Thesis (M.Sc. (Physical Chemistry))--Mahidol University, 1982.

Thesis (Master)--İzmir Institute of Technology,İzmir, 2005 / Includes bibliographical references (leaves. 84-89).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1958. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 71-76).

In this study, coal combustion by-products mainly fly ash, commercial fibers and a natural fiber i.e., human hair were applied to stabilize the kaolinite clay and local Carbondale soil i.e., silty clay. During recent decades, the demand for infrastructures such as highways, buildings, bridges have greatly increased, especially in the areas where population was growing rapidly. All of these infrastructures need a stable foundation and in many cases the original land couldn't sustain the load from the infrastructures. In such situation, soil stabilization becomes an essential step before the foundation is laid. There are several ways to stabilize soil, viz., mechanical stabilization, chemical stabilization, stabilization by inclusion and confinement etc. It has been reported by several researchers that fly ash and fibers can significantly improve the strength of soil. Fly ash and natural fiber i.e., human hair are both waste materials, and commercial fibers are low-cost compared to other soil stabilizers. In this study, class C fly ash was used to stabilize commercially available clay i.e., Kaolinite; while both human hair and commercially available fibers (e.g., glass fiber and plastic fiber) were used to stabilize Kaolinite and Carbondale local soil. Based on this research, it could be concluded that the class C fly ash can improve the Unconfined Compressive Strength (UCS) value of Kaolinite clay significantly; fibers also could increase the UCS value of both Kaolinite and Carbondale local soil. While, the tensile strength of Kaolinite and Carbondale local soil sometimes increases or decreases depending on the percentages of fiber content used into Kaolinite and Carbondale local soil. The current research on soil stabilization by fly ash and those fibers may provide a new possibility for soil stabilization.

A utilização de argila como matéria-prima acompanha a evolução humana desde a Pré-história, ao longo do tempo o ser humano vem utilizando as argilas para produzir objetos variados, como vasos, estatuetas e tijolos. Nos dias atuais muitas indústrias utilizam os diferentes tipos de argilas encontradas na natureza. Neste trabalho foi utilizado um caulim proveniente da Bahia e o outro caulim proveniente de São Paulo. Os caulins foram caracterizados através das técnicas e ensaios de difração de raios X (DRX), microscopia eletrônica de varredura (MEV), espectroscopia por energia dispersiva (EDS), microscopia estereoscópica (MO), infravermelho (IV), análises térmicas (TG e DSC), fluorescência de raios X (FRX), análise química (IQ), análise granulométrica, área superficial (BET), inchamento de Foster, incorporação de solventes, capacidade de troca catiônica (CTC), ensaios cerâmicos, ensaio de adsorção, quantificação da matéria orgânica, ensaio de plasticidade, viscosidade Fann e umidade base seca e base úmida. Todos os resultados foram utilizados para realizar uma comparação entres as propriedades dos dois caulins selecionados para este estudo. Em seguida os caulins foram submetidos ao processo de organofilização. Os resultados mostram que as duas argilas são compostas pelo argilomineral caulinita, todos os resultados apresentaram-se compatíveis com argilas cauliníticas e a organofilização dos caulins foi comprovada principalmente pelos resultados do infravermelho (IV) e teste de inchamento de Foster. / The use of clay as raw material accompanies human evolution since the prehistory, over time humans have been using clays to produce various objects, such as vases, figurines and bricks. Now days many industries use different types of clays found in nature. The clays are formed by a claymineral or a mixture of various clayminerals, there is a certain content of alkali and alkaline earth elements, have low particle size and acquires plasticity when in contact with water, also have impurities such as organic matter, soluble salts, quartz particles, mica and other minerals, and some residual amorphous minerals. In this study was used a kaolin from Bahia and other kaolin from São Paulo. The Kaolins were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), stereoscopic microscopy (SM), infrared (IR) , thermal analysis, X-ray fluorescence (XRF), chemical analysis (CA), particle size analysis, surface area (BET), Foster swelling, incorporation of solvent, cation exchange capacity (CTC), ceramic tests, adsorption, organic matter, plasticity, Fann viscosity and humidity. All results were used to make a comparison between the two kaolins properties. Then the kaolins were subject to an organophilization process. The results show that both clays are composed of kaolinite with properties compatible with those of kaolins. Organophilization mainly been proven by the results of infrared (IR) and Foster swelling test.

The system kaolinite - carbon black consisting of cheap precursors has been investigated, in terms of its potential to form A1₂ O₃ - SiC composites. The carbothermal reduction process of mullite and silica was studied, in detail, in the range 1275° to 1810° C and over different periods, both under sintering as well as hot-pressing conditions. It was established that the reduction of mullite and silica starts around 1450° C, where the rate of reaction is very slow. Until about 1800° C during the reduction of mullite, SiO₂ gets preferentially reduced, thus forming a composite ceramic consisting of SiC and A1₂ O₃ phases. The kinetics of the formation of SiC + A1₂ O₃ were followed in the range 1590° - 1660° C and it was noted that under hot-pressing conditions they follow a contracting cylinder model. The rate of reaction increased with the increase in temperature and followed a parabolic path with time because of the geometry of the hot-pressed specimens at each temperature. This indicated that the gas diffusion in and out of the system along the edges of the cylindrical specimens is the rate controlling step. The activation energy of the reduction process was calculated to be 922 KJ/mole. The application of pressure prior to the carbothermal reduction process seemed to be not favourable for the formation of SiC and A1₂ O₃, however, when applied after the beginning of soaking period, this greatly improved the densities and formation of SiC and A1₂ O₃. The microstructure of the samples was analysed using SEM and TEM. It was found that the grain size of the composite ceramic was of the order of 0.2μm. SiC was present mainly in the form of fine platelets. Finally, the isothermal compaction behaviour of the system was studied under a constant pressure in the temperature range 1200° C - 1800° C, during which the formation and carbothermal reduction of mullite and silica took place. A mathematical model based on the least squares fitting was used to fit the compaction curves. Due to the complex nature of the compaction data an empirical approach was used to interpret the data and a viscoelastic model was developed. It was found that the interactive-double-Kelvin unit having two elastic and two viscous components explained the type of compaction behaviour observed in the kaolinite + C system. One of the viscous components (η₁) and one of the elastic components (M₁) were found to be temperature sensitive. It is concluded that starting from the cheap precursors (kaolinite and carbon black) a particulate composite of A1₂ O₃,-SiC can be produced by hot-pressing technique. SiC-whisker formation is not encountered in this system. The very fine grain size of the paniculate composite, resulting in a small flaw size, should provide the composite ceramic with good mechanical properties. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Brick clay deposits, in the area north of Cape Town, were formed as a result of three independent geological processes. The intrusion of the syn- to post tectonic granitoids into micaceous (indicated by the absence of halloysite; Orris, 1998), feldspathic Malmesbury sandstone beds, approximately 500 Ma ago, created a hydrothermal vein structure, which enriched the shale with feldspar/kaolinite and quartz, restricted to the vein network. This was followed by extensive in-situ weathering of these hydrothermally altered rocks resulting in residual kaolin deposits, the effects of which were more pronounced along the more permeable shear zones. The final process, formation of ball clay deposits, initiated by the erosion of the primary kaolinite deposits, which have been transported in water, together with organic material, to shallow depressions where clays were deposited. Brick clay is exclusively used for the manufacturing of clay brick products and must derive its value from the sales revenue generated from these products. Evidence from the two exploration programs described, suggests that the clay deposits explored has no value as individual deposits as the clay from both deposits lack specific ceramic properties to successfully manufacture clay bricks. It is however clear that if the clay from the two deposits is mixed in specific proportions; body mixes with ceramic properties suitable for light coloured clay face brick manufacturing is possible. The value of the beneficiated product, clay bricks, may then be used to determine the value of both clay deposits. Discounted Cash Flow Models (DCFM) and Net Present Values (NPV) were used to determine the fundamental value of the clay deposits explored, as it determines the time value of money (Kernot, 1999). These models clearly showed the dependency of the value of clay brick deposits on variables such as raw material quality, capital expenditure and clay brick yields. Geological, chemical and ceramic knowledge of individual brick clay deposits and the management of the raw materials extracted from these deposits is key to the profitable manufacturing of clay bricks. Risks, at the quarrying level, related to these aspects need to be managed to ensure the profitable and efficient functioning of the entire brick production process. / Dissertation (MSc (Earth Science Practice and Management))--University of Pretoria, 2007. / Geology / MSc / unrestricted

Porous silica-based nanocomposites are promising ceramics, as they exhibit high specific surface area, highly porous network, and a surface that can be easily functionalized. This dissertation describes the results of a study on the formation and properties of porous silica nanoparticle-based composites, using techniques of freeze casting and sintering. Kaolinite platelets and silica nanorods were added into the nanoparticle system, and their effects on modifying the porous microstructures and physical properties were investigated. During freeze casting, homogeneous microstructures with highly interconnected porosity are fabricated. Kaolinite addition results in large and more interconnected pores, while added silica nanorods cause a pore morphology evolution from circular to elongated spherical pores with increasing aspect ratio. The specific surface areas (area/mass) of the particles are conserved during freeze casting and values for the resulting composites can be accurately predicted using the area and mass of the components assuming conservation of area. Both kaolinite platelets and silica nanorods effectively improved the strength of the freeze cast green composites as they distribute any applied stress over a larger portion of the sample. Upon sintering, added kaolinite is found to modify the sintering behavior of the silica nanoparticles and a transitioning interfacial phase is identified when sintering temperature is above 1250 °C. This new phase contributes to the further enhancement of strength and this strengthening effect depends on composition and initial solids loading. After sintering at 1250 °C for 1 h, a ceramic containing 10 vol% kaolinite and 8 vol% silica has a maximum strength while maintaining a ~69% porosity. The kaolinite-silica composites with lower solids loading exhibit faster sintering (e.g. larger shrinkage, more extensive thickening of the pore walls), which, in turn, results in a rapid increase in mechanical strength. Based on the understanding of the composite properties and the underlying principles, a novel method for creating nanocomposites with precisely controllable specific surface area is developed. With repeated nanoparticle suspension infiltration, freeze drying, and sintering, the specific surface area can be varied from less than one to well over 100 m2/g, demonstrating potential application as liquid membranes. / Ph. D.

Results are presented of an investigation into the effect of the anion and cation of various catalytic additives on the mullite development in a Georgia Kaolin. The sodium and potassium compounds investigated were found to be poor catalysts. The calcium compounds were very good catalysts while the lithium compounds ranged from poor to very good for lithium chloride. It was found that the catalysis of mullite is affected by the anion although its effect is not as pronounced as that due to the cation. / Master of Science

Les latérites couvrent plus de 30% des surfaces émergées. Comprendre leur évolution future est essentiel pour prédire les changements qui affecteront le fonctionnement de la Zone Critique dans les siècles à venir. La littérature a pu montrer que les horizons indurés de ces sols comportaient plusieurs générations de minéraux secondaires qui pouvaient être reliées à différents événements paléoclimatiques. Des études isotopiques ont montré que les horizons non indurés de ces sols pouvaient aussi posséder des générations distinctes de minéraux secondaires. La datation par Résonance Paramagnétique Électronique, a été appliquée sur des kaolinites de latérites dans le but d’identifier si ce minéral possède bien plusieurs générations au sein d’un même profil et si ces dernières étaient corrélables avec des événements paléoclimatiques globaux ou régionaux. Au cours de cette thèse, deux régolithes du Plateau du Karnataka (Inde), quatre du bassin du Rio Négro (Brésil) et un de la région de Syerstone (Australie) ont été étudiés. Les résultats de ces datations ont permis de distinguer différentes générations de kaolinites au sein de chacun des profils étudiés. Ces dernières sont par ailleurs toutes corrélables avec des périodes de fortes précipitations liées aux évolutions climatiques régionales et/ou globales. Ces résultats confirment aussi l’existence du phénomène de rajeunissement profils latéritiques au cours des temps géologiques. Le travail de cette thèse corrobore l’hypothèse de l’évolution épisodique de ces sols tropicaux et souligne leur importante stabilité dans les temps géologiques. / Laterites are covering a third of the continental surfaces. Understanding their evolution through the ongoing climate change is critical to predict the future Critical Zone transformation. Laterite duricrusts can contain several generations of secondary minerals that can be correlated with distinct paleoclimatic events. Isotopic studies showed that loose laterites may also be formed by several generations of secondary minerals. The objective of this PhD was to confirm that loose laterites contain several generations of kaolinites and that they formed during regional and/or global paleoclimatic events. With this aim in view, a recent dating methodology, the Electron Paramagnetic Resonance dating of kaolinites, was used on tropical regolith profiles from three continents with distinct geodynamic histories: India (Karnataka plateau), South America (Rio Negro basin, Brazil) and Australia (Syerstone region, New South Wale). The data set of this PhD confirms that a regolith contains several generations of kaolinites. All the identified generations of the present study can be correlated with regional paleoclimatic events or with tropical weathering favourable periods initiated by global paleoclimatic trends. Kaolinite generations formed preferentially during high precipitations periods and result from the rejuvenation of laterite profiles. The results of this PhD confirm that laterites have an episodic evolution.