Dissertations / Theses on the topic 'E. Reactive infiltration'
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San, Marchi Christopher William. "Processing of aluminum-nickel intermetallics by reactive infiltration." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43369.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1997.Includes bibliographical references (p. 107-111).
by Christopher William San Marchi.
Ph.D.
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Ventakesh, T. A. 1970. "Reactive infiltration processing and compression creep of NiAl and NiAl composites." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50458.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1998.Includes bibliographical references (p. 116-118).
Reactive infiltration processing of bulk and composite NiAl was investigated with powder and wire preforms of nickel. Inhomogeneous microstructures were often obtained with powder preforms because their high surface-to-volume ratio, low permeability, and irregular infiltration paths lead to simultaneous infiltration and reaction. Homogenous NiAl could be obtained with nickel-wire preforms which had a lower surface-to-volume ratio, higher permeability, and regular infiltration paths, because infiltration was completed before the onset of reaction. Composites with continuous tungsten (W) and sapphire fibers were also successfully fabricated by reactive infiltration, while composites with molybdenum particulates and short-fibers showed significant dissolution in NiAl. The high-temperature uni-axial compression creep behavior of uni-directionally reinforced continuous fiber composite materials was investigated using NiAl-W as a model system for the case where both the NiAl matrix and the W fiber underwent plastic deformation by creep. The creep behavior of the constituents NiAl and W and NiAl composites reinforced with 5-20 volume % W was characterized at 1025 °C and 715 °C. At 1025°C, the NiAl-W composites exhibited three stage creep behavior with distinct primary, secondary, and tertiary creep, wherein the composite creep-rate decreased monotonically, remained constant, and increased rapidly, respectively. At 715C, the NiAl-W composites exhibited insignificant primary and tertiary creep but significant secondary creep. Microstructurally, primary and secondary creep were characterized by pure uni-axial compression of W fibers while brooming, bulging, buckling, and kinking were four fiber deformation modes that contributed to tertiary creep. The composite primary creep was modeled by solving for transient stress-states while loads transferred from the weaker phase (matrix) to the stronger phase (fiber) as the composite transitioned from the elastic state present at loading to steady-states attained at later times. The effects of primary creep of the constituents on the primary creep of the composite were also captured. Composite primary creep strains were predicted to be significant at high applied composite stresses and for high fiber volume fraction composites, while the composite primary time was uniquely related to the composite steady-state creep-rate by a power-law at a given temperature and for the stress range investigated. Good correlation between the primary creep model predictions and experiments was obtained when the observed composite steady-state creep behavior converged to the McLean steady-state. The composite secondary creep was observed to correlate reasonably well with the rule-of-mixtures model developed by McLean. The composite tertiary creep was modeled by solving for global or local kink-band evolution with composite deformation respectively contributing to fiber buckling or kinking. The model predicted the critical threshold strain for the onset of tertiary stage to be most sensitive to the initial kink angles while being relatively insensitive to the initial kink-band heights and varied inversely with the volume fraction of fiber in the composite. Reasonable correlation between the model and experiments was obtained when the observed composite steady-state correlated well with the McLean steady-state.
by T.A. Venkatesh.
Ph.D.
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Caccia, Mario. "Synthesis and Processing of SiC-based Composite Materials by Reactive Infiltration." Doctoral thesis, Universidad de Alicante, 2016. http://hdl.handle.net/10045/72732.
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ZHOU, HONG. "KINETICS, PROCESSING, AND PROPERTIES OF Si/SiC COMPOSITES FABRICATED BY REACTIVE-MELT INFILTRATION." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin994941745.
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Kütemeyer, Marius [Verfasser], and D. [Akademischer Betreuer] Koch. "Development of Ultra High Temperature Matrix Composites using a Reactive Melt Infiltration Process / Marius Kütemeyer ; Betreuer: D. Koch." Karlsruhe : KIT-Bibliothek, 2021. http://d-nb.info/1230475699/34.
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Fatehi, Pouladi Soheil. "Phosphorus Removal from Domestic Wastewater Using Dual Reactive Materials Polonite® and Absol®." Thesis, KTH, Miljögeokemi och ekoteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-95429.
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Private wastewater treatment facilities release tons of phosphorus to the aquatic environment due to the insufficient removal efficiency in conventional soil infiltration systems. Reactive filter materials have demonstrated promising P removal rates. Laboratory-scale column experiments were carried out using Absol® and Polonite® in dual infiltration media and results were compared with Polonite® functioning as the only layer of reactive filter material. Two sets of experiments were arranged with layer lengths of 5 cm and 15 cm which were operated for 50 and 119 days respectively. Columns with an additional layer of Absol® demonstrated very good average removal rates of 85.99 % and 99.13 % in both experiments while the effluent in the former exceeded the maximum allowed P concentration shortly after half of the total time of the experiment. On the other hand, O-P concentration in collected samples from dual filter media with 15 cm layers of Absol® and Polonite® (column B1) was as low as 0.04 mg/l after 119 days of operation exhibiting high potentials for Absol® in local wastewater treatment. Levels of pH in treated samples showed a decreasing trend in all columns which was similarly simultaneous with high removal rates observed in B1.
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Valhondo, Cristina. "A reactive barrier to enhance the removal of emerging organic compounds during artificial recharge of aquifers through infiltration basins." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/405794.
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Artificial recharge of aquifers through infiltration basins (AR) improves water quality and in- creases groundwater resources, which make of it an appropriate technique for the renaturalization of waters affected directly or indirectly by wastewater effluents. Emerging organic compounds (EOCs), typically present in such waters, are mainly reduced during AR by sorption and biotrans- formation.
We installed a reactive barrier in an infiltration basin (5000 m2) to enhance the removal of EOCs in the recharge water. The barrier consisted of sand, vegetable compost, iron oxide and clay. Vegetable compost was aimed at: 1) release organic carbon to be used as a carbon source by the microbial community thus promoting the generation of diverse redox conditions, and 2) to adsorb neutral EOCs. Clay and iron oxides were aimed at increasing sorption sites for cationic and anionic EOCs, respectively.
Field application of such a design was tested by comparing the redox indicators and behavior of EOCs prior and after the installation of the reactive barrier. Residence time distributions of the recharge water at the monitoring points were obtained by a pulse tracer test. These distributions were used for calibrating a conservative transport and flow model of the aquifer. Finally, first order rates and retardation factors of several EOCs were estimated by fitting model outputs to observed concentrations. The estimation of the first order decay rates and retardation factors of several EOCs allowed the comparison of such values with values reported from other field sites and column experiments.
The reactive barrier succeed in releasing organic carbon and achieving diverse redox condi- tions. The transformation of most EOCs was enhanced after the installation of the reactive barrier. In fact, first order rates and retardation factors were higher in the reactive barrier than in the rest of the aquifer and similar or higher than those from literature.
In summary, addition of proposed reactive barrier significantly enhanced the performance of artificial recharge via infiltration basins, thus contributing to the renaturalization of recharged waters.La recarga artificial de acuíferos a través de balsas de infiltración (AR) mejora la calidad del agua y aumenta recursos de aguas subterráneas, convirtiéndola en una técnica apropiada para la renaturalización de las aguas afectadas directa o indirectamente por los efluentes de aguas residuales. En este tipo de aguas la presencia de compuestos orgánicos emergentes (EOCs) es más que frecuente. Durante la recarga artificial este tipo de compuestos es eliminado principalmente debido a la adsorción y a la biotransformación. Para mejorar la eliminación de los EOCs durante la infiltración del agua de recarga se instaló una barrera reactiva en una balsa de infiltración. La barrera consistía en arena, compost vegetal, óxidos de hierro y arcilla. La finalidad del compost vegetal era por un lado la de aportar carbono orgánico disuelto para ser utilizado como principal fuente de carbono por la comunidad microbiana promoviendo así la generación de diversas condiciones redox, y por otro lado la de adsorber EOCs neutros. La Arcilla y los óxidos de hierro se pusieron con la intención de aumentar los sitios de adsorción para los EOCs catiónicos y aniónicos, respectivamente. La efectividad de la barrera en el campo se estudió comparando el comportamiento de los indicadores redox y de los EOCs antes y después de la instalación de la barrera. Mediante un ensayo de trazadores tipo pulso se obtuvieron las distribuciones de los tiempos de residencia del agua de recarga a los puntos de observación. Estas distribuciones se utilizaron para calibrar un modelo de flujo y transporte conservativo del acuífero. Por último, las tasas de degradación de primer orden y los factores de retardo de varios EOCs se estimaron mediante el ajuste de los resultados del modelo con las concentraciones observadas. Las tasas de degradación y los factores de retardo estimados se compararon con valores encontrados en la bibliografía. La barrera reactiva cumple su función aportando carbono orgánico y generando diversas condiciones redox. Muchos de los EOCs estudiados mostraron una mejor transformación cuando la recarga se realizó con la barrera reactiva. Las tasas de degradación y factores de retardo estimados en la barrera son mayores que los estimados para el resto del acuífero, y del mismo orden o superiores a los encontrados en la bibliografía. En resumen, la barrera reactiva propuesta mejora significativamente el rendimiento de la recarga artificial a través de balsas de infiltración, contribuyendo así a la renaturalización de las aguas recargadas
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Richet, Nicolas. "Elaboration et caractérisation d'une protection anti-oxydation pour matériaux carbonnes : le système HfB(2)-SiC." Limoges, 2003. http://www.unilim.fr/theses-doctorat/2003LIMO0023/html/index-frames.html.
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L’objectif de ce travail a été la réalisation et la caractérisation d’une protection contre l’oxydation de matériaux carbonés, constituée d’une couche composite HfB2SiC et d’une couche d’accrochage de SiC. Le procédé d’élaboration utilise l’infiltration de silicium liquide dans une préforme poreuse constituée de grains de HfB2 et de carbone issu de la décomposition d’une résine. La réaction entre le silicium et le carbone forme une matrice de SiC et à l’interface le silicium réagit avec le substrat pour donner SiC et assurer un accrochage chimique et mécanique. Les conditions d’élaboration ont été étudiées afin de réaliser un revêtement compact et homogène. La microstructure obtenue se compose de grains de HfB2 et de nanoparticules de SiC mise en évidence par microscopie électronique en transmission. Une phase intermédiaire contenant Hf-B-Si-C a été détectée, par spectrométrie Auger, en périphérie des grains de HfB2. Le comportement à l’oxydation a été étudié dans un large domaine de pression d’oxygène (1-200 mbar) en montée linéaire de température et en régime isotherme. Deux domaines correspondant respectivement à l’oxydation de la phase intermédiaire vers 600°C-700°C et des nanoparticules de SiC vers 900-1000°C, conduisent à la formation d’un verre borosilicaté cicatrisant. La présence de B2O3 à haute température favorise la dissolution de HfO2 dans le verre. La phase vitreuse stable à très haute température constitue alors une barrière de diffusion à l’oxygène de quelques dizaines de microns. En régime isotherme, la cinétique tend rapidement vers un régime parabolique très lent jusqu’à 1700°C. A basse pression partielle d’oxygène un domaine d’oxydation active apparaît. La comparaison avec le carbure de silicium montre que le verre formé est plus stable que la silice pureThe aim of this work is the elaboration and the caracterisation of HfB2SiC oxidation protection coating for carbon based materials. Silicon carbide is formed by reactive infiltration of silicon through a porous carbon/HfB2 grains layer. The coating microstructure is composed of HfB2 grains surrounded by SiC nanoparticles and a phase containing Hf-B-Si-C at the interface between HfB2 and Sic. The oxidation behaviour was studied between 1 and 200 mbar by linear increase of temperature and under isothermal conditions. A sealing refractory glass, more stable than pure silica, is formed. The oxidation kinetic follows very quickly a slow parabolic law up to 1 700°C
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Quet, Aurélie. "Composites de friction à matrice céramique : relation composition / structure / comportement tribologique." Bordeaux 1, 2007. http://www.theses.fr/2007BOR13512.
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Les composites C/C sont acutellement les matériaux les mieux adaptés aux exigences du freinage aéronautique. Ils présentent cependant un taux d'usure accru pour les freinages de taxiage. Les composites à matrice SiC se caractérisent par un lissage de cette bosse d'usure observée aux basses températures mais ils ne satisfont pas aux exigences du freinage de détresse. L'objectif de la thèse est d'introduire un autre carbure que le SiC dans la matrice des composites de friction et d'évaluer son influence sur le comportement tribologique des composites élaborés. Des composites C/C-ZrC et C/CTiC ont ainsi été élaborés via le procédé RMI (Reactive Melt Infiltration). Ces matériaux ont été caractérisés à travers des analyses morphologiques, chimiques et structurales. Une décohésion est présente à l'interface matrice de carbone/carbure. L'utilisation d'alliages, notamment à base de silicium, permet de limiter ce phénomène de décohésion. Les matériaux éléborés ont ensuite été testés sur un banc de simulation de freinage. Les composites C/C-ZrC e C/CTiC satisfont les conditions du RTO. Cependant, les composites à matrices ZrC montrent une usure très élevée à haute température en relation avec leur comportement à l'oxydation. Les composites à matrice TiC présentent une usure acceptable à haute température et une troncature de la bosse d'usure observée aux faibles températures, ce qui est lié à des coefficents de frottement faiblesC/C composites are nowadays the most suitable materials for needs of aircraft braking. However, they show a high wear during taxiing. SiC matrix composites are characterised by a smoothing of the wear peak noticed at low temperatures but they don't meet requirements of rejected take-off (RTO). The aim of this work is to put another carbide than SiC in the matrix of friction composites and to assess its influence on tribological properties of materials. C/C-ZrC and C/C-TiC composites were manufactured using RMI processing route (Reactive Melt Infiltration). Materials were characterised with mophological, chemical and structural analysis which reveal especially a decohesion between carbon phase and carbide phase. This gap can be limited using alloys as Zr-Si and Ti-Si alloys. Triboligical behaviour of the resulting materials was then investigated with an inertial dynamometer simulating brake stops. C/C-ZrC and C/C-TiC composites meet RTO requirements. Neverless, ZrC matrix composites have a high wear for high temperature brake stops linked to their oxidation behaviour. TiC matrix composites present moderate wear at high temperature and a lower wear at low temperature compared to C/C composites in relation to low friction coefficients
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Mills, Kevin. "The response of reactive clay soils to wetting agents in the presence of active vegetation." Thesis, Queensland University of Technology, 1998.
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Eveborn, David. "Bed filters for phosphorus removal in on-site wastewater treatment : Removal mechanisms and sustainability." Licentiate thesis, KTH, Land and Water Resources Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12048.
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For many surface waters, phosphorus (P) leaching is a serious problem that should be minimized to prevent eutrophication. In Sweden there is a demand for physical and technical development of high-performance P removal techniques to reduce phosphorus leaching from on-site wastewater treatment systems to the Baltic Sea. However, although these systems are designed to reduce eutrophication there are also other environmental impacts to be considered when implementing them in on-site systems; energy use and global warming potential are two examples. This study has investigated several bed filter materials (reactive media and natural soils) for their total environmental impact (in commercial applications) as well as for the predominating chemical phosphorus removal mechanisms. The use of life cycle assessment revealed that several reactive bed filters are relatively energy-consuming due to the material manufacturing process. Characterization of phosphorus compounds in used reactive media provided evidence for calcium phosphate precipitation as the predominating P removal mechanism in alkaline filter materials. However, in soil treatment systems with noncalcareous soils, batch experiments and extractions suggested that aluminium compounds were important for P removal. According to mass balance calculations that compared accumulated P with the estimated P load in a soil treatment system, the long term P removal capacity was very low; only 6.4 % of the applied phosphorus had been removed during 16 years of operation.
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Liégaut, Caroline. "Élaboration de composites à matrice céramique ultra-réfractaire résistants aux très hautes températures sous flux gazeux." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0035/document.
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Les composites de type Cf/C sont utilisés en tant que pièces structurales dans les propulseurs spatiaux du fait de leurs excellentes propriétés mécaniques dans le domaine des très hautes températures. Néanmoins, l’atmosphère oxydante et corrosive créée lors du décollage des lanceurs et les hauts flux gazeux dégradent ces matériaux. Afin d’améliorer les performances de ces matériaux vis-à-vis de l’oxydation/corrosion, une protection composée de céramiques ultra-réfractaires (dites UHTC) peut être appliquée. Pour une efficacité de protection optimale, des phases UHTC ont été introduites en tant que constituants de la matrice. Dans ces travaux de thèse, la matrice a été réalisée par l’intermédiaire d’un procédé d’élaboration en phase liquide combinant : (i) l’introduction de poudres et (ii) la densification par infiltration réactive d’un métal fondu. La composition de la matrice appartient au système (B;C;Si;Zr). La caractérisation des matériaux après élaboration a permis de comprendre les mécanismes d’infiltration et les réactions permettant de mieux contrôler la composition chimique et la répartition des phases. Des essais sous torche oxyacétylénique ont été utilisés pour se placer dans des conditions proches de l’application visée. La caractérisation post-test des matériaux a permis d’évaluer l’efficacité de la protection dans le cas d’une utilisation unique et également d’une possible réutilisation. Les résultats en oxydation/corrosion ont permis de classer les matériaux en fonction de leur efficacité de protectionSince many decades, Carbon/Carbon composites are used as structural parts in rocket engines due to their excellent thermomechanical properties. However, under highly oxidizing/corrosive atmosphere and high gas flow rates, carbon suffers from severe oxidation. To improve oxidation resistance of these composites, Ultra High Temperature Ceramics (UHTC) can be used as a protection. To protect the whole composite, the introduction of UHTC as a matrix has been done using a liquid phase process combining: (i) slurry infiltration process and (ii) reactive melt infiltration. Matrix constituents belong to the (B;C;Si;Zr) system. Material characterisation allowed a better understanding of the infiltration mechanisms and of the phase distribution and composition in respect to the processing conditions. To select the best composition, oxyacetylene torch testing has been done to recreate spacecraft launch environmental conditions. Post-test characterisation has been done to evaluate protection efficiency of each matrix composition for single use and possible reuse. Finally, advantages and drawbacks assessment of each composition allowed to highlight the most protective composition and phase distribution
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Dutto, Mathieu. "Procédé micro-ondes pour l’élaboration de composites B4C-SiC par infiltration et réaction de silicium, en vue d’applications balistiques." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEM021/document.
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De nombreuses études ont montré la faisabilité de la fabrication de pièces composites en carbure de bore et de silicium par l’infiltration de silicium fondu dans une préforme poreuse en carbure de bore (Reaction bonding). Cette méthode permet l’obtention d'un composite fortement chargé en carbure de bore (phase qui nous intéresse pour les applications balistiques), sans pour autant avoir besoin de monter à des températures de frittage de plus de 2200°C (température habituellement utilisée pour fritter le B4C). Dans notre cas la température maximale est comprise entre 1400-1600°C. Cette thèse s’intéresse plus particulièrement à l’adaptation du procédé de « reaction bonding » au chauffage sous champ micro-ondes. Les micro-ondes sont particulièrement intéressantes en ce qui concerne la rapidité du cycle thermique et le chauffage préférentiel de certaines phases (dans le cas des multi-matériaux). Pour ce faire, plusieurs verrous technologiques ont dû être levés (travail sous atmosphère et sous champs électromagnétiques, température élevée, …). Les composites obtenus sont comparés à leurs équivalents en chauffage conventionnel. Des différences microstructurales ont été observées au niveau du SiC formé lors de la réaction. Cette thèse nous a donc permis de :-trouver des conditions de fabrication de pièces en carbure de bore par chauffage micro-ondes (Argon/Hydrogéné10%, légère surpression : 1.4 bars)-montrer que les propriétés mécaniques (dureté, module d’Young,…) obtenues en four micro-ondes sont équivalentes à celles obtenus en four conventionnel (dureté : 14-20GPa) -montrer d’importante différences microstructurales du carbure de silicium formé, entre les échantillons obtenus sous vide (four conventionnel) et ceux obtenus sous atmosphère contrôlée (micro-ondes et four conventionnel).-montrer que le passage à des plus grandes tailles est possible, il est même plus simple d’infiltrer de grandes pièces que de petites à cause de l’effet de la masse sur la réponse du matériau aux champs électromagnétiques des micro-ondes.Ces résultats sont très prometteurs pour des applications balistiques : fabrication de gilets pare-balles et blindages légersMany studies have shown the feasibility of processing silicon-boron carbide composite by infiltration of molten silicon through a porous preform made of boron carbide (Reaction Bonding Process). Using this method, the obtained composite contains a large amount of boron carbide, which is the hardest and the most interesting phase for ballistic application. In our developed process, the maximum processing temperature is 1600°C, which is far below the usual high temperature stage/pressure conditions commonly used to sinter B4C by conventional method (respectively 2200°C and40MPa). The main goal of this thesis is to develop a novel reaction bonded process based on microwave heating. Microwaves heating has many interesting features, including fast heating process, selective heating mechanism (in case of heating multi-materials) and volumetric heating distribution. . To fulfill our goal, many technological issues need to be addressed (working in controlled atmosphere and under microwave field, high temperature ...). This thesis reports the development of this novel process, and materials made from it, exhibit similar properties compared to those made conventionally. However, some microstructural differences were observed in SiC resulting phases. This thesis has allowed to-find out the boron carbide composite piece fabrication conditions in microwave cavity (Argon/Hydrogen10%, slight overpressure: 14bars)-show that mechanical properties (hardness, Young’s modulus…) obtained are comparable to those measured on conventionally reaction bonded produced materials. -show that formed SiC has some microstructural peculiarities, between vacuum samples (for conventional) and ones obtained in hydrogenous argon (using microwave).-show that it is possible to produce larger size piece (66mm of diameter). These results are shown to be promising for ballistic applications, including the fabrication of bulletproof jacket and light armor
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Kleine, Barbara I. "How do metamorphic fluids move through rocks? : An investigation of timescales, infiltration mechanisms and mineralogical controls." Doctoral thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-115172.
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This thesis aims to provide a better understanding of the role of mountain building in the carbon cycle. The amount of CO2 released into the atmosphere due to metamorphic processes is largely unknown. To constrain the quantity of CO2 released, fluid-driven reactions in metamorphic rocks can be studied by tracking fluid-rock interactions along ancient fluid flow pathways. The thesis is divided into two parts: 1) modeling of fluid flow rates and durations within shear zones and fractures during greenschist- and blueschist-facies metamorphism and 2) the assessment of possible mechanisms of fluid infiltration into rocks during greenschist- to epidote-amphibolite-facies metamorphism and controlling chemical and mineralogical factors of reaction front propagation. On the island Syros, Greece, fluid-rock interaction was examined along a shear zone and within brittle fractures to calculate fluid flux rates, flow velocities and durations. Petrological, geochemical and thermodynamic evidence show that the flux of CO2-bearing fluids along the shear zone was 100-2000 times larger than the fluid flux in the surrounding rocks. The time-averaged fluid flow velocity and flow duration along brittle fractures was calculated by using a governing equation for one-dimensional transport (advection and diffusion) and field-based parameterization. This study shows that fluid flow along fractures on Syros was rapid and short lived. Mechanisms and controlling factors of fluid infiltration were studied in greenschist- to epidote-amphibolite-facies metabasalts in SW Scotland. Fluid infiltration into metabasaltic sills was unassisted by deformation and occurred along grain boundaries of hydrous minerals (e.g. amphibole) while other minerals (e.g. quartz) prevent fluid infiltration. Petrological, mineralogical and chemical studies of the sills show that the availability of reactant minerals and mechanical factors, e.g. volume change in epidote, are primary controls of reaction front propagation.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.
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Keedi, Caroline Bosquê. "Análise do efeito do dimetacrilato contra a infiltração bacteriana pela interface implante/componente protético através da PCR Real Time: um estudo in vivo." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/23/23150/tde-18032015-154447/.
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A interface do implante com o componente protético geralmente apresenta lacunas que servem de nichos para a colonização bacteriana. A proposta deste estudo é verificar a eficácia do dimetacrilato na vedação desta interface. Foram utilizados 20 implantes ósseos Bone Level® Straumann, indicados para reabilitação protética unitária cimentada. Os pilares protéticos foram instalados nos grupos controle e experimental, adicionando-se o dimetacrilato à interface da conexão protética. Foram realizadas uma coleta inicial e uma coleta ao final do período de 90 dias no interior de cada implante, e através da técnica de PCR quantitativo foi analisada a infiltração e a detecção das espécies bacterianas Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia. No Grupo Controle, todas as amostras apresentaram quantificação de microrganismos, confirmando infiltração bacteriana. No Grupo Experimental, apenas 30% das amostras apresentou quantificação após o período estudado. Assim, a ausência de bactérias no Grupo Experimental foi associada ao tratamento com o dimetacrilato para o período. Quando considerada a presença de pelo menos uma das bactérias específicas estudadas nas amostras, a diferença também foi estatisticamente significante. Entretanto, mais estudos devem ser desenvolvidos a fim de verificar se a vedação será eficiente por períodos mais longos.The implant/prosthetic component interface often has gaps that serve as niches for bacterial colonization. The purpose of this study is to verify the effectiveness sealing this interface with dimethacrylate. Twenty two Straumann ® Bone Level implants was installed in areas with indication for single cemented prosthetic rehabilitation. The prosthetic components were installed in the control and experimental groups following the fabricant instructions, and adding the dimethacrylate in the interface of the experimental group. An initial collection and a second collection at the end of 90 days within each implant were performed, and after that, the technique of quantitative PCR was developed to analyze whether there was infiltration and detection of four bacterial species: Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia. In the control group, all samples showed quantification of microorganisms, confirming bacterial percolation. In the control group, only 30% of the samples submitted quantification after the study period. Thus, the absence of bacteria in the experimental group was associated with the treatment for the period dimethacrylate. Considering the presence of at least one specific bacteria in the samples studied, the difference was also statistically significant. However, more studies should be conducted to verify that the seal will be effective for longer periods.
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Mazilu, Irina. "Nanoparticules métalliques déposées sur des matériaux poreux multifonctionnels pour des applications catalytiques." Thesis, Poitiers, 2017. http://www.theses.fr/2017POIT2268.
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L’objectif de cette thèse est le développement de nouveaux systèmes catalytiques à base de nanoparticules métalliques non nobles (Cu et/ou Co MNPs) déposées sur des supports mésostructurés multifonctionnels. Plusieurs supports ont été préparés par dopage de silices SBA-15 avec des hétéroatomes de type Al, Ga et Fe en utilisant la méthode de saut de pH ou par recouvrement de la surface de la SBA-15 par les oxydes correspondants en utilisant l’infiltration des sels fondus. Egalement, des supports SBA-15 hybrides organique-silice sont synthétisés par élimination partielle du porogène, et ont été utilisés pour la dispersion des phases métalliques. Les caractérisations et les résultats catalytiques démontrent que la fonctionnalisation des supports SBA-15 avec des hétéroatomes ou avec des groupements polyéthers permettent d’obtenir un contrôle amélioré de l’environnement local des MNPs hébergées, permettant d’ajuster à la fois l'interaction métal-support et la taille des nanoparticules, pour finalement affiner les performances catalytiques en termes d'activité et de chimiosélectivité pour l'hydrogénation en phase liquide d'aldéhydes insaturés tels que le cinnamaldéhyde. De plus, les matériaux SBA-15 dopés par l’oxyde de fer, isolé et/ou fortement dispersé, présentent d’excellentes propriétés catalytiques pour la dégradation de polluants dans l’eau (Reactive Red 120)The objective of the Ph.D. thesis is the development of new catalytic systems based on non-noble metal nanoparticles (Cu and/or Co MNPs) hosted in functional mesostructured hosts. To this aim, various supports are prepared by doping SBA-15 with Al, Ga and Fe heteroatoms using the two-step pH-adjustment method or by coating the SBA-15 surface with Al, Ga and Fe oxides using the melt infiltration approach. Likewise, hybrid organic-silica SBA-15 supports are obtained by partial extraction of the Pluronic P123 surfactant. The characterization and catalytic results show that the functionalization of SBA-15 supports with heteroatoms or with polyether groups originating from the native surfactant represents new strategic lines to achieve an enhanced control on the local environments of hosted MNPs and to engineer both the metal-support interaction and nanoparticle size, ultimately to fine tuning the performances of Cu and/or Co-based nanocatalysts in terms of activity and chemoselectivity for the liquid-phase hydrogenation of unsaturated aldehydes, such as cinnamaldehyde. Furthermore, SBA-15 materials containing Fe species in isolated and/or highly dispersed states are evaluated for the Fenton-type peroxidation of Reactive Red 120 azo dye, exhibiting excellent catalytic properties for the dye degradation
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Laduye, Guillaume. "CVD du carbure de silicium à partir du système SiHxCl4-x/CyHz/H2 : étude expérimentale et modélisation." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0116/document.
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Le carbure de silicium est un matériau souvent employé comme matrice dans les composites thermostructuraux. Le précurseur classiquement utilisé pour son élaboration par dépôt/infiltration par voie gazeuse est CH3SiCl3. La thèse vise à évaluer le remplacement de ce précurseur par des précurseurs gazeux bi-sourcés de SiC où carbone et silicium sont apportés séparément.A partir du système SiHCl3/C3H8/H2, l’influence du débit total, de la température, de la pression totale et de (C/Si)gaz sont évaluées et comparées aux résultats obtenus avec le système CH3SiCl3/H2. La mesure in situ de la vitesse de dépôt permet de définir des lois cinétiques apparentes. L’analyse IRTF de la phase gazeuse indique que les évolutions des pressions partielles des différents produits stables sont corrélées avec les transitions cinétiques et les changements de composition du solide. Les simulations numériques de l’évolution de la phase gazeuse montrent une bonne corrélation avec les résultats expérimentaux et permettent de proposer des mécanismes homogènes et hétérogènes qui pourraient expliquer les écarts à la stoechiométrie du dépôt.L’étude de six précurseurs supplémentaires permet de mieux identifier le rôle des principales espèces en phase homogène et hétérogène, et notamment les précurseurs effectifs de dépôt. Enfin, l’étude de l’infiltration de matériaux poreux modèles révèle des améliorations significatives en termes d’homogénéité de vitesse de dépôt.Ainsi, des conditions propices à l’infiltration de carbure de silicium peuvent être obtenues en adaptant la réactivité de la phase gazeuse par la sélection de précurseurs initiaux et des chemins réactionnels qui en découlentSilicon carbide (SiC) is material of choice for the matrix of Ceramic Matrix Composites (CMC).CH3SiCl3/H2 mixtures are currently used as gas precursor for the synthesis of the CVI-SiC matrices.The present work considers the dual-source approach with two separate carbon and silicon precursorsmolecules.In the case of SiHCl3/C3H8/H2 mixture, systematic studies of total flow rate, temperature, total pressureand C/Si ratio of initial gaseous phase are realized. Kinetics obtained with growth rate measurements and solid composition are compared with results from CH3SiCl3/H2 mixture. On the basis of the apparent reaction orders and activation energies, experimental kinetic laws are derived. Through IRTF analysis of the gas phase, the partial pressures of the different stable products are correlated with deposition kinetic and solid composition. Results obtained in gas-phase kinetic simulation show a good correlation with the experimental results and a mechanism of homogeneous decomposition is proposed. A better understanding of the role of the principal species in homogenous and heterogeneous phase is obtained through the study of six other gas systems and the roles of some effective precursors are discussed. Finally, infiltration results of porous material models with different precursor systems reveal significant improvements as homogeneity of kinetic deposit.Hence, favourable conditions to silicon carbide infiltration can be obtained by adapting the reactivity of the gas phase, with the choice of initial precursors and homogeneous chemistry associated. Asystematic study of the process evidences promising working windows for the infiltration of pure SiCin porous performs
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沈宗憲. "Fabrication of the ceramic/metal composites by reactive infiltration." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/09689197866075200449.
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Xie, Zhen Ming, and 謝振銘. "Application of polymers in reactive infiltration of silicon carbide preforms." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/61124202715314721376.
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Nasery, Hesam. "Fabrication of AlN-MgO-MgAl2O4 ceramic composite by spontaneous reactive infiltration." Thesis, 2008. http://spectrum.library.concordia.ca/975845/1/MR40916.pdf.
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Aluminum nitride ceramics are in high demand in electronic industries as substrate materials for applications requiring high thermal conductivity. Sintering and hot pressing are the most common processing methods used to make dense AlN ceramics. However, all methods of AlN sintering involve high temperatures and long times. Therefore, it is an expensive material. Removing oxygen, as a main impurity of aluminum nitride, by a low cost method in order to achieve dense and high thermal conductivity aluminum nitride ceramics has been pursued for many years. A pressureless infiltration technique at low (650-950°C) temperature was developed to fabricate aluminum nitride-based ceramic matrix composites. The process involves forming a particulate porous compact of non-sintered aluminum nitride and introducing magnesium alloy into the channel network by spontaneous infiltration in a nitrogen atmosphere. Magnesium oxide and spinel phase (MgAl 2 O 4 ) were formed in-situ, when nitrogen gas was used. Densification, thermal properties, and microstructure of the products have been studied. Microstructural, phase, and chemical analysis show that AlN-MgO-MgAl 2 O 4 ceramic composites can be fabricated successfully. Metallic phases were not observed in the samples fabricated at higher than 800°C and electrical conductivity results show that they are insulators. Thermal diffusivity and heat capacity have been measured using nano-flash and differential scanning calorimetry techniques, respectively. Thermal conductivity results are strongly influenced by the residual porosity. Maximum thermal conductivity and density at room temperature were measured to be 95.88 W/m.K and 2.451 g/cm 3 , respectively
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Shamekh, Mohammed. "Processing and Characterization of Mg Matrix Composites Reinforced with TiC and TiB2 Phases using an In-situ Reactive Infiltration Technique." Thesis, 2011. http://spectrum.library.concordia.ca/36024/1/Shamekh_PhD_F2011.pdf.
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Magnesium matrix composites are attractive for different applications especially in automotive and aerospace industries due to their superior specific properties. The main purpose of this work is to produce a new magnesium matrix composite reinforced with a network of TiC and TiB2 compounds via an in-situ reactive infiltration technique. In this process, the ceramic reinforcement phases, TiC and TiB2, were synthesized in-situ from the starting powders of Ti and B4C without any addition of a third metal powder such as Al. The molten magnesium infiltrates the preform of 3Ti-B4C by capillary forces. Furthermore, adding Mg or MgH2 powder with different weight percentages to the 3Ti-B4C preforms was used in an attempt to increase the Mg content in the fabricated composites. The results of the in-situ reaction mechanism investigation of the Ti-B4C and Mg-B4C systems show that the infiltrated magnesium not only infiltrates through the 3Ti-B4C preform and thus densifies the fabricated composite as a matrix metal, but also acts as an intermediary making the reaction possible at a lower temperature than that required for solid-state reaction between Ti and B4C and accelerates the reaction rate. The investigation of the in-situ reaction mechanism after adding Mg or MgH2 powder to the 3Ti-B4C preforms show that the reaction mechanisms are similar. However, the presence of the Mg or MgH2 in the preform accelerates the reaction rate making the reaction take place and finish in a shorter time.
Also, the results of the parametric study show that the processing conditions such as temperature, holding time and green compact relative density have a significant influence on the reaction mechanism and the fabrication of the composite. Based on this work, it is recommended to fabricate the composite samples at 900ºC for 1.5 h and using a green compact of 70% relative density. The required equilibrium phases, TiCx and TiB2, formed in the composites with very small amounts of the residual Ti, boron carbide and intermediate phases such as TiB, Ti3B4 and MgB2. The fabrication of composites at these processing conditions avoids significant oxidation of Mg and formation of the ternary compound (Ti2AlC) in the cases of AZ91D or AM60B alloys composites, which can adversely affect the mechanical properties of the composites.
Furthermore, the results reveal that the percentage of reinforcing phases, when the optimal processing parameters are used, can be tailored by controlling either the green compact relative density or the weight percentages of Mg or MgH2 powder added to the 3Ti-B4C preform.
Microstructural characterization reveals a relatively uniform distribution of the reinforcing phases TiCx and TiB2 in the magnesium matrix. Mechanical properties of these composites such as elastic modulus, flexural and compressive strengths are greatly improved compared with those of the unreinforced Mg or Mg alloys. In contrast, the ductility of TiCx-TiB2/Mg composites is lower than that of the unreinforced Mg or Mg alloys. However, this lower ductility was improved by the addition of Mg or MgH2 powder in the preform. Secondary scanning electron microscopy was used to investigate the fracture surfaces after the flexural strength test. The composites show signs of mixed fracture; cleavage regions and some dimpling. In addition, microcracks observed in the matrix show that the failure might have initiated in the matrix rather than from the reinforcing particulates. Also, the results show that the hardness and the wear resistance of the composites are improved, compared with those of the unreinforced Mg alloy.
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Roulier, Stephanie. "Caractérisation hydro-dispersive in situ de sols non saturés par infiltration d'eau et de soluté : cas de sols structures et de sols hétérogènes." Phd thesis, 1999. http://tel.archives-ouvertes.fr/tel-00802313.
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La modélisation quantitative du transfert de l'eau et des solutés dans la zone non saturée des sols nécessite la mesure in situ des paramètres hydro-dispersifs. L'infiltrométrie sous pression controlée couplée à l'utilisation de traceurs de l'écoulement de l'eau est pour cela un outil efficace et simple à mettre en oeuvre sur le terrain. La modélisation des transferts et l'analyse des résultats des calculs conduit à une methode simplifiée de caracterisation hydro-dispersive par infiltrométrie. La conductivité hydraulique K et la sorptivité S sont estimées à partir de l'analyse aux temps courts ou aux temps longs de l'infiltration cumulée. La méthode mono-tracage est utilisée pour le calcul de la fraction d'eau mobile F. Une nouvelle méthode d'estimation du coefficient de dispersion D est proposée. Elle est telle que D reste l'unique paramètre à ajuster sur les données issues de l'échantillonnage du sol à la fin de l'infiltration. L'incertitude d'estimation est de plus définie pour chacun des paramètres. Le domaine de validité des méthodes est precisé à partir de données genérées numeriquement. Pour le calcul de K, S et F, il est défini à partir des temps caracteristiques de l'écoulement de l'eau, de la lame de solution infiltrée et de la dispersivité du milieu. La validité du mode de détermination de D dépend du nombre adimensionnel pext. Trois sols sont caracterisés in situ. La porosité bimodale des deux premiers induit une forte augmentation des paramètres hydrodynamiques à l'approche de la saturation, et de F avec la taille moyenne de pores hydrauliquement fonctionnels. Le troisième est soumis à l'encroutement de surface. Les résultats de la caractérisation hydro-dispersive renforcés par l'observation du réseau poral sur lames minces montre que le rôle des croutes de surface sur l'infiltrabilité est minimisé par rapport à celui du sol sous-jacent. De plus, le sol sous-jacent semble protegé de la coalescence par les croutes de surface.
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Sithebe, Humphrey Samkelo Lungisani. "The preparation and characteristics of cBN ceramics with Al-based binder phases." Thesis, 2008. http://hdl.handle.net/10539/5876.
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The goal of this PhD thesis was to develop dense aluminium compound-cubic boron nitride
composites with a high cBN content. To achieve this goal, two different strategies were used:
infiltration of cBN preforms and hot pressing of cBN-Al mixtures. The particle size of the cBN
and the amount of aluminium were systematically varied and the influence of these parameters
on densification and selected properties was evaluated. A basic understanding of the product
that was formed over certain temperatures and times provides information that can be used in
optimizing the infiltration and hot pressing of cBN with Al. For this reason, the reaction kinetics
between Al and cBN was initially investigated.
The reaction kinetics of the chemical interactions between Al and cBN was investigated in detail
using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The reaction was
studied using samples containing 50 volume percent of Al and 50 volume percent of cBN (12 μm)
hot pressed at 800 oC. The prepared samples were allowed to react isothermally at temperatures
between 1 000 oC and 1 400 oC under nitrogen (N2) and argon (Ar) atmospheres. It was found
that the degree and rate of the reactions increased with increasing temperature in both N2 and
Ar atmospheres. The degree of aluminium nitride (AlN) formation was considerably higher
under N2 than under Ar. The difference in the formation of AlN between the two atmospheres
was attributed to the reaction of N2 gas with the sample due to the open porosity. The infiltration of partially hexagonalized cBN matrix with molten Al was studied. The samples
were found to have a density higher than 97% of the theoretical density. It was found that the
amount of soft hBN phase present in the sample (due to hexagonalization) increases at
temperatures higher than 1 300 oC, resulting in a hardness of the final material of Hv10 = 6.5 ±
4.8 GPa. Because of thie poor hardness this route was abandoned.
Cubic boron nitride powder (12 μm) without hexagonal boron nitride (hBN) was also infiltrated
with aluminium. The infiltrated samples were found to exhibit a density higher than 96% of the
theoretical density. The Al reacted with cBN and no hBN was observed at temperatures below
1 400 oC. The resulting product showed a Vickers hardness of Hv10 = 14.4 ± 1.6 GPa compared
with Hv10 = 6.5 ± 4.8 GPa obtained with the partially hexagonalized cBN matrix. Infiltration of
3 μm cubic boron nitride increased the Vickers hardness to 22.0 ± 0.6 GPa. However, this
infiltration was not very reproducible. Al-cBN cermets were hot pressed at temperatures between 800 oC and 1 750 oC and at a
pressure of 50 MPa in vacuum. The effect of the particle size of the starting powders, as well as
the effect of the starting compositions and temperature, was investigated. The materials could
only densify up to 80 – 92% of the theoretical density. After hot pressing at 800 oC, only Al and
cBN could be observed by XRD, whereas higher hot-pressing temperatures resulted in the
formation of AlN and AlB2 which retard the densification. The microstructure of the hot-pressed
materials was studied using SEM. It was observed that there are oxide layers at the interface
between the Al and cBN phases. The presence of these oxide layers prevented the Al from
spreading, thereby preventing full densification.
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Ghanem, Hanadi [Verfasser]. "Processing of biomorphic porous ceramics by chemical vapor infiltration and reaction technique (CVI-R) = Herstellung biomorpher, poröser Keramiken mittels chemischer Gasphaseninfiltration und Reaktion / vorgelegt von Hanadi Ghanem." 2008. http://d-nb.info/991601882/34.
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Almeida, Streitwieser Daniela [Verfasser]. "Kinetic investigation of the chemical vapor infiltration and reaction (CVI-R) process for the production of SiC and TiC biomorphic ceramics from paper preforms = Kinetische Untersuchung der chemischen Gasphaseninfiltration und Reaktion zur Hertsellung von SiC- und TiC-biomorphen Keramiken aus Papier-Vorformen / Daniela Almeida Streitwieser." 2005. http://d-nb.info/974205966/34.
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Boily, Nicolas. "Caractérisation du microbiote tumoral influençant la réponse immunitaire et de son importance pronostique dans le cancer du sein." Thèse, 2017. http://hdl.handle.net/1866/20432.
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