La perméabilité est l'un de paramètres importants pour tous les procédés faisant intervenir des transferts couplés de chaleur et de masse. Sa valeur est directement liée à la morphologie du réseau de pores, clairement double échelle dans le cas du bois. Il existe plusieurs outils d’investigation 3-D par exemple la micro-tomographie voire nano-tomographie pour décrire la morphologie des pores. Néanmoins, ces investigations 3-D échouent pour les plus petits pores dans le bois, qui peuvent avoir une taille largement inférieure au micromètre. Ce travail de thèse utilise l'effet du libre parcours moyen du gaz sur la perméabilité apparente pour identifier la taille des pores utilisés par le cheminement du fluide.Une approche équilibrée entre expérimentation et modélisation est proposée. Dans la première partie du travail, nous avons développé un dispositif original destiné à mesurer la perméabilité apparente sur une large plage de niveau de pression moyenne. Ce dispositif ne comporte pas de débitmètre : le flux massique est simplement obtenu par la relaxation de la différence de pression entre deux réservoirs de volume connu.Ce dispositif a permis de mesurer la perméabilité apparente en fonction de la pression moyenne pour différents matériaux. Les valeurs obtenues de perméabilité intrinsèque sont en bon accord avec les publications précédentes.L'effet de la pression moyenne sur la perméabilité apparente a été analysé pour identifier des paramètres structuraux des milieux poreux. Partant d'un agencement série/parallèle de pores, les paramètres structuraux sont identifiés par méthode inverse en tirant profit du changement de régime d’écoulement avec le nombre de Knudsen (du régime de Darcy vers le régime de glissement moléculaire lorsque le nombre de Knudsen passe de zéro à l’infini).Cette approche a été validée avec des membranes à pore monodisperse grâce à une observation en microscopie électronique à balayage. Les paramètres ont ensuite été identifiés sur des échantillons de bois, selon différentes directions et sur des matériaux à base de bois. Ils confirment certaines données de la littérature, et apportent un éclairage nouveau, notamment sur les chemins de migration transverse chez le hêtre. / Permeability is one of the important parameters for all processes involving coupled heat and mass transfer. Its value is directly related to the morphology of the pore network, clearly a dual scale organisation in the case of wood. Nowadays, several 3D investigative tools exist, such as micro-tomography or nano-tomography. However, these 3-D investigations fail for the smallest pores active in fluid flow in wood, due to their submicron size. The present work takes advantage of the effect of the mean free path on the apparent gaseous permeability to identify the pore size of the pore network.A balanced approach between experimentation and modelling is proposed. In the first part of the work we have developed an original device for measuring the apparent permeability over a wide range of average pressure. This device was conceived to work without flowmeter: the mass flow is obtained by the relaxation of the pressure difference between two tanks. This device was used to measure the apparent permeability as a function of the average pressure for different materials.The intrinsic permeability values obtained are in good agreement with literature data.The effect of the average pressure on the apparent permeability was analysed to identify structural parameters of the porous media. Starting from a serial / parallel arrangement, the structural parameters are identified by inverse method taking advantage of the dependence of the flow regime with Knudsen's number (from Darcy's regime to pure molecular slip regime when Knudsen's number shifts from zero to infinity).This approach was validated with a monodisperse membrane, whose pore size was determined using a scanning electron microscopy. Structural parameters were then identified on wood samples, measured along different directions and on wood-based materials. They confirm literature data and bring new outcomes, namely regarding the fluid pathway in beech in radial and tangential directions.

The production of fuel and chemicals is expected to be based on renewable energies in the next few years. However, combustion causes CO2 emission. Its reduction is one of the main focuses to regulate greenhouse effect, as expected by the Kyoto protocol. One combustion technology which could reduce CO2 emissions is chemical-looping combustion coupled to a CO2 capture device. This technique involves the use of a bed-material, with a size between 100 and 500 µm, composed of an oxide supported by a porous ceramic. This oxide acts as an oxygen carrier and circulates from a reducing atmosphere reactor, where oxygen reacts with CO to produce CO2, to an oxidising reactor, where combustion occurs. In order to improve the reactivity of this carrier, a fluidized bed reactor is used and involves gas velocity. Attrition resistant granulates are therefore needed because of the high impacts occurring in the reactors. Moreover, large pore network is expected to improve the reactivity of the carrier because of the higher accessibility of the gas. Granulates studied for oxygen carrier supports are frequently based on γ-alumina, which is highly mesoporous. In order to understand the importance of microstructure, three different routes were studied with samples composed of macropores, mesopores and a sample composed of both type of pores. Pore size could be successfully tailored with addition of diatomite, composed of pores in the micrometer range. This thesis aims to describe the tailoring of microstructure with addition of diatomite and at understanding its influence on attrition resistance. To be able to verify the performance of the developed supports, impregnation of copper oxide and looping experiments were performed.

Porous metal phosphonate framework materials were synthesised by solvothermal reaction of bis(α-aminomethylenephosphonic acid) ligands with divalent and trivalent metal cations. The syntheses and characterisation by NMR and, where possible, single crystal X-ray diffraction of seven bisphosphonic acid ligands, including N,N′-piperazinebis(methylenephosphonic acid) (H₄L), its racemic and enantiopure (R) 2-methyl (H₄L′ and R-H₄L′) and 2,5-dimethyl (H₄L′′) derivatives, and N,N′-4,4′-bipiperidinebis(methylenephosphonic acid) (H₄LL) are reported. Syntheses of the known phase Y₂(LH₂)₃·5H₂O and the new phases, STA-13(Y) (St Andrews microporous material No. 13) and Y₂(R-L′H₂)₃·4H₂O, from reactions of Y(AcO)₃ with H₄L, H₄L′ and R-H₄L′ respectively are reported. The as-prepared and dehydrated structures of each phase have been determined from either laboratory or synchrotron powder X-ray diffraction data. Reaction of Y(AcO)₃ and H₄L′′ is shown to form a phase with a different structure. The features determining which structure crystallises are discussed. Syntheses of other rare-earth forms of STA-13 (Sc³⁺, Gd³⁺–Yb³⁺) and the porosity of each phase to N₂ are reported. STA-13(Y) is the most porous form with loadings of ∼3 mmol g⁻¹ and ∼4 mmol g⁻¹ for N₂ and CO₂ respectively. MIL-91(Fe) was synthesised for the first time from reactions of Fe³⁺ cations with H₄L. Its structure was confirmed by Rietveld refinement, but it was not porous. The first syntheses of [Fe₄L₁.₅(AcO)₁.₅(OH,H₂O)₃]·0.5NH₄5.5H₂O (L= L or L′) are reported, from reactions of H₄L or H₄L′ in the presence of an excess of Fe³⁺ cations. The phase is related to a previously reported Co phase. The synthesis of divalent metal bisphosphonate STA-12(Mg) (Mg₂(H₂O)₂L·5.6H₂O) was reported for the first time and its structure determined from single crystal X-ray diffraction. The dehydration behaviour of this material was compared with the known forms of STA-12. STA-12(Mg) is porous to both N₂ (∼5.5 mmol g⁻¹) and CO₂ (~ 8.5 mmol g⁻¹). Reaction of H₄LL with Co²⁺ and Ni²⁺ gave two materials isoreticular with STA-12, labelled STA-16(Co) and STA-16(Ni). The structures of both materials were solved from synchrotron powder X-ray diffraction data. On dehydration, STA-16(Co) undergoes a reversible structural transition to an unknown structure. By contrast, STA-16(Ni) retains the same symmetry in the dehydrated form and its structure was determined from synchrotron powder X-ray diffraction data. Both materials are porous to N₂, with an uptake of up to 22.2 mmol g⁻¹, and CO₂ with maximum loading of 21.7 mmol g⁻¹. NLDFT analysis of N₂ adsorption data confirm the crystallographically determined pore radii. Syntheses of other frameworks with divalent cations and initial reactions of H₄LL with trivalent cations are also reported.

Dans une optique de développement de nouvelles membranes innovantes, ce travail de thèse a permis l'élaboration de films minces nano-structurés et nano-poreux à partir de particules de polymère (copolymères ABA, AB, et homopolymère/MOF). Ces films ont notamment pu être utilisés en tant que membranes de filtration d'eau ou de mélange de gaz. Concernant les copolymères triblocs de type ABA (PS-PNaSS-PS), cette étude a montré que des films nano-poreux présentant des structures variées (nid d'abeilles, isoporeuse et compacte) pouvaient être obtenus. Les morphologies de ces particules pouvaient être adaptées en fonction de la taille des blocs hydrophiles et hydrophobes du copolymère, de la composition en solvant et de la concentration. Pour l'élaboration de films à partir de copolymère diblocs, des nanoparticules sphériques monodisperses, constituées de PDMAEMA-PMMA, ont été préparées in situ (PISA) par polymérisation RAFT en dispersion dans l'éthanol, à partir d'un agent de transfert fonctionnalisé coumarine. Les expériences successives d'irradiation UV ont montré que les nanopaticules ainsi fonctionnalisées pouvaient être connectées de façon réversible via la dimérisation de la coumarine. Les films minces ainsi élaborés présentaient des propriétés dynamiques dues à l'établissement de la formation réversible du cyclobutane lors de l'irradiation UV de la coumarine. Ce travail de thèse a été clôturé par la préparation de « Mix Matrix Membranes (MMMs) » à partir d'un mélange de polyimide (Matrimid®) et de nanoparticules de ZIF-8 pour la réalisation de membranes à perméation gazeuse. Une nouvelle approche d'élaboration des MMMs a permis d'obtenir la formation de membranes parfaitement homogènes avec une cohésion améliorée entre les MOF et la matrice de polymère. Une meilleure séparation du mélange de gaz CH4/CO2 a ainsi pu être obtenue. / This thesis deals with the development of nano-structured thin nano-porous films from polymeric particles (ABA, AB copolymers and polymer/MOF) in perspective of developing new innovative membranes. The obtained films have been used as water filtration or gas separation membranes. Regarding the ABA triblock copolymer made of polystyrene-sodium polystyrene sulfonate-polystyrene (PS-PNaSS-PS) it was shown that nano-porous films with various structures (honeycombs, isoporous and compact), could be made. The morphologies of these nanoparticles could be tuned depending on the hydrophobic and hydrophilic block ratios, solvent composition and concentration. Concerning the study of the diblock copolymer, monodisperse spherical nanoparticles of PDMAEMA-b-PMMA were made in situ (PISA) using a coumarin functionalized RAFT chain transfer agent in ethanol. Upon UV irradiation, these particles could be connected reversibly through the dimerization of the coumarin function present on their corona. The resulting thin films had dynamic characteristic due to the establishment of the reversible formation of the cyclobutane ring under UV irradiation. This manuscript was concluded by preparation of Mix Matrix Membranes (MMMs) from mixture of polyimide (Matrimid®) and ZIF-8 nanoparticles to be used as gas permeation membrane. The employed new approach in this study led to formation of perfectly homogeneous membranes with improved cohesion between the MOF structure and the polymeric matrix. A better separation of CH4 / CO2 gas mixtures was achieved using the prepared MMM.

Abstract The present thesis describes a method for characterization of liquid crystals in confined spaces by means of NMR of probe atoms and molecules. 129Xe isotope enriched xenon gas and 13C isotope enriched methyl iodide and methane were used as probes. Behavior of solutes and liquid crystals confined to porous materials was investigated using 129Xe and 13C NMR spectroscopy. Uniaxial nematic liquid crystals Phase 4 and ZLI 1115 were used as a medium. Controlled pore glass with well defined and known properties was used as a porous material. The behavior of liquid crystals and solutes in various different size pores, temperatures and magnetic fields at different solute concentrations was explained. The average pore diameter of the material varied from mesopores to macropores. The studied temperature range covered solid, nematic and isotropic phases of bulk liquid crystals, and the highest magnetic field was 2.5 times stronger than the lowest one used (4.70 T). The chemical shifts, intensities, and line shapes of the resonance signals from the solutes were observed to contain lots of information about the effect of confinement on the state of the liquid crystals. Especially the line shape of the 13C resonances of methyl iodide was observed to be very sensitive to the liquid crystal orientation distribution in the pores. By varying experimental conditions the relative contribution of field and the surface forces of pore walls to the orientation of liquid crystal molecules inside the pores was seen to change quite drastically. In addition, it was also observed that when the sample is cooled very rapidly, xenon atoms do not squeeze out from the freezing medium but they are occluded inside the solid lattice, and their chemical shift is very sensitive to crystal structure. Furthermore, because solutes experienced on average isotropic environment inside the smallest pores, isotropic value of the shielding tensor could be determined at exactly the same condition and temperature as anisotropic counterpart between the pore particles. Thus, for the first time in the solution state, shielding anisotropies could be determined as a function of temperature.

L’industrie du nucléaire produit de grandes quantités d’effluents radioactifs de sources diverses nécessitant des traitements spécifiques en fonction de leur composition chimique. Le césium 137 fait partie, avec le strontium 90, des radioéléments majoritairement présents dans ces effluents qui doivent être extraits le plus efficacement possible en produisant un minimum de déchets secondaires. Le traitement en colonne est parmi les procédés les plus adaptés pour ce type d’extraction sur support solide. Son principe repose sur la capacité de sorption du radioélément par des hexacyanoferrates (HCF) de cuivre, des échangeurs ioniques minéraux très sélectifs du césium. Des investigations sur les HCF ont permis de mettre en avant les modifications structurales intervenant lors de l’échange avec le césium, à l’origine de leur forte affinité pour cet ion. La fonctionnalisation des HCF sur des monolithes de silice à porosité hiérarchique a mis à profit les propriétés remarquables de ces supports pour une utilisation en colonne. Les cinétiques de sorption évaluées jusqu’aux concentrations traces ont montré une capture rapide du césium qui justifie l’intérêt de ce matériau pour un emploi en colonne. Par ailleurs, la compétitivité des monolithes fonctionnalisés par rapport à des lits particulaires a été démontrée. Ces matériaux ont enfin été mis en œuvre pour la décontamination simultanée du césium et du strontium par des mécanismes couplés d’échange d’ions et de coprécipitation du sulfate de baryum, rendue possible par la grande perméabilité des monolithes. Un modèle simplifié du transport réactif basé sur la morphologie du monolithe a été développé avec le code HYTEC en supposant un écoulement dispersif dans les canaux du squelette et la diffusion dans les parois du squelette et les agrégats de HCF. / The nuclear industry produces high amounts of contaminated water from various sources that require specific treatments depending on their chemical composition. Cesium-137 and strontium-90 are among the most abundant radionuclides in those effluents, which have to be removed as efficiently as possible in order to generate the lowest amount of waste. The column process is one of the most suitable processes to achieve this solid-phase extraction. Its principle is based on the sorption capacity of the radionuclide by copper hexacyanoferrates (HCF), highly cesium-selective mineral ion-exchangers. Investigations on HCF pointed out the structural effects of the cesium insertion within the crystal, which were linked to the high affinity of HCF for this ion. The functionalization of HCF on silica monolith with hierarchical pore structure was carried out in order to benefit the remarkable properties of these supports used as a column. Sorption kinetics evaluated down to trace concentrations have shown a fast capture of the cesium, which proves the interest of this material for a column process purpose. In addition, the performances of functionalized silica monolith have been highlighted in comparison with those made of particulate fixed beds. Finally, those materials were implemented for a simultaneous decontamination of cesium and strontium by a double extraction mechanism of ion exchange and coprecipitation of barium sulfate, allowed by the high permeability of the monolith. A simplified model of reactive transport was built with the HYTEC code, based on the actual morphology of the monolith. To do so, a dispersive flow in the macroporous intraskeletal channels and a diffusive flow inside the walls of the structure and the HCF aggregates were assumed.

No description available.

<p> The tire air cavity mode is known to be a significant source of vehicle structure-borne road noise near 200 Hz. A porous lining placed on the inner surface of a tire is an effective countermeasure to attenuate that resonance. The two noticeable effects of such a lining are the reduction in frequency and the attenuation of the air cavity mode. In this thesis, through both theoretical and numerical analysis, the mechanism of the effects of a porous lining was studied. A two-dimensional duct-shaped theoretical model and a torus-shaped numerical model were built to investigate the lined tire in conjunction with the Johnson-Champoux-Allard model describing the viscous and thermal dissipative effects of the porous material. Design parameters of the porous lining were varied to study their impact and optimal ranges of the design parameters were identified. Finally, in an experimental analysis, the sound attenuation and the frequency drop were observed in measurements of force, acceleration, and sound pressure. In conclusion, it was demonstrated that the suggested theoretical and numerical models successfully predict the effects of porous linings and that the frequency reduction results from the decreased sound speed within the tire owing to the presence of the liner. </p>

In this study, two major internal erosion initiation processes, suffusion and concentrated leak mechanisms, which lead to both defect formation in a dam’s body and its foundation and high throughflow in dams subjected to internal erosion were studied. This understanding has the potential to facilitate numerical modelling and expedite dam safety assessment studies.  The throughflow properties of coarse rockfill material were studied by; analysing filed pump test data, performing extensive laboratory experiments with a large-scale apparatus and numerically simulating the three-dimensional flow through coarse rock materials, replicating the material used in the laboratory experiments. Results from the tests demonstrate that the parameters of the nonlinear momentum equation of the flow depend on the Reynolds number for pore Reynolds numbers lower than 60000.  Numerical studies were also carried out to conduct numerical experiments. By applying a Lagrangian particle tracking method, a model for estimating the lengths of the flow channels in the porous media was developed.  The shear forces exerted on the coarse particles in the porous media were found to be significantly dependent on the inertial forces of the flow. Suffusion and concentrated leak mechanisms were also studied by means of laboratory experiments to develop a theoretical framework for continuum-based numerical modelling. An erosion apparatus was designed and constructed with the capability of applying hydraulic and mechanical loading. Results were then used to develop constitutive laws of the soil erosion as a function of the applied hydromechanical load for both suffusion and concentrated leak mechanisms. Both the initiation and mass removal rate of were found to be dependent on the soil in-situ stresses. A three-dimensional electrical-resistivity-based tomography method was also adopted for the internal erosion apparatus and was found to be successful in visualising the porosity evolution due to suffusion. / <p>QC 20161006</p>

L’objectif de cette thèse porte sur le développement de nouveaux moyens de caractérisation mécanique de matériaux poreux inorganiques. La technique de microindentation instrumentée avec indenteur sphérique a été utilisée pour déterminer les propriétés mécaniques du plâtre pris, utilisé comme matériau modèle, à deux porosités différentes (30 et 60%vol). Les méthodes analytiques, développées initialement en nanoindentation, ont permis d’extraire la dureté et le module d’élasticité des deux matériaux, ainsi que les courbes contrainte-déformation d’indentation. Une méthodologie d’essai a été notamment détaillée afin de pouvoir appliquer cet essai d’indentation sphérique à l’étude de céramiques à forte porosité. Une approche numérique a permis de compléter les méthodes analytiques et d’identifier une loi de comportement élastoplastique pour le matériau modèle. Un modèle éléments finis 2D-axisymétrique a ainsi été développé pour simuler les essais d’indentation sphérique. Un module d’indentification inverse, MIC2M, a ensuite été utilisé pour identifier les paramètres associés au critère de Drücker-Prager (cohésion, frottement et dilatance) pour minimiser l’erreur entre la courbe expérimentale et numérique. La simulation de l’indentation Vickers, ainsi que des essais de compressions uniaxiaux et œdométriques ont permis de valider les paramètres matériaux identifiés par indentation sphérique. L’utilisation des techniques de tomographie aux rayons X et de microscopie électronique à balayage (MEB) a permis de mettre en évidence une densification du matériau au cours de l’indentation. Aucune fissure macroscopique fragile n’a par contre été observée, confirmant les différences de comportement mécanique entre des céramiques à fort taux de porosité et des céramiques denses. La méthodologie ainsi développée a ensuite été appliquée au cas d’une céramique biorésorbable à base de phosphate de calcium, famille de matériaux largement utilisée pour la substitution osseuse. Des cylindres de ciments brushitique ont subi un vieillissement in vitro d’une durée maximale de deux mois dans une solution de Phosphate Buffered Saline rafraichie. La méthode de microindentation a permis de suivre l’évolution des différents paramètres mécaniques au cours de la cinétique de dégradation des ciments. Les résultats ont montré une bonne corrélation entre les évolutions des propriétés mécaniques et physicochimiques des échantillons, suivies par diffraction des rayons X et MEB. Ainsi, après une dissolution initiale du ciment, la précipitation de nouvelles phases de phosphates de calcium plus stables a entraîné une augmentation des caractéristiques mécaniques en cours de vieillissement, mesurées par indentation. Cette méthode d’essai semble donc être un outil prometteur pour le suivi des propriétés d’explants biomédicaux et, plus généralement, des céramiques à fortes porosités. / The objective of this study is to develop a methodology to characterize the mechanical behaviour of porous inorganic materials. Spherical instrumented indentation tests were used to determine the mechanical properties of a model material, gypsum, with two different porosities (30 and 60% vol.). Classical analytical methods, initially developed for nano-indentation, were used to extract the hardness and the elastic modulus of both materials, as well as stress-strain indentation curves. A methodology has been detailed in order to apply spherical indentation test to study high porous ceramics. To complete this analytical analysis, a numerical approach is used to identify an elastoplastic constitutive law for the material model. A 2D axisymmetric finite element model was developed to simulate spherical indentation tests. An inverse identification module, MIC2M, was then used to identify parameters associated to Drücker-Prager criterion (cohesion, friction and dilatancy) by minimizing the error between the experimental and the simulated indentation curves. These parameters were validated through the numerical simulation of a Vickers indentation test. Uniaxial compression and oedometer tests were also carried out on cylindrical samples to estimate the accuracy of the identified parameters. The mechanisms occurring during indentation were investigated using RX tomography and SEM. A large densified zone was noted below the indented area, with extensive gypsum crystal fracture. No macroscopic brittle crack could be observed confirming the differences between the mechanical behaviour of high porous ceramics and dense ceramics. The methodology developed in this study was applied to calcium phosphate cements, widely used for bone substitution. In-vitro degradation tests were performed on cylindrical samples of cements during 2 months into a refreshed Phosphate Buffered Saline solution. The micro-indentation method was enabled to follow mechanical properties of degraded samples and was discriminant enough to monitor the degradation process and its kinetics. Results showed a good correlation between evolutions of mechanical and physico-chemical properties of the cement investigated by X-ray diffraction and SEM. Thus, after initial cement dissolution, precipitation of more stable phosphate calcium phases implied an increase of the mechanical properties during aging. This method seems to be a promising tool for monitoring biomedical explants properties and, more generally, high porous ceramics.