In this study production and characterization of activated carbon from an agricultural waste, pistachio-nut shells, was investigated. To determine optimum production conditions by chemical activation method, effect of tempreature (300, 500, 700 and 900 oC) and effect of impregnation ratio (1:1, 2:1 and 3:1 as activation agent:sample) were investigated by applying two different methods (raw material activation and char activation) and with two different activation agents (phosphoric acid and potassium hydroxide). To produce activated carbon, all the impregnated samples were heated to the final activation temperature under a continuous nitrogen flow (100 cm3/min) and at a heating rate of 10 oC/min and were held at that temperature for 1 hour. Pore structures of activated carbons were determined by N2 adsorption and micro-mesopore analysis was made by &ldquo / Non-local Density Functional Theory&rdquo / and &ldquo / Monte Carlo Simulation&rdquo / method (NLDFT-Monte Carlo Simulation Method). BET surface areas of produced activated carbons were found from N2 adsorption data in the relative pressure range of 0.01 to 0.15. BET surface areas of phosphoric acid activated carbons by raw material activation method were found between 880 and 1640 m2/g. The highest value of the BET surface area was obtained in the case of the activated carbon which was produced with an impregnation ratio of 3/1 (g H3PO4/g raw material), at an activation temperature of 500 oC. The repeatibility was also investigated on phosphoric acid activated carbons which were produced with conventional raw matererial activation method. Results showed that, both the BET surface area values and pore size distributions were consistent among themselves. On the other hand char activation experiments with phosphoric acid produced activated carbons having lower BET surface areas than the ones obtained with raw material activation method by creating mesoporous structure. When the same char activation method was tried with potassium hydroxide, it was concluded that elevated temperatures could help in producing activated carbons with high BET surface areas by creating microporous structure. Results also showed that properties of activated carbon such as ash content, slurry pH value, true density, elemental composition, methylene blue number and surface morphology were strongly affected by both production conditions and production method, as pore structure was affected considerably.

Activated Carbon was produced from strong cation-exchange resins, sulphonated styrene divinylbenzene copolymers originally in H+ form, by means of carbonization and steam activation in an electrical furnace. One macroporous resin produced by BAYER Chemicals Inc., Lewatit MonoPlus SP 112 H, was used in the research. Products of carbonization and activation were characterized by using BET, Mercury Porosimetry, Helium Pycnometry and SEM techniques. The effect of carbonization time and temperature on the BET surface areas of the resins were also investigated. Two sets of carbonization experiments (Set 1 and 2) were performed in which time and temperature were varied in order to study their effects on the BET surface areas of the products. In activation experiments (Set 3), carbonized ion-exchangers (600 oC, 1 hr) were activated with steam at 900&deg / C, changing the time of activation and the steam flow rate. The temperatures of the water bath used for steam generation were selected as 60&deg / C, 80&deg / C and 90&deg / C. The pore structures of activated carbons were determined by proper techniques. The volume and area of macropores in the pore diameter range of 8180-50 nm were determined by mercury intrusion porosimetry. Mesopore (in the range of 50-2 nm) areas and volumes were determined by N2 gas adsorption technique at -195.6oC, BET surface areas of the samples were also determined, in the relative pressure range of 0.05 to 0.02, by the same technique. The pore volume and the area of the micropores with diameters less than 2 nm were determined by CO2 adsorption measurements at 0oC by the application of Dubinin Radushkevich equation. In the experiments of Sets 1 and 2, the BET surface area results of the six different carbonization times ranging from 0.5 to 3 hours gave almost the same value with a maximum deviation of 5% from the average showing almost no effect on the areas of the products. In the experiments of Set 3 , the sample activated at 800&deg / C for 6 hrs had the highest BET area, 2130 m2/g, and the one activated at 800&deg / C for 1 hr had the lowest BET area 636 m2/g. N2 adsorption/ desorption isotherms showed no distinct hysteresis indicating a cylindrical geometry of the pores. Adsorption isotherms further indicated that the pores are both highly microporous and mesoporous. N2 (BET) and CO2 (D-R) surface areas of the samples were in the range of 636-2130m2/g and 853-1858 m2/g, respectively. Surface areas of the samples consisted of about 8-53% mesopores and 47-92% micropores.

Within the different available electrochemical energy storage systems, supercapacitors stand out due to their high power densities and ultra-long cycle life. Their key-components are the electrode materials where the charge accumulation takes place and therefore many different approaches for the synthesis of carbonaceous electrode structures with well-defined pore systems are available. This review focuses on different strategies for tailoring porous carbon materials from the micropore level, over mesopores to macropores and even external or inter-particular porosity. A wide range of materials such as activated carbons, templated carbons, carbide-derived carbons, carbon nanotubes, carbon aerogels, carbon onions, graphenes and carbon nanofibers are presented, always in relation to their pore structure and potential use in supercapacitor devices.

No description available.

La synthèse d'une membrane composite formée d'une couche fine de surface de structure très réticulée et permsélective aux gaz déposée sur un substrat poreux a été étudiée comme solution pour accroître la perméabilité aux gaz tout en conservant une sélectivité importante. Une couche mince de polymère-plasma SiOCH a été retenue comme membrane de séparation gazeuse car elle possède une structure dont l'ultramicroporisté peut être contrôlée en ajustant les paramètres du procédé plasma comme la puissance, le flux de monomère et la pression de travail. Néanmoins, dans la membrane SiOCH, la taille moyenne des pores et leur distribution sont difficiles à appréhender par des techniques de caractérisation classiques, notamment proche de la surface car elle est très fine. Ce mémoire de thèse concerne le contrôle de la structure poreuse dans une couche mince de polymère-plasma SiOCH déposée sur un substrat polymère en utilisant un précurseur organosilicié. La spectroscopie d'annihilation de positron couplée à un faisceau de positron lent a été utilisée pour identifier la microstructure de couches minces SiOCH avec la profondeur. Ceci a nécessité tout d'abord l'acquisition d'une bonne connaissance de la caractérisation de l'annihilation de positron de matériaux polymères et céramiques. Des couches minces de SiOCH conformes ou superhydrophobes (SHP) ont été obtenues à deux fréquences différentes, respectivement à 13,56 MHz ou 40 kHz. Pour une couche conforme, le type de substrat, la structure chimique du précurseur et la puissance RF sont les paramètres majeurs qui influencent la structure des pores. Quand les films de SiOCH sont composées de deux couches (couche uniforme de surface et couche de transition) déposées sur un substrat poreux, l'analyse PAS met en évidence une couche de transition large et l'ensemble possède une perméabilité aux gaz élevée grâce à la porosité de surface du support. Lors de la préparation des couches minces SHP, quand la pression totale dépasse 0,6 mbar, la nucléation en phase gaz apparaît ce qui augmente la rugosité de la surface. Ceci induit des angles de contact à l'eau supérieurs à 160° et une hystérésis d'angles de contact avancée-reculée de seulement 2°. La préservation des chaînes carbonées et la microstructure sont les facteurs déterminant pour accroître l'hydrophobicité des couches minces de SiOCH. / In gas separation, the fabrication of composite membranes consisting of a permselective thin top layer with high cross-linking structures and a porous substrate has been regarded as a solution for improving gas permeability and simultaneously retaining high selectivity. A plasma-polymerized SiOCH film has been known as an appropriate gas separation membrane because it possesses a dense structure, the crosslinking degree of which could be controlled by adjusting plasma parameters such as plasma power, monomer flow rate, and system pressure. However, the pore size and distribution in SiOCH films, especially in the region of depth profile, are difficult to measure by conventional techniques because of they are very thin.This thesis is concerned with the control of pore structure in a plasma-polymerized SiOCH film on a polymeric substrate by using an organosilicon source. The positron annihilation spectroscopy (PAS) coupled to the slow positron beam technique was used to identify the microstructure of SiOCH films as a function of depth. This step required to have a good understanding of the positron annihilation characteristics of different materials such as organic, inorganic, and hybrid materials. Depending on plasma frequency adjustments, SiOCH films with a flat and a superhydrophobic (SHP) surface were fabricated at 13.56 MHz and 40 kHz, respectively. For a flat SiOCH film, substrate type, chemical structure of precursor, and RF power were the major variables that influenced the pore structure. When SiOCH films composed of two layers (bulk and transitions layers) were deposited on porous substrates, they displayed a long transition layer based on the PAS analysis and possessed a high gas permeability due to the surface porosity of the substrate. When the precursor used possessed a cyclic ring structure, an opportunity of a break-up of the cyclic ring would increase with increasing RF power and then induce formation of new big pores. For the preparation of SHP films, when the total pressure was higher than 0.6 mbar, the gas nucleation reaction was enhanced to induce roughness on SiOCH films, and it would show a high WCA of over 160o and a low WCAH of only 2 degrees. Both the hydrocarbon preservation and microstructure were the main factors in improving the surface superhydrophobicity of SiOCH films.

Le stockage géologique du CO2 est l'une des diverses technologies étant explorées afin de réduire les émissions de carbone atmosphérique des processus industriels (i.e. combustion de l'énergie fossile). L'une des spécifiques caractéristiques de l'injection du CO2 en profondeur reste la possibilité de réactions géochimiques (dissolution-précipitation) entre la saumure réactive mobile (e.g. eau de formation enrichie en CO2) et la roche encaissante durant l'évolution spatiale et temporelle du CO2, conduisant à des modifications dans la structure des pores et par conséquent dans les propriétés d'écoulement du réservoir (e.g. la perméabilité k). Donc, ces changements structuraux peuvent largement contrôler l'injectivité, ainsi que le champ de pression dans le réservoir et aussi la propagation du CO2. Il demeure ainsi crucial d'explorer les changement dans les propriétés de réservoirs (e.g. structurales et hydrodynamiques) induits durant une injection de CO2 et explicitement les relations existantes entre eux (e.g. k ou surface réactive-Sr versus porosité- , k versus hétérogénéité de la roche), afin de développer des outils de modélisation prédictive des processus de transport et réactionnels se produisant durant une injection de CO2 et d'évaluer de façon fiable les risques. Dans le cas des réservoirs carbonatés, l'application des modèles prédictifs de transport réactif demeure toujours un enjeu, car contrainte par la forte hétérogénéité en leur sein ainsi que par l'incertitude dans la cinétique de réactions des minéraux carbonatés dans ce contexte. Dans cette optique, nous avons réalisé des expériences de percolation à travers des échantillons de roches carbonatées dans les conditions thermodynamiques de stockage en profondeur (T = 100°C et P =12 MPa). L'évolution de la perméabilité est suivie au cours des expériences ; et la variation de la porosité est calculée à partir des résultats d'analyses chimiques au ICP-AES des fluides de sortie échantillonnés. L'investigation des modifications apportées à la structure des pores est réalisée par le biais de la Micro-Tomographie haute résolution à rayon X, acquise au synchrotron de Grenoble (e.g. ESRF). Dépendant du régime de dissolution, contrôlé par la fabrique de la roche réservoir et la composition chimique de la saumuré chargée en CO2 (e.g. PCO2 engagée), on a observé qu'une modification de la structure de la roche peut soit améliorer soit détériorer (résultat atypique en contexte de dissolution) la valeur de la perméabilité k. Mots clés : Stockage géologique du CO2, transport, réactions géochimiques, structure des pores, propriétés hydrodynamiques, expériences de percolation de CO2, micro-tomographie à rayon X. / Geological storage of CO2 is one of diverse technologies being explored to reduce atmospheric carbon from industrial processes (i.e. fossil fuel combustion). One of the specific features of CO2 injection is the possibility of geochemical reactions (dissolution – precipitation) between mobile reactive brine (e.g. formation water enriched in CO2) and the host rock during the spatial and temporal evolution of CO2. That leads to modifications in the pore structure which in turn change the flow dynamics of the reservoir (e.g. the permeability k). Then, theses structural modifications can largely control the injectivity, so that the pressure field in the reservoir and also the CO2 propagation. Accordingly, it is crucial to explore the changes in the reservoir properties (e.g. structural and hydrodynamic) induced during a CO2 injection and specially the relationships between them (e.g. k or reactive surface-Sr versus porosity- , k versus rock heterogeneity), for developing predictive modelling tools of the transport and reaction processes occurring during a CO2 injection and reliable risk assessment. In the case of carbonate rocks, the application of the predictive models of transport and reaction is still challenging, because of their high heterogeneity so that the incertitude in the reaction kinetics of carbonate minerals. From this perspective, we realized brine-enriched in CO2 percolation experiments through carbonate rock samples in thermodynamic conditions expected during CO2 injection in deep reservoirs (T = 100°C et P =12 MPa). The permeability changes k(t) is monitored during the experiments and the porosity variation is calculated from chemical analyses of the sampled outlet fluids, using ICP-EAS. The pore structure modifications are investigated from high resolution X ray micro tomography images acquired from the synchrotron of Grenoble (ESRF). Depending to the dissolution regime, controlled by the reservoir rock fabric and the chemical composition of the brine (e.g. PCO2), we observed that a modification of pore structure can either improve (atypical result in dissolution context) or impair the value of the permeability k. Keywords: CO2 geological storage, transport, geochemical reactions, pore structure, hydrodynamic properties, brine enriched in CO2 percolation experiments, X ray microtomography.

The gas diffusion layer (GDL) is one of the key components in a polymer electrolyte membrane (PEM) fuel cell. It performs several functions including the transport of reactant gases and product water to and from the catalyst layer, conduction of both electrons and heat produced in the catalyst layer, as well as mechanical support for the membrane. The overarching goal of this work is to thoroughly examine the GDL structure and properties for use in PEM fuel cells, and more specifically, to determine how to characterize the GDL experimentally ex-situ, to understand its performance in-situ, and to relate theory to performance through controlled experimentation. Thus, the impact of readily measured effective water vapor diffusivity on the performance of the GDL is investigated and shown to correlate to the wet limiting current density, as a surrogate of the oxygen diffusivity to which it is more directly related. The influence of microporous layer (MPL) design and construction on the fuel cell performance is studied and recommendations are made for optimal MPL designs for different operating conditions. A method for modifying the PTFE (Teflon) distribution within the GDL is proposed and the impact of distribution of PTFE in the GDL on fuel cell performance is studied. A method for characterizing the surface roughness of the GDL is developed and the impact of surface roughness on various ex-situ GDL properties is investigated. Finally, a detailed analysis of the physical structure and permeability of the GDL is provided and a theoretical model is proposed to predict both dry and wet gas flow within a GDL based on mercury intrusion porosimetry and porometry data. It is hoped that this work will contribute to an improved understanding of the functioning and structure of the GDL and hence advance PEM fuel cell technology.

De nos jours, l’utilisation de liants à faible teneur en clinker est de plus en plus courante. Or la cinétique de réaction des additions minérales utilisées est plus lente que celle du clinker. Si les conditions de cure ne sont pas adaptées, le matériau aura une structure poreuse plus importante, ce qui le rendra plus sensible à la pénétration des agents agressifs extérieurs comme le CO2 ou les Cl-. La carbonatation du béton est l’un des principaux phénomènes pouvant diminuer la durée de vie d’une structure en béton armé. En effet, elle entraine une diminution du pH de la solution interstitielle qui a pour conséquence une dépassivation des armatures, puis la corrosion de ces dernières si les conditions s’y prêtent.L’objectif de cette thèse est d’étudier l’impact de la carbonatation au jeune âge sur des liants à faible teneur en clinker. Pour cela l’étude se compose de deux aspects : le premier est l’étude de l’impact de l’hydratation et de la carbonatation sur les propriétés de transport et les isothermes de sorption hydrique, et le second est l’étude de l’impact du couplage hydratation-séchage-carbonatation sur la microstructure et la structure poreuse. Pour le premier aspect, les propriétés de transport étudiées sont la diffusion de l’O2, la diffusion de la vapeur d’eau, la perméabilité à l’eau liquide qui sont des données d’entrée dans les modèles de carbonatation ainsi que la perméabilité aux gaz qui est un indicateur de durabilité. Pour le second aspect, l’impact du couplage est mesuré par ATG et DRX pour déterminer l’assemblage de phases, de plus de la porosimétrie par intrusion de Mercure et des pesées hydrostatiques sont effectuées pour détecter le changement de la structure poreuse. Les matériaux étudiés sont des pâtes de ciment et des bétons avec un rapport eau/ liant de 0,57 avec l’un des trois liants suivants : CEM I, CEM I +30% de cendres volantes et CEM I +60% de laitiers.Pour le premier aspect, les résultats montrent que pour les pâtes de CEM I le temps de cure a un faible impact sur les isothermes de sorption de vapeur d’eau s’il est compris entre 3 jours et 6 mois. Alors que, pour les pâtes de CEM I + 60% de laitier, l’augmentation du temps de cure accroit significativement la teneur en eau (pour HR=65%, tcure=3 jours et pour tcure=6 mois ) dû à une augmentation de la teneur en C-S-H. D’autre part, la carbonatation entraine une diminution de la teneur en eau de l’échantillon, ainsi que l’amplitude de l’hystérésis. De plus, le gel a une porosité plus grossière. Par ailleurs, la carbonatation entraine une augmentation de la perméabilité aux gaz des matériaux. Pour le second aspect, les résultats montrent que l’utilisation d’additions minérales diminue la résistance à la carbonatation du matériau et que cette résistance augmente avec le temps de cure si l’échantillon contient des additions. La carbonatation de la portlandite, des C-S-H et des aluminates est concomitante. De plus, pour les matériaux aux laitiers, les résultats montrent qu’ils sont plus sensibles à la carbonatation des C-S-H et des aluminates que les CEM I. En effet quand le rapport variation molaire de CaCO3 sur variation molaire de Portlandite est calculé, il vaut 1.8 pour le CEM I et environ 3.5 pour les matériaux aux laitiers. Enfin, la carbonatation entraine une diminution du degré de saturation de l’échantillon. En effet, le degré de saturation à la surface de l’échantillon passe de 50% à 35% après carbonatation pour les échantillons de CEM I et de 50% à 5% pour les échantillons de CEM I + 60% de laitiers. Cette diminution peut s’expliquer par la diminution de la surface spécifique qui est divisée par 2 après carbonatation due à la décalcification des C-S-H. Même si la carbonatation entraine une diminution de porosité cette dernière est trop faible dans ce cas pour contrer cet effet / Nowaday, low clinker content binders are used more and more often. But the kinetics reactions of the supplementary cementitious materials (SCM) are slower than this one of clinker. If the curing conditions are not adapted, material will have a bigger pore structure and becomes more sensitive to the ingress of aggressive species from the environment like the CO2 or Cl-. Carbonation is one of main phenomena which can lead to decrease the life time of reinforced concrete structure. Indeed, it leads to a decrease of pore solution pH which leads to the depassivation of rebar. Then these rebars can be corroded if the conditions are appropriate.The aim of this thesis is to study the impact of carbonation at early age for binder with a low clinker content. This study was composed of two aspects: the first one is focus on the impact of hydration and carbonation on the transport properties and the water vapour sorption isotherms (WVSI), and the second one is focus on the impact of coupling hydration – drying-carbonation on the microstructure and the pore structure. For the first aspect, the studied transport properties was O2 diffusivity, water vapour diffusivity, water liquid permeability which are inputs for carbonation modelling and the intrinsic gas permeability which is a durability factor. For the second aspect, the coupling impact was measured by TGA and DRX to determine the phase assemblage; moreover Mercury intrusion porosimetry (MIP) and hydrostatic weigh were carried out to measure the change in the pore structure. The studied materials were cement pastes and concretes with water to binder ratio of 0.57 with one of the following binders: CEM I, CEM I +30% PFA and CEM I + 60% GGBS.For the first part, results show that a curing time between 3 days and 6 months has a low impact on the WVSI for the CEM I paste. Whereas, in the CEM I +60% GGBS paste, when the curing time increases, the water content increases (for a RH=65%, tcuring=3 days and for tcuring=6 months ), this is due to the increase of the C-S-H content. Moreover, carbonation leads to decrease the water content and the hysteresis becomes flat. Additionally, carbonation leads to increase the intrinsic gas permeability. For the second part, the results show that the use of SCM decreases the carbonation resistance and this resistance increases with the curing time. Carbonation of Portlandite, C-S-H and aluminates occurs in the same time. Moreover, the CEM I +60% GGBS paste are more sensitive to the carbonation of C-S-H and aluminates than the CEM I paste. Indeed, the molar variation of CaCO3 to the molar variation of Portlandite ratio has a value around 3.5 for the CEM I +60% GGBS and 1.8 for the CEM I. Finally, carbonation leads to decrease the water saturation degree at the surface of sample. Indeed, the degree of saturation at the surface of the sample increases from 50% to 35% after carbonation for the CEM I paste and from 50% to 5% for the CEm I +60% GGBS paste. This decrease can be explained by the decrease of the BET specific surface which is divided by 2 after carbonation. It is due to the decalcification of C-S-H. Although carbonation leads to a decrease of porosity, this one is too small in this case to counter this effect

The use of mineral adition in concrete is a widely studied theme for several researchers that looking for features like: save cement for reducing costs, durability improvement to increase mechanical strenght and use of industrial wastes for reducing environmental pollution. This study intend to analize the microstructure of concretes mixtures with ungrounded residual rice husk ash addition without burn control unground (RHAN), like a partial cement substitute in conventional concrete for reducing costs, since cement is the most expensive component, and the use RHAN avoiding dumping on environment like a ground and water pollutant. Five different concrete mixtures proportions: 2 mixes of RHAN, with 15% and 25% of partial cement substitution, 2 mixes of ground RHA (RHAM), with 15% and 25% of partial cement substitution, for comparison, and a control design, withouth adition. All concrete disigns were developed for 3 water/binder relationships (0,45, 0,55 e 0,65), 15 differents concrete design in total, for ages 28 and 91 days, were done. Tests like: axial compressive strenght, percentual of chemically combined water, mercury intrusion porosimetry,X-ray difraction and image analysis by scanning eletronic microscope (SEM) combined energy dispersive spectroscopy (EDS) were done. Tests results proved that RHA use is feasible for 15% of substitution of cement by RHAN, since concretes had values of compressive strenght few smaller than control concrete values, at 28 days, however higher than it at 91 days. Because of pozolanic reaction and filler efect combination, of RHAN and RHAM particles, concrete with RHA adition had microstructural changes like: size pore refinement, total porosity reduction and calcium silicate hydrate (C-S-H) formation through pozolanic reaction. RHA Inert particles created nucleation sites improving hydrate crystals formation. / O uso de adições minerais em concretos é um tema bastante estudado por vários pesquisadores que buscam características como: redução do consumo de cimento para redução de custos, aumento da durabilidade, aumento da resistência mecânica e aproveitamento de resíduos industriais para redução da poluição ambiental. Este estudo pretende analisar a microestrutura dos concretos dosados com adição de cinza de casca de arroz residual sem controle de queima e sem moagem (CCAN), em substituição parcial de cimento em concretos convencionais com a finalidade de redução de custos, já que o cimento é o componente mais caro do concreto e também aproveitar a CCAN evitando assim que seja descartada no ambiente como um poluente de água e solo. Foram estudados diferentes traços de concreto: 2 traços com CCAN em teores de 15 e 25% de substituição parcial de cimento, 2 traços com CCA moída (CCAM) em teores de 15 e 25% de substituição parcial de cimento, para comparação, e um traço de referência, ou seja sem substituição de cimento. Cada traço foi desenvolvido para 3 relações a/ag (0,45, 0,55 e 0,65), totalizando então 15 diferentes traços, que foram estudados para as idades de 28 e 91 dias. Foram realizados ensaios de resistência à compressão axial, teor de água quimicamente combinada, porosidade por intrusão de mercúrio, difração de raios x e análise de imagens no microscópio eletrônico de varredura (MEV) combinado com a espectrometria de dispersão de raios X (EDS). Os resultados demonstraram que a utilização da CCAN é viável para teores de 15% de substituição de cimento, já que produziu concretos com valores de resistência à compressão pouco inferiores aos valores do concreto de referência, aos 28 dias, porém superiores a este quando a idade analisada é 91 dias. Devido à combinação da reação pozolânica e efeito filler das partículas de CCAN e CCAM, os concretos com adição de CCA apresentaram modificações da microestrutura como: refinamento dos poros, redução da porosidade total, formação de silicatos de cálcio hidratados (C-S-H) a partir da reação pozolânica. Partículas inertes de CCA criaram também espaços para a nucleação aumentando a formação de cristais hidratados.

This thesis is focused on the study of the influence of crystalline ingredients XYPEX, on the rheology of fresh concrete and durability of hardened concrete. It examines the influence of crystalline additives on the rheology of cement pastes with different types of cement with different temperatures, increasing water tightness and gas tightness and compressive strength. Also assesses pore structure with different bridging cracks.