The amino acids L-lysine, L-arginine and L-ornithine, and the L-carnosine dipeptide were immobilized on cationic clays by ion exchange reaction. Some experimental parameters were evaluated in the preparation of hybrid materials: hydrogen ion concentration (pH) of reaction suspension, clay/amino acid proportion and reaction time. Pristine clays and hybrid materials were characterized by X-ray diffraction, infrared and Raman vibrational spectroscopies, thermogravimetric analyses coupled to mass spectrometry and chemical analysis of carbon. The materials values of interlayer distance (d(001)) suggest that the carbon chain of the organic species is oriented parallel to the layers of clay minerals. The infrared vibrational spectra are dominated by the inorganic structure bands; however the bands between 1800 and 1400 cm-1 related to the functional groups of the amino acid allow to infer about the protonation degree in the hybrid material. The Brönsted acidity generated by the polarization of water molecules associated with the clay was observed for montmorillonite samples used in this study. Materials prepared in suspensions in which the pH value was greater than the value of the first acid constant (pKa1) show bands assigned to the C=O stretching of protonated carboxylate group. Raman spectra were obtained only for the synthetic clay, since the natural ones luminesce. Raman spectrum of L-carnosine immobilized on Laponita indicates the presence of mostly zwitterionic species; the displacement of bands assigned to amide and carboxylic groups of the dipeptide to the lower energy region suggests the formation of hydrogen bonds with the Laponita silanol groups. The results of thermogravimetric analyses coupled to mass spectrometry of hybrid materials are different from those observed for the free amino acids. The onset temperature of the organic species decomposition is practically unmodified after the immobilization on clays, but thermal processes are postponed up to higher temperature, revealing the inorganic structure influence on the amino acids thermal decomposition. Data on the carbon and water amounts in the samples were used to calculate the concentration of amino acids in the hybrid materials (mass of amino acid / 100 grams of material). The highest concentrations of amino acid (between six and eight percent) was observed for Cloisite and Veegum HS samples, isolated under conditions in which the electrostatic interaction between the layers and the positively charged amino acids are predominant. Under the experimental conditions employed in this study no saturation of clay with amino acids was observed, i.e. the layer charges were not completely neutralized by the organic ions.

Pollution of the earth's water resources, including freshwater sources such as lakes and rivers, by heavy metals have been a detriment to the environment for as long as the industrial age of man. As these metallic pollutants accumulate in the supply of precious groundwater and drinking water the need for clean-up technologies to combat the increasing threat is becoming of more importance to government and industry alike. Previous work has established the possibility of using known chelating agents, such as LIX-54® supported on silica gel in the removal of selected heavy metal ions such as copper(II), nickel(II) , and cadmium(II) from standard aqueous solutions (Norris and coworkers, 1996). Remediation of heavy metals using coordinating agents such as dithiooxamides and aliphatic amines has also been an environmental cleanup technology that has proven to be effective in the uptake of selected heavy metals from aqueous media (Poore and coworkers, 1996). The current study illustrates the effectiveness of using relatively inexpensive coordinating agents such as aliphatic amines and aliphatic thiols supported on silica gel and other solid supports to remove selected monovalent and divalent metals from aqueous standard solutions to achieve similar results. This study also reports the significance and results of an investigation involving the use of bifunctional compounds, such as 2-mercaptoethanol, to chemically attach and modify the silica gel, montmorillonite KSF, and magnetite, and subsequently be used in the uptake of selected heavy metals such as copper(II), cadmium(II), lead(II), nickel(II) and silver(I) ions.

Ce travail est consacré à l'élaboration de phyllosilicates de type montmorillonite et à l'étude de la répartition des éléments métalliques dans leur charpente.<br />Des généralités concernant les phyllosilicates sont d'abord abordées, en particulier les formes dioctaédriques à trois couches (2:1) dont la montmorillonite fait partie. Les méthodes de synthèse de ce minéral sont passées en revue. La synthèse hydrothermale en milieu fluoré et les techniques analytiques utilisées pour caractériser les matériaux (DRX, TG-ATD, analyses chimiques) sont ensuite présentées. Une attention particulière est donnée à la description de la RMN et de l'EXAFS. Une étude systématique des produits de synthèse est alors réalisée pour les deux systèmes : MO-Al2O3-SiO2 (M = Mg ou Zn). Les hydrogels sont préparés en se basant sur la formule chimique de demi-maille : Na2x[Al2(1-x)M2x]Si4O10(OH)2 (x : taux de substitution octaédrique théorique). Un phyllosilicate de type montmorillonite est obtenu pour un taux de magnésium 0,10 < x < 0,25 et le taux de zinc x = 0,10. Outre les substitutions Mg/Al en couche octaédrique, des substitutions Al/Si en couche tétraédrique sont observées par RMN du 29Si et de 27Al. La RMN du 19F montre l'existence d'une ségrégation des éléments octaédriques pour le phyllosilicate(Mg). Dans le cas du système MgO-Al2O3-SiO2, l'étude de la durée de cristallisation montre que la kaolinite est une phase intermédiaire. Le pH optimal est compris entre 5,0 et 5,5. La présence d'une petite quantité d'ion F- dans le milieu réactionnel acide est nécessaire (0,05 < F/SiO2 < 0,10). L'ion Na+ mobilise le moins les substitutions tétraédriques. Enfin, l'EXAFS au seuil K de Zn et Mg montre une distorsion des couches du feuillet et pour le phyllosilicate(Zn), une ségrégation des éléments octaédriques. Une méthode de détermination quantitative de Al total contenu dans un phyllosilicate de type montmorillonite par RMN de 27Al, permettant l'accès au rapport AlVI/AlIV est mise au point.

Ce travail a pour objectif l'étude de la réalisation de nanocomposites polypropylène (PP)/argile organophile (org-MMT) par mélange à l'état fondu. Il s'est articulé autour de trois thèmes principaux, qui sont l'effet des compatibilisants de type PP-g-MA et l'influence du procédé d'extrusion bivis sur l'état de dispersion, ainsi que le comportement rhéologique des nanocomposites en régime transitoire. L'importance des compatibilisants (PP-g-MA), et notamment leur concentration dans le système PP/PP-g-MA/org-MMT, a été mise en évidence. Un modèle rhéologique simple (loi de Carreau-Yasuda à seuil), a été proposé pour caractériser quantitativement le degré de dispersion à travers la valeur du seuil d'écoulement. En extrusion bivis, l'état de dispersion dépend fortement des conditions opératoires (vitesse de rotation N et débit Q), principalement du rapport Q/N. Des prélèvements locaux le long des vis ont révélé que l'essentiel de l'exfoliation s'est effectué lors de la fusion. Cette dernière apparaît comme l'étape gouvernant le processus de dispersion en extrusion bivis. Les relations entre le procédé et l'état de dispersion ont également été étudiées à l'aide du logiciel Ludovic©. Enfin, le comportement rhéologique des nanocomposites en régime transitoire a été étudié. On observe un pic de contrainte au démarrage, ainsi qu'un effet de restructuration après un temps de repos. Deux modèles théoriques développés initialement pour des suspensions colloïdales et des suspensions de fibres ont été utilisés pour décrire les phénomènes observés.

Les défauts d'irradiations dans les minéraux présents à la surface de la terre ont donné lieu à de nombreuses études. Parmi ces minéraux, les argiles ont des propriétés (capacité de rétention des radioéléments, gonflement...) qui les rendent utiles dans le cadre du stockage des déchets radioactifs. Afin de s'assurer de la stabilité des argiles se trouvant autour du colis de déchets, il est nécessaire d'étudier leurs propriétés physico-chimiques après irradiation. Cette thèse est séparée en trois parties qui sont axées autour de cette thématique. Dans une première partie, nous verrons quels sont les effets des rayons alpha sur la surface spécifique de la kaolinite et nous exposerons les phénomènes physique induits par ces rayonnements ionisants. La seconde partie traitera de la solubilité des smectites amorphisées dans un milieu basique et plus particulièrement de la cinétique de dissolution. Nous verrons que cette dissolution est favorisée par l'amorphisation. Enfin dans une troisième partie, nous nous sommes intéressés au géosystème analogue naturel de Nopal (Chihuahua, Mexique), où le dosimètre kaolinite peut permettre d'étudier les migrations anciennes de l'uranium au sein de la roche.

This thesis deals with the diffusion of ions in compactedbentonite clay. Laboratory experiments were performed toexamine in detail different processes that affect thediffusion. To demonstrate that the results obtained from thelaboratory investigations are valid under in situ conditions,two different kinds of in situ experiments were performed. Laboratory experiments were performed to better understandthe impact of ionic strength on the diffusion of Sr2+ and Cs+ions, which sorb to mineral surfaces primarily by ion exchange.Furthermore, surface related diffusion was examined anddemonstrated to take place for Sr2+ and Cs+ but not for Co2+,which sorbs on mineral surfaces by complexation. The diffusion of anions in bentonite clay compacted todifferent dry densities was also investigated. The resultsindicate that anion diffusion in bentonite clay consists of twoprocesses, one fast and another slower. We ascribe the fastdiffusive process to intralayer diffusion and the slow processto diffusion in interparticle water, where anions are to someextent sorbed to edge sites of the montmorillonite. Two different types of in situ experiments were performed,CHEMLAB and LOT. CHEMLAB is a borehole laboratory, where cation(Cs+, Sr2+ and Co2+) and anion (I- and TcO4-) diffusionexperiments were performed using groundwater from a fracture inthe borehole. In the LOT experiments cylindrical bentoniteblocks surrounding a central copper rod were placed in a 4 mdeep vertical borehole. The borehole was then sealed and theblocks are left for 1, 5 or&gt;&gt;5 years. When the bentonitewas water saturated the central copper rod is heated tosimulate the temperature increase due to radioactive decay ofthe spent fuel. Bentonite doped with radioactive Cs and Co wasplaced in one of the lower blocks. Interestingly, the redox-sensitive pertechnetate ion (TcO4-)which thermodynamically should be reduced and precipitate asTcO2·nH2O, travelled unreduced through the bentonite.However, at some spots in the clay, the Tc activity wasconsiderably higher. We ascribe these activity peaks toiron-containing minerals in the bentonite, by which Tc(VII) hasbeen reduced to Tc(IV) and precipitated. The cations Sr2+, Cs+and Co2+, as well as the anion I-, behaved in the CHEMLABexperiments as expected from laboratory studies. Three experiments in the LOT series are completed. The firsttwo diffusion experiments in LOT were less successful, thefirst due to the fact that saturation of the bentonite was notobtained during the experimental period and the radionuclidesdid not move at all. In the second, the uptake of the bentoniteparcel was less successful. Water from the drilling flushedaway large pieces of the top part of the bentonite and thelower part of the test parcel was super-saturated with waterand expanded when released from the rock. The activity distribution in the second experiment wasanalysed. The Co2+ profile looked as we had expected, while Cs+had spread more than our calculations indicated. However, thethird experiment was successful from emplacement, watersaturation and heating to uptake. The activity distribution forboth cations was as expected from laboratory studies. Altogether the three different types of experiments give auniform picture of radionuclide diffusion in bentonite clay forthe ions investigated. / QC 20100621