Dissertations / Theses on the topic 'Porosity'

We investigate porous sets and differentiability of Lipschitz functions. A set P is upper (lower) porous if each point of P sees, on arbitrarily small scales (all sufficiently small scales), nearby holes in P of radius proportional to their distance away. The set P is called directionally upper/lower porous if, for each point of P, the corresponding holes can be chosen with centres on a fixed line. After an overview of porosity and differentiability, we begin by highlighting a difference between upper porosity and lower porosity. Upper porous sets in Rn are necessarily directionally upper porous. We show there exists a lower porous set in R2 which is not even a countable union of directionally lower porous sets. Next we investigate

The sediment movement system in a river basin consists of sediment production process in the mountainous region, sediment supply process to the torrents and sediment deposition process in the lower reach and coastal area. There are human impacts as well as natural impacts in the system. These impacts affect the topographical feature and ecosystem in the basin including the coastal area. Bed variation model is one of the tools for assessing the topographical feature of river. In previous riverbed variation calculations, engineers or researchers conventionally assumed that the porosity in riverbed material is a constant, regardless of whether the grain sizes of the riverbed material was uniform. Since there is no doubt that the porosity depends on the grain sizes distribution, fixing the porosity at a constant value is inadequate for simulating practical sediment movements, such as the removal of fine materials out of the riverbed material or the deposition of fine material into voids between the coarse material. Voids in a riverbed themselves are also important as habitat for aquatic biota. Not only natural sediment transport phenomena, such as floods and debris flows induced by heavy rainstorms, but also artificial impacts, such as the construction of dams or sediment flushing from reservoirs, seriously affect the voids in the riverbed. So far no bed variation model has been available for the analysis of the change in porosity. As the void of bed material plays an important role in fluvial geomorphology, infiltration system in riverbeds and river ecosystem, a structural change of the void with bed variation is one of the concerned issues in river management. Thus, a bed-porosity variation model is strongly required and it is expected that the model contributes the analysis of those problems as a tool for integrated sediment management. The objectives of this work are: 1) to point out recent problems in a volcanic river basin, as well as the impacts on riverbed variation and ecosystem; the problems in Merapi volcano area and Progo River, Indonesia were chosen as case studies; 2) to develop a method for identifying the type of grain size distribution and two methods for obtaining the porosity for the different type of grain size distribution; 3) to develop a framework and a bed variation model available for the analysis of the change in porosity of bed material as well as the bed variation. The report consists of four subjects and organized into six chapters as shown in the diagram below (Figure 1). The following diagram shows the framework of proposed bed-porosity variation model and the correspondence of each chapter of this report. In Chapter 2, the sediment-related problems in volcanic area, particularly in Mt. Merapi and Progo River, Indonesia and the impacts on bed variation and ecosystem were pointed out. The sediment-related problems persist in the upper reach, middle reach, also in lower reach. Some problems are triggered by natural activities such as volcanic activity of Mt. Merapi and heavy rainfall, and many others are occurred due to the human interfere such as deforestation, construction of sabo dam and sand mining. Uncontrolled sand mining is the serious problem in this area. Those problems are increasing the susceptibility in the downstream and deteriorating the watershed. A flume experiment was conducted to realize the impact of mining pit on bed variation. Countermeasures of sediment problems, which have been done in Mt. Merapi area and Progo River, were also presented. Finally, the necessity of a tool for integrated sediment management in consideration of the ecosystem in river was indicated. In Chapter 3, the method for classifying and geometrically identifying the type of grain size distribution was presented. First, grain size distribution was classified into some typical types and those characteristic parameters were found out. Then a method for geometrically identifying the type of grain size distribution by using geometric indices .. and .. was presented. Based on the geometrical analysis of typical grain size distributions, a diagram on classification of grain size distribution type was indicated. The presented identification method was then applied to the natural grain size distribution data and the validity of the method was verified. In Chapter 4, two methods for estimating the porosity of sediment mixtures were presented. One was based on a particle packing simulation model and the other was based on a measurement method. The porosity of particle mixtures depends on not only the grain size distribution but also the compaction degree. However, the compaction degree could not be intentionally controlled in the model. Both of the methods were applied to estimate the porosity of three typical grain size distributions, namely lognormal distribution, modified-Talbot distribution and bimodal distribution. Particularly in the measurement, it was very difficult to mix the sediment evenly. Consequently, the coarser particle lies at higher position than the finer particle. This grading process made the porosity larger, while in the simulation the particles were mixed evenly. Thus, the particles packing in the simulation might be denser than the packing of particles in the measurement. The results showed that the relationship between grain size distribution and porosity could be determined by using the characteristic parameters of typical grain size distribution. This relation could be introduced into the bed variation model. In Chapter 5, a one dimensional bed-porosity variation model was developed for simulating the changes in porosity of bed material as well as the bed variation. Analytical model for binary mixtures with much different grain sizes and the relationship between the characteristic parameters of grain size distribution and porosity presented in Chapter 4 were introduced into the bed variation model. Two numerical methods were employed to solve the governing equations, i.e., standard successive approximation and MacCormack scheme. A flume experiment was conducted to realize the transformation processes of void structure for two conditions; one was the only fine sediment was removed from a sediment mixture and another was the fine sediment deposited into a coarser bed material. After the validity of the presented model was verified using a data set provided by the experiment, the model was applied to the bed and porosity variation process for bed material with binary mixtures and continuous grain size distribution. Its performance was examined in detail for two conditions; (1) no sediment supply condition and (2) sediment supply condition. The simulation results showed the model could produce a reasonable distribution of porosity of the riverbed material in the longitudinal and vertical directions for both conditions. A one-dimensional bed-porosity variation model proposed in this study is different from the previous model from a viewpoint of considering the porosity of bed material. Hence, the proposed model is available for the analysis of the change in porosity of bed material as well as the bed variation. The model contributes in two aspects; from the hydraulics point of view, the model provides an improvement of the accuracy in the riverbed variation calculation and from ecological point of view, the model provides the changes in porosity with the bed variation. In the case of binary mixtures, the validity of the model has been verified using a data set provided by the experiment and the simulation result showed that the model produced a reasonable result on the change in porosity as well as the bed variation. In the case of sediment mixtures with continuous grain size distribution, although the validity of the model has not been verified yet, the simulation result showed the model available for analysis of bed and porosity variation.
Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第13795号
工博第2899号
新制||工||1428(附属図書館)
26011
UT51-2008-C711
京都大学大学院工学研究科社会基盤工学専攻
(主査)教授 藤田 正治, 教授 中川 一, 教授 戸田 圭一
学位規則第4条第1項該当

Geopolymers are synthetic materials formed by alkali-activation of aluminosilicate particles. They have attracted increasing attention as sustainable materials, being obtained from different raw materials, including industrial by-products, and by production processes at low temperature. Thanks to the good properties showed by these materials (thermal stability, fire-resistance, etc.), and the intrinsic mesoporosity, geopolymers have been studied as new materials for applications in many industrially relevant fields. To achieve full advantage of their porous structure, it is necessary to control its formation. The geopolymer production process in aqueous medium allows to tailor the porosity from nanometric to millimetric range since water acts as pore former. Moreover, ultra-macroporosity may be induced in the materials exploiting different techniques, commonly used for the production of porous ceramics, determining the possibility to obtain materials with different architectures, pore size and shape, etc. Hierarchical pore systems, where the mesopores of the geopolymer skeletal materials are directly connected to macro- and finally to ultra-macropores, may be constructed in this way. The main goal of this research project was to investigate the use of different process techniques applied to geopolymer matrices to generate porous structures characterized by peculiar porosities able to determine specific properties and functionalize the materials. In detail, the porosity was induced by direct foaming or addition of lightweight aggregates. Furthermore, geopolymers with main unidirectional anisotropic macropores were produced, for the first time, using a freeze-casting technique. All the materials produced were deeply investigated to optimize the production processes and evaluate the final properties, many of which arising from the intrinsic and induced porosity generated, in order to address the materials for potential applications as, for example, thermal insulating panels or heat transfer devices.

Geopolymers are synthetic materials formed by alkali-activation of aluminosilicate particles. They have attracted increasing attention as sustainable materials, being obtained from different raw materials, including industrial by-products, and by production processes at low temperature. Thanks to the good properties showed by these materials (thermal stability, fire-resistance, etc.), and the intrinsic mesoporosity, geopolymers have been studied as new materials for applications in many industrially relevant fields. To achieve full advantage of their porous structure, it is necessary to control its formation. The geopolymer production process in aqueous medium allows to tailor the porosity from nanometric to millimetric range since water acts as pore former. Moreover, ultra-macroporosity may be induced in the materials exploiting different techniques, commonly used for the production of porous ceramics, determining the possibility to obtain materials with different architectures, pore size and shape, etc. Hierarchical pore systems, where the mesopores of the geopolymer skeletal materials are directly connected to macro- and finally to ultra-macropores, may be constructed in this way. The main goal of this research project was to investigate the use of different process techniques applied to geopolymer matrices to generate porous structures characterized by peculiar porosities able to determine specific properties and functionalize the materials. In detail, the porosity was induced by direct foaming or addition of lightweight aggregates. Furthermore, geopolymers with main unidirectional anisotropic macropores were produced, for the first time, using a freeze-casting technique. All the materials produced were deeply investigated to optimize the production processes and evaluate the final properties, many of which arising from the intrinsic and induced porosity generated, in order to address the materials for potential applications as, for example, thermal insulating panels or heat transfer devices.

Les porosités dont témoigne le design contemporain en font un champ ouvert où viennent s’imprimer et s’entrelacer les enjeux d’autres domaines, aujourd’hui prédominés par la science. Situé à la croisée des territoires, le designer exerce un art de la protéiformité — un ars proteus — révélant, par les objets qu’il conçoit, les métamorphoses et les questionnements que suscite la science — et plus particulièrement la médecine et ses conséquences sur une pensée du corps.Le design aurait-il le pouvoir de rendre visibles les enjeux les plus imperceptibles qui se trament à des échelles qui dépassent la mesure humaine ? Le design contemporain questionne l’échelle du corps dans les objets : peuvent-ils contribuer à faire émerger ou à matérialiser un imaginaire corporel que notre époque ferait subrepticement éclore ? L’organoplastie dans le design est cette possible formulation d’un glissement de territoire qui se produit entre le corps et l’objet, entre la genesis et la technè. Que cette organoplastie soit réelle (comme avec les objets à croissance spontanée de François Azambourg ou de Tobie Kerridge), ou bien métaphorique, elle engendre de nouvelles conceptions de l’objet mais aussi des moyens de production et de création, tout en accompagnant l’émergence d’un imaginaire biologique de nos artefacts. Le designer serait-il le pourvoyeur d’une seconde genèse, d’une néogenèse dont les formes organiques autonomes se constitueraient sur le modèle naturel de la croissance, donnant une nouvelle consistance à l’élaboration d’un monde artificiel ?
Porosity highlighted by the contemporary design makes of this one an open field where issues ofother areas, dominated by science, are intertwined. Placed at the crossroads of different territories, thedesigner creates a protean art- an ars proteus- revealing by the objects, the metamorphosis andproblematics elicited by science- and more particularly by medicine and its impact on our bodyconception.Could the design have the power to detect the most imperceptible issues which are plotted beyondhuman measure? The contemporary design questions the scale of the body in the objects: can itcontribute to show or materialize a body imaginary that our time would have secretly create?The organoplastie in design is a word which could express a sliding that occurs between the bodyand objects, between genesis and technè. The organoplastie, either real (like François Azambourg orTobie Kerridge's spontaneous growth objects) or metaphorical, generates new designs of the objectand, moreover, new ways of production and creation, while supporting the advent of a biologicalimaginary of our artifacts. Could the designer be the purveyor of a second genesis, or a neogenesiswhose autonomous organic forms would be based on the natural growth mode!, giving a newconsistencv in the development of an artificial world?

Les zéolites sont des catalyseurs industriels importants ; leur sélectivité basée sur la forme unique de leurs pores est à l’origine de plusieurs applications importantes. Cependant, la seule présence des micropores limitent le transport de réactifs et de produits et par la suite entrave l’efficacité de zéolites. Surmonter ou réduire les limitations de diffusion dans les zéolites est important pour améliorer leurs performances catalytiques et leurs capacités séparation. Le présent sujet de doctorat rapporte la préparation de zéolites avec une porosité accrue par la méthode de post-synthèse « etching ». Ce travail vise à créer une porosité secondaire (mésopores) liée à la microporosité native sans altération des propriétés intrinsèques de zéolites. Trois types de zéolites de différentes tailles de pores sont étudiés : petit pore SSZ-13 (CHA), pore moyen ZSM-5 (MFI) et grand pore zéolite L (LTL). L'étude de la Zéolite « L » consiste sur la comparaison des capacités de solutions NH4F et NH4HF2 dans la création des mésopores. Les résultats obtenus montrent que NH4F peut être remplacé par NH4HF2. L’utilisation des solutions de NH4HF2 à 1 et 2 % en masse aboutit à la création d’une (méso-) porosité similaire à celles obtenus avec des solutions de NH4F à 20 et 40 % en masse. Ainsi, en remplaçant NH4F par NH4HF2, on observe une diminution substantielle de la quantité de fluor utilisée. SSZ-13 est traité avec 40 % en masse de NH4F, ce qui a généré des mésopores dans tous les échantillons préparés. Les résultats obtenus révèlent que la génération de mésopores commence à partir de la surface du cristal, en raison des contraintes de diffusion d'ions bifluorure hydratés à travers les petits canaux de pores. Le traitement de zéolites de différentes tailles de pores (8, 10, 12 MR) avec l'acide chromique révèle que ce processus de dissolution dépend de la taille de l'ouverture des pores car les zéolithes à 8 MR et 10 MR sont plus résistantes au traitement à l'acide chromique qu’une zéolite à 12 MR. En général, l'acide chromique ne génère pas de mésopores substantielles. Le nombre de sites acides accessibles dans les dérivés obtenus par « etching » est proche de celui du matériau d'origine, bien qu'une certaine désalumination préférentielle soit observée
Zeolites are important industrial catalysts; their unique shape-selectivity is the basis of important applications, but also a pitfall limiting their efficiency. Overcoming or decreasing the diffusion limitations in zeolites is important to improve their catalytic and separation performance. The present Ph.D. thesis reports work on the preparation of zeolites with increased porosity via post-synthesis chemical etching. The work aims to create secondary porosity (mesopores) connected to the native microporosity without altering the intrinsic zeolite properties. Three zeolite types are studied: a small pore SSZ-13 (CHA), a medium pore ZSM-5 (MFI), and a large pore zeolite L (LTL). Zeolite L study compares the etching abilities of NH4F and NH4HF2 solutions in the hierarchization of zeolite L. The results show that NH4F can be replaced with NH4HF2. The etching with 1 and 2 wt/% NH4HF2 solutions yield hierarchical derivatives similar to those obtained with 20 and 40 wt/% NH4F solutions. Thus by replacing NH4F with NH4HF2 a substantial decrease in the used fluorine is achieved. SSZ-13 is etched with 40 wt/% NH4F, which generates mesopores in all prepared samples. The results reveal the mesopore generation starts from the crystal surface due to the constrained diffusion of hydrated bifluoride ions through the small pore channels. Chromic acid etching of zeolites with different pore opening (8, 10, 12 MR) reveals that this dissolution process is dependent on the size of the pore opening as 8 MR and 10 MR zeolites are more resistant to etching with chromic acid than 12 MR zeolite. In general, the chromic acid does not generate substantial mesopore formation. The number of accessible acid sites in etched derivatives is close to the parent material, although some preferential dealumination is observed

An analysis of the surface of my paintings through Jean Baudrillard’s notion of seduction and the cool mechanism of the airbrush. I further investigate my work through the metaphor of the black mirror also known as a Claude Mirror and the connections between my work, Claude Lorrain’s landscape painting and divination through the use of reflective surfaces known as catopotromancy. Considering the notion of assemblage as outlined by Gilles Deleuze and Bruno Latour’s Action Network Theory I attempt to navigate the part/whole relationships found in painting, and in society.

The Adaptive Foam Reticulation (AFR) technique, a combination of foam reticulation and freeze casting, has been investigated for producing bone repair bioscaffolds from hydroxyapatite (HA), titanium (Ti) and titanium-aluminium-vanadium (Ti-6Al-4V). Scaffolds have a network of macropores of diameter between 94 and 546 mm, with struts 20 to 118 mm thick. The structure was dependent on the template from which structures were produced, the number of coats of slurry applied to the template and the sintering temperature. The struts contained numerous micropores, the size of which was increased from 2-5 to 20-30 mm by decreasing the freezing temperature. Whilst the size of individual micropores was independent of the amount of porogen in the slurry, there was some coalescence at higher percentages. Scaffolds exhibited porosities of between 76 and 96%, with porosity consistently decreased by increasing the number of coats from one to five. The mechanical strength of all samples was determined theoretically by the novel incorporation of a shape factor conventially used for microporous structures into an existing equation used to calculate the yield stress of porous structures. In most cases this agreed with the experimentally obtained yield stress. With compressive yield stresses of 0.002 to 0.18MPa and 0.002 to 1.8 MPa respectively, HA and Ti structures are only suitable in non-load bearing situations. However Ti-6Al-4V scaffolds had yield stresses of 0.21-13.7 MPa, within the range of cancellous bone. AFR-fabricated HA scaffold offered greater in-vitro cell viability than a commercially available porous HA disc. Including a porogen offered no improvement in viability compared to structures fabricated without porogen, except at the highest inclusion where a statistically significant increase was observed. The weak compressive strength of scaffolds needs improving, and fabrications require in-vivo analyses. However, AFR could offer a viable alternative to other manufacturing techniques.

The presence of shale in a sandstone reservoir can negatively affect the producibility of that reservoir. It is hence important to quantify not only the volume of shale but also the distribution types. The shale distribution types are described as laminar shale, dispersed shale, and structural shale. The shale distribution types can exist in any number of combinations in a reservoir. However, most previous works have considered only the single-type distribution models (laminar, dispersed, and structural shales) and the two-type laminar-dispersed and laminar-structural models. A previous thesis expanded on previous works to include the dispersed-structural and three-type shale distribution system, expanding the total porosity versus total volume of shale crossplot technique, and devised the ratio method for further analysis. This research provides an additional methodology to quantify the shale distribution types using the density porosity versus neutron-density volume of shale crossplots. Applying the ratio method in terms of the gamma-ray volume of shale and neutron-density volume of shale showed that considering a third component in the volume of shale distribution led to an increase in the volume of dispersed shale. Both the laminar-dispersed and laminar-structural models provide the most optimistic scenarios in the reservoir where the volume of dispersed shale is calculated at its lowest potential value and, hence, the effective sandstone porosity is highest. The ratio method allows for the calculation of a range of scenarios starting from the most optimistic to the most pessimistic. Using the VshND tool as an additional method in a case study in this work revealed that the VshND calculated the volume of shale at higher values than the VshGR, thus providing a more conservative analysis in this case.

An investigation is made of porosity in polycrystals which have an idealised microstructure, comprising regular polyhedral grains of uniform size. The stability of networks of grain edge pores is considered in Chapter Two. In this chapter a new model of interlinked grain edge porosity is derived on physically realistic grounds and takes into account the variation in the dihedral angle of the porosity along its length. The model also improves extant work by paying careful attention to the surface morphology of the porosity in the region of the grain corners, where grain edge tunnels interlink. The relaxation of porous structures of general dihedral angle, to configurations of minimum energy, is the subject of Chapter Three. A mathematical model of the surface diffusion driven morphological changes in grain edge pores is developed. The model employs the sophisticated analysis of Chapter Two to describe the surface morphology of the porosity at any instant in time. In the later chapters the surface diffusion shape change model is extended to include the effects of diffusion in the grain boundaries. Thus the diminution of pore volume, by the condensation of vacancies on the grain boundaries, together with the enhancement of shape changes, by the mechanisms of grain boundary diffusion and surface diffusion acting in parallel, is introduced into the model. The results of a computer program capable of simulating the relaxation of both open, interlinked grain edge networks and closed, isolated edge pores is presented. The significance of these results to the phenomena of fission-gas release in nuclear fuels and sintering in ceramic polycrystals is discussed.

For example for battery diagnosis it is essential to understand mechanisms during discharge and because of aging to optimize cell design and operating conditions. Therefore the overall battery behavior can be modeled by combining models of relevant mechanisms like porosity, charge transfer reaction and diffusion. The aim of this contribution is to define one transmission line model for modeling several of these mechanisms. Thereby a sophisticated normalization strategy allows to eliminate ambiguity and to quantify the influence of each model parameter. The results allow a better understanding of impedance measurements and can for example be used for battery diagnosis and simplified simulations of electrochemical systems. Fitting derived impedance models to measurement data by nonlinear parameter extraction techniques allows to monitor battery parameters during discharge and because of aging. Thereby a sophisticated normalization strategy is essential for unambiguous parameter extraction and useful to quantify the influence of each model parameter.

L’objectif de la thèse est la synthèse et l’optimisation des supports monolithiques et l’évaluation de leur efficacité en cuisson kraft et lors du recyclage (essai des catalyseurs dans un réacteur de capacité 5 kg). Lors de cette thèse, nous avons montré que l’utilisation des monolithes styréniques anthraquinoniques à base de diméthacrylate de diéthylèneglycol et de divinylbenzène en cuisson permettent d’économiser de l’alcali actif consommé et d’augmenter le rendement en pâtes à des indices kappa faibles. Les monolithes à base de diméthacrylate de diéthylèneglycol sont plus efficaces en cuisson que ceux à base de divinylbenzène, avec des gains comparables à l’effet de l’anthraquinone commerciale et gardent leur activité catalytique lors du recyclage
The objective of the thesis is the synthesis and optimization of monolithic supports and the evaluation of their efficiency in the kraft process and after recycling (test of catalysts inside a 5 kg capacity reactor). In this work, we showed that the presence of monoliths styrene-anthraquinone-diethyleneglycoldimethacrylate or styrene-anthraquionone-divinylbenzene in the kraft process could save up the active alkali consumed and could increase the yield in pulp at low indice kappa. The monoliths styrene-anthraquionone-diethyleneglycoldimethacrylate are more efficiently in cooking process than those containing divinylbenzene. Their performance is closed of that of the commercial anthraquinone and this catalytic activity persists even after recycling

Un procédé de création de surfaces poreuses sur deux aciers inoxydables respectivement austénitique et ferritique a été étudié. Ce procédé est en deux étapes. Une couche d’oxyde, dont l’épaisseur et la composition sont contrôlées, est d’abord générée par de la vapeur d’eau à 1100 °C. Puis cette couche est ensuite réduite par du dihydrogène à haute température. Ces travaux ont pour objectifs de mieux comprendre les mécanismes de formation des pores ainsi que l’influence des divers paramètres de réaction, tant pour l’oxydation que pour la réduction.Une caractérisation complète des couches d’oxydes a été d’abord réalisée. Le principal paramètre influent est la structure de l’alliage, austénitique ou ferritique. Par la suite, les surfaces poreuses ont été étudiées afin d’établir, étape par étape, les mécanismes mis en jeu.Il a été établi que la non-stœchiométrie des oxydes de fer préalablement formés sur l’acier austénitique est à l’origine de la formation des pores sur la surface de cet acier.Un nouveau type de porosité a pu être obtenu par la formation préalable de couches d’oxydes riches en chrome formées sur l’acier ferritique. Les morphologies ainsi que les mécanismes sont ici totalement différents. Un processus de formation des pores spécifique a été proposé
A process for pore creation on the surface of two stainless steels, respectively austenitic and ferritic, has been investigated. That process follows two steps. An oxide scale with controlled thickness and composition is firstly generated by water vapour exposition at 1100 °C. That layer is subsequently reduced at high temperature by dihydrogen. The present work aims to better understand the mechanisms of pore formation and the influence of various reaction parameters on both oxidation and reduction course.A comprehensive characterisation of the oxide layers has been first performed. The main parameter is the alloy structure, austenitic or ferritic. The porous surfaces have been thereafter studied to establish step by step the formation mechanisms involved.It was demonstrated that the non-stoichiometry of iron oxides formerly developed on the austenitic steel is behind the pore growth mechanism on that steel.A new kind of porosity could be obtained through the preliminary building of chromium-rich oxide scales on the ferritic steel. The morphologies are in that case completely different as well as the pore formation mechanism. A specific process for the pore growth has been proposed

Cette étude a pour objectif d'améliorer les connaissances sur l'effet des irradiations sur le comportement des géopolymères vis-à-vis du dégagement de dihydrogène et de la tenue générale du matériau afin de les envisager comme une solution alternative aux matrices d'enrobage cimentaires usuelles pour certains déchets nucléaires. A l'aide de diverses techniques de caractérisation du géopolymère (adsorption d'azote, DSC basse température, spectroscopie IRTF et RMN 1H) et au moyen d'irradiations de simulation (gamma, ions lourds), il a été montré que toute l'eau présente au sein du géopolymère était radiolysable et qu'il existait un effet du confinement sur la radiolyse de l'eau sous irradiation à faible TEL, dû probablement à des transferts d'énergie efficaces de la matrice solide vers la solution interstitielle. Trois régimes de production de dihydrogène ont été identifiés en fonction de la dose selon la concentration de dioxygène dissous et l'accumulation de dihydrogène dans la matrice géopolymère. La bonne tenue mécanique du géopolymère a été démontré jusqu'à 9 MGy en irradiation gamma et serait dû à sa grande stabilité sous irradiation. Ceci s'expliquerait par la recombinaison rapide des défauts observés par spectroscopie RPE. Cependant, des cristallisations de phases ont été révélées lors d'irradiations avec des ions lourds, pouvant induire une certaine fragilisation du réseau du géopolymère sous irradiation alpha. L'ensemble des résultats a permis d'appréhender la phénoménologie au sein d'un colis de déchets en conditions de stockage
This study aims to improve knowledge about the radiation effect on geopolymer behavior in terms of dihydrogen release and general strength in order to consider them as an alternative to usual nuclear waste cementitious coating matrices. Using various characterization techniques (nitrogen adsorption, low temperature DSC, FTIR and 1H NMR spectroscopy) and by means of simulation irradiations (gamma, heavy ions), it has been shown that all the water present in the geopolymer could be radiolyzed and that there was a confinement effect on the water radiolysis under low LET irradiation, probably due to efficient energy transfers from the solid matrix to the interstitial solution. Three dihydrogen production rates have been identified with the absorbed dose, depending on the concentration of dissolved dioxygen and the dihydrogen accumulation in the geopolymer matrix. The good mechanical strength of the geopolymer has been shown up to 9 MGy under gamma irradiation and is due to its high stability under irradiation. This could be explained by the fast recombination of the defects observed by EPR spectroscopy. However, phase crystallization was revealed during irradiation with heavy ions, which may induce some weakening of the geopolymer network under alpha irradiation. The overall results helped to understand the phenomenology in a waste package under storage conditions

It has generally been assumed that porosity reduction during mechanical compaction of a sediment is controlled by the increase in vertical effective stress. But the theory of mechanical compaction shows that it is the mean effective stress which controls porosity reduction. According to published data, horizontal stresses increase with overpressure, as well as with depth, so mean stress and vertical stress profiles are poorly correlated in overpressured sections. In this study, a new methodology was developed whereby mudrock pore pressures were estimated principally by comparison of void ratios calculated from wireline log response with hydrostatic mean effective stress (the mean effective stress assuming the pore pressure is hydrostatic). These pressure estimates in the low permeability units were compared to the direct measurements in the aquifer units and an interpretation is made as to the origin of the excess pressure. The results of analysis of seven wells from SE Asia are presented including one study where seismic velocity analysis and basin modelling were performed to assess the pore pressure. The main conclusions of the study are: The proposed new methodology for estimating shale pore pressure from void ratio and mean effective stress analysis appears to be more consistent with the data and represents an improvement on previous methodologies using porosity and vertical effective stress or depth. Analysis of the mudrocks in this study indicates that the shales often appear to have significantly higher pressures than the adjacent aquifer units. The results of using mean (as opposed to vertical) effective stress analysis indicates that the pressure profiles in the wells studied, the profiles disequilibrium compaction can account for all or nearly all of the encountered overpressures. Evidence has been found for significant overpressure generated by fluid expansion in one of the seven wells studied.« Further work to refine the Breckels and Van Eekelen (1982) relationship between overpressure and horizontal stress is proposed to improve the accuracy of the methodology used in this study.

Thesis (M.S.)--West Virginia University, 2000.
Title from document title page. Document formatted into pages; contains viii, 63 p. : ill. (some col.), maps Includes abstract. Includes bibliographical references (p. 54-55).

Cabonate-hosted hydrocarbon reservoirs will play an increasingly important role in the energy supply, as 60% of the world's remaining hydrocarbon resources are trapped within carbonate rocks. The properties of carbonates are controlled by deposition and diagenesis, which includes calcite cementation that begins immediately after deposition and may have a strong impact on subsequent diagenetic pathways. This thesis aims to understand the impact of early calcite cementation on reservoir properties through object-based modelling and Lattice Boltzmann ow simulation to obtain permeability. A Bayesian inference framework is also developed to quantify the ability of Lattice Boltzmann method to predict the permeability of porous media. Modelling focuses on the impact of carbonate grain type on properties of early cemented grainstones and on the examination of the theoretical changes to the morphology of the pore space. For that purpose process-based models of early cementation are developed in both 2D (Calcite2D) and 3D (Calcite3D, which also includes modelling of deposition). Both models assume the existence of two grain types: polycrystalline and monocrystalline, and two early calcite cement types specific to these grain types: isopachous and syntaxial, respectively. Of the many possible crystal forms that syntaxial cement can take, this thesis focuses on two common rhombohedral forms: a blocky form 01¯12 and an elongated form 40¯41. The results of the 2D and 3D modelling demonstrate the effect of competition of growing grains for the available pore space: the more monocrystalline grains present in the sample, the stronger this competition becomes and the lesser the impact of each individual grain on the resulting early calcite cement volume and porosity. The synthetic samples with syntaxial cements grown of the more elongated crystal form 40¯41 have lower porosity for the same monocrystalline grains content than synthetic samples grown following more blocky crystal form 01¯12. Moreover, permeability at a constant porosity is reduced for synthetic samples with the form 40¯41. Additionally, synthetic samples with form 40¯41 exhibit greater variability in the results as this rhombohedral form is more elongated and has the potential for producing a greater volume of cement. The results of the 2D study suggest that for samples at constant porosity the higher the proportion of monocrystalline grains are in the sample, the higher the permeability. The 3D study suggests that for samples with crystal form 01¯12 at constant porosity the permeability becomes lower as the proportion of monocrystalline grains increase, but this impact is relatively minor. In the case of samples with crystal form 40¯41 the results are inconclusive. This dependence of permeability on monocrystalline grains is weaker than in the 2D study, which is most probably a result of the bias of flow simulation in the 2D as well as of the treatment of the porous medium before the cement growth model is applied. The range of the permeability results in the 2D modelling may be artificially overly wide, which could lead to the dependence of permeability on sediment type being exaggerated. Poroperm results of the 2D modelling (10-8000mD) are in reasonable agreement with the data reported for grainstones in literature (0.1-5000mD) as well as for the plug data of the samples used in modelling (porosity 22 - 27%, permeability 200 - 3000mD), however permeability results at any given porosity have a wide range due to the bias inherent to the 2D flow modelling. Poroperm results in the 3D modelling (10 - 30, 000mD) exhibit permeabilities above the range of that reported in the literature or the plug data, but the reason for that is that the initial synthetic sediment deposit has very high permeability (58, 900mD). However, the trend in poroperm closely resembles those reported in carbonate rocks. As the modelling depends heavily on the use of Lattice Boltzmann method (flow simulation to obtain permeability results), a Bayesian inference framework is presented to quantify the predictive power of Lattice Boltzmann models. This calibration methodology is presented on the example of Fontainebleau sandstone. The framework enables a systematic parameter estimation of Lattice Boltzmann model parameters (in the scope of this work, the relaxation parameter τ ), for the currently used calibrations of Lattice Boltzmann based on Hagen-Poiseuille law. Our prediction of permeability using the Hagen-Poiseuille calibration suggests that this method for calibration is not optimal and in fact leads to substantial discrepancies with experimental measurements, especially for highly porous complex media such as carbonates. We proceed to recalibrate the Lattice Boltzmann model using permeability data from porous media, which results in a substantially different value of the optimal τ parameter than those used previously (0.654 here compared to 0.9). We augment our model introducing porosity-dependence, where we find that the optimal value for τ decreases for samples of higher porosity. In this new semi-empirical model one first identifies the porosity of the given medium, and on that basis chooses an appropriate Lattice Boltzmann relaxation parameter. These two approaches result in permeability predictions much closer to the experimental permeability data, with the porosity-dependent case being the better of the two. Validation of this calibration method with independent samples of the same rock type yields permeability predictions that fall close to the experimental data, and again the porosity-dependent model provides better results. We thus conclude that our calibration model is a powerful tool for accurate prediction of complex porous media permeability.

Modification of the eutectic silicon in Al-Si foundry alloys by adding strontium is accompanied by an increase of porosity in the casting. This effect on porosity is due to an increase in both the pore size and the pore number density. In an attempt to understand the nature of this problem, the effect of strontium on the probable causes for porosity occurrence due to modification has been investigated.
Experimental findings indicate that the addition of strontium to Al-Si alloys increases the volumetric shrinkage due to an increase in solid density, and at the same time reduces the surface tension and increases the viscosity of the liquid. Metallographic observations show that Sr addition slightly decreases the dendrite arm spacing and changes the solid-liquid interface to a more regular shape. Moreover, Sr-modification decreases the eutectic temperature, and therefore, increases the length of the mushy zone while the total solidification time remains constant.
In addition, Sr addition increases the melt inclusion content, but these inclusions do not have a significant effect on pore nucleation. Hydrogen measurement in the liquid shows that Sr-modification has no effect on the rate of melt hydrogen pick-up and does not introduce hydrogen into the melt. Strontium also reduces the hydrogen solubility in the liquid state but has virtually no effect on the solid state solubility.
A solidification model for pore formation has been developed to study the significance of the changes in these parameters on porosity formation. Based on the experimental results and the theoretical analysis, it is concluded that the decrease in the hydrogen solubility in the liquid, the eutectic temperature (or the length of the mushy zone) and the surface tension are the reasons for the observed increase in porosity in modified alloys. Among these parameters, the decrease in the hydrogen solubility in the liquid plays the main role in causing enhanced porosity formation.

This thesis demonstrates the use of a mixture of standard and novel petrophysical techniques to estimate physical parameters of mudstone and explores the use of a generic, clay fraction-dependent compaction model in the context of pore pressure evaluation. Mudstones are often highly heterogeneous, yet many authors use a single compaction trend to describe their behaviour. Previous work has shown that the rate of a mudstone's compaction with vertical effective stress is a function of its clay fraction, the proportion of the sediment matrix with a particle diameter of less than 2μm. This observation forms the basis of the generic mudstone compaction model used in this thesis. The use of the generic compaction model is explored in two case studies using characterised mudstone samples and wireline log data from the Gulf of Thailand and Gulf of Mexico. Further mudstone samples from the Central North Sea were characterised. An error analysis showed that the compaction model can provide estimates of pressure to within ±1.8MPa at a burial depth of 3km (equivalent to ±0.5ppg mudweight) when the input parameters are constrained to an attainable level. In both cases studied, standard methods of analysis could not provide reasonable estimates of pressure in mudstone using wireline resistivity and porosity log data compared to pressure measurements in associated sand bodies. The deep sediments of the two wells studied from the Gulf of Thailand are overconsolidated with respect to their current stress state. The generic compaction model was used to determine that the overconsolidated sediments were uplifted by 1,300m and have been reburied beneath 900m of sediment that now overlies a regional unconformity. The generic compaction model was used in conjunction with an artificial neural network technique for the characterisation of mudstones from wireline data to determine pressure estimates in the mudstones of three deepwater wells in the Gulf of Mexico. A pressure transition zone in one well was shown to be associated with a 10% increase of mudstone clay fraction within the zone compared to surrounding rocks. In both case studies disequilibrium compaction was identified as the key overpressure generation mechanism.

Claims in the metaphysics of strong emergence, featuring autonomous and possibly reflexive downward causal capacity, methodologically require, though ultimately ignore, units of analysis qua unified wholes. I argue that this avoidance of mereological and wider metaphysical debates denies the metaphysics of emergence clarity and cohesion and urgent application to conceptions of structure and agency. In this thesis, using a refined, non-linear, irreproducible, non-ontologically reductionist open-system physicalism and empiricism, I show that claims in the metaphysics of emergence hastily assume first the integration and subsequently the individuation of objects that become the subject of these strong claims. These assumptions, I believe, are actually the cause for the insurmountable gap between pure ontological reduction on the one side, and pure ontological and irreducible property emergence on the other. Furthermore, in using this new physicalism in the context of strong emergence, the traditional boundary between ontology and epistemology—going far beyond the standard weak-strong divide in the emergence discourse—can no longer be respected. As such, the nature of emergent properties is critical to assessing the nature of objects qua wholes with respect to the conditions for their integration and individuation. The major contribution to the metaphysics of emergence that this thesis provides is the realisation that, when we assume all physical objects are open and porous, all claims for persisting, emergent wholes are necessarily based on physical assumptions of integration and individuation. Synthetically I offer a method for understanding the individuation of ‘quidditious’ objects via properties when such a physicalist framework is employed.

Currently, a controversy exists as to whether oil charge in reservoirs has an inhibiting effect on quartz cementation. The Brae Formation sandstone reservoirs in the Miller and Kingfisher oilfields display in some areas anomalously high porosity (25-30%) preserved to depths in excess of 4km (~120°C). The high porosity in these sandstones is directly linked to low quartz cement volumes (<5%). In the Miller Field, the crestal areas of the reservoir have porosities of up to 25% and a quartz cement content of <5%. Towards the oil-water contact (OWC), and in the aquifer of this same reservoir, porosity decreases and quartz cement content increases to 14% and 15% respectively. In the Kingfisher Field, two reservoirs separated by a mudstone layer are present. The lower reservoir, which connects with the reservoir in the adjacent Miller Field, displays porosities ~14% and quartz cement contents of ~10%. The upper reservoir is of overall high porosity (25-30%) and exhibits low quartz cement contents (<5%). Combined results from fluid inclusion and basin modelling studies in the Brae Formation reservoirs show that the duration of quartz cement precipitation is linked to hydrocarbon emplacement. In the Miller Field. quartz cementation in the high porosity (up to 25%) parts of the reservoir continued until the sandstones were buried to 95-105°C. This temperature corresponds to the burial depth (3km) and time (40Ma) at which oil entered the reservoir. Results for the Kingfisher Field indicate a similar oil emplacement time in the upper reservoir with 25-30% porosity and <5% quartz cement content, but a more recent (l5Ma) oil-fill for the lower reservoir with ~14% porosity and ~10% quartz cement content. Kinetic modelling of the quartz cementation process reveals that quartz cementation rates in the oil-filled parts of reservoirs examined (10^-22 moles/cm².s) are at least two orders of magnitude smaller than in the aquifers (10^-19 moles/cm².s).

Two different soils may be generated from open-pit mining: lumpy soils with a granular structure and clay mixtures, depending on the length of the conveyor belt and the strength of the original soils. Lumpy soils may be created for a high strength of the excavated soils. They are dumped as landfills without any compaction, which permits the water and air flows via the inter-lump voids. As a result, a new structure consisting of the lumps and reconstituted soil within the inter-lump voids can be created. However, if the original soil has a low strength or a long transportation takes place, the material may disintegrate into small lumps and thoroughly mix soils from different layers. Landfills consisting of clay mixtures arise in this way. The stability and deformation of landfills are crucial for design of occupied area and landfill slopes. For this reason, three different landfill materials will be investigated in this thesis: (1) the lumpy granular soil from fresh landfills, (2) the lumpy composite soil corresponding to old landfills and (3) clay mixtures. Firstly, an artificial lumpy soil was investigated. It is a transition form between the reconstituted and natural lumpy soils. Compression, permeability and strength of lumpy materials have been evaluated based on oedometer and triaxial tests. The shear strength of the normally consolidated lumpy specimens lies approximately on the Critical State Line of the reconstituted soil. The reconstituted soil, which exists in the inter-lump voids, plays a crucial role in the behaviour of artificial lumpy materials. Similarly to the artificial lumpy soil, inter-lump voids of the natural lumpy soil are mainly closed above a relatively small stress level, which is induced by the rearrangement of the lumps. However, its limit stress state is located above the Critical State Line of the reconstituted soil, which may be caused by the diagenetic soil structure in the natural lumps. The structure transition of the lumpy granular material can be divided into three possible stages related to the stress level. Firstly, the compressibility of a fresh lumpy is relativity high due to the closure of the inter-lump voids within a low stress range. In this stage, the hydraulic conductivity is mainly controlled by the inter-lump skeleton due to the existence of macro drainage paths, while the shear strength is controlled by the reconstituted soil around the lumps. Afterwards, its compressibility decreases with the consolidation stress and the soil behaves similarly to an overconsolidated soil. The clayfill appears to be uniform visually in this stage, but its structure is still highly heterogeneous and the hydraulic conductivity is higher than that of the reconstituted soil with the same overall specific volume. Finally, the loading reaches the preconsolidation stress of the lumps, and the whole soil volume becomes normally consolidated. Isotropically consolidated drained triaxial shear tests were performed on artificially prepared specimens with parallel and series structures. The laboratory tests show that the specimens with the series structure have the same failure mode as the constituent with the lower strength; the specimens with the parallel structure have a failure plane which crosses both constituents. As a result, the shear strength of the series specimens is only slightly higher than that of the constituent with the lower strength and the strength of the parallel specimens lies between those of the constituents. Afterwards, the behaviour of an artificial lumpy material with randomly distributed inclusions is investigated using the Finite Element Method. The computation results show that the stress ratio, defined as the ratio of the volume-average stress between the lumps and the reconstituted soil within the inter-lump voids, is significantly affected by both the volume fraction and the preconsolidation pressure of the lumps under an isotropic compression path, while the volume fraction of the lumps plays a minor role under a triaxial compression path. Based on the simulation results and analysis of the two basic configurations, a homogenization law was proposed utilizing the secant stiffnesses. The compression behavior of the lumpy composite soil was analyzed within the homogenization framework. Firstly, the volume of the composite soil was divided into four individual components. The inter-lump porosity was introduced to account for the evolution of the volume fractions of the constituents, and it was formulated as a function of the overall porosity and those of its constituents. A homogenization law was then proposed based on the analysis of the lumpy structure together with a numerical method, which gives a relationship for tangent stiffnesses of the lumpy soil and its constituents. Finally, a simple compression model was proposed for the composite lumpy material, which incorporates both the influence of the soil structure and the volume fraction change of the reconstituted soil. Furthermore, a general framework for the consolidation behaviour of the lumpy composite soil was proposed based on the double porosity concept and the homogenization theory. To describe the behaviour of lumps with low stress level, a new failure line was proposed with help of the equivalent Hvorslev pressure and critical state concept. The structure effect was incorporated into the nonlinear Hvorslev surface within sensitivity framework and the generalized Cam clay model proposed by McDowell and Hau (2003) was adopted on the wet side of the critical state. A secant stiffness, defined as the ratio between the deviatoric stress and deviatoric strain, was used in the homogenization law. Finally, a simple model for the natural lumpy soil was proposed within the homogenization framework. The physical properties, compression behaviour and remolded undrained shear strength of clay mixtures were investigated by reproducing the soils artificially in the lab. Afterwards, the models for the compression and undrained shear strength of clay mixtures were proposed. The model for the strength of the clay mixture originated from simplifying the structure of a clay mixture, in which the elements of the constituents are randomly distributed in a representative elementary volume. By defining a water content ratio (the ratio of water contents between the constituents), the undrained shear strength of each constituent was estimated separately and then combined together with corresponding volume fractions. A homogenization law was proposed afterwards based on the analysis of the randomly arranged structure. A simple compression model considering $N$ constituents was proposed within the homogenization framework, which was evaluated by a mixture with two constituents
In einem Tagebau können die feinkörnigen Böden in unterschiedlichen Zustandsformen entstehen. Dies sind zum einen klumpige Böden mit einer granular ähnlichen Struktur (Pseudokornstruktur) und einer hohen Konsistenzzahl und zum anderen Mischungen aus mehreren Tonen oder Schluffen mit niedriger Konsistenzzahl. Der Zustand wird dabei massgebend von dem Transport (z.B. Länge des Förderbandes) und dem Ausgangszustand (z.B. der Anfangsscherfestigkeit) beeinflusst. Klumpige Böden entstehen bei der Abbaggerung des natürlichen Materials auf der Abbauseite, welches eine hohe Festigkeit besitzt. Alle Böden werden normalerweise ohne Verdichtung verkippt, so entstehen bei der Verkippung von klumpigen Böden grosse Makro-Porenräume zwischen den Klumpen, welche sehr luft- bzw. wasserdurchlässig sind. Nach einiger Zeit entsteht eine neue Struktur aus den Klumpen und dem Material des sich von aussen auflösenden Klumpens, welches das Füllmaterial bildet. Wenn die Festigkeit des Ausgangsmaterials niedrig ist oder lange Transportwege stattfinden, zerfallen die Klumpen. Zudem werden die Böden von verschiedenen Schichten der Abbauseite unter einander gemischt, wodurch die Tongemische entstehen. Sowohl für die Dimensionierung und Berechnung der aus den Verkippungen entstehenden Tagebaurandböschungen sowie für eine spätere Nutzung des ehemaligen Tagebaugebietes ist die Kenntnisüber das Deformations- und Verformungsverhalten von Kippenböden notwendig. Daher wurden in dieser Arbeit Tagebauböden und ihr zeitlich veränderliches Verhalten untersucht. Dabei werden diese, bezugnehmend auf den Anfangszustand, in drei typische Materialien unterschieden: (1) der frisch verkippte klumpige Boden, (2) eine Mischung aus Klumpen und Füllmaterial, welche höhere Liegezeiten repräsentiert und (3) Mischungen von feinkörnigen Ausgangsböden. Zunächst wurden künstlich hergestellte klumpige Böden untersucht. Sie bilden eine Übergangsform zwischen aufbereiteten und natürlichen klumpigen Böden. Das Kompressions- und Scherverhalten sowie die Durchlässigkeit wurden an Ödometer und Triaxialversuchen bestimmt. Das Füllmaterial, welches die Makroporen zwischen den Klumpen füllt, spielt eine entscheidende Rolle für das Materialverhalten. Ähnlich wie bei den künstlich hergestellten klumpigen Böden schliessen sich auch bei den Böden im Tagebau die Makroporenschen bei niedrigen Spannungen. Dabei werden die Klumpen umgelagert. Allerdings befindet sich die Grenze des Spannungszustandes oberhalb der Critical State Line des Füllmaterials, was möglicherweise mit den unter Diagenese entstandenen Bodenstrukturen erklärt werden kann. Die Strukturänderung der klumpigen Böden kann aufgrund des Spannungsniveaus in drei mögliche Stufen unterteilt werden. Am Anfang ist die Kompressibilität der frischen verkippten Klumpen hoch, da sich die Makroporen bereits bei geringen Spannungen schliessen. Zu diesem Zeitpunkt sind auch die Durchlässigkeiten in erster Linie von den grossen Porenräumen der Makroporen, welche als Entwässerungspfade dienen, beeinflusst. Die Scherfestigkeit hingegen, wird durch die aufgeweichten Böden an den Oberflächen der Klumpen massgebend beeinflusst. Bei höheren Konsolidationspannungen sinkt die Kompressibilität und der Boden verhält sich wie einüberkonsolidierter Boden. Obwohl die Struktur aufgrund der veränderten Klumpenoberflächen zu diesem Zeitpunkt homogener wirkt, ist die Struktur noch heterogen und die Durchlässigkeit ist höher als bei einem aufbereiteten Boden mit gleichem spezifischem Volumen (Porenzahl). Letztendlich erreicht der aktuelle Spannungszustand den derüberkonsolidierten Klumpen und der gesamte Boden verhält sich wie ein normal konsolidierter Boden. Des Weiteren wurden isotrop konsolidierte drainierte Triaxialversuche an künstlich aus zwei Ausgangsmaterialien hergestellten Proben mit parallelen und seriellen Strukturen durchgeführt. Die Laborversuche zeigten, dass die Proben mit seriellem Aufbau dieselben Gleitflächen haben, wie der Ausgangsboden mit der niedrigeren Scherfestigkeit. Die Gleitfläche der Proben mit parallelen Strukturen verlief durch beide Materialien. Es wurde festgestellt, dass die Scherfestigkeit der seriell aufgebauten Proben geringfügig höher, als die des Bodens mit der niedrigeren Scherfestigkeit ist. Die Scherfestigkeit der parallel aufgebauten Proben liegt zwischen den beiden Ausgangsmaterialien. Danach wurde das Verhalten der künstlich erzeugten klumpigen Böden mit zufällig verteiltem Füllmaterial mit Hilfe der Finiten Elemente Methode verglichen. Die Simulationen zeigten, dass unter einer isotropen Kompressionsbelastung das Spannungsverhältnis, definiert aus dem Verhältnis der Spannung des Volumendurchschnitts zwischen den Klumpen und dem Füllmaterial, deutlich durch die Volumenanteile und die Vorkonsoliderungsspannung der Klumpen beeinflusst wird. Während das Volumenverhältnis eine untergeordnete Rolle in den in Triaxialzellen unter Scherung belasteten Proben spielt. Aus den Simulationsergebnissen und den Laborversuchen der beiden Grundkonfigurationen wurde ein Homogenisierungsgesetz abgeleitet, welches die Sekandensteifigkeiten verwendet. Das Kompressionsverhalten der Mischungen aus Klumpen und Füllmaterial wurde mit Blick auf die Homogenisierung analysiert. Zunächst kann das Volumen der Mischungen in 4 individuelle Komponentenanteile zerlegt werden. Die Makroporosität zwischen den Klumpen wurde zur Entwicklung der Volumenanteile des Füllmaterials eingeführt. Sie wurde als eine Funktion der totalen Porosität und der Materialien formuliert. Auf Grundlage einer theoretischen Analyse an klumpigen Böden und unter Zuhilfenahme einer numerischen Methode wird ein Gesetz zur Homogenisierung vorgeschlagen. Dieses enthält eine Beziehung zwischen der Tagentensteifigkeit der Klumpen und seinem Füllmaterial. Abschliessend wird ein einfaches Kompressionsmodel für die Mischung aus Klumpen und Füllmaterial vorgeschlagen, welches den Einfluss der Bodenstruktur und der Änderung des Volumenanteils des Füllmaterials berücksichtigt. Darüber hinaus wurde eine allgemeine Formulierung für das Konsolidationsverhalten der klumpigen Böden mit Füllmaterial vorgeschlagen, welche sich auf das Konzept der doppelten Porosität (Klumpen und Füllmaterial) und eine Homogenisierungstheoerie bezieht. Um das Verhalten der Klumpen bei niedrigen Spannungen zu beschreiben, wird eine neue Grenzbedingung unter Zuhilfenahme der äquivalenten Hvorslev-Spannung und des Criticial State Konzeptes vorgeschlagen. Der Struktureffekt für sensitive Böden wurde in die nichtlineare Hvorslev-Oberfläche eingebaut. Das allgemein gültige Cam-Clay-Model von McDowell und Hau (2003) wurde um die nasse Seite des Critical State Konzeptes erweitert. Eine Sekandensteifigkeit, definiert aus dem Verhältnis zwischen der Deviatorspannung und der Deviatordehnung, wurde für das Homogenisieurungsgesetz ebenfalls verwendet. Abschliessend wird ein Modell für natürliche klumpige Böden vorgestellt, welches auch eine Homogenisierung beinhaltet. Die physikalischen Eigenschaften, das Kompressionsverhalten und die undrainierten Scherfestigkeiten von aufbereiten Tongemischen wurden im Labor unter Herstellung künstlicher Bödengemische untersucht. Anschliessend wurde ein Kompressions- und Schermodell für aufbereitete Tongemische vorgeschlagen. Das Modell der Scherfestigkeit der Tongemische entstand aus der Vereinfachung der Tongemischstruktur, in welcher die Elemente der Ausgangsmaterialien zufällig in dem Einheitsvolumen verteilt sind. Werden Wassergehaltsverhältnisse (das Verhältnis der Wassergehalte der Ausgangsmaterialien) definiert, kann die undrainierte Scherfestigkeit für alle Bestandteile separat geschätzt werden und dannüber die Volumenanteile bestimmt werden. Ein Homogenisierungsgesetz wurde auf Grundlage der theoretischen Analyse von zufällig angeordneten Strukturen entwickelt. Ein einfaches Kompressionsmodell, welches N-Ausgangsmaterielien bzw. Tone und eine Homogenisierung enthält, wird vorgeschlagen, und an einer Mischung aus 2 Bestandteilen im Labor validiert

Mesoporous MOFs are currently record holders in terms of the specific surface area with values exceeding 7000 m2 gˉ¹, a textural feature unattained by traditional porous solids such as zeolites, carbons and even by graphene. They are promising candidates for high pressure gas storage and also for conversion or separation of larger molecules, whose size exceeds the pore size of zeolites. The rational strategies for synthesis of mesoporous MOF are outlined and the unambiguous consistent assessment of the surface area of such ultrahighly porous materials, as well as present challenges in the exciting research field, of mesoporous MOFs are discussed. The crystallinity, dynamic properties, functional groups, and wide range tunability render these materials as exceptional solids, but for the implementation in functional devices and even in industrial processes several aspects and effective characteristics (such as volumetric storage capacities, recyclability, mechanical and chemical stability, activation) should be addressed.

Carbide-derived carbon (CDC) aerogel monoliths with very high porosity are synthesized starting from polymeric precursors. Cross-linking by platinum-catalyzed hydrosilylation of polycarbosilanes followed by supercritical drying yields preceramic aerogels. After ceramic conversion and silicon extraction in hot chlorine gas, hierarchically porous carbon materials with specific surface areas as high as 2122 m² g⁻¹ and outstanding total pore volumes close to 9 cm³ g⁻¹ are obtained. Their pore structure is controllable by the applied synthesis temperature as shown by combined nitrogen (-196 °C) and carbon dioxide (0 °C) measurements coupled with electron microscopic methods. The combination of large micropore volumes and the aerogel-type pore system leads to advanced adsorption properties due to a combination of large storage capacities and effective materials transport in comparison with purely microporous reference materials as shown by thermal response measurements.

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.

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2014.
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Para melhor compreender a formação de falhas de solidificação e de porosidade na soldagem híbrida laser - GMAW de chapas de aço com grande espessura, foram feitos ensaios com variação de diâmetro do feixe laser, de potência do feixe laser, de metal de adição, de velocidade de soldagem e com oscilação transversal do feixe laser. Esses ensaios foram realizados utilizando-se uma fonte de laser de disco com 16 kW de potência máxima e duas tochas GMAW em chapas de aço alta resistência e baixa liga que atende ao grau de qualidade X70 da API 5L e depois foram avaliados através de imagens metalográficas e de raios-X. Acredita-se que a geometria do cordão de solda tem grande influência na formação de falhas de solidificação e esse trabalho investigou a relação que há entre uma protuberância no cordão de solda e a falha de solidificação, sugerindo ainda uma forma de medir a severidade dessa protuberância: o ângulo de alargamento da protuberância. Foi verificado também como os parâmetros supracitados influenciam o ângulo de alargamento da protuberância e a formação das falhas de solidificação. Duas novas explicações para a discrepância de resultados encontrados na literatura quanto à formação da falha de solidificação foram propostas. Por fim, analisou-se a porosidade encontrada nos cordões de solda através das imagens metalográficas e de raios-X para determinar as suas principais causas na soldagem híbrida laser - GMA de chapas grossas de aço API 5L X70.

Abstract : To achieve a better understanding of the solidification flaw and porosity formation in hybrid laser - GMA welding of thick steel plates, tests were carried with varying laser beam width, laser beam power, filler metal, welding speed and with transverse beam oscillation. Those tests were carried using a 16 kW maximal power disk laser source and two GMAW torches on high strength low alloy steel plates that complies with the grade X70 from API 5L that were later analyzed through metallographic and X-ray imaging. It is believed that the weld seam geometry has a high influence on the solidification flaw formation and it was investigated in this work the relation between a bulge in the weld seam and the solidification flaw, introducing a new way to measure the severity of the bulge: the bulge widening angle. It was also verified how the aforementioned parameters influence the bulge widening angle and the solidification flaw formation. Two new explanations for the discrepancy found in the literature regarding the formation of the solidification flaws were proposed. Lastly, the porosity found in the weld seams was analyzed through the metallographic and X-ray images to determine its main causes in the hybrid laser - GMA welding of thick API 5L X70 steel plates.

La porosité d'une plaque composite carbone / époxy de type RTM est connue par tomographie X. Une méthode de détermination de cette porosité par mesure de l'atténuation des ondes longitudinales à travers l'épaisseur de cette plaque est proposée. Ces mesures sont effectuées sur des surfaces de dimensions variables (quelques cm2 à quelques mm2) et permettent l’obtention de cartographies. Une correspondance porosité (tomo X) – atténuation (onde US) est déduite et analysée en fonction de la structure du matériau composite. Dans chaque cas, on estime la qualité des relations obtenues et on en déduit les limites de validité de la correspondance porosité-atténuation. Des premiers résultats de tomographie acoustiques sont obtenus
The porosity of a composite plate in carbon / epoxy of type RTM is known by used of tomography X. A method of determination of this porosity by measure of the mitigation of the longitudinal waves through the thickness of this kind of plate is proposed. These measures are made on surfaces of different sizes (from some cm2 to some mm2) and allow the obtaining of cartographies. A correspondence porosity (tomo X) - Mitigation (US wave) is deducted and analyzed according to the structure of the composite material. In every case, we estimate the quality of the obtained relations and we deduct the limits of validity of the correspondence between porosity and mitigation. First results of acoustic tomography are obtained

Les propriétés texturales des supports sont intimement liées à l’organisation des cristallites de boehmite (AlOOH, nH2O) lors des procédés de synthèse et mise en forme. La modification de cette organisation par dispersion de la boehmite dans des alcools a pour conséquence une exaltation de la porosité extrêmement intéressante pour les applications en catalyse sensibles aux limitations diffusionnelles. La mise en place d’une voie originale de préparation des supports par dispersion de boehmite dans un mélange de solvants protiques polaires a permis de mettre en évidence un contrôle de la porosité en fonction des ratios entre les solvants. La nature du solvant influe sur la cinétique d’agrégation et donc sur l’organisation des particules. La modulation de l’encombrement stérique et de l’affinité du solvant pour la surface de la boehmite permettent de contrôler l’épaisseur de la couche de solvatation formée à la surface. En conséquence de cette microstructure particulière en dispersion, les propriétés de l’alumine finale peuvent être ajustées sur une large gamme de porosité à surface spécifique constante. L’impact sur les autres propriétés fonctionnelles du matériaux, comme les propriétés mécaniques et catalytiques a été évalué. Une approche par la micromécanique à plusieurs échelles a été élaborée et conduit à des modules élastiques proches de ceux mesurés par microindentation. L’activité en hydrodémétallation est significativement améliorée avec l’élévation de la porosité, tout en gardant une activité en hydrodésulfuration élevée. Cette démarche est prometteuse pour la prédiction des propriétés du support final à partir du contrôle de la microstructure de la dispersion
Textural properties of catalytic supports are closely related to the organization of boehmite crystallites (AlOOH, nH2O) during the synthesis and the shaping. The modification of this organization by mixing the boehmite with alcohols leads to an increase of the porosity which is very interesting for catalysis processes sensitive to diffusional limitations. A novel way of support preparation obtained by dispersing boehmite in mixed protic polar solvents allows highlighting a control of the porosity depending on the solvents ratio. The kinetic of aggregation, and hence the particles organization, is influenced by the solvent nature. The tuning of the steric effect and the affinity of the solvent for the boehmite surface allows controlling the solvation layer thickness. Consequently of this particular microstructure in dispersion, the porosity can be tuned on a wide range, while keeping a constant specific surface area. The impact on the functional properties of the support, like the mechanical and the catalytic properties, are estimated. A two-nested scales micromechanical approach was carried out and leads to elastic modulus close to the experimental one. Hydrodemetallization activity is greatly enhanced with the porosity, while preserving a high hydrodesulfurization activity. This study is promising in order to predict the properties of the final support from the control of the dispersion microstructure

Thesis (M. S.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2008.
Hess, Dennis, Committee Member ; Teja, Amyn, Committee Member ; Kohl, Paul, Committee Chair ; Allen, Sue Ann Bidstrup, Committee Co-Chair.

Les aérogels sont des matériaux ultra-poreux et nanostructurés aux possibilités d’applications variées. Une nouvelle génération d’aérogels à base de polysaccharides est aujourd’hui en plein essor : les bio-aérogels. Ils sont particulièrement prometteurs pour leur respect de l'environnement et leur biocompatibilité. De nos jours, la production de bio-aérogels sous forme de monolithes est maîtrisée. Pour optimiser leur procédé de fabrication et pour répondre à des besoins spécifiques d'applications (pharmaceutiques, alimentaire, absorption ou adsorption, etc), les aérogels doivent avoir la forme de particules. Ce travail était focalisé sur la préparation et caractérisation de billes d’aérogels à base de cellulose et a été réalisé dans le cadre du projet Européen « Nanohybrids ». Deux objectifs principaux ont été atteints. Le premier était la préparation et la compréhension des propriétés de nouveaux matériaux, tout en diminuant leurs coûts de production. Deux types de matériaux poreux ont été produits et étudiés : • Des xérogels à base de cellulose (en évitant le séchage sous CO2 supercritique), avec des propriétés comparables à celles de leurs homologues aérogels (densité autour de 0,12 g cm-3 et surface spécifique jusqu'à 300 m² g-1). • Des aérogels à base de pâte à papier. L'influence de chaque composant de la pâte (cellulose, hémicellulose, lignine) et de leur teneur sur la structure et les propriétés des aérogels a été évaluée. Le deuxième objectif était le développement de méthodes de mise en forme d'aérogels de cellulose sous forme de billes de différentes tailles. Deux techniques ont été appliquées avec succès : • Le "JetCutting" : des billes d’aérogels à base de cellulose et de pâte à papier, de taille variant de centaines de micromètres à quelques millimètres, dissout dans deux types solvants (NaOH-eau et liquides ioniques) ont été obtenus. • L'émulsification : des particules d’aérogels de cellulose d’une dizaine de micromètres ont été préparé par le développement d'une nouvelle méthode d'émulsification-coagulation
Aerogels are ultra-porous and nanostructured materials with a wide range of applications. Bio-aerogels is a new generation of polysaccharide-based aerogels. These fast developing materials are particularly promising for their environmental friendliness and biocompatibility. Nowadays, the production of bio-aerogels in the form of monoliths is mastered. To optimize their manufacturing process and to meet specific application needs (pharmaceutical, food, absorption or adsorption, etc.), aerogels must be in the form of particles. This work focused on the preparation and characterization of cellulose aerogel beads and was conducted in the framework of the European project "Nanohybrids". Two main objectives were achieved. The first was the preparation and understanding of the properties of new materials while reducing their production costs. Two types of porous materials were produced and studied: • Cellulose-based xerogels (obviating drying under supercritical CO2), with properties comparable to those of their aerogel counterparts (density around 0.12 g cm-3 and specific surface area up to 300 m² g-1). • Pulp-based aerogels. The influence of each pulp component (cellulose, hemicellulose, lignin) and their content on the structure and properties of aerogels was assessed. The second objective was the development of methods for shaping cellulose aerogels into beads of different sizes. Two techniques were successfully applied: • JetCutting: aerogel beads based on cellulose and pulps, varying in size from hundreds of micrometres to a few millimetres, dissolved in two types of solvents (NaOH-water and ionic liquids) were obtained. • Emulsification: cellulose aerogel particles of about few tens of micrometres were prepared by the development of a new method of emulsification-coagulation

In the field of energy storage, two main factors are essential for storage devices: the power density and energy density, both of which can be provided by supercapacitors. Supercapacitors offer a power to mass and cycle life greater than batteries and an energy density that is much greater than capacitors, making them appropriate for use in portable electronics, hybrid vehicles, and similar applications. Power to mass and discharge time are still not fast enough, however, for use in, for example flash cameras or cell phones or power quality applications. Charging time and power in these devices are often limited by the rate of ion transport into the electrodes. The hypothesis proposed in this thesis is that making electrodes porous increases their speed and hence power, but may reduce the capacitance at the same time. So in order to investigate the hypothesis various electrodes (e.g. pure polypyrrole (PPy) and its composites (carbon nanofiber (CNF) plus PPy) with varying porosities are made. Techniques used to investigate these samples are Cyclic Voltammetry (CV), Ionic Conductivity (IC) measurements, Electrochemical Impedance Spectroscopy (EIS) and Nuclear Magnetic Resonance (NMR) measurements. Through these techniques, it is found that the time constant reduces significantly (by ~ 1 x10⁴ times) for very porous electrodes as expected from hypothesis, and the capacitance reduces by a small factor (by ~ 7 times) compared to that. Even for least porous samples a huge time constant reduction (by ~ 37 times) compared to pure PPy is achieved with only ~ 2 times reduction in volumetric capacitance. The plausibility of these improvements is checked by analyzing the rate-limiting factors in ion transport and it is found that ionic time constants at very high porosities are not representative of the speed of the full cell. The reason for this is due to solution resistance becoming a rate-limiting factor for porosities more than ~ 50%. In this case, any improvements in speed (power) can be achieved by reducing that resistance. Other methods for further improving the power densities are also suggested and they include reducing the separator and electrode thicknesses for instance.

In the strive towards reduced fuel consumption and lower emissions, low structural weight is becoming a key factor in the design of advanced vehicle and aerospace structures. Whereas most traditional construction materials are seemingly reaching their limitations, composite materials with their high specific properties offer possibilities to further reduce weight. In high demand structural applications, the quality of the composite material is of utmost importance, requiring the material to be void free and the matrix well distributed as a binder for the load carrying reinforcement. To achieve proper wetting of the fibres, knowledge of the flow resistance of the porous fibre reinforcement is required. It is normally expressed in terms of permeability. Fibre reinforcements in composite materials are normally regarded as a heterogeneous porous media since both fabric and tows are porous but at different length scales. In order to numerically compute the permeability of such media, one of following two approaches can be used. Either filaments are added one-by-one into the modelled geometry (resolved model) or the tows are considered as porous homogenised media. In the latter case expression for the intra-tow permeability is needed. In this thesis, a porous homogenised tow model is benchmarked with a resolved model to the level of refinement possible without being too expensive computationally. Based on this approach, the permeability of complex three- dimensional (3D) textiles is computed utilizing computational fluid dynamics (CFD) analysis. The effect of inter- and intra-tow porosity on the overall permeability of 2D and 3D structures is analysed and discussed in relation to contradictions found in past studies. A clearer picture of the problem is presented, which will be helpful in future modelling and understanding of the permeability of complex structures. In an experimental study, the overall fibre volume fraction as well as the tow compaction are varied and their influence on the permeability is measured. Experimental studies show good agreement with numerical simulations. The interlaminar shear strength of thermoplastic composite materials is studied and the influence of specimen size is examined. Using finite element (FE) analysis it is shown that size effects may be partly due to statistical effects and partly due to the higher number of composite layers in thicker specimens. The effect of processing on the interlaminar delamination toughness of car-bon/polyamide 12 (C/PA12) is studied. It is observed that processing conditions have vital effect on the interlaminar delamination of thermoplastic composites. The mode I crack energy release rate (GIc) of C/PA12 is found to be 15 times higher than for conventional thermoset based composites and 1.5 times higher than for a thermoset composite with stitched reinforcement through the thickness. The best performing C/PA12 composite is manufactured in a hydraulic press equipped with a cold tool, thereby showing potential for both cost and time efficient manufacturing.

QC 20150602