Functional nanoparticles have garnered considerable attention due to their intriguing physical properties at the nanoscale for a broad range of applications, such as photocatalysis, capacitive energy storage, thermoelectric power generation, solar energy harvesting, flexible and transparent electronics, drug delivery, biomolecular electronics, and analytic chemistry, etc. Successful synthesis of nanoparticles and precise control over their shapes are critical to achieving desired functions. In the first part of my thesis, an effective synthetic route to plain nanoparticles is briefly introduced. Based on this general route, the synthesis of solid iron oxide nanoparticles and a slightly modified synthetic method of solid silica nanoparticles are presented in detail. In the second part of my thesis, simulation of optical absorption spectra and plasmonic near-field maps of gold nanoparticle and gold/titanium oxide nanoparticle are explored, and the effectiveness of simulation in predicting, optimizing, and guiding experimental design is emphasized.

This study focuses on investigating the effect of the electronic spin transition of iron on the elasticity of the candidate lower mantle ferropericlase (Mg,Fe)O. This may be relevant to our understanding of the seismic velocity structures of the Earth’s lower mantle. The elastic constants of (Mg₀.₉₂Fe₀.₀₈)O at high-spin (HS) state, low-spin (LS) state, and through the pressure-induced HS-to-LS transition has been measured using both Brillouin Light Scattering (BLS) and Impulsive Stimulated Scattering (ISS). There is a large pressure range in which c₁₁ and c₁₂ exhibit a softening, while c₄₄ does not register such an anomaly. Compared with previously published data of ferropericlase with similar compositions ([Marquardt et al., 2009b], BLS measurement of (Mg₀.₉Fe₀.₁)O and [Crowhurst et al., 2008], ISS measurement of (Mg₀.₉₄Fe₀.₀₆)O), this study provides more reliable elastic constants measurements by taking the advantage of simultaneous measurements on Vp and Vs using both BLS and ISS. Our results show that bulk sound velocity of ferropericlase has a large but smooth softening in the spin transition pressure region. The elastic constants of ferropericlase at the spin transition region and the LS state have been well studied in this thesis, and a relaxation behavior has also been observed in this study. Those two subjects are not well documented in literature. The temperature effect of the spin state transition and its consequential effect on mineral’s elastic properties have not been studied in this project, but further research on this subject will follow. However, even in the room temperature, our results don’t show sudden changes in seismic velocities. Moreover, current theoretical and experimental studies [Sturhahn et al., 2005, Tsuchiya et al., 2006, Lin et al., 2007] indicate that the spin transition takes place over an extended range of depth along an expected lower-mantle geotherm, where sudden changes in compressional and bulk sound velocity are not expected. / text

L’obtention de nanoparticules d’or nécessite le contrôle de nombreux paramètres et la compréhension du mode d’interaction entre l’or et le support. Pour cela, le choix du support est très important. Le premier volet de la thèse concerne la préparation contrôlée des catalyseurs à base d’or supporté sur les oxydes mésoporeux réductibles TiO₂, CeO₂ et Fe₂O₃ synthétisés via deux stratégies Soft et hard template en utilisant respectivement comme agents structurants le tribloc copolymère (Pluronic 123) et la silice mésoporeuse SBA-15. Les différentes techniques de caractérisation mettent bien en évidence que le taux de dépôt de l’or dépend de la concentration initiale de HAuCl₄, de la méthode de préparation (DPU, DP NaOH), de la teneur en or visée et de la nature du support ; Ces résultats sont à relier à la spéciation des espèces or en solution en fonction du pH final de la solution. Les taux de dépôt de l’or sont plus importants sur CeO₂ et ceci quelle que soit la teneur en or visée dans ce travail. Une dispersion très élevée est obtenue (la taille moyenne des particules d’or est de 2nm) sur les catalyseurs à 1% et 2%Au/CeO₂ préparés par la méthode DPU et calcinés à 400°C. Le deuxième volet de cette étude concerne l’oxydation en phase gaz d’une molécule organique modèle le toluène et l’oxydation en phase liquide d’une molécule organique modèle le phénol par des réactions de type Fenton et photo Fenton. Dans l’oxydation du toluène en phase gazeuse, les catalyseurs à base d’or supportés sur oxydes mésoporeux sont totalement sélectifs en CO₂ et H₂O. Les performances catalytiques dépendent des conditions de synthèse des catalyseurs et de la nature de l’oxyde utilisé ; le catalyseur 1%Au/CeO₂ est très actif et très stable au cours de quatre cycles successifs et au cours du temps. L’oxydation en phase liquide d’une molécule organique modèle le phénol par des réactions de type Fenton et photo Fenton a été effectuée sur les catalyseurs FeSBA-15 synthétisés via différentes stratégies : introduction du fer par voie postsynthétique et par voie hydrothermale en milieu faiblement et fortement acide respectivement à pH=6 et pH=3. Les performances catalytiques dépendent du rapport Si/Fe et de la taille des particules des espèces de fer, la taille des particules étant directement liée à la stratégie de synthèse des catalyseurs. Le catalyseur FeSBA-15(Si/Fe=60) synthétisé à pH=6 est un candidat potentiel dans la dégradation de polluants organiques par procédé Fenton et photo-Fenton en milieu neutre. / Well dispersed gold nanoparticles are the key to obtain an active gold catalyst. Obtaining gold nanoparticles requires control of many parameters and understanding of the interaction mode between gold and the support. For this reason the choice of the support is very important. The first part of this thesis concerns the controlled preparation of gold catalysts supported on reducible mesoporous oxides TiO₂, CeO₂ and Fe₂O₃ synthesized via two strategies Soft and Hard template using respectively. triblock copolymer (Pluronic 123) and mesoporous silica SBA-15 as template. This study clearly shows that the gold loading depends on the initial concentration of HAuCl₄, the method of preparation (DPU DP NaOH), theoretical gold content and the nature of the support. These results are to relate to the gold speciation which is a function of pH of the solution. The gold loading is higher on CeO₂ than on TiO₂ and Fe₂O₃ whatever the theoretical gold content. Very high gold dispersion is obtained (the gold particle size is 2 nm) on 1wt% and 2wt% Au/CeO₂ prepared by DPU and calcined at 400°C. The second part of this study concerns the toluene oxidation in the gas phase on Au/mesoporous oxide catalysts and the Fenton and photo-Fenton degradation of phenolic aqueous solutions by H₂O₂ on FeSBA-15 catalysts prepared following different synthesis routes, direct synthesis by adjusting pH at 3 and 6 and with post synthesis procedure. In the toluene oxidation in the gas phase Au/mesoporous oxide catalysts are totally selective for CO₂ and H₂O. The catalytic performances depend on the synthesis conditions of catalysts and the support; the 1wt% Au/CeO₂ catalyst is very active and exhibits a long-term stability. In the Fenton and photo-Fenton degradation of phenolic aqueous solutions the catalytic performances depend on the Si/Fe ratio and the particle size of the iron species, the particle size being directly related to the synthesis strategy of the catalysts. The catalyst FeSBA-15 (Si/Fe = 60) synthesized at pH = 6 is a potential candidate in the degradation of organic pollutants by Fenton and photo-Fenton process in neutral medium. / م لخصمسقني لمعلا يف هذه ةحورطألا ىلإ نيئزج:OiT 2ب وا سطة OeC 2و , Fe2O ي خ تص الاول ال ق سم ب تح ض يرمح فزات من ال ذهبن وع من م يزوب ري ة ب مواد مدعم 3ان واع مخ ت لف ال تح ض ير. ت شخ يص ف ي ال م س ت عم لة ال ت ق ن يات مخ ت لفت ب ين ال مح ضرة ل مح فزات انال دعم ط ب ي عة ك ذا و ال مح فز ت ح ض ير وطري قة HAuCl ت ر سب معدل ي ت ع لق ل ذه با ت رك يز ع لى 4ي ع ضو جزيء و سطغازي enèuloT أك سدة ف ي ال مواد هذه ب تط ب يق ي ت ع لق ال ثان ي ال ق سم ف يال مح فز ت ح ض ير Ò طرق ك ذا و ل ت فاعل هذا ع لى ال مؤث رة ل عوامل ب درا سة ق م نا سال فا ال مذك ورة ل لمح فزات ال ف عال ية ع لان واع مخ ت لف ب وا سطة FeSBA- ي ع ضو جزيء lonehP ت فاعل ب وا سطة notneF سائ ل و سط ف ي وعمن 51 ن مح فزات ع لىوHp ال و سط Si/Fe قلعتي ةبسنب FeSBA- ريضحتلا.ادأء 1515FeSBA-15, Fenton, Phenol, Toluène, TiO و 2 CeO2, Fe2O3, SBA- ال ك لمات ال م ف تاح ية ׃م يزوب وري ة ,

Lors d’un accident grave dans un réacteur nucléaire à eau pressurisée, le combustible nucléaire va réagir avec le gaines en Zircaloy, les absorbants neutroniques et les structures métalliques environnantes pour former un mélange partiellement ou complètement fondu. Ce cœur fondu peut ensuite interagir avec la cuve en acier du réacteur pour former un mélange appelé corium en cuve. Par la suite, le corium peut percer la cuve et venir se déverser sur le radier en béton en-dessous du réacteur. En fonction du scénario considéré, le corium qui va réagir avec le béton peut être constitué soit d’une seule phase liquide oxyde ou de deux liquides, métallique et oxyde. L’objectif de la thèse est l’étude de la thermodynamique du corium en cuve, prototypique U-Pu-Zr-Fe-O. L’approche utilisée est basée sur la méthode CALPHAD, qui permet de développer un modèle thermodynamique sur ce système complexe à partir de données expérimentales thermodynamiques et de diagramme de phases. Des traitements thermiques sur le système O-U-Zr ont permis de mesurer deux conodes dans la lacune de miscibilité à l’état liquide à 2567 K. De plus, des températures de liquidus ont été mesurées sur trois échantillons riches en Zr, en utilisant le montage de chauffage laser de l’ITU. Par la même méthode, des températures de solidus ont été obtenues sur le système UO2-PuO2-ZrO2. L’influence de l’atmosphère réductrice ou oxydante sur le comportement à la fusion de ce système a été étudiée pour la première fois. Les résultats montrent que la stœchiométrie en oxygène de ces oxydes dépend fortement du potentiel d’oxygène et de la composition en métal des échantillons. La lacune de miscibilité à l’état liquide a également été mise en évidence dans un échantillon U-O-Zr-Fe. L’ensemble de ces nouvelles données expérimentales avec celles de la littérature a permis de développer le modèle sur le système U-Pu-Zr-Fe-O. Pour tous les échantillons, des calculs de chemin de solidification avec ce modèle ont servi à interpréter les microstructures de solidification observées. Un bon accord est obtenu entre les calculs et les résultats expérimentaux. Des traitements thermiques sur deux échantillons de corium hors cuve ont permis de montrer l’influence de la composition du béton sur la nature des phases liquides formées à haute température. Les microstructures de solidification ont été interprétées à l’aide de calculs avec la base de données TAF-ID. En parallèle, un nouveau montage expérimental appelé ATTILHA, utilisant la lévitation aérodynamique et le chauffage laser, a été conçu et développé pour mesurer des données de diagramme de phase à haute température. Ce montage a été validé avec des systèmes oxydes bien connus. De plus, cette méthode a permis d’observer in-situ à l’aide de la caméra infra-rouge la formation de la lacune de miscibilité à l’état liquide dans le système O-Fe-Zr lors de l’oxydation d’une bille d’alliage Fe-Zr. La prochaine étape du développement est la nucléarisation du montage pour effectuer des mesures sur des échantillons contenant de l’uranium. La mise en place d’une caméra ultra rapide (5000 Hz) pour l’étude de propriétés thermo-physiques de mélanges de corium en cuve et hors cuve est également envisagée. La synergie entre le développement de ces outils expérimentaux et de calcul devrait permettre d’améliorer la description thermodynamique du corium et des codes de calcul sur les accidents graves utilisant ces données thermodynamiques. / During a severe accident in a pressurised water reactor, the nuclear fuel can interact with the Zircaloy cladding, the neutronic absorber and the surrounding metallic structure forming a partially or completely molten mixture. The molten core can then interact with the reactor steel vessel forming a mixture called in-vessel corium. In the worst case, this mixture can pierce the vessel and pour onto the concrete underneath the reactor, leading the formation of the ex-vessel corium. Furthermore, depending on the considered scenario, the corium can be formed by a liquid phase or by two liquids, one metallic the other oxide. The objective of this thesis is the investigation of the thermodynamics of the prototypic in-vessel corium U-Pu-Zr-Fe-O. The approach used during the thesis is based on the CALPHAD method, which allows to obtain a thermodynamic model for this complex system starting from phase diagram and thermodynamic data. Heat treatments performed on the O-U-Zr system allowed to measure two tie-lines in the miscibility gap in the liquid phase at 2567 K. Furthermore, the liquidus temperatures of three Zr-enriched samples have been obtained by laser heating in collaboration with ITU. With the same laser heating technique, solidus temperatures have been obtained on the UO2-PuO2-ZrO2 system. The influence of the reducing or oxidising on the melting behaviour of this system has been studied for the first time. The results show that the oxygen stoichiometry of these oxides strongly depends on the oxygen potential and on the metal composition of the samples. The miscibility gap in the liquid phase of the U-Zr-Fe-O system has been also observed. The whole set of experimental results with the literature data allowed to develop the thermodynamic model of the U-Pu-Zr-Fe-O system. Solidification path calculations have been performed for all the investigated samples to interpret the microstructures of the solidified samples. A good accordance has been obtained between calculation and experimental results. Heat treatments on two ex-vessel corium samples showed the influence of the concrete composition on the nature of the liquid phases formed at high temperature. The observed microstructures have been interpreted by means of calculation performed with the TAF-ID database. In parallel, a novel experimental setup named ATTILHA based on aerodynamic levitation and laser heating has been conceived and developed to obtain high temperature phase diagram data. This setup has been validated on well-known oxide systems. Furthermore, this technique allowed to observe in-situ, by using an infrared camera, the formation of a miscibility gap in the liquid phase of the O-Fe-Zr system by oxidation of a Fe-Zr sample. The next step of the development will be the nuclearization of the apparatus to investigate U-containing samples. The implementation of a very fast visible camera (5000 Hz) to investigate the thermo-physical properties of in-vessel and ex-vessel corium mixtures is also underway. The synergy between the development of experimental and calculation tools will allow to improve the thermodynamic description of the corium and the severe accident code using thermodynamic input data.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

In this work we studied the magnetic properties referring to the MgFe2O4 nanoparticles precipitated in monocrystalline solid solution of [Mg, Fe]O, with 2.2% iron, obtained at different temperatures and times. These particles grow coherently with the matrix lattice and present shapes of small octahedrons whose diagonals are parallel to the [100] directions. The results presented here refer to samples treated in the temperature range between 400 and 900 º C for 2, 6 and 10 hours. They were analyzed by X-ray diffraction (XRD), magnetization as a function of field (hysteresis curves) and magnetization as a function of temperature (Zero Field Cooled e Field Cooled Warming). It was observed that in samples treated for 6 hours, the system shows increasing values of magnetization remanent and coercive field for temperatures of precipitation from 600 º C, which can be attributed to the precipitation and growth of nanoparticles magnesioferrite matrix. The variation of coercive field with temperature measurement was studied using two different theoretical models. By comparing the remanent magnetization and coercive field of the samples, it was found that the variation of the inversion parameter of magnesioferrite in the studied range of precipitation temperature decreases as reported by other authors. / Neste trabalho foram estudadas as propriedades magnéticas do sistema de nanopartículas de MgFe2O4 obtidas por precipitação em solução sólida monocristalina de [Mg;Fe]O, com 2,2% de ferro, em diferentes tempos e temperaturas de precipitação. Estas partículas crescem de forma coerente com a matriz, exibindo a forma de pequenos octaedros cujas diagonais são paralelas às direções [100] da rede cristalina da matriz, que possui simetria cúbica. Os resultados aqui apresentados são referentes a amostras tratadas no intervalo de temperaturas entre 400 e 900ºC durante 2, 6 e 10 horas. As mesmas foram analisadas por difração de raios X (DRX), magnetização em função do campo (curvas de histerese) e magnetização em função da temperatura (Zero Field Cooled e Field Cooled Warming). Observou-se que, em amostras tratadas durante 6 horas, o sistema apresenta valores crescentes de magnetização remanente e campo coercivo para temperaturas de precipitação a partir de 600ºC, fato que pode ser atribuído à precipitação e ao crescimento de nanopartículas de magnesioferrita na matriz. A variação do campo coercivo com a temperatura de medição foi estudada utilizando-se dois diferentes modelos teóricos e, a partir da comparação da magnetização remanente e do campo coercivo das amostras tratadas em diferentes temperaturas, verificou-se que a variação do parâmetro de inversão da magnesioferrita na faixa de temperaturas de precipitação estudada decresce como reportado por outros autores.

European iron production is to a large extent dependant on massive Kiruna type apatite-iron ore deposits. In this contribution, high-temperature magnetite samples from apatite-iron-oxide deposits are investigated by means of Electron Backscattered Diffraction. However, the origin of Kiruna-type deposits is still unresolved. Although magmatic processes are likely, it is not clear how small-scale processes can form giant Kiruna-type deposits. The sample suite consists of magnetite samples from six global apatite-iron-oxide deposits: the famous Kiirunavaara deposit and the Malmberget deposit, both located in northern Sweden, the Grängesberg deposit in south-central Sweden, the iconic El Laco deposit in north-eastern Chile, the Bafq deposit in central Iran, and the Varena deposit in south Lithuania. Fe-O systematics has been conducted to complement existing δ18O and δ56Fe isotope data and ensure magmatic origin of the samples from the Malmberget deposit (n=6) and the Varena deposit (n=2). This is the first effort to characterise magnetite samples from apatite-iron-oxide deposits utilising EBSD. In total, twelve EBSD maps have been produced. Evaluation of the EBSD data have been performed to quantify the preferred orientation of the magnetite crystals. Four deposits, with Kiirunvaara being the prime example, shows no preferred alignment of the magnetite crystals. Whereas the El Laco samples exhibits a strong preferred alignment of {111}. The EBSD data from magnetite samples in equilibrium with a magmatic source indicate that apatite-iron-oxide deposits are formed in both intrusive and extrusive environment and that magmatic crystal accumulation is a key process in aggregating magnetite to form large and even giant Kiruna-type deposits. / Europeisk järnmalmsproduktion är i stor utsträckning beroende av massiva apatit-järnmalmsfyndigheter av Kiruna-typ. I det här arbetet, undersöks magnetitprover av hög-temperaturs ursprung från olika apatit-järnmalmsfyndigheter med Elektron Bakåtspridande Diffraktion. Bildningsmekanismen av apatit-järnmalmsfyndigheter av Kiruna-typ är än idag oklar. Bevisen indikerar magmatiska bildningsprocesser, det är dock fortfarande oklart hur småskaliga magmatiska processer bildar gigantiska apatit-järnmalmsfyndigheter av Kiruna-typ. Provserien består av magnetitprover från sex globala apatit-järnmalmsfyndigheter: den världsberömda Kiirunavaara fyndigheten och Malmberget fyndigheten, båda lokaliserade i Norrbotten, Sverige, Grängesberg fyndigheten i Bergslagen, Sverige, den ikoniska El Laco fyndigheten i nordöstra Chile, Bafq fyndigheten i centrala Iran, och Varena fyndigheten i södra Litauen. För att fastställa ett magmatiskt ursprung och komplettera befintlig δ18O och δ56Fe isotopdata har Fe-O-systematik utförts på magnetitproverna från Malmberget (n=6) och Varena (n=2). Det här är den första dokumenterade EBSD-undersökningen av magnetitprover från apatit-järnmalmsfyndigheter. Totalt tolv EBSD-kartor har producerats. Utvärdering av EBSD-data har utförts för att kvantifiera den föredragna riktningen på magnetitkristallerna. I fyra fyndigheter, med Kiirunvaara som typexempel, uppvisar magnetitkristallerna ingen föredragen riktning, medan magnetitproverna från El Laco uppvisar en tydlig föredragen riktning längs {111}. EBSD-data från magnetitprover i jämnvikt med en magmatiskkälla påvisar att apatit-järnmalmer bildas i både intrusiva miljöer och extrusiva miljöer och att magmatisk ackumulation är en nyckelprocess för att aggregera magnetitkristaller och bilda stora till gigantiska apatit-järnmalmsfyndigheter av Kiruna-typ.

A new class of materials, known as multi-functional energetic structural materials (MESMs), has been developed. These materials possess both strength and energetic functionalities, serving as candidates for many exciting applications. One of such applications is ballistic missiles, where these materials serve as part of structural casing as well as explosive payload. In this study, the dynamic compressive behavior of two types of MESMs in the intermediate strain rate regime is investigated. The first type is a thermite mixture of Al and Fe₂O₃ particles suspended in an epoxy matrix. The second type is a shock compacted mixture of Ni and Al powders. Compression experiments on a split-Hopkinson pressure bar (SHPB) apparatus are carried out at strain rates on the order of 103 s-1. In addition, a novel method for investigating the dynamic hardness of the Al + Fe₂O₃ + Epoxy materials is developed. In this method, high-speed digital photography is used to obtain time-resolved measurements of the indentation diameter throughout the indentation process. Experiments show that the shock compacted Ni-Al material exhibits a rather ductile behavior and the deformation of the Al + Fe₂O₃ + Epoxy mixtures is dominated by the polymer phase and significantly modulated by the powder phases. The pure epoxy is ductile with elastic-plastic hardening, softening, and perfectly plastic stages of deformation. The Al and Fe₂O₃ particles in Al + Fe₂O₃ + Epoxy mixtures act as reinforcements for the polymer matrix, impeding the deformation of the polymer chains, alleviating the strain softening of the glassy polymer matrix at lower levels of powder contents (21.6 - 29.2% by volume), and imparting the attributes of strain hardening to the mixtures at higher levels of powder contents (21.6 - 49.1% by volume). Both the dynamic and quasi-static hardness values of the Al + Fe₂O₃ + Epoxy mixtures increase with powder content, consistent with the trend seen in the stress-strain curves. To quantify the constitutive behavior of the 100% epoxy and the Al + Fe₂O₃ + Epoxy materials, the experimentally obtained stress-strain curves are fitted to the Hasan-Boyce model. This model uses a distribution of activation energies to characterize the energy barrier for the initiation of localized shear transformations of long chain polymeric molecules. The results show that an increase in powder content increases the activation energy, decreases the number of transformation sites, causes redistribution of applied strain energy, and enhances the storage of inelastic work. These effects lead to enhanced strength and strain hardening rate at higher levels of powder content.

No description available.