Dissertations / Theses: 'Solid Precipitation'

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Schöll, Jochen. "Nucleation, growth, and solid phase transformations during precipitation processes /." Zürich : ETH, 2006. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=16779.

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Durán, Alárcon Claudio. "Ground-based remote sensing of Antarctic and Alpine solid precipitation." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAU024/document.

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Les précipitations solides jouent un rôle crucial dans le système climatique terrestre, ainsi que dans le maintien des écosystèmes et le développement des activités humaines. Les incertitudes associées aux estimations quantitatives des précipitations ainsi que celles concernant les projections des modèles climatiques font de cette composante du cycle hydrologique un sujet de recherche important. La télédétection permet de suivre les précipitations et les nuages dans des régions où les observations in situ sont rares et dispersées, mais avec une résolution temporelle limitée ainsi qu’une zone aveugle près du sol pour les capteurs spatiaux, et une visibilité limitée dans la basse atmosphère en terrain complexe pour les radars au sol. Les objectifs de cette thèse sont les suivants : 1) caractériser les nuages et les précipitations en Antarctique, en détectant la présence d’eau liquide surfondue et de particules de glace près du sol à l'aide d'un lidar 532-nm, polarisé, au sol ; 2) caractériser la structure verticale des précipitations dans deux régions contrastées mais importantes de la cryosphère, l’Antarctique et les Alpes, dans la basse troposphère, en utilisant des radars au sol.Dans cette étude, une méthode de détection des hydrométéores dans les nuages et les précipitations est proposée à l'aide de données lidar complétées par celles d’un <> (MRR) en bande K pour améliorer la détection des précipitations, ces deux instruments étant déployés à la station Dumont d'Urville (DDU) en Antarctique de l’Est. Une méthode fondée sur le facteur de dépolarisation lidar, le coefficient de rétrodiffusion atténué et l'utilisation d’un partitionnement en k-moyennes est développée. La classification des particules des nuages et des précipitations permet de documenter la distribution verticale de l'eau liquide surfondue, ainsi que des particules de glace sous différentes formes. La comparaison entre les classifications obtenues depuis le sol et celles obtenues à partir des données satellitaires montre des formes similaires pour la distribution verticale de l'eau liquide surfondue dans les nuages.La structure verticale des précipitations près de la surface est analysée à l'aide des moments Doppler obtenus à partir de trois MRRs situés à DDU, à la station Princess Elisabeth (PE) à l'intérieur de l'Antarctique de l’Est, et à la station du Col de Porte (CDP) dans les Alpes françaises. Ces analyses montrent que le climat local joue un rôle important dans la structure verticale des précipitations. En Antarctique, les forts vents catabatiques soufflant du haut plateau jusqu'à la côte diminuent le facteur de réflectivité radar près de la surface en raison de la sublimation des flocons de neige. Les moments Doppler fournissent aussi de riches informations pour comprendre les processus liés aux précipitations, tels que l'agrégation et le givrage, observés notamment à DDU et au Col de Porte.Les résultats montrent également qu'à l'intérieur du continent Antarctique, une partie significative (47%) des profils de précipitations présentent une sublimation complète avant la surface en raison des conditions atmosphériques sèches, alors que sur la côte de l'Antarctique, cela ne concerne qu’environ un tiers des profils (36%). Dans les Alpes, ce pourcentage est réduit à 15%. La majeure partie de la sublimation est observée en dessous de l'altitude où les profils de CloudSat sont contaminés par la proximité du sol. Par conséquent, ce phénomène ne peut pas être entièrement décelé depuis l'espace avec les capteurs actuels.Cette thèse contribue à l'étude de la structure verticale des précipitations neigeuses dans la basse troposphère ; elle est utile pour l'évaluation des produits de télédétection concernant les précipitations qui peuvent présenter de fortes limitations à la proximité de la surface
Solid precipitation plays an important role in the Earth's climate system, as well as for the maintenance of ecosystems and the development of human society. The large uncertainty in precipitation estimates and the discrepancies within climate model projections make this component of the hydrological cycle important as a research topic. Remote sensing allows to monitor precipitation and clouds in regions where in-situ observations are scarce and scattered, but with limited temporal resolution and a blind zone close to the ground level for spaceborne sensors, and limited visibility in the lower atmosphere in complex terrain for ground-based radars. The objectives of this dissertation are the following: 1) to characterize cloud and precipitation in Antarctica, detecting the presence of supercooled liquid and ice particles near the ground level using a ground-based 532-nm depolarization lidar; 2) to characterize the vertical structure of the precipitation in two contrasted but important regions of the cryosphere, Antarctica and the Alps, in the low troposphere using ground-based radars.In this study, a cloud and precipitation hydrometeor detection method is proposed using lidar data, complemented with a K-band micro rain radar (MRR) to improve the detection of precipitation, both instruments deployed at the Dumont d'Urville (DDU) station in East Antarctica. A method based on lidar depolarization and attenuated backscattering coefficient and the use of k-means clustering is developed for the particle classification. The classification of cloud and precipitation particles provides the vertical distribution of supercooled liquid water, as well as planar oriented ice and randomly oriented ice particles. The comparison between ground-based and satellite-derived classifications shows consistent patterns for the vertical distribution of supercooled liquid water in clouds.The vertical structure of precipitation near the surface is analyzed using the Doppler moments derived from three MRR profiles at DDU, the Princess Elisabeth (PE) station, at the interior of East Antarctica, and at the Col de Porte (CDP) station, in the French Alps. These analyses demonstrate that local climate plays an important role in the vertical structure of the precipitation. In Antarctica, the strong katabatic winds blowing from the high plateau down to the coast decrease the radar reflectivity factor near the surface due to the sublimation of the snowfall particles. Doppler moments also provide rich information to understand precipitation processes, such as aggregation and riming, as observed at DDU and CDP.The results also show that in the interior of the Antarctic continent a significant part (47%) of the precipitation profiles completely sublimate before reaching the surface, due to the dry atmospheric conditions, while in the coast of Antarctica it corresponds to about the third part (36%). In the Alps, this percentage is reduced to 15%. The major occurrence of particle sublimation is observed below the altitude where CloudSat profiles are contaminated by ground clutter. Therefore, this phenomenon cannot be fully captured from space with the current generation of sensors.This dissertation contributes to the study of the vertical structure of snowfall in the low troposphere, useful for the evaluation of precipitation remote sensing products, which may have severe limitations in the vicinity of the surface

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Carter, Geoffrey A. "Controlling precipitation of value added zirconia." Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/1356.

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Advanced zirconia-based materials have many important applications in electronics and medical applications, and of most interest to this research, solid oxide fuel cells (SOFC) which is a key technology for alternative and hydrogen-based energy generation. The SOFC in its most basic form is a device for converting hydrogen and oxygen into water with a resulting generation of power. Most SOFC manufacturers/developers are using zirconia doped with yttria as the electrolyte with variations on the amount of yttria. The SOFC places high demands on the ceramic components, placing significant demands on powder processing technology to enable fabrication of reliable components. It has been shown that the process of co-precipitation of three initially mixed chlorides, aluminium chloride, yttrium chloride and zirconium oxychloride in aqueous solutions, can produce an oxide powder that can be used in SOFC manufacture. Zirconia powders synthesised from aqueous solution in this way have been found, however, to include hard agglomerates which are detrimental to further processing and applications.Industrial manufacture of zirconia and zirconia-yttria products can best be summarised as four step operation; (1) hydrolyse of zirconyl chloride and mixing of other solutions, (2) precipitation, (3) calcination (4) forward processing for particle size, surface area and handle-ability characteristics . The use of aqueous solutions allows for lower costs of production and reduced waste. However such production is hampered by limited understanding of the fundamental chemistry particularly during aqueous processing which limits the development of better powders for the widespread use of SOFC’s. The aim of this project was to develop an understanding of these problems based on an industrial process that is in use within Western Australia. The work has been broken up into five sections, with the first four dealing with predominately non-stabilized zirconia and tracks the process from aqueous chemistry through to final ceramic. The final section does the same for a 3 mole% yttrium partially stabilised zirconia.The influence of concentration and added chloride salts on the solution speciation of zirconyl chloride solutions, and the precipitate formed upon addition of aqueous ammonia, has been investigated using a combination of techniques, such as SAXS, DLS, ICP-OES, TEM and SEM.To further investigate the precipitation process the effect of pH of precipitation, starting solution concentration, and agitation levels on the particle size of hydrous zirconia precipitates have been investigated. The pH of precipitation was also found to have a significant impact on the type of hydrous zirconia produced. TGA/DTA, micro combustion and TEM / EDS were used to investigate the difference in the powders produced at pH 3 and 12.The two hydrous zirconium manufactured at pH 3 and 12 have been studied as further processing consistent with industrial procedures was undertaken, including how the differences in structure due to the pH of precipitation, may effect the calcination, in situ and ex situ x-ray diffraction was used for this.With the knowledge developed thus far, two 3 mol% partially stabilised zirconia (P-SZ) samples suitable for the SOFC market were manufactured from solutions through to ceramics.The combination of SAXS, DLS, in situ XRD, TEM, ICP, TGA/DTA, micro combustion, and standard ceramic testing was found to be excellent for providing comprehensive information on changes through an industrial process and will allow optimisation to produce powders suitable for SOFC applications.

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Wang, Jianfeng. "A study of rare earth element substituted strontium hexaferrite produced by chemical co-precipitation and hydrothermal synthesis." Thesis, University of Birmingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288888.

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Hexaferrites are still a very important component of the permanent magnets market because of their low price combined with reasonably attractive magnetic properties. In such a context, any improvement of the magnet data would be of great importance. In recent years, work has been carried out on improving the magnetic properties by a combined substitution of La and Co into the Sr-ferrite composition. This improvement was largely associated with an increase of coercivity and the underlying magneto-crystalline anisotropy. The possibility of replacing Sr by La and the subsequent improvement of the magnetic properties of the M-type ferrite stimulated our interest in studying other rare-earth ion substitutions. This thesis focuses on the effects of rare-earth element substitutions on the magnetic properties of strontium hexaferrite, SrM (SrFe12O19b)y chemical co-precipitation and by hydrothermal synthesis,a s well as on the properties-microstructure relationship. In order to produce the nanosized SrM powder, chemical co-precipitation was employed and subsequently proved to be an effective route for producing nanosized single domain SrM powder, where the SrM phase crystallises from the mainly amorphous co-precipitates through an exothermic reaction after calcination at >650°C. A very high intrinsic coercivity of 518. OkA/m (6509 Oe) with magnetisation at I IOOkA/m of 67 J/T. kg was obtained for the sample calcined at 850°C for 2h in air. The coercivity is close to the theoretical limit and is one of the highest values reported so far for isotropic SrM particles. Nanosized SrM powders with Sm and La-Zn additives were also studied. It was found that Sm doping increased slightly the coercivity of SrM and exhibited higher values than those of the corresponding samples with La additives. However, the values of magnetisation decreased slightly with the increase of the Sm/Sr ratio, which can be correlated with the increased proportion of weakly magnetic SrFeO3_pxh ase in the Sm doped SrM. Sm doping slightly increasedt he ferritization temperatureo f SrM. In the case of the La-Zn substitution, single phase Sri_,(,L aZn),,F e12_XO19 nanosized powders were produced successfully for all x, where x varied from 0 to 0.4. La-Zn substitution caused a decrease of the Curie temperature. The values of magnetization, remanence and coercivity decreased with La-Zn content. Unlike the results of La-Zn doped SrM particles prepared by conventional ceramic methods and the results of La-Zn doped SrM film prepared by rf sputtering, no improvement of the magnetisation was observed, which suggested that the properties of these materials are strongly processing-dependent and that the site preference of the Zn 2+ cation is not identical in all cases but would be affected by the processing route. Mainly single phase RE (RE=Sm, Nd, Pr and La) substituted SrM plate-like particles with the magnetoplumbite structure could be produced by hydrothermal synthesis and subsequent calcination. Under the particular hydrothermal conditions, RE elements did not substitute totally into the SrM structure and this resulted in incomplete reactions between Fe 3+ and Sr2+, indicated by traces of a-Fe2O3 and RE203 in all the RE substituted SrM samples. The presence of a-Fe2O3 and RE203 increased with the increase of the RE/Sr ratio. High temperature calcination homogenizes the materials and promotes the substitution of RE elements, resulting generally in the disappearance of a-Fe2O3 and RE203 after calcinations at >_ 1100°C. A higher calcination temperature was required to obtain the SrM single phase for a high RE/Sr ratio. The SrFe03_xp hase was found to be present in most of the RE substituted samples after calcination above 1100°C. Except for the La substitution, the other RE elements reduced the rate of grain growth during the calcination. Generally, the magnetization values of the RE substituted samples were almost the same as that of SrM. On the other hand, their intrinsic coercivities generally increased upon RE doping. Thus, an appropriate amount of RE substitution resulted in a useful increase in the intrinsic coercivity (18% for Sm, 14% for Pr, 11 % for Nd and 5% for La) without causing any significant deterioration in the saturation magnetisation or in the remanence. The improvement in the coercivity as a result of the RE substitutions is discussed in terms of the extrinsic effect associated with the microstructure and the intrinsic effect associated with an increase in the magnetocrystalline anisotropy. Finally, anisotropic SrM magnets with Sm substitution, which is observed to have the largest enhancement of coercivity among the other elements, were studied. All the magnets with Sm additions exhibit a bigger coercivity and remanence than those of the SrM magnet and the coercivity of the magnets increases with increasing Sm/Sr ratio. The average grain size of the samples decreases with increasing Sm/Sr ratio. EDX quantitative analysis suggests that the solubility of Sm 3+ in the SrM-type structure is very small and that the Sm3+ preferably goes into SrFe03_Xw, hich is probably located around the SrM grain boundaries. The coercivity mechanism of the magnets is nucleation controlled. The formation and the distribution of the SrFe03_x phase around the SrM grain boundraies probably provides the inhibition of SrM grain growth, the reduction of the reverse domain nucleation at the grain surface and the isolation of the SrM grains. All these factors would contribute to the improvements of the coercivity of the magnets with Sm additions.

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Manfoumbi, Christian. "Précipitation des gels de silice en solution aqueuse sursaturée à forte acidité : mécanismes et mésostructures, application à la filtrabilité des pulpes dans les procédés hydrométallurgiques." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30251/document.

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La formation de gels de silice dans les procédés hydrométallurgiques est très souvent problématique pour la performance des étapes de séparation solide-liquide, en raison du colmatage des filtres. Ces étapes interviennent en aval des étapes de lixiviation visant à mettre en solution les éléments d'intérêts, notamment dans des milieux à forte acidité. Egalement mis en solution au cours de ces attaques acides, le silicium précipite alors sous forme d'oxyde de silicium et forme des gels extrêmement préjudiciables à la filtration. Dans le cadre d'une collaboration avec ERAMET Research, centre de recherche d'ERAMET, groupe minier français qui conçoit des procédés hydrométallurgiques, nous avons étudié l'influence des conditions de lixiviation d'un minerai spécifique sur la cinétique de dissolution du silicium ainsi que sur les mécanismes de précipitation de la silice en milieu acide. Nous avons montré qu'en-dessous d'une valeur de pH égale à 2, la silice polymérise pour former des gels suivant des mécanismes indépendants de la composition ionique de la solution. L'étude structurale des gels obtenus, réalisée par diffusion de rayonnement aux petits angles (SAXS) nous a conduit à proposer un modèle pour la mésostructure qui permet de comprendre leur impact sur les vitesses de filtration. Par la suite, des stratégies consistant à modifier la mésostructure des gels par des approches physiques ou physico-chimiques ont été considérées. Les résultats obtenus ont montré la possibilité d'utiliser à court terme ces stratégies pour améliorer la filtrabilité des gels de silice dans un procédé hydrométallurgique
The formation of silica gels in hydrometallurgical processes is very often problematic for the performance of the solid-liquid separation steps, due to clogging of the filters. These steps are carried out downstream of leaching aiming to solubilize the elements of interests, in particular in solutions with strong acidity. Also dissolved during acidic leaching, the silicon then precipitates in the form of silicon oxide and forms gels extremely detrimental to filtration. In collaboration with ERAMET Research, a research center of ERAMET, a french mining group that designs hydrometallurgical processes, we studied the influence of the leaching conditions of a specific ore on the dissolution kinetics of silicon as well as on the mechanisms of precipitation of silica in an acidic solution. We have shown that below a pH value of 2, silica polymerizes to form gels following mechanisms independent of the ionic composition of the solution. Based, on the structural study of the gels, carried out by small angle radiation scattering (SAXS) we proposed a model for the mesotructure, which explain the impact on filtration rates. Subsequently, strategies to modify the mesostructure of the gels by physical or physicochemical approaches were considered. The results have shown the potentialities of these strategies in the short term to improve the filterability of precipitated silica gels in a hydrométallurgical process

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Chen, Gang. "The role of interfacial structure in the evolution of precipitate morphology." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/40065.

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Gioseffi, Katherine C. M. "Insights into the kinetics of solid gypsum dehydration from wide and small-angle synchrotron X-ray scattering." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/127714/1/Katherine_Gioseffi_Thesis.pdf.

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Fluids liberated through the dehydration of hydrous minerals play a major role during earthquake formation, volcanism, metasomatism, and metamorphism in the lithosphere. The kinetics of the dehydration of natural gypsum rock are studied here with novel in-situ dehydration experiments using synchrotron transmission X-ray scattering. Powdered materials are used most commonly when studying dehydration kinetics of gypsum and other minerals. The presented experiments on natural rock highlight the physical importance of rock microstructure and grain-scale stresses in dehydration processes. This result has important implications for future experimental design and upscaling of kinetic data to understand crustal processes in real rocks.

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Ding, Weixuan. "Syntheses of ternary oxyhydrates and oxides in the calcium-uranium system : stoichiometric influences on their structural affinity, precipitation mechanisms, and solid-state transformations." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/19431/.

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Calcium uranyl(VI) oxyhydrates and uranates are structurally related U(VI)-phases featuring uranium oxo-polyhedral sheets, with calcium ions occupying the interlayer. Both coordination environments appear throughout the nuclear fuel-cycle as alteration products, colloids, and sorption complexes. However, concerted studies spanning the aqueous precipitation mechanisms of uranyl(VI) oxyhydrates, their solid-state transformations, and structural relationships with uranates, have hitherto remained largely unexplored. A series of calcium-based uranyl(VI) oxyhydrates were precipitated via alkalisation of aqueous precursor solutions in titration and batch reactions. The bulk stoichiometric ratio of calcium to uranium (Ca/U) of precipitates was varied by modifying precursor stoichiometry, reaction temperature, or extraction pH. The rate of precipitation and its dependency on temperature was quantified in-situ using a quartz crystal microbalance. Novel insight was revealed on the mechanisms influencing nucleation and growth, by determining associated kinetic barriers as a function of precursor-Ca/U. Remarkably, as the bulk precipitate Ca/U increased from ~⅛ to unity, there was a transition from crystalline Becquerelite to primary or secondary amorphous phases, with uranate-like coordination environments. Formation of the latter was driven by solution alkalinity, and comprises a poorly-ordered matrix with occlusions of Ca2+-rich nano-clusters. A congruency limit lies Ca/U of ~1.5 Ca/U, whereupon discrete Portlandite crystallises. Solid-state transformation of all Ca2+-U(VI)-phases studied involved dehydration, dehydroxylation-decarbonation, and desorption processes. Associated kinetic barriers were catalysed by higher Ca2+-contents, and was reflected by reaction enthalpies for dehydration and desorption. Crystalline Becquerelite (~⅛ Ca/U) underwent amorphisation-crystallisation via partial egress of interlayer calcium, followed by reduction of β-UO3 to form a novel intercalation compound Ca0.18.α-U3O8. The endmember uranates Ca3U11O36, CaU2O7, Ca2U3O11, and CaUO4 crystallised from amorphous precursors with higher bulk Ca/U (~⅓, ~½, ~⅔, ~1), where Ca3U11O36 is a novel compound that is isostructural to (Pb/Sr)3U11O36. Nucleation and growth became predominant in the presence of Ca2+-rich occlusions. A higher Ca2+-loading facilitated the progressive ingress of interlayer-Ca2+, inducing a concerted axial compression in uranyl(VI) oxo-polyhedra towards the uranate-like coordination environment.

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Masood, Muhammad Talha. "Synthesis of SrxRe1-xFeO3 cathode materials by carbonate co-precipitation for intermediate temperature solid oxide fuel cells : Re stands for rare earth elements." Thesis, KTH, Materialvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103277.

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Ma, Yangzhou. "Modeling and development of new materials for fuel cells solid electrolyte." Thesis, Belfort-Montbéliard, 2016. http://www.theses.fr/2016BELF0286/document.

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Les piles à combustibles à électrolyte solide de type SOFC permettent de transformer directement l’énergie de la réaction chimique de formation de l’eau à partir de l’hydrogène et de l’oxygène, en énergie électrique. De nos jours, les apatites de type silicates de terres rares présentent beaucoup d’intérêt comme électrolyte solide en raison de leurs propriétés de transport élevées avec une forte conductivité ionique et une faible énergie d'activation. Ils peuvent fonctionner de manière stable à une température intermédiaire sur une large plage de pression partielle d'oxygène en maintenant d'excellentes performances. Ils sont ainsi considérés comme de bons candidats pour les électrolytes de piles de type IT-SOFC. Parmi cette série de conducteurs, le type La-Si-O possède une conductivité plus élevée et leur performance serait modifiée par différents éléments dopants.L'objectif de cette thèse est d'étudier les effets des éléments de substitution / dopage ainsi que les méthodes de synthèse sur les propriétés structurales ainsi que sur la conductivité des apatites de type silicates de lanthane. Dans cette étude, nous utilisons une double approche: une approche de simulation et une approche expérimentale pour optimiser la pureté et les performances des matériaux d'électrolyte.Dans l'approche de simulation, le calcul basé sur la DFT (Théorie de la fonctionnelle de la densité) a été réalisée en vue d’étudier l'effet des positions de dopage: dopant Sr à La position de La et dopant Ge à la position de Si. Les résultats obtenus par le calcul concernant la conductivité ionique confirment ceux obtenus par l’expérience.Avec l’approche expérimentale, nous présentons la synthèse et la caractérisation de La10Si6O27 (LSO) dopé par Sr et élaboré par des procédés sol-gel. Les résultats montrent que la conductivité ionique est activé thermiquement et que les valeurs se situent entre 4,5 × 10-2 et 1 x 10-6 S·cm-1 à 873 K et dépend des conditions d’élaboration et de la composition de la poudre
The Solid Oxide Fuel Cell (SOFC) defined by its ceramic and oxide electrolyte, is an electrochemical energy conversion device that produces electricity directly from the chemical reaction of fuel. Nowadays, apatite type rare earths silicates and germaniums attract many interests as the solid electrolyte due to the superior transport properties with high ionic conductivity and low activation energy. They can operate stably at intermediate temperature over a wide oxygen partial pressure range and maintain excellent performances, being considered as a candidate for IT-SOFC electrolytes. Among this series of conductors, the La-Si-O type has a higher conductivity and the performance would be modified by different doping elements.The objective of this thesis is to study the effects of element substitution/doping and synthesis methods on the structural and conductivity properties of apatite type lanthanum silicates. In this study, we use a double approach: a simulation approach and an experimental approach to optimize the electrolyte materials purity and performance.Using simulation approach, a first principle calculation based on DFT (Density Functional Theory) was carried out to investigate the effect on doping positions: Sr dopant at La position and Ge dopant at Si position. The calculation results give a connection to the ionic conductivity obtained by experiments.With experimental approach, we present the synthesis and characterization of Sr-doped La10Si6O27 (LSO) prepared through an optimized water-based sol-gel process. The results show that the ionic conductivity is thermally activated and values lies between 4.5×10-2 and 1×10-6 Scm-1 at 873 K as a function of the composition and powder preparation conditions

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Mkhize, Buyisile. "Determination of Rifapentine and 25-O-desacetyl Rifapentine from 100 µl human breastmilk by LC-MS/MS using protein precipitation and solid phase extraction." Master's thesis, Faculty of Health Sciences, 2019. https://hdl.handle.net/11427/32087.

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There is currently no information available on the transfer of the second-line anti-TB drug, rifapentine and its metabolite, into breastmilk. The subsequent implications to the breastfed infant, as well as consequences of long-term exposure to potentially sub-therapeutic drug levels with regards to the development of drug resistant bacteria is therefore not known. A liquid chromatography method with detection by mass spectrometry (LC-MS/MS) is described for the quantification of rifapentine and its metabolite, 25-O-desacetyl rifapentine in human breastmilk, using rifampicin-d3 as an internal standard. An AB Sciex 4000 mass spectrometer at unit resolution in the multiple reaction monitoring (MRM) mode was used to monitor the transition of the protonated precursor ions m/z 877.5, m/z 835.4 and m/z 827.4 to the product ions m/z 151.1, m/z 453.2 and m/z 151.200 for rifapentine, 25-Odesacetyl rifapentine and rifampicin-d3, respectively. Ions were produced using Electro spray ionisation (ESI) in the positive ionisation mode. An Agilent Poroshell 120 EC-C18 (4.6 x 50 mm, 2.7 μm) column was used for chromatographic separation using an isocratic method of acetonitrile containing 0.1% formic acid and water containing 10% methanol and 0.1% formic acid (55:45, v/v), at a flow rate of 450 µl per minute. The retention times for rifapentine, 25- O-desacetyl rifapentine and rifampicin-d3 were ≈2.67, ≈1.88 and ≈1.96 minutes, respectively. The method was developed and validated according to FDA guidelines. The extraction method consisted of a combination of protein precipitation and C18 solid phase extraction. Rifapentine and 25-O-desacetyl rifapentine showed no significant carry over on the Agilent autosampler. The method was reproducible when analysed with human breastmilk from six different sources from Western Cape Maternity Breastmilk Bank. Rifapentine mean extraction yield was 84.2% (%CV = 1.7) and that of 25-O-desacetyl rifapentine was 71.1% (%CV = 10.8). Rifapentine had a mean process efficiency of 80.4% (%CV = 4.7) and that of 25-O-desacetyl rifapentine was 95.7% (%CV = 5.7). Intra- and inter day validations over 3 days were performed. The calibration curves fit a quadratic regression with 1/x weighting over a concentration range of 2 - 2000 ng/ml for both rifapentine and 25-Odesacetyl rifapentine based on the analyte/internal standard peak area ratios, the accuracy ranged from 92.9% to 105.5% for both rifapentine and 25-O-desacetyl rifapentine standards. The Quality Controls accuracy ranged from 97.4% to 106.0% for both rifapentine and 25-Odesacetyl rifapentine. Stock solutions were shown to be stable for 69 days at -80°C. v Rifapentine and 25-O-desacetyl rifapentine were stable in human breastmilk for up to 72 hours at approximately -80°C and -20°C, on benchtop for ≈4.5 hours on ice and after three freeze-thaw cycles. Rifapentine and 25-O-desacetyl rifapentine were shown to be stable on the autosampler over a period of approximately 48 hours after which the entire batch could be reinjected. Autosampler stability revealed a decrease in peak area ratios, indicating that a partial batch cannot be reinjected after 48 hours in case of instrument failure. This method will be utilized in the analysis of patient samples from a clinical study in South Africa in breastfeeding women with tuberculosis.

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Maharaj, Bikash Chandra. "Based mathematical models for assessing the effect of trace elements dynamics on solid waste anaerobic digestion." Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC2039.

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La digestion anaérobie (MA) est l’un des processus métaboliques les plus riches en oligoéléments (TE) en biologie. En effet, les TE sont des composants structuraux importants de diverses enzymes dans le processus AD. Le rôle et le devenir des TE (Fe, Ni et Co) dans l’AD est mal compris en raison de leur biogéochimie complexe. La faible limite de détection des instruments d’analyse et le temps et la nature exigeante des procédures expérimentales sont des obstacles majeurs à la quantification des TE dans la MA. Dans cette thèse, trois modèles mathématiques distincts basés sur l’ADM1 ont été développés pour simuler la dynamique des TE et le profil de spéciation dans un réacteur AD. En particulier, un modèle de précipitation/dissolution TE, un modèle de complexation TE et un modèle d’adsorption TE ont été développés progressivement pour prédire l’effet, le rôle et le devenir (...)
Anaerobic digestion (AD) is one of the most trace element (TE) rich metabolic processes in biology. Indeed, TEs are important structural components of various enzymes in the AD process. The role and fate of TEs (Fe, Ni and Co) in AD is poorly understood due to their complex biogeochemistry. The low detection limit of analytical instruments and the time consuming and challenging nature of the experimental procedures are major obstacles to the quantification of TEs in AD. In this thesis, three separate mathematical models based ADM1 have been developed to simulate the TEs dynamics and speciation pattern in an AD reactor. In particular, a TE precipitation/dissolution model, a TE complexation model and a TE adsorption model have been progressively developed to predict the effect, role and fate of TEs in an AD batch system. In all the models the extent of microbial activity in the AD process is a function of the free TE concentration in the liquid phase, which is in equilibrium with the physicochemistry of the AD reactor. The precipitation/dissolution model considers the interactions of TEs with inorganic carbon (e.g. HCO3- and CO32-), phosphorous (e.g. PO43-, HPO42-, H2PO4-) and sulfur (e.g. HS- and S2-) components. New chemical equilibrium acid-base and precipitation reactions have been implemented to study the interactions of Fe, Ni, Co with carbonate, phosphate and sulfide components. The effects of deficiency, stimulation, inhibition and toxicity of TEs on microbial activity have been modelled based on a hormesis type TE dose-response inhibition function. The microbial uptake of TE and the TE inhibition on special microbial activities have been defined as well. Release of TEs as a disintegration product has been also considered to account for the TE content of the organic substrate. Model scenarios have been simulated to analyze the dynamics of TEs, starvation of TEs and the effect of initial sulfur-phosphorus ratio. In the complexation model, the interactions of TEs with organic chelators have been predicted. TE complexation reactions with VFAs and EDTA have been incorporated in the extended ADM1 model in addition to TE precipitation/dissolution processes. New acid-base chemical equilibrium reactions have been incorporated to model the dynamics of EDTA species. Complexation process rates have been defined as well. The model is able to quantify the effect of EDTA/VFA -TE complexation on methane production. Further, effect of initial Ca and Mg concentration on TE complexation has been predicted in a separate modeling scenario. Finally, a general framework able to take into account the precipitation/dissolution and complexation reactions, as well as the interaction of TEs with various surfaces available in the AD system has been developed. The model tracks the TEs dynamics in a batch anaerobic digester and as an extension of the previous contributions, incorporates the adsorption reactions of TEs with biomass, inert and precipitate (FeS). The concepts of free and occupied binding sites, and binding site density for the various surfaces have been incorporated into the model. Simulation scenarios were able to predict the effect of various organic matter concentrations, initial TE concentrations, initial Ca-Mg concentrations, initial EDTA concentrations and change in TE binding site density for biomass, inert and precipitate on cumulative methane production and TE speciation

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Beltran, Carbó Antoni. "Synthesis of novel molecularly imprinted polymers and their application to the solid-phase extraction of water-based matrices." Doctoral thesis, Universitat Rovira i Virgili, 2010. http://hdl.handle.net/10803/9049.

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La present tesi s'ha desenvolupat dintre de la línia de recerca que el grup té sobre el desenvolupament de nous sorbents polimèrics per a aplicar-los com a sorbents en extraccions en fase sòlida.
En aquest cas, els sorbents sintetitzats són altament selectius per a la molècula d'interès i es coneixen com a sorbents d'empremta molecular.
Pel que fa al mètode de síntesi s'han explorat diferent tipus de polimeritzacions així com diferents tipus d'interacció entre els components que constitueixen el polímer a fi de millorar tant el procés de síntesi com el reconeixement de la molècula objectiu un cop obtingut el polímer per tal d'obtenir extraccions altament selectives.
Aquest sorbents s'han aplicat per a l'extracció de compostos considerats com a contaminants orgànics emergents en mostres tant d'orina humana com aigües de riu o de depuradora amb resultats satisfactoris en tots els casos, demostrant que aquest sorbents són una bona opció a l'hora de realitzar extraccions altament selectives.
The present thesis has been developed within the research trend that the group has on the development of new polymeric materials for their used as sorbents in solid-phase extraction.
In this case, the sorbents synthesised are highly selective for the molecule of interest and are known as molecularly imprinted polymers.
Regarding the synthesis of these polymers, several polymerisation protocols as well as several kinds of interactions that can be established between all the components involved in the synthesis of the polymers have been exploited.
The sorbents obtained were further applied in the selective extraction of several compounds framed within the group of emerging organic pollutants from human urine, river water or effluent water from sewage plants. In any case, a successful extraction of the target analyte was easily achieved by using any of the sorbents developed, thus proving that these sorbents are a good option when aiming to selectively extract the compound of interest from highly complex matrices.

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Depci, Tolga. "Synthesis And Characterization Of Lithium Triborate By Different Synthesis Methods And Their Thermoluminescent Properties." Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610530/index.pdf.

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Lithium triborate, (LiB3O5), is a technologically important material for diverse applications, such as nonlinear optical materials and surface acoustic wave devices or, etc. Furthermore, it is suggested as an efficient thermoluminescent material. LiB3O5, suitable to dosimetric usage, was produced by different synthesis methods which were high temperature solid state reaction, microwave solid state reaction, microwave assisted high temperature solid state reaction and precipitation assisted high temperature solid state reaction. After the synthesis, metal oxides were doped into LiB3O5 to enhance its thermoluminescent properties. Identification and characteristics of LiB3O5 were determined by X-ray diffraction (XRD), Fourier Transform Infra red (FTIR) analyses, Differential Thermal Analyses (DTA), Scanning Electron Microscopy (SEM) and Particle Size Analyzer. The glow curves were obtained by using thermoluminescent (TL) reader. Among four different synthesis methods applied, high temperature solid state method needs very high temperatures and long duration of heating. Therefore, the effect of the reaction temperature, the time intervals, and also starting materials on production of LiB3O5 were investigated. Characterization studies indicated that LiB3O5 could be produced at 710 °
C for 4 hours. Among the starting materials used, Li2CO3 and H3BO3 combination was found the most suitable for the synthesis of LiB3O5 considering phase impurity as well as cost. LiB3O5 synthesized by microwave energy was unsuccessful. However, LiB3O5 could be synthesized by microwave assisted synthesis method by adding distilled water, urea and sucrose separately as thermal auxiliaries in microwave pre-heating step. The use of microwave and conventional ovens subsequently shortened the duration of heating. The crystallinity of LiB3O5 was the best in 40 % sucrose addition to initial mixture. The best method for synthesis of LiB3O5 has been found as precipitation assisted high temperature solid state method. This method yields LiB3O5 with higher phase purity as compared to these produced by other methods applied in this thesis and reported in the literature. It seems to be rather attractive since it is simple and needs less energy. Rare earth metal oxides, CuO and Al2O3 were added to LiB3O5 as activators to improve its TL properties. LiB3O5 synthesized by precipitation assisted high temperature solid state reaction and doped by 5 % wt Al2O3 showed the best TL property. Its main dosimetric characteristics revealed that LiB3O5 seemed to be suitable to medical and radiotherapy applications, since it was non-toxic, tissue equivalent, and chemically inert to body fluids.

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Koh, Pei Yoong. "Deposition and assembly of magnesium hydroxide nanostructures on zeolite 4A surfaces." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37159.

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A deposition - precipitation method was developed to produce magnesium hydroxide / zeolite 4A (Mg(OH)₂ - Z4A) nanocomposites at mild conditions and the effect of processing variables such as precursor concentration, type of base added, and synthesis time on the composition, size, and morphology of the nanocomposite were studied. It was determined that the precursor concentration, basicity, and synthesis time had a significant effect on the composition, size, and morphology of the deposited magnesium hydroxide (Mg(OH)₂) nanostructures. The properties of the Mg(OH)₂ - Z4A such as surface area, pore volume and composition were characterized. Mg(OH)₂ - Z4A samples and bare zeolite 4A were dispersed in Ultem® polymer to form a mixed matrix membrane. The thermal and mechanical properties of the resulting films were investigated. It was found that the addition of rigid bare zeolites into the polymer decreased the mechanical properties of the polymer composite. However, some of these adverse effects were mitigated in the polymer composite loaded with Mg(OH)₂ - Z4A samples. Isotherms for the adsorption of Mg(OH)₂ petals on zeolite 4A were measured in order to determine the optimum conditions for the formation of magnesium hydroxide / zeolite 4A nanocomposites at ambient conditions. The loading of the Mg(OH)₂ can be determined from the adsorption isotherms and it was also found that the adsorption of Mg(OH)₂ on zeolite A occurs via 3 mechanisms: ion exchange, surface adsorption of Mg²⁺ ions, and surface precipitation of Mg(OH)₂. Without the addition of ammonium hydroxide, the predominant processes are ion exchange and surface adsorption of Mg²⁺ ions. In the presence of ammonium hydroxide, Mg(OH)₂ crystals are precipitated on the surface of zeolite 4A at moderate Mg²⁺ ions concentration and the loading of Mg(OH)₂ was found to increase with increasing Mg²⁺ ions concentration. A detailed examination of the interactions between Mg(OH)₂ and functional groups on the zeolite surface was conducted. Solid-state 29Si, 27Al, and 1H NMR spectra were coupled with FTIR measurements, pH and adsorption studies, and thermogravimetric analyses to determine the interactions of Mg(OH)₂ with surface functional groups and to characterize structural changes in the resulting zeolite after Mg(OH)₂ deposition. It was discovered that acid - base interactions between the weakly basic Mg(OH)₂ and the acidic bridging hydroxyl protons on zeolite surface represent the dominant mechanism for the growth of Mg(OH)₂ nanostructures on the zeolite surface.

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Lazarevic, David Andrew. "In-situ Removal of Hydrogen Sulphide from Landfill Gas : Arising from the Interaction between Municipal Solid Waste and Sulphide Mine Environments within Bioreactor Conditions." Thesis, KTH, Industriell ekologi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-32770.

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This project was compiled in co-operation with the Royal Institute of Technology, Stockholm and Veolia Environmental Services (Australia) at the Woodlawn Bioreactor in NSW, Australia. Hydrogen sulphide is an unwanted component of landfill gas, raising occupational health and safety concerns, whilst leading to acid gas corrosion of power generation equipment and increased emissions of SOx, a primary constituent of acidification. Australian governmental requirements to place a periodic cover over the unused proportion of the tipping surface of landfills and bioreactors create an interesting opportunity for the removal of the hydrogen sulphide component of landfill gas. Using waste materials containing a high concentration of metals as waste cover can enhance the precipitation of sulphur in the form of metal sulphides. The reduction of sulphate via sulphate reducing bacteria is prevalent in sites that have a sizeable inflow of sulphate. The Woodlawn Bioreactor is located in an area where the influence of sulphate has a critical influence of bioreactor performance and production of hydrogen sulphide. Through a series of experimental bioreactors it was established that from the use of metalliferous periodic waste covers, the hydrogen sulphide component of landfill gas was maintained at an extremely low level when compared to the levels of hydrogen sulphide produced in waste under the influence of high sulphate loads with no waste cover.
www.ima.kth.se

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Gubán, Ivan. "Slitiny s vysokou entropií připravené SPS kompaktací vysokoenergeticky mletých práškových prekurzorů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-377882.

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The subject of this thesis is preparation of CoCrFeMnNiNx high entropy mixtures via the methods of mechanical alloying and spark plasma sintering (SPS). Three series of specimens were fabricated in this thesis: samples milled in argon (benchmark materials), samples milled in nitrogen atmosphere (to observe their ability of nitrogen absorption) and samples microalloyed with CrN, FeN nitrides (to observe their dissociation into the solid solution potential). The fabricated powders and SPS compacts were subsequently observed by electron microscopy and their phase content by X-Ray diffraction (XRD) and elemental composition by EDS analysis were carried out. A method of reduction melting in inert atmosphere was used to determine the exact oxygen and nitrogen content in powders, while the respective particle size distribution measured by laser diffraction method. The influence of nitrogen content on the hardness of the samples was studied via the microhardness measured. After completing the process of mechanical alloying under the Nitrogen atmosphere was the maximal concentration of nitrogen in the structure 0,208% after 24 hours of milling (dependency on time was linear), which means, the method of milling under the Nitrogen atmosphere was successful. XRD of milled samples showed the existence of the only FCC single solid solution phase, while samples milled under the Nitrogen atmosphere showed the trend of the growth of the lattice parameter with the increasing nitrogen content. There was observed the presence of the chromium nitrides precipitates on the grain boundaries of the FCC phase in microalloyed samples. All specimen were contaminated by a mixture of metallic oxides and manganeese sulphides, which were present in the default manganeese powder. The greatest value of microhardness showed the duplex sample. The increase in values of microhardness (344 HV 0,3) in comparison with the standard sample (262,9 HV 0,3) was recorded on the samples milled under the nitrogen atmosphere, which conforms the positive influence of the nitrogen content on strength characteristics of this alloy.

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Teyssier, Angélique. "Caractérisation des phases solides colmatantes observées lors du traitement acide de minerais uranifères : contribution à l’étude des équilibres liquides-solides dans le système complexe Al – Fe – K – P – S – H2O (± Ca et Mg)." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10132.

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Lors de l'extraction de l'uranium par lixiviation acide, AREVA fait face à des phénomènes transitoires de précipitation de phases mal cristallisées entrainant un colmatage des installations. Les analyses de ces précipités ont mis en évidence la formation d'un solide jaune minoritaire et d'un blanc majoritaire composé de sulfate de calcium et d'hydroxysulfate d'aluminium. Afin de comprendre les phénomènes menant à la précipitation et pour prévoir, éviter ou limiter leur apparition, les travaux de thèse ont consisté en l'étude expérimentale des équilibres solides-liquide du système complexe Al–Fe–K–P–S–H2O (± Ca et Mg) en milieu acide à 25°C, avec pour objectif l'identification des solides susceptibles d'apparaître en conditions industrielles. Les résultats permettront ainsi de compléter les bases de données thermodynamiques utilisées pour modéliser le comportement global du milieu lors des opérations. Après la mise au point de techniques analytiques appropriées, le travail s'est porté sur la délimitation des équilibres liquide-solides du système relatif au précipité blanc et particulièrement sur l'analyse des ternaires impliquant les hydroxysulfates d'aluminium. Le colmatage se produisant durant la phase d'acidification, l'évolution de la précipitation de ces hydroxysulfates en fonction du pH a été étudiée, afin de caractériser les solides formés en présence de cations minoritaires (Na+, K+, Mg2+, Ca2+) et de définir leurs constantes de solubilités à partir d'un modèle de calcul des coefficients d'activités des ions en solution. Des tests dynamiques sur colonne à partir de minerai naturel ont également été effectués et comparés aux résultats statiques
During the uranium extraction by acid leaching, AREVA observed the precipitation of not well crystallized solid phases, leading to the clogging of various equipment. The analyses of these precipitates highlighted the formation of a minor yellow precipitate and a major white precipitate containing calcium sulphate and aluminium hydroxisulphate. To understand the phenomena leading to the precipitation and to predict, prevent or at least limit their formation, this thesis work consisted of the solid-liquid equilibria experimental study of the Al–Fe–K–P–S–H2O (± Ca and Mg) system in an acidic environment at 25°C, with the identification of solid phases which may appear in natural ore as the major goal. The results could complete the thermodynamic database used to model global behaviour of the environment during acid mining. Based on the observed precipitates, two quaternary systems were defined, such as the H2O-Al3+, Ca2+ // O2-, SO42- system. After the development of appropriate analytical techniques, the work focused on the delimitation of the liquid-solid equilibria of the system based on the white precipitate and particularly on the analysis of the ternaries involving aluminium hydroxisulphates. As clogging occurs during acidification, the hydroxisulphate precipitation depending on the pH was studied in the presence of minority cations (Na+, K+, Mg2+, Ca2+), in order to characterise the solid phases which were formed, and to define their solubility constants. For the solubility constant determination, a calculation model of the ion activity coefficients in solution was used. A dynamic survey on a column containing natural ore was done and compared to static results

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Zander, Johan. "Modelling mechanical properties by analysing datasets of commercial alloys." Licentiate thesis, Stockholm : Industriell teknik och management, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4527.

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20

Hendricks, Nicolette Rebecca. "The application of high capacity ion exchange adsorbent material, synthesized from fly ash and acid mine drainage, for the removal of heavy and trace metal from secondary Co-disposal process waters." Thesis, University of the Western Cape, 2005. http://hdl.handle.net/11394/1455.

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In South Africa, being the second largest global coal exporter, coal mining plays a pivotal role in the growth of our economy, as well as supplying our nation’s ever increasing electricity needs; while also accounting for more than 10% of the 20 x 109 m3 water used annually in the country. Coal mining may thus be classified as a large-scale water user; known to inevitably generate wastewater [acid mine drainage (AMD)] and other waste material, including fly ash (FA). Current and conventional AMD treatment technologies include precipitation–aggregation (coagulation/flocculation) – settling as hydroxides or insoluble salts. The process stream resulting from these precipitation processes is still highly saline, therefore has to undergo secondary treatment. The best available desalination techniques include reverse osmosis (RO), electro dialysis (ED), ion exchange and evaporation. All available treatment methods associated with raw AMD and its derived process stream fall prey to numerous drawbacks. The result is that treatment is just as costly as the actual coal extraction. In addition, remediation only slows the problem down, while also having a short lifespan. Research conducted into converting fly ash, an otherwise waste material, into a marketable commodity has shown that direct mixing of known ratios of FA with AMD to a pre-determined pH, erves a dual purpose: the two wastes (AMD and FA) could be neutralized and produced a much cleaner water (secondary co-disposal [FA/AMD]-process water), broadly comparable to the process water derived from precipitation-aggregation treated AMD. The collected post process solid residues on the other hand, could be used for production of high capacity ion exchange material (e.g. zeolite A, faujasite, zeolite P, etc.). The produced ion exchange material can subsequently be utilized for the attenuation of metal species in neutralized FA/AMDprocess waters.
Magister Scientiae - MSc

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21

Abi, rached Eleonora. "Molybdates de zirconium-cérium/plutonium issus du retraitement du combustible nucléaire usé : structure locale et mécanismes de précipitation." Electronic Thesis or Diss., Centrale Lille Institut, 2022. http://www.theses.fr/2022CLIL0010.

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Le recyclage du plutonium issu du combustible nucléaire usé des réacteurs à eau pressurisée permet une économie significative des ressources et une diminution de la radiotoxicité des déchets à long terme. La mise en œuvre du multi-recyclage permettrait d’accroitre ces avantages, cependant, son impact sur la composition des solutions de dissolution et, par voie de conséquence, sur la précipitation de phases indésirables telles que les molybdates de zirconium doivent au préalable être étudié avec attention.Travaillant à des concentrations permettant d’optimiser la quantité de précipité à des fins d’étude, une première thèse sur le sujet a permis d’établir le diagramme de prédominance des molybdates de zirconium en fonction de la teneur en éléments IV de la solution de dissolution. La présente thèse a été réalisée dans l’objectif de reproduire les essais de précipitation dans des conditions plus proches du milieu de dissolution industriel, de comprendre les mécanismes de formation des phases, et de déterminer l’origine des écarts de composition de l’une d’entre elles par rapport au composé de référence, ZrMo2O7(OH)2(H2O)2.La mise en œuvre de techniques de caractérisation variées portant à la fois sur la solution et le solide (diffraction X sur poudre, diffusion X in situ à plusieurs échelles, RMN, Raman) a permis d’affiner le diagramme d’existence des molybdates de zirconium et d’éléments IV en utilisant ces concentrations proches des conditions industrielles, à la fois en système simulant (cérium) et en actif (plutonium), de proposer des mécanismes de précipitation passant par la néoformation de clusters mais également d’envisager un mécanisme de substitution entre le molybdène et le zirconium au sein de la phase ZrMo2O7(OH)2(H2O)2, qui permettrait d’expliquer la sur-stœchiométrie en molybdène des échantillons précipités
The recycling of plutonium from spent nuclear fuel, coming from pressurized water reactors, allows a significant saving of resources and a reduction of the long-term radiotoxicity of waste. The implementation of multi-recycling would increase these advantages. However, its impact on the composition of the dissolution solution and, consequently, on the precipitation of undesirable phases such as zirconium molybdate must be carefully studied in advance.A first thesis was able to establish the predominance diagram of zirconium molybdates, as a function of the element IV content in the dissolution solution, by using concentrations that allow the optimization of the amount of precipitate for research purposes. The present thesis was carried out with the objective of reproducing the precipitation studies under conditions closer to the industrial dissolution environment, aiming to understand the mechanisms of the phase formation, and to determine the origin of the composition differences of one of them compared to the reference compound, ZrMo2O7(OH)2(H2O)2.The application of various characterization techniques involving the solution and the solid (powder X-ray diffraction, in situ X-ray scattering at several scales, NMR, Raman) has permitted to refine the existence diagram of zirconium and element IV molybdates using those concentrations that are similar to the industrial conditions in both simulant (cerium) and active (plutonium) system. These techniques has also allowed to suggest precipitation mechanisms through the cluster neoformation and to consider a substitution mechanism between molybdenum and zirconium within the ZrMo2O7(OH)2(H2O)2 phase, which would explain the molybdenum over-stoichiometry of the precipitated samples

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USSUI, VALTER. "Preparacao e caracterizacao de ceramicas de ZrOsub(2)-Ysub(2)Osub(3)-TiOsub(2) para aplicacoes em celulas a combustivel do tipo oxido solido." reponame:Repositório Institucional do IPEN, 2003. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11081.

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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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23

Lachal, Marie. "Etude des mécanismes d'insertion/désinsertion des cations alcalins (Li+/Na+) au sein de la structure olivine FePO4 pour accumulateurs Li-ion et Na-ion." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI035/document.

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Dans le cadre du développement des technologies Na-ion, le composé NaFePO4, équivalent chimiquedu matériau très attractif LiFePO4, représente une alternative intéressante aux problèmes deressourcement du lithium. Toutefois, les composés LiFePO4 et NaFePO4 de structure olivineprésentent des divergences de comportement structural et électrochimique lors de l'insertioncationique. Ce travail présente une analyse des mécanismes de (dés)insertion des ions Li+ et Na+ ausein de la phase FePO4 par voie chimique et électrochimique. Les échantillons de LiFePO4 ont étésynthétisés par deux méthodes différentes (hydrothermale et précipitation), puis délithiéschimiquement via différents procédés. Dans un premier temps, les analyses structurales (DRX)associées aux analyses nucléaires ont permis d'effectuer un suivi de la cinétique de réaction. Nousavons montré que la présence de joints de grains, issus du traitement thermique effectué, limitefortement la vitesse de délithiation. L'analyse de l’évolution des domaines de cohérences a permis deproposer un mécanisme de délithiation original de type "Coeur-Coquille" avec un coeur de LiFePO4,confirmé par HRTEM et STEM-EELS. Dans un deuxième temps, afin de comparer les mécanismes dedélithiation chimique et électrochimique, l’insertion et la cyclabilité des ions Li+ et Na+ ont étécaractérisées en demi-cellules lithium et sodium. Bien que la signature électrochimique des matériauxLiFePO4 et NaFePO4 soit différente, les performances en termes de capacité restituée ou de tenue enpuissance s'avèrent similaires. Enfin, l'insertion électrochimique des ions Li+ et Na+ au sein d'unepoudre comportant des défauts structuraux a été caractérisée par DRX Operando durant un cycle decharge / décharge effectué à régime lent. Ces analyses ont révélées que la co-insertion cationiques'effectue via une solution solide de type LixNayFePO4 (0
As part of the development of Na-ion technology, NaFePO4 compound, chemical equivalent of theattractive LiFePO4 material, would be a promising option facing possible lithium shortage. However,olivine-type LiFePO4 and NaFePO4 display different structural and electrochemical behaviors duringcationic insertion. This thesis presents an analysis of the (de)insertion mechanisms of Li+ and Na+ ionswithin olivine-type FePO4 by chemical and electrochemical means. Samples of LiFePO4 weresynthesized by two different methods (hydrothermal and precipitation), then chemically delithiated bydifferent processes. In a first step, structural analysis (XRD) associated with nuclear analyses enabledfollowing the reaction kinetics. We have pointed out that the presence of grain boundaries, resultingfrom the heat treatment, strongly limits the delithiation kinetics. The analysis of the evolution of thecoherency domains enabled us to propose an original "Shrinking Core" type delithiation mechanismwith a core of LiFePO4, observed by HRTEM and STEM-EELS. In a second step, in order to comparechemical and electrochemical mechanisms, insertion and cyclability of Li+ and Na+ were characterizedin lithium and sodium half-cells. Although the electrochemical signature of LiFePO4 and NaFePO4materials is different, the performances in terms of restored capacity or power capability are similar.Finally, electrochemical insertion of Li+ and Na+ in a powder comprising structural defects wascharacterized by operando XRD, during a charge / discharge cycle performed at low rate. Theseanalyses revealed that the cationic co-insertion takes place via a solid solution LixNayFePO4(0

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Peçanha, Bruna Rachel de Britto. "Síntese de polímeros de impressão molecular e sua aplicação na técnica de extração em fase sólida." Niterói, 2017. https://app.uff.br/riuff/handle/1/3102.

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Polímeros de impressão molecular (MIPs) foram sintetizados e aplicados como adsorventes na técnica de extração em fase sólida (EFS). O método de polimerização por precipitação foi utilizado para a síntese dos polímeros, devido à simplicidade de preparo, altos rendimentos e obtenção de partículas mais uniformes, devido a não trituração do polímero. O MIP foi sintetizado com ácido metacrílico (MAA) como monômero funcional, trimetacrilato de trimetilolpropano (TRIM) e dimetacrilato de etilenoglicol (EDMA) como agentes de reticulação e o cloridrato de amilorida (AMI) foi escolhido como molécula-molde. Diferentes proporções de MAA, TRIM, EDMA, volume e tipo de solvente foram utilizadas para ajuste das condições ideais de síntese. Os MIP foram avaliados quanto à capacidade de adsorção comparando-se a polímeros sintetizados na ausência da molécula-molde (NIP, polímeros não impressos). O solvente de elevada polaridade empregado na síntese (THF:MeOH:H2O) permitiu o emprego da técnica para moléculas polares como AMI. O controle no volume de solvente permitiu a obtenção de partículas maiores, de modo que a EFS foi realizada em condições usuais, o que confere um potencial para aplicação dessa técnica de polimerização na preparação de adsorventes para EFS. O polímero que apresentou maior capacidade adsortiva no ensaio realizado em tampão citrato-acetato pH 6,5 foi o MIP/NIP 12 (AMI:MAA:TRIM 1:8:10), com uma taxa média de adsorção de 83 e 88% para NIP e MIP, respectivamente. A adsorção foi elevada devido a interação iônica entre MAA e AMI promovida pelo controle de pH, porém foi não específica. O polímero MIP/NIP 12 foi aplicado como adsorvente na EFS, onde a recuperação de AMI foi avaliada nos resíduos de carregamento e eluição com solventes. O carregamento com tampão citrato-acetato pH 6,5 foi o ideal, favorecendo a interação iônica do polímero com o analito. A eluição total de AMI do cartucho somente ocorre após lavagem com o solvente na presença de ácido, que protona os grupos carboxila do polímero, rompendo assim a interação iônica com o analito
Molecularly imprinted polymers (MIPs) were synthesized and applied as adsorbents in solid-phase extraction technique (SPE). The polymers have been synthesized by precipitation polymerization method because of its simplicity, high yields and good control of final size and shape of particles. MIP was synthesized using methacrylic acid (MAA) as functional monomer, trimethylolpropane trimethacrylate (TRIM) and ethyleneglycol dimethacrylate (EDMA) as cross-linker and amiloride hydrochloride (AMI) was chosen as template. Different ratios of MAA, TRIM and EDMA, volume and type of solvent were used to adjust the optimal synthesis conditions. The MIP were tested for adsorption capacity compared to the polymers synthesized in the absence of template molecule (NIP, non-imprinted polymers). The polar solvent mixture used (THF:MeOH:H2O) allowed the synthesis of MIP of polar molecules as AMI. The solvent volume control afforded the larger particles so the SPE was performed in the usual conditions, giving a potential application for this polymerization technique in the preparation of adsorbents for SPE. The polymers with higher adsorption capacity at the test performed in citrateacetate buffer pH 6,5 was MIP/NIP 12 (AMI:MAA:TRIM 1:8:10) with adsorption rate of 83 and 88% for NIP and MIP, respectively. The recognition of MIP was due to ionic interaction between MAA and AMI promoted by pH control, but was not specific. The polymer MIP/NIP 12 was used as a solid-phase extraction sorbent and the recoveries of AMI was evaluated using different loading and elution conditions. The loading with buffer citrate-acetate pH 6,5 was optimal, due to ionic interaction of the polymer with the analyte. Total elution of AMI bound to the polymers only occurs after washing with a acid-containing solvent, because of protonation of the carboxyl groups of the polymer and disrupting the ionic interaction with the analyte

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Bamini, Edwige. "Influence de l'azote dans les aciers inoxydables austénitiques sur les phénomènes de précipitation et sur la résistance à la corrosion." Grenoble INPG, 1997. http://www.theses.fr/1997INPG4212.

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Les caracteristiques metallurgiques et la resistance a la corrosion localisee de deux nuances d'aciers austenitiques inoxydables a forte teneur en azote de type 316ln sont etudiees en vue d'une utilisation sous des sollicitations mecaniques dans un milieu corrosif (fatigue-corrosion et frottement-corrosion contre un polymere uhmwpe). La presence d'azote en forte teneur dans la matrice austenitique augmente les caracteristiques mecaniques. L'origine provient d'un durcissement par solution solide interstitielle et d'un durcissement par affinement de grains du a la presence de nitrures crnbn dans l'acier hypertrempe. Une analyse microstructurale apres traitements thermiques a mis en evidence la formation d'autres nitrures (cr#2n) et de phases intermetalliques ( et ). La phase z (crnbn), stable jusqu'a la temperature de fusion de l'acier est issue d'une transformation de nitrures nb#xn#y. En milieu acide et en milieu chlorure, la presence d'azote augmente considerablement la resistance a la corrosion par piqure et par crevasse, et ameliore les cinetiques de repassivation apres une depassivation mecanique. L'azote intervient en s'accumulant en extreme surface du film passif par segregation anodique et reagit avec le milieu sous la forme nh#3 et nh#4#+.

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Vélez, José Sebastián López. "Equilíbrio sólido-líquido na precipitação de lisozima usando succinato, tartrato e citrato de sódio." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-22092016-085821/.

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A precipitação e cristalização de proteínas são operações unitárias amplamente utilizadas na indústria biotecnológica. A formação de precipitado nestas operações é muitas vezes atingida por meio da adição de um sal que diminui a solubilidade da proteína, ou seja, o chamado fenômeno de saltingout. A principal informação para o estudo da precipitação e da cristalização é o diagrama de fases, em que a solubilidade da proteína é apresentada em função das variáveis do sistema (temperatura, pH, concentração de sal). Outra medida importante é o segundo coeficiente virial, que é uma medida indireta da interação intermolecular. A combinação de ambas as informações é fundamental para a identificação das condições em que fases cristalina ou amorfa são obtidas. O equilíbrio sólido-líquido da lisozima de clara de ovo de galinha em soluções aquosas contendo sais biodegradáveis (succinato de sódio, citrato de sódio e tartarato de sódio) foi estudado por meio da determinação da solubilidade da proteína e do segundo coeficiente virial em função da força iônica. Os dados experimentais do segundo coeficiente virial em função da força iônica foram medidos por meio de cromatografia de autointeração. Estes dados foram correlacionados por modelos apropriados. As informações de solubilidade e do segundo coeficiente virial da proteína foram combinadas para gerar condições experimentais adequadas na identificação da janela de cristalização, i.e., as condições em que uma fase cristalina é obtida. Uma matriz do tipo placa de cultivo foi usada para os experimentos de cristalização. Os resultados experimentais mostraram que as regiões das fases cristalina e amorfa no diagrama de fases são funções simultâneas do segundo coeficiente virial, como parâmetro termodinâmico, e da supersaturação, como parâmetro cinético. Os três sais foram capazes de induzir o efeito salting-out, sendo o succinato de sódio o sal mais eficaz na diminuição da solubilidade da lisozima, seguido pelo tartarato de sódio e pelo citrato de sódio. No caso da lisozima, cristais foram obtidos em soluções de succinato de sódio e tartarato de sódio, e as condições nas quais a fase cristalina é formada foram identificadas; no entanto, para o citrato de sódio somente fase amorfa foi observada. Em conjunto, estes resultados mostram que estes sais biodegradáveis são agentes precipitantes promissores.
The precipitation and crystallization of proteins are unit operations widely used in the biotechnology industry. The formation of a solid phase in these operations is often achieved by adding a salt that lowers the protein solubility, the so-called salting-out phenomenon. The key information to study precipitation or crystallization is the phase diagram, in which the solubility of a protein is presented as a function of system variables (temperature, pH, salt concentration). Another important parameter is the second virial coefficient, which is an indirect measure of intermolecular interactions. The combination of both kinds of information is fundamental to identify the conditions in which crystal and amorphous phases can be formed. The solid-liquid equilibrium of hen egg-white lysozyme in aqueous solutions containing biodegradable salts, viz., sodium citrate, sodium tartrate and sodium succinate, was studied by determining both the protein solubility and the second virial coefficient as a function of ionic strength. Experimental data for second viral coefficient as a function of ionic strength were obtained through self-iteration chromatography. These data were correlated by appropriate models. The protein solubility and the second virial coefficient information were combined to generate adequate experimental conditions to identify the so-called crystallization slot, i.e., the conditions in which a crystalline solid phase is obtained. A plate matrix disposition was used for the crystallization experiments. The experimental results show that the crystal and amorphous regions in the phase diagram depend simultaneously on the second virial coefficient, as a thermodynamic parameter, and on the supersaturation ratio, as a kinetic parameter. All these salts were able to induce salting-out, being sodium succinate the most effective one in decreasing lysozyme solubility, followed by sodium tartrate and sodium citrate. For lysozyme in sodium succinate and sodium tartrate solutions, the conditions for which a crystal phase is formed were identified; however, for sodium citrate only amorphous solid phases were observed.! Overall, these results show that these biodegradable salts are promising precipitating agents.

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Jebavá, Alžběta. "Polovodičová keramika pro termoelektrické aplikace." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2015. http://www.nusl.cz/ntk/nusl-217139.

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This diploma thesis focuses on the syhnthesis of multicomponent ceramic system based on Ca-(Mn,Co)-O. The thesis is devided in theoretical and experimental part. The theoretical part is describing ceramic materials for thermoelectric application, preparation and synthesis of these materials and their processing. The experimental part is dealing with synthesis of ceramic powder which is processed to the porous ceramics. The properties of prepared porous ceramics are observed.

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Guerin, Guillaume. "Évaluation du devenir de la circulation atmosphérique dans le sud-est de la France et de l'enneigement dans les Alpes du Sud entre 1950 et 2100." Electronic Thesis or Diss., Université Côte d'Azur, 2024. http://www.theses.fr/2024COAZ2034.

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La thèse explore les impacts du réchauffement climatique sur la circulation atmosphérique et l'enneigement dans le sud-est de la France, en particulier les Alpes du Sud. Le réchauffement climatique affecte la région méditerranéenne de manière significative, provoquant des variations dans les précipitations neigeuses et la couverture neigeuse depuis les années 1980. Les Alpes du Sud, dépendantes du manteau neigeux pour le tourisme hivernal, sont particulièrement vulnérables à ces changements. L'étude s'articule autour de plusieurs objectifs clés : analyser les évolutions historiques des précipitations neigeuses, comprendre les mécanismes synoptiques responsables des chutes de neige, et projeter l'avenir de l'enneigement en utilisant des modèles climatiques. Les questions de recherche incluent également l'identification des circulations atmosphériques spécifiques influençant les précipitations neigeuses. La thèse s'appuie sur des réanalyses climatiques (ERA-INTERIM et ERA5), des modèles de projections CMIP6 et des observations locales de stations nivologiques du réseau Météo-France, pour analyser les tendances passées et futures. Des techniques statistiques avancées, telles que l'analyse en composantes principales et la classification ascendante hiérarchique, sont utilisées pour développer une classification précise des types de circulation atmosphérique. Les résultats montrent une tendance générale au réchauffement, avec une augmentation des températures et une variabilité accrue des précipitations solides. Les configurations cycloniques et méridionales sont identifiées comme favorisant les chutes de neige abondantes, particulièrement en présence de dépressions sur l'Atlantique Nord et l'Europe occidentale. Les scénarios SSP (Shared Socioeconomic Pathways) montrent des variations à la baisse dans la fréquence des circulations atmosphériques favorables aux précipitations neigeuses, suggérant des changements significatifs dans la dynamique climatique de la région. La thèse apporte donc une contribution importante à la climatologie régionale en améliorant la compréhension des interactions entre circulation atmosphérique et précipitations solides dans les Alpes du Sud. Elle propose des projections futures cruciales pour la gestion des ressources en eau et l'adaptation des infrastructures touristiques dans un contexte de réchauffement climatique
The thesis explores the impacts of climate change on atmospheric circulation and snow cover in southeastern France, particularly in the Southern Alps. Climate change significantly affects the Mediterranean region, causing variations in snowfall and snow cover since the 1980s. The Southern Alps, which rely heavily on snow cover for winter tourism, are particularly vulnerable to these changes. The study focuses on several key objectives : analyzing historical trends in snowfall, understanding the synoptic mechanisms responsible for solid precipitation, and projecting the future of snowfall using climate models. The research questions also include identifying specific atmospheric circulations that influence snowfall. The thesis draws on climate reanalyses (ERA-INTERIM and ERA5), CMIP6 projection models, and local observations from the Météo-France network of snow stations to analyze past and future trends. Advanced statistical techniques, such as Principal Component Analysis and Hierarchical Ascendant Classification, are used to develop a precise classification of atmospheric circulation types. The results show a general warming trend, with rising temperatures and increased variability in solid precipitation. Cyclonic and meridional configurations are identified as favoring heavy snowfalls, particularly in the presence of depressions over the North Atlantic and Western Europe. SSP (Shared Socioeconomic Pathways) scenarios show a downward trend in the frequency of atmospheric circulations favorable to snowfall, suggesting significant changes in the region's climate dynamics. The thesis thus makes an important contribution to regional cli-matology by enhancing the understanding of interactions between atmospheric circulation and solid precipitation in the Southern Alps. It offers crucial future projections for water resource management and the adaptation of tourist infrastructure in a warming climate context

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Velaga, Sitaram P. "Preparation of Pharmaceutical Powders using Supercritical Fluid Technology : Pharmaceutical Applications and Physicochemical Characterisation of Powders." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4006.

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Arnaud, Brigitte. "Evolution des microstructures de fatigue à chaud dans des solutions solides à base nickel : mise en évidence d'une cavitation intragranulaire." Paris 6, 1986. http://www.theses.fr/1986PA066054.

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Analyse par microscopie électronique à transmission de l'évolution structurale des alliages Ni-4%atsi et Ni-6%atge sollicités en traction-compression. Analyse de l'évolution des grains, des sous-grains, des réseaux de dislocation formés au cours de la fatigue, des agglomérations de lacunes ou d'interstitiels avec formation de cavités ou de précipités.

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Swash, Peter Michael. "The hydrothermal precipitation of arsenical solids in the Ca-Fe-AsO4-SO4 system at elevated temperatures." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244068.

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Tuel, Alain. "Caracterisation de la structure de silices de precipitation par resonance magnetique nucleaire de solide et de leur morphologie." Paris 6, 1987. http://www.theses.fr/1987PA066653.

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Etude par rmn en phase solide et par analyses d'images de microscopie electronique. Evaluation du pourcentage des differentes especes, de la densite en hydroxyles et de leur evolution en fonction d'un traitement thermique determine. Etude de la structure geometrique des surfaces apres griffage de petites molecules (diols et alcools). Proposition d'un modele ou la surface des silices de precipitation est constitue d'une couche tres desorganisee d'epaisseur donnee. Caracterisation des projections bidimensionnelles des agregats de silice par des exposants fractals, a partir des micrographies electroniques

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Lützenkirchen, Johannes. "Description des interactions aux interfaces liquide - solide a l'aide des modeles de complexation et de precipitation de surface." Université Louis Pasteur (Strasbourg) (1971-2008), 1996. http://www.theses.fr/1996STR13111.

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Nous avons applique des modeles de complexation et precipitation de surface a des equilibres dans le cas des interfaces solution aqueuse-(hydr)oxyde. Dans ce contexte, nous nous sommes interesses a la fois a des problemes d'estimation de parametres pour ces modeles et plus particulierement a des systemes cd et zn en presence de silices cristallines (quartz et cristobalite). Les resultats experimentaux indiquent une difference significative quant aux deux systemes (quartz et cristobalite) et quant aux cations (cd et zn). La raison de la difference entre le quartz et la cristobalite a pu etre mise en evidence par une approche experimentale (titrages potentiometriques et etudes de spectroscopie de surface). Elle est due a des impuretes de sodium a la surface de la cristobalite. Aussi, avons-nous discute les problemes provenant de ces impuretes lors de l'application aux experiences en colonne du modele permettant de decrire la sorption de cd et zn sur la cristobalite. La difference entre le comportement de cd et de zn ne peut pour l'instant provenir que des essais de modelisation, ou dans plusieurs cas la formation de complexes de surface monodentates (cd) et bidentates (zn) a du etre supposee. Des donnees experimentales de spectroscopie de surface permettant de verifier ces hypotheses de modelisation n'existent pas a ce jour. Nous avons constate des problemes d'estimation de parametres pour des donnees de titrages et des donnees de sorption et propose des alternatives en ce qui concerne des hypotheses et les codes de calcul utilises

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Larguet, Nour-Eddine. "Contribution à l'étude de la formation de l'état quasicristallin." Rouen, 1995. http://www.theses.fr/1995ROUES025.

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Le retour à l'équilibre d'une solution solide sursaturée contenant 2 à 3 at % de Mn d'une part et l'effet du recuit à 530° C sur la structure de la phase T2 du système Al-Li-Cu d'autre part ont été étudiés par diffraction X in-situ et par M. E. T. Dans le système Al-Mn et pour la première fois, la précipitation d'une phase quasicristalline à partir d'une solution solide sursaturée a été mise en évidence. Elle constitue une étape intermédiaire métastable du retour à l'équilibre vers la phase stable Al6Mn. La teneur en Mn de cette phase a été déterminée par des mesures en diffraction X et par MET/EdX. La valeur obtenue comprise entre 9,4 et 10,8 at%, est fonction de la concentration nominale de l'alliage et fixe ainsi la limite inférieure de formation d'une structure quasicristalline dans le système Al-Mn. Dans le système Al-Li-Cu des échantillons de composition Al6Li3Cu, ayant subi des recuits isothermes à 530°C sous 40 atm. D'argon, ont été étudiés. Nous avons entrepris une étude quantitative des écarts au modèle du quasicristal parfait par des mesures de diffraction X à température ambiante. Le recuit prolongé élimine progressivement les défauts de type phason, accompagnant une modification de la composition chimique de la phase T2. Des modèles de structures approximantes ont été simulés par un calcul des spectres de diffraction électronique et de rayons X. Les modèles les plus proches de l'expérience correspondent à des approximants orthorhombiques d'ordre (5/3, 5/3, 3/2) pour l'alliage brut de coulée et (8/5, 5/3, 5/3) pour le matériau recuit. Les paramètres de maille varient de 50 à 60 ang

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Lopez, Jean-Marie. "CARACTERISATION DE LA PRECIPITATION DU CARBONE DANS DES ALLIAGES Fe-C PAR DES MESURES MAGNETIQUES ET MAGNETOMECANIQUES." Toulouse, INSA, 1986. http://www.theses.fr/1986ISAT0018.

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ETUDE SUR DES ALLIAGES Fe-C AVEC DES TENEURS EN CARBONE COMPRISES ENTRE 65 ET 500 PPM EN POIDS, POUR LES TROIS ETATS STRUCTURAUX SUIVANTS: LE CARBONE EST EN SOLUTION SOLIDE (200 PPM), LE CARBONE PRECIPITE DANS LA MATRICE SOUS FORME DE CARBURES (0,1 MU M A 1,5 MU M), LE CARBONE PRECIPITE ESSENTIELLEMENT AUX JOINTS DE GRAINS SOUS FORME DE CARBURES PLUS GROSSIERS (5 A 10 MU M). CARACTERISATION DE CES ETATS PAR DES METHODES MAGNETIQUES. ETUDE DE LA PRECIPITATION DU CARBONE DANS LE PREMIER ETAT STRUCTURAL APRES VIEILLISSEMENT A 80 C ET 200 C.

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Countess, Stephanie Jean. "Evaluating Leachability of Residual Solids from Hydraulic Fracturing in the Marcellus Shale." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/56156.

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The process of natural gas extraction through hydraulic fracturing produces large quantities of fluid containing naturally-occurring salt, radionuclides, and heavy metals which form residual solids during storage and treatment. The purpose of this research was to characterize the residual solids from hydraulic fracturing operations in the Marcellus Shale to predict the leaching behavior of select elements in disposal environments. Samples collected for this research were: (1) drilling mud, (2) treated sludge from the chemical treatment of process waters, (3) solids from the gravity settling of produced water, and (4) sludge solidified prior to disposal in a municipal landfill. These samples were subjected to various digestion techniques to determine the composition and leaching potential for elements of concern. Strong acid digestions were performed to determine the total environmentally available composition, whereas weak acid digestions were used to predict the leaching potential of these solids under various environmental conditions. The extraction fluids for the leaching experiments included weak acetic acid, acid rain, reagent water, and synthetic landfill leachate. Solids were agitated in a standard tumbling apparatus to simulate worst-case conditions based on ASTM and EPA recommendations. Results from EPA's Toxicity Characteristic Leaching Procedure (TCLP) were used to determine if solids were considered hazardous based on the metal leaching potential. The results from strong and weak acid digestions were compared to better understand the types and quantity of materials that have the potential to leach from the samples. This research may be used to develop best management practices for hydraulic fracturing residual solids.
Master of Science

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Brancho, Jennie. "Effects of Precipitation Patterns on Sediment, Nutrient, and Biofilm Dynamics in an Acid Mine Drainage Stream." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou155439364661881.

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Schmuck-Pareige, Cristelle. "Etude par sonde atomique tomographique et simulation Monte Carlo de la mise en ordre et de la séparation de phase dans des superalliages modèles Ni-Cr-Al." Rouen, 1997. http://www.theses.fr/1997ROUES073.

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La formation de précipités de type Ni3Al à partir d'une solution solide NiCrAl, fait intervenir les processus de mise en ordre et de séparation de phases. Ces processus peuvent être simultanés ou non, continus ou de type germination et croissance. Nous avons étudié les chemins de transformations dans des alliages NiCrAl, à l'échelle atomique et dans l'espace réel 3D, par sonde atomique tomographique et par simulation Monte Carlo. La méthode Monte Carlo utilisée est basée sur la modélisation du mécanisme de diffusion lacunaire. L'étude expérimentale d'un alliage faiblement sursaturé a montré qu'un régime de germination et croissance intervient. Dans le cadre de la théorie de coalescence de LSW, l'aluminium peut être considéré comme le seul soluté qui contrôle la cinétique de coalescence. L'énergie interfaciale des précipités ' est voisine de celle mesurée dans les alliages binaires NiAl. Après paramétrisation du modèle de simulation utilisé, la confrontation des résultats simulés aux résultats expérimentaux a montré que la méthode Monte Carlo décrit de manière quantitative les cinétiques. L'étude des tout premiers stades de transformations dans des alliages de différentes sursaturations a révélé que les précipités ' se forment à partir de petites zones ordonnées enrichies en aluminium qui présentent la même concentration en chrome que leur environnement. Avant la formation de ces zones, un ordre à courte distance de type Ni3Cr et des fluctuations d'ordre à grande distance l1#2 se développent. La taille et la densité de ces fluctuations d'ordre à grande distance l1#2 sont d'autant plus importantes que la concentration nominale en aluminium est élevée et/ou que la concentration nominale en chrome est faible. Lorsque la sursaturation de l'alliage augmente, on tend vers un ordre à grande distance l1#2 envahissant l'espace, caractérisé par une forte densité de parois d'antiphases.

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Tochon, Patrice. "Etude numérique et expérimentale d'électrofiltres industriels." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10233.

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Ce travail porte sur les filtres electrostatiques ou electrofiltres servant a epurer les gaz charges de particules solides. Par l'intermediaire d'un banc d'essais en encrassement controle, concu et realise sur la plate-forme esther du greth (groupement pour la recherche sur les echangeurs thermiques) et d'un modele numerique developpe lors de ce travail a partir du logiciel trio (concu au cea), l'etude des performances de differentes geometries de filtres a ete menee. Les differents parametres electriques, hydrauliques et particulaires regissant la collecte de particules solides en presence de champ electrique ionise ont ete identifies, mesures et modelises. Le modele numerique, valide avec les resultats experimentaux obtenus lors de cette etude et issus de la litterature, permet de decrire tres fidelement les phenomenes locaux et globaux qui se produisent dans une geometrie quelconque. De plus, des etudes parametriques ont ete menees afin de proposer quelques geometries ameliorees permettant d'augmenter les performances de collecte d'electrofiltres industriels. Enfin, en collaboration avec le cetiat (centre technique des industries aerauliques et thermiques), des campagnes de mesures sur un site industriel ont permis d'identifier le type de poussieres susceptibles d'etre rejetees dans l'atmosphere, ainsi que les problemes propres aux installations industrielles de grandes dimensions. Le modele numerique a egalement ete eprouve sur les donnees issues de ces campagnes. Au terme de cette etude, un outil experimental en encrassement controle performant, la boucle pacific, et un outil de simulation numerique permettant une aide au dimensionnement d'electrofiltres sont disponibles.

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Macchi, Juan Agustin. "Phase transformations, microstructure heterogeneities and resulting mechanical properties in as-quenched and tempered martensitic steels." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0248.

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Les aciers martensitiques sont connus et utilisés depuis des millénaires, mais l'origine de leur résistance et de leur écrouissage est restée une source de controverse. Depuis quelques années, la compréhension de leur comportement mécanique est en train de changer de paradigme. De nombreux chercheurs ont mis en évidence l'intérêt de ne pas décrire la martensite en lattes comme une microstructure homogène mais plutôt comme un agrégat multi phasé, un composite, résultant de la nature séquentielle de la transformation de phase à basse température. Selon ces nouveaux schémas, le comportement de la martensite est contrôlé par les hétérogénéités microstructurales, c'est-à-dire la distribution spatiale des tailles des lattes, des dislocations, des ségrégations de carbone et des carbures, et pas seulement par leurs valeurs moyennes. A ces éléments microstructuraux observables s'ajoutent de grandes distributions de contraintes internes hydrostatiques et déviatoriques résultant du processus de transformation de phase displacive. Ce travail contribue à ce nouveau mouvement en fournissant une description quantitative de ces distributions dans les aciers martensitiques trempés et revenus et leur impact sur leurs comportements mécaniques grâce à une approche micromécanique complète. Nous avons d'abord développé une méthodologie pour déterminer les densités de dislocation dans la martensite et dans l'austénite le long de la transformation par des expériences in situ de DRXHE. Sur la base d'un raisonnement métallurgique, la distribution spatiale de la densité de dislocation ainsi que le durcissement associé ont été estimés pour la première fois. Des expériences de revenu en DRXHE in situ ont également été réalisées pour caractériser la restauration de l'état trempé. Une approche originale de modélisation tenant compte de la distribution spatiale des dislocations a été mise en place pour prédire la diminution de leur densité lors d'un traitement thermique. De même, les microtextures des microstructures étudiées ont été étudiées par MEB-EBSD afin d'évaluer la distribution en taille des différentes caractéristiques de la martensite, comme les lattes, les blocs, les paquets et les grains d'austénite antérieurs. Une approche statistique combinant cette dernière contribution au durcissement avec celle associée aux dislocations explique avec succès la distribution observée de la limite d'élasticité locale dans les microstructures telles que trempées.Des expériences de revenu DRXHE in situ et des observations complémentaires APT et MET ont été utilisées pour caractériser également l'état de précipitation respectif des carbures de transition et de la cémentite ainsi que les ségrégations de carbone au cours des traitements thermiques. Tout ce travail expérimental a servi à développer et calibrer un modèle de transformation de phase pour calculer la ségrégation du carbone sur les dislocations, les carbures de transition et les états de précipitation de la cémentite. Ce modèle a par exemple permis de prédire la suppression de la précipitation des carbures de transition dans les aciers à très faible teneur en carbone. L'étude du revenu est nécessaire pour comprendre le renforcement dû au seul carbone dans la martensite.Enfin, notre modèle micromécanique original décrivant le comportement de la martensite comme une transition élastique/plastique étendue tient compte du durcissement combiné précédent dû aux effets de taille et aux dislocations, de la distribution des contraintes internes dues à la transformation et de l'état de revenu (relaxation, restauration, ségrégation et état de précipitation). Le modèle explique avec succès la résistance et l'écrouissage des aciers étudiés (trempés et revenus)
Martensitic steels have been known and used for millennia now, but the origins of their strength and work hardening have remained a source of controversy. Since few years, the understanding of their mechanical behavior is changing paradigm. Many researchers have put into evidence the interest not to describe lath martensite as an homogeneous microstructure but more as a multiphase aggregate, a composite, resulting from the sequential nature of the phase transformation at low temperature. According to such new schemes, the martensite behavior is controlled by the microstructural heterogeneities, ie. the spatial distribution of lath sizes, of dislocations, of carbon segregations and of carbides and not only by their mean values. To these observable microstructural elements are added large distributions of hydrostatic and deviatoric internal stresses resulting from the displacive phase transformation process. This work contributes to this new movement by providing a quantitative description of these distributions in as-quenched and further tempered martensitic steels and their impact on their mechanical behaviors thanks to a complete micromechanical approach.We have first developed a methodology to determine the dislocation densities in martensite and in austenite along the transformation by in situ HEXRD experiments. Based on a metallurgical reasoning, the spatial dislocation density distribution as well as its associated hardening were estimated for the first time. In situ HEXRD tempering experiments were also performed to characterize the recovery from the as-quenched state. An original modeling approach accounting for the spatial distribution of dislocations was set up to predict their density decrease during a heat treatment.In the same way, the microtextures of the studied microstructures were investigated by SEM-EBSD in order to assess the size distribution of the different features of martensite, as laths, blocks, packets and prior austenite grains. A statistical approach combining this latter contribution to the hardening with the one associated with dislocations explains successfully the observed distribution of the local yield strength in the as-quenched microstructures.In situ HEXRD tempering experiments and additional APT and TEM observations were used to characterize also the respective precipitation state of transition carbides and cementite as well as the carbon segregations along heat treatments. All this experimental work has served to develop and calibrate a phase transformation model to calculate carbon segregation on dislocations, transition carbides and cementite precipitation states. Such model was for instance able to predict the suppression of transition carbide precipitation in very low carbon steels. The investigation of tempering is necessary to understand the strengthening due the sole carbon in martensite.Finally, our original micromechanical model describing the martensite behavior as an extended elastic/plastic transition accounts for the previous combined hardening due to size effects and dislocations, the distribution of internal stresses due to the transformation and the tempering state (relaxation, recovery, segregation and precipitation state). The model successfully explains the strength and work-hardening of the studied steels (as quenched and tempered)

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41

Hui-YuYang and 楊蕙瑜. "Room temperature precipitation of Bi2-xVxO3+x powder for solid electrolytes." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/53283143904632030621.

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碩士
國立成功大學
資源工程學系碩博士班
101
In the present work,  phased Bi2-xVxO3+x powder has been prepared via chemical precipitation using bismuth chloride (BiCl3) and ammonium metavanadate (NH4VO3) as starting materials while NaOH was applied as the precipitating agent. The precipitation was performed under room temperature. In the first part of this study, the influence of the NaOH/Bi (N) ratio, on the phase composition of the precipitate was investigated. XRD and SEM results revealed that  phase Bi2-xVxO3+x crystals in cubic morphology could be only obtained at a N ratio above 80.; otherwise, BiOCl3 was coexisted. The second part is to observe their reaction mechanism by changing the reaction time. According to the time-resolved experiment, XRD peaks of the precipitate showed a shift to the higher degree due to the incorporation of V5+ ions into the g-Bi2O3 structure with increasing the reaction time. The peak shift became unchanged after reacting for 12 hours, implying that the introduction of V5+ ions was limited. In the third part of this study, the doping ratio of V5+ (Bi2-xVxO3+x, x = 0.01 – 0.5) was varied. The XRD and SEM characterizations showed that some rod-like crystals corresponding to the α phased Bi2O3 was coexisted when the V5+ doping ratio was less than x = 0.03. With increasing V5+ doping ratio, the amount of g-Bi2O3 in cubic morphology gradually increased and became the unique phase when the V5+ doping ratio was more than x = 0.1. According to the DTA/TG investigation, an endothermic peak was observed at 830 °C which is related to the transformation of g-Bi2O3 to d-Bi2O3. Accordingly, the compacts of the synthesized Bi2-xVxO3+x, (x = 0.1 – 0.5) powders were sintered at 800ºC for 24 h to increase the bulk density higher than 90%. It was shown that the sintering treatment did not change the phase composition for Bi2-xVxO3+x, (x = 0.1 – 0.4); however a second phase related to a new cubic-structure Bi2O3 (JCPDS 74-1373) was appeared for Bi2-xVxO3+x (x = 0.5). It implied that this second phase could be only formed under high temperature. The ion electric conductivity of Bi2-xVxO3+x (x = 0.1 – 0.5) sintering bodies was measured by DC method. It was observed that the conductivity increased with increasing the amount of V5+ up to x = 0.4. When Bi3+ was replaced by V5+, interstitial oxygen ions were produced in order to reach the structural charge balance that promoted the conductivity. The conductivity was attained 0.0075 S/cm at 800 °C for Bi2-xVxO3+x (x = 0.4) and abruptly decreased for Bi2-xVxO3+x (x = 0.5) mainly due to the formation of second phase.

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42

"The isotopic study on solid precipitation from a convective cloud : observation and modeling." Thesis, 1989. http://hdl.handle.net/2237/12594.

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43

杉本, 敦子, and Atsuko Sugimoto. "The isotopic study on solid precipitation from a convective cloud : observation and modeling." Thesis, 1989. http://hdl.handle.net/2237/12594.

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44

Dieckmann, Gunther Hans. "Gas-solid precipitation reactions in lamellar solids ; Processing effects and substrate interactions in thin films of Bi₂CaSr₂Cu₂O₈₊x." 1988. http://catalog.hathitrust.org/api/volumes/oclc/19365454.html.

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45

"Effect of calcium (II) and iron (II) on the precipitation of calcium carbonate and iron carbonate solid solutions and on scale inhibitors retention." Thesis, 2012. http://hdl.handle.net/1911/70201.

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Mineral scale formation is important to many areas of science and engineering, from drinking water treatment to oceanography to oil and gas production. In some cases mineral deposition is beneficial, as in water treatment for heavy metal or arsenic removal, and sometimes it is deleterious, as occurs in oil and gas production due to co-produced water. In either case, understanding the mechanisms of precipitation and inhibition is critical. Work in this thesis has focused on the impact of metal ions on mineral scale formation, and control. The results reveal that the addition of metal ions in the pill solution significantly improved the retention of scale inhibitors. Both BHPMP and DTPMP returns were significantly extended by the addition of Ca 2+ and Fe 2+ Also trace levels of Zn 2+ significantly enhanced the performance and retention of both BHPMP and DTPMP. The enhanced scale inhibition may be caused by a complex of metal ions with amine group of polyamino- polyphosphonates. It is known that the effectiveness of inhibitors varies upon the type of scale formed where it has been mentioned in the literature that common calcium carbonate inhibitors are not effective for preventing iron carbonate. Therefore, this work was also intended to investigate the impact of calcium and iron ions in the co-precipitation of iron-calcium carbonate solid solutions (Fe x Ca 1-x CO 3 ). Three different experimental methods were applied to investigate and predict the precipitation of Fe x Ca 1-x CO 3 : Free drift, continuous feeding, and constant composition experiments. The results from all methods showed that calcium carbonate was kinetically favored to precipitate rather than iron carbonate when the solution is supersaturated with respect to calcium carbonate and iron carbonate. In the constant composition experiments a series of solid solutions of iron-calcium carbonate ranging from calcium-rich to iron-rich was precipitated. Based upon the experimental results and the theoretical derivation, a new model in a form of logistic function was developed to predict the stoichiometry of Fe x Ca 1-x CO 3 as a function of the aqueous solution composition. The model showed an excellent representation for the experimental results with R 2 greater than 0.97 and 0.88 for Fe x Ca 1-x CO 3 and Ba x Ca 1-x CO 3 , respectively. The experimental equipment and procedures described in this work provide an effective means of producing and handling oxygen sensitive solid solutions. The precipitation kinetics of a number of solid solutions in aquatic systems could be studied by adapting the experimental design developed herein.

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46

Bhadak, Bhalchandra. "Phase-ﬁeld modeling of equilibrium shapes of precipitate and growth instabilities in the presence of coherency stresses." Thesis, 2020. https://etd.iisc.ac.in/handle/2005/4538.

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Precipitation-hardened alloys are one of the most technologically signiﬁcant materials that are used for structural applications, where an important mode of strengthening is due to the impediment to the movement of dislocations. The alloys, particularly possessing coherent precipitate-matrix interface, give rise to the coherency strain ﬁelds producing the coherency stresses in the matrix, which further interact with the dislocations to provide necessary strengthening. In this context, the control of the shape and distribution of the precipitates as a function of material and process parameters is important. In this thesis, we propose a diﬀuse-interface approach in order to compute the equilibrium shape of precipitates, which also allows us to minimize the grid-anisotropy related issues that occur in the classical sharp interface methods. The method is based on the minimization of the functional consisting of the elastic free energy and the interfacial energy, while the volume of the precipitate is conserved. Using this technique we reproduce the shape bifurcation diagram from 2D simulations for isotropic, inhomogeneous elastic energy with dilatational misﬁt, which is compared against the analytical solution provided by Johnson-Cahn and an existing sharp interface FEM technique. Thereafter the model has been utilized for the investigation of equilibrium shapes for diﬀerent combinations of elastic misﬁt matrices and cubic anisotropy. Additionally, we incorporate the anisotropy in the interfacial energy, which has not been studied by previous sharp interface techniques and investigate its inﬂuence on shape bifurcation. Finally, we extend the model to calculate the equilibrium shapes of the precipitate in 3D which resembles the precipitate structures observed in real microstructures. We notice that the nature of shape bifurcation diagram in 3D is diﬀerent than that observed in 2D, which is principally because there exist multiple variants of precipitate shapes for the same precipitate size e.g. prolate-like or oblate-like structures that are not equivalent. We also compute a range of equilibrium shapes in 3D, that can form as a result of symmetry breaking for diﬀerent forms of anisotropy in the elastic energy. In the next part of the thesis, we extend the phase-ﬁeld model for computing the equilibrium shape of single precipitates for consideration of multiple variants that allows us to investigate the equilibrium conﬁgurations of precipitates. Here, given the properties of the material such as the magnitude of misﬁt strain and its signs, the magnitude of the shear moduli and the size of the precipitate, one can determine the equilibrium conﬁguration that can form during solid-state precipitation reactions. Using this method, we investigate three solid-state precipitation reactions, i.e. formation of a core-shell type of precipitates in the microstructure and two symmetry-breaking transitions namely, cubic to tetragonal (typically observed in the superalloys with γ' − γ'' microstructure) and hexagonal to orthorhombic (formation of multi-variant precipitate pattern in Ti-based alloys). We evaluate the criteria for the formation of core-shell type microstructures and show that while the formation of such structures is purely due to interfacial conditions (satisfying the wetting condition), the reaction pathway leading to their formation is assisted by elastic interactions between the precipitates. In the symmetry-breaking transitions, we investigate the formation of equilibrium conﬁgurations of the multi-variant precipitates using energetic calculations. Here, we observe that the formation of such conﬁgurations involving multiple variants is favored over the nucleation of a single precipitate of the same equivalent volume beyond a certain precipitate size. In the last part of the thesis, we relax the condition of volume preservation of the precipitates and study precipitate growth in a supersaturated matrix in the presence of anisotropy in the elastic energy. To achieve this, we utilize a phase-ﬁeld model based on the grand-potential formulation for coupling the chemical driving forces with coherency stresses. Using this model we investigate the speciﬁc problem of solid-state dendrite formation occurring during certain precipitation reactions. Here, we ﬁnd that the anisotropy in the elastic energy gives rise to the formation of the dendrite-like structures that are typically observed in solidiﬁcation microstructures as an eﬀect of the Mullins-Sekerka in stabilities. We determine the dendrite tip shape and tip velocity, as the precipitate grows in size as a function of diﬀerent materials parameters such as the magnitude of misﬁt strain, supersaturation in the matrix, and the anisotropy strength in both the energies. We notice that in all the cases, the dendrite tip shape and tip velocity does not achieve steady-state which is in contrast with the dendrites observed during solidiﬁcation. This modiﬁcation is due to the presence of coherency stresses.

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47

Kučerová, Kateřina. "Příprava a hodnocení lipidických nanočástic jako nosičů léčiv." Master's thesis, 2020. http://www.nusl.cz/ntk/nusl-411747.

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Charles University in Prague, Faculty of Pharmacy in Hradci Králové Department of: Pharmaceutical Technology Supervisor: PharmDr. Ondřej Holas, Ph.D. Consultant: Mgr. Jana Kubačková Student: Kateřina Kučerová Title of thesis: Preparation and evaluation of lipid based nanoparticles as drug carriers Solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) are promising drug delivery systems. Their capability to encapsulate both hydrophilic and lipophilic molecules, biocompatibility and biodegradability of lipids make them a suitable alternative for well-established drug carries. The aim of this thesis was to determine suitable ratios of composition of nanoparticles with acceptable properties (especially reduced size and polydispersity, high zeta potential absolute values), to investigate status and thermodynamic behaviour of the nanoparticles and lipids used and to examine drug encapsulation efficiency. Nanoprecipitation method was used to prepare nanoparticles from stearic acid as a solid lipid and in the case of NLC preparation isopropyl myristate as a liquid lipid was used. Kolliphor® P 188 as a surfactant and Span® 20 as a co-surfactant were the best choice to meet intended characteristics. It was shown that usually lower the concentration of surfactant and co-surfactant was the...

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48

Lu, Wei-Chen, and 盧韋丞. "The Effects of Precipitation in the Watershed on the Suspended Solids in Water Column." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/49015365235156579247.

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碩士
國立中正大學
應用地球物理研究所
99
The research in Feitsui Reservoir had been conducted from November 2004 to December 2005, 406 days totally. We monitored total suspended solids concentrations at several depths, and collected settling particle by using sediment traps deployed at depths of 20m and 70m for investigating the spatial and temporal variation of suspended solids in the reservoir. It’s observed that heavy rainfall derived by typhoons, winter cold fronts, and summer thundershowers in the watershed, induced high inflow into the reservoir. The mean of the depth-weighted total suspended solids concentrations is 4.32±4.76 mg/l (0.92~23.81 mg/l), and the mean of depth-weight total suspended solids concentration of 7.82±5.43 mg/l during the typhoon period (November 2004 to January 2005 and July to October 2005) was higher than that during non-typhoon period. After typhoon occurred, high suspended solids concentrations in mid-depth of reservoir (between depth of 20m and 70m) were found. During the typhoon period, the mean settling flux at depth of 70m of 41.87 g/m2/d is higher than that during the non-typhoon period (6.46 g/m2/d), and the mean of settling flux at depth of 70m of 41.87 g/m2/d is higher than that at depth of 20m (8.8 g/m2/d). These results show that water discharge caused by typhoons entered the reservoir as a turbidity interflow, then increase quantity of suspended solids settling downward to sediment. It might result in decreasing effective storage and shortening reservoir life.

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Dissertations / Theses on the topic 'Solid Precipitation'

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