In this study, pharmaceutical-grade and food-grade linker-based lecithin self-emulsifying delivery systems (SEDS) were developed with a combination of lipophilic and hydrophilic linkers. These additives at suggested concentrations are safe for pharmaceutical and food applications. The ratio of surfactant lecithin and linkers in these systems was optimized to develop surfactant in oil preconcentrates. The preconcentrates containing different surfactant concentrations and oil were diluted with fed state simulated intestinal fluid to produce pseudo-ternary phase diagrams and to identify the formulations that produced self-emulsifying or self-microemulsifying delivery systems. Optimal SEDS preconcentrates were evaluated using a dialyzer model to simulate intestinal uptake. An uptake of 39.6 mg/cm2 for the pharmaceutical-grade SEDS was obtained within 72 minutes, which promises substantial improvement in the bioavailability of hydrophobic actives. The optimal uptake of 12.2 mg/cm2 for food-grade SEDS suggests enhancement in the bioavailability of omega-3 fatty acids.

ARAÚJO, Jorge Luiz Bezerra de. Auto-organização de partículas patchy carregadas. 2014. 75 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2014. / Submitted by Edvander Pires (edvanderpires@gmail.com) on 2014-08-29T19:48:06Z No. of bitstreams: 1 2014_dis_jlbaraujo.pdf: 26529309 bytes, checksum: 0b19a8cf79d0505ad5749c382dddd8c7 (MD5) / Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2014-08-29T20:27:12Z (GMT) No. of bitstreams: 1 2014_dis_jlbaraujo.pdf: 26529309 bytes, checksum: 0b19a8cf79d0505ad5749c382dddd8c7 (MD5) / Made available in DSpace on 2014-08-29T20:27:12Z (GMT). No. of bitstreams: 1 2014_dis_jlbaraujo.pdf: 26529309 bytes, checksum: 0b19a8cf79d0505ad5749c382dddd8c7 (MD5) Previous issue date: 2014 / The current stage of development of experimental techniques allow the synthesis of particles complex colloidal, whose surface can be precisely "decorated" with physical properties and/or chemical combinations. Such colloids are usually defined as patchy particles. As result of the modification of parts of the surface of such particles, the interaction between them is generally characterized by an anisotropic potential. Study and understand the process of self-organization of this particular system is of great interest both from the scientific point of view as technology, because of its use in functional materials. In this dissertation, we study. The behavior of a two-dimensional system patchy charged particles, in which the surface is decorated with a timely charge sign opposite that located in the particle center. Thus, patchy each particle has a net charge C, which is result of the difference between the point charges on the surface and that in the particle center patchy. This study uses the technique of computer simulation of molecular dynamics to study the process of self-organization of particles patchy depending on the density and temperature. Initially, we present the model of patchy particles studied here and there is the behavior of the interaction energy between two particles and its dependence on load effective particle (liquid charge) and the number of active sites (p) that decorate the surfaces of colloids, called patches . The study of these parameters is important for understanding the self-organized structures obtained. Presents the stable structures of minimum energy a system with p=2 and C=0 as a function of temperature and density. In general, we observe two well defined phases were distinguished by calculation of thermodynamic properties during the simulation. Results for different values of p and C are also presented order to show the influence of this parameter in the system configuration. In general, it is observed that for large values of the charge and/or number of patches, the repulsive potential prevails causing the system to stabilize in a crystalline configuration. On the other hand, for a system composed of particles with a low value of charge and/or the number od patches interaction potential is attractive inducing predominantly resulting composite structures in the form of clusters of ring and lines particles. / O atual estágio de desenvolvimento de técnicas experimentais permite a síntese de partículas coloidais complexas, cuja superfície pode ser precisamente "decorada" com propriedades físicas e/ou químicas diferentes. Tais coloides são usualmente definidos como partículas patchy. Como resultado da modificação de partes da superfície de tais partículas, a interação entre as mesmas é geralmente caracterizada por um potencial anisotrópico. Estudar e compreender o processo de auto-organização desse sistema particular é de grande interesse tanto do ponto de vista científico como tecnológico devido sua utilização em materiais funcionais. Nessa dissertação, estuda-se o comportamento de um sistema bidimensional de partículas patchy carregadas, nas quais a superfície é decorada pontualmente com uma carga de sinal contrário do centro da mesma de modo que cada coloide possua uma carga total C responsável pelo potencial de interação. Neste trabalho foi utilizada a técnica de simulação Dinâmica Molecular para estudar o processo de auto-organização dessas partículas para diversas densidades e temperaturas. Contudo, antes de apresentar resultados numéricos apresenta-se o modelo de partícula patchy e verifica-se o comportamento da energia de interação com dependência na carga efetiva da partícula e com o número de sítios ativos (p) que decoram as superfícies dos coloides, chamados de patches. Nota-se que o estudo de tais parâmetros é fundamental na previsão de estruturas que o sistema se estabiliza. Apresentam-se as estruturas de mínima energia estáveis, de um sistema com p=2 e carga total neutra, em um diagrama de fases com dependência na temperatura e densidade para p=2. Esse diagrama apresenta claramente duas fases bem definidas que foram distinguidas através de cálculos de propriedades termodinâmicas durante a simulação. Resultados para diferente p e carga total também são apresentados a fim de mostrar a influencia do número de patches, e da carga total, na configuração do sistema. Em geral, observa-se que para altos valores da carga total e/ou número de patches de cada partícula, o potencial repulsivo prevalece fazendo com que o sistema se estabilize em uma configuração cristalina. Por outro lado, um sistema composto de partículas com baixo valor de carga total ou numero de patches as partículas apresentam um potencial atrativo induzindo diferentes tipos de configurações no sistema, como, por exemplo, estruturas na forma de anéis e linhas de partículas.

At their discovery in 2008, iron pnictide superconductors (IPS) provoked tremendous scientific interest, comparable to the discovery of the cuprate superconductors. So far, IPS reached critical temperatures T c up to 56K. Typically, they show an antiferromagnetic (afm) spin density wave (SDW) which has to be suppressed by doping before superconductivity develops, which then is supported by further doping. Due to the close vicinity of the magnetic and the superconducting (sc) phase, magnetic fluctuations are discussed to be responsible for the sc pairing mechanism in IPS. A special member of the IPS is LiFeAs, because it does not need doping to become sc. It is a stoichiometric superconductor at a T c of 18K. In fact, doping is suppressing its T c . Also, there is no sign of an afm SDW present. Therefore, LiFeAs is a interesting material to study the properties of the IPS in an undisturbed material. In 2010, experiments of the Leibniz Institute for Solid State and Materials Research Dresden (IFW Dresden) revealed further surprising properties of LiFeAs. Samples with a Li deficiency undergo a ferromagnetic (fm) phase transition at 165K. Theoretical calculations suggest that fm fluctuations could induce triplet superconductivity in LiFeAs. This would cause a nonvanishing dynamic susceptibility below T c , which is supported by nuclear magnetic resonance (NMR) experiments. This thesis is discussing the results of the IFW Dresden experiments, and concludes that this ferromagnetism is of weak itinerant nature. The origin might be an increase of the density of states (DOS) at the Fermi level, which is causing an instability towards fm order, as proposed by the Stoner model. For further doping experiments, the synthesis procedure of polycrystalline LiFeAs was optimized to get samples with maximum T c and minimum impurities. Therefore, nuclear quadrupole resonance (NQR) was used. The NQR line width is a measure of impurities in the sample. By minimizing the NQR line width, optimal samples were synthesized. These samples are able to compete with the properties of single crystals. To investigate the doping behavior of LiFeAs, a scenario with four different kinds of impurities and deficiencies was performed with the optimized synthesis procedure. 24 different samples were analyzed, by means of NQR and electrical conductivity. It was found that in fact Fe excess is responsible for changing the physical properties of LiFeAs, and not Li deficiency. It is causing a shrinking of the unit cell volume, as seen by X-ray diffraction (XRD) measurements and it causes a decrease of T c . It also leads to a decrease of room temperature resistivity, which is supporting an increase of the DOS at the Fermi level. The NQR frequency is scaling with the amount of Fe excess and can be used to draw the sc and fm phase diagram of off-stoichiometric LiFeAs. At an amount between 3.2 and 3.6% o f Fe excess LiFeAs undergoes the fm transition.

Os métodos de primeiros princípios dentro da Teoria do Funcional Densidade têm se desenvolvido bastante, devido aos avanços computacionais ocorridos nas últimas décadas. Por outro lado, a Termodinâmica e a Mecânica Estatística têm representado um papel importante na compreenssão da Física de Materiais, em especial no estudo dos materiais intermetálicos ordenados. A aliança entre estas duas abordagens têm se tornado cada vez mais factível, uma vez que os cálculos de estrutura eletrônica de primeiros princípios são hoje capazes de proporcionar resultados extremamente precisos para energias de formação de compostos estequiométricos. É dentro deste contexto que neste trabalho investigamos o diagrama de fases composição-temperatura do sistema Fe-Al-Mo, na estrutura cúbica de corpo centrado utilizando o método Full-Potential Linear Augmented Plane Wave (FP-LAPW) aliado ao Método Variacional de Clusters (CVM) na aproximação do tetraedro irregular. Através do método FP-LAPW determinamos a energia total de configurações cristalinas do sistema Fe-Mo-Al cúbico de corpo centrado. Estes valores são utilizados como parâmetros de entrada do CVM para determinação do potencial termodinâmico do sistema em suas diferentes fases e os correspondentes equilíbrio entre estas fases em função da composição e da temperatura, ou seja, o diagrama de fases do sistema. Embora o Fe-Al tenha grande interesse tecnológico, o seu comportamento magnético é bastante complicado e normalmente mal descrito pelos métodos de cálculos usuais. Este trabalho procura enfrentar este problema com ferramentas \"estados de arte\" e apontam para as limitações inerentes ao procedimento geral aqui utilizado. / First-principles methods within the framework of Density Functional Theory, have been developed sufficiently, due to the computational advances occurrences in the last decades. On the other hand, the Thermodynamics and the Statistical Mechanics have represented an important role in the understanding of the Physics of Materials, in special in the study to ordered intermetallic compounds. The alliance between these two approaches has become each more feasible with the time due to the fact that electronic structure calculations of first principles are today to provide almost exact results for the formations energies of stoichiometric compounds. It is inside of this context that in this work we investigate the composition-temperature phases diagram of the Fe-Al-Mo system, in the body centered cubic structure (BCC), using the Full-Potential Liner Augmented Plane Wave (FP-LAPW) method allied to the Cluster Variation Method (CVM) in the irregular tetrahedron approximation. Through the FP-LAPW method we determined the total energy of crystalline configurations of BCC Fe-Mo-Al system. These values are used as input parameters of the CVM for the determination of the thermodynamic potential of the system in its different phases and corresponding to the equilibria between these phases as a function of the composition and the temperature, that is the phase diagram of the system. Although the Fe-Al has great technological interest, its magnetic behavior is complicated and badly described by the methods used in the actual ab-initio calculations. This work faces this problem with state-of-art tools and points to the inherent limitations of the general procedure used here.

Universidade Federal do Cearà / O atual estÃgio de desenvolvimento de tÃcnicas experimentais permite a sÃntese de partÃculas coloidais complexas, cuja superfÃcie pode ser precisamente "decorada" com propriedades fÃsicas e/ou quÃmicas diferentes. Tais coloides sÃo usualmente definidos como partÃculas patchy. Como resultado da modificaÃÃo de partes da superfÃcie de tais partÃculas, a interaÃÃo entre as mesmas à geralmente caracterizada por um potencial anisotrÃpico. Estudar e compreender o processo de auto-organizaÃÃo desse sistema particular à de grande interesse tanto do ponto de vista cientÃfico como tecnolÃgico devido sua utilizaÃÃo em materiais funcionais. Nessa dissertaÃÃo, estuda-se o comportamento de um sistema bidimensional de partÃculas patchy carregadas, nas quais a superfÃcie à decorada pontualmente com uma carga de sinal contrÃrio do centro da mesma de modo que cada coloide possua uma carga total C responsÃvel pelo potencial de interaÃÃo. Neste trabalho foi utilizada a tÃcnica de simulaÃÃo DinÃmica Molecular para estudar o processo de auto-organizaÃÃo dessas partÃculas para diversas densidades e temperaturas. Contudo, antes de apresentar resultados numÃricos apresenta-se o modelo de partÃcula patchy e verifica-se o comportamento da energia de interaÃÃo com dependÃncia na carga efetiva da partÃcula e com o nÃmero de sÃtios ativos (p) que decoram as superfÃcies dos coloides, chamados de patches. Nota-se que o estudo de tais parÃmetros à fundamental na previsÃo de estruturas que o sistema se estabiliza. Apresentam-se as estruturas de mÃnima energia estÃveis, de um sistema com p=2 e carga total neutra, em um diagrama de fases com dependÃncia na temperatura e densidade para p=2. Esse diagrama apresenta claramente duas fases bem definidas que foram distinguidas atravÃs de cÃlculos de propriedades termodinÃmicas durante a simulaÃÃo. Resultados para diferente p e carga total tambÃm sÃo apresentados a fim de mostrar a influencia do nÃmero de patches, e da carga total, na configuraÃÃo do sistema. Em geral, observa-se que para altos valores da carga total e/ou nÃmero de patches de cada partÃcula, o potencial repulsivo prevalece fazendo com que o sistema se estabilize em uma configuraÃÃo cristalina. Por outro lado, um sistema composto de partÃculas com baixo valor de carga total ou numero de patches as partÃculas apresentam um potencial atrativo induzindo diferentes tipos de configuraÃÃes no sistema, como, por exemplo, estruturas na forma de anÃis e linhas de partÃculas. / The current stage of development of experimental techniques allow the synthesis of particles complex colloidal, whose surface can be precisely "decorated" with physical properties and/or chemical combinations. Such colloids are usually defined as patchy particles. As result of the modification of parts of the surface of such particles, the interaction between them is generally characterized by an anisotropic potential. Study and understand the process of self-organization of this particular system is of great interest both from the scientific point of view as technology, because of its use in functional materials. In this dissertation, we study. The behavior of a two-dimensional system patchy charged particles, in which the surface is decorated with a timely charge sign opposite that located in the particle center. Thus, patchy each particle has a net charge C, which is result of the difference between the point charges on the surface and that in the particle center patchy. This study uses the technique of computer simulation of molecular dynamics to study the process of self-organization of particles patchy depending on the density and temperature. Initially, we present the model of patchy particles studied here and there is the behavior of the interaction energy between two particles and its dependence on load effective particle (liquid charge) and the number of active sites (p) that decorate the surfaces of colloids, called patches . The study of these parameters is important for understanding the self-organized structures obtained. Presents the stable structures of minimum energy a system with p=2 and C=0 as a function of temperature and density. In general, we observe two well defined phases were distinguished by calculation of thermodynamic properties during the simulation. Results for different values of p and C are also presented order to show the influence of this parameter in the system configuration. In general, it is observed that for large values of the charge and/or number of patches, the repulsive potential prevails causing the system to stabilize in a crystalline configuration. On the other hand, for a system composed of particles with a low value of charge and/or the number od patches interaction potential is attractive inducing predominantly resulting composite structures in the form of clusters of ring and lines particles.

La2Mo2O9, premier composé de la famille LAMOX, est intéressant pour des applications comme électrolyte dans des piles à combustible car il présente une conductivité ionique élevée. Il a été découvert durant l'investigation du diagramme de phases de La2O3 -MoO3. Cela montre bien le rôle important de l'étude de diagrammes de phase dans la découverte de nouveaux matériaux qui est devenue un objectif majeur de nombreux chimistes du solide. Selon ce concept, les deux diagrammes de phases ternaires La2O3-Nb2O5-WO3 et La2O3-Nb2O5-MoO3 ont été explorés et analysés pour la première fois en utilisant la synthèse par voie solide. Les structures des échantillons obtenus ont été caractérisées par diffraction des rayons X et des neutrons sur poudre et par microscopie électronique en transmission tandis que leurs propriétés électriques ont été testées par spectroscopie d'impédance complexe sur des pastilles frittées.La majorité des zones mono-, bi- et tri-phasées de ces deux diagrammes ont été définies. Plus particulièrement, les structures de deux nouvelles phases La3NbWO10 et La5NbMo2O16 ont été résolues ab-initio. La connaissance des structures des 2 nouveaux composés a permis une meilleure approche du diagramme de phase ternaire. D'une part, la mailleLa3NbWO10 est une sur structure de la maille fluorine(2aF*2aF*2aF) avec un axe c allongé. En considérant la formulation La18Nb6W62O604 (Z = 6), on constate aisément que la structure présente 2 types de défauts:des lacunes anioniques et cationiques sur les sites des atomes d'oxygène et de lanthane. D'autre part, la phaseLa5NbMo2O16 est un isotype du composé Pr5Mo3O16. Sa maille correspond aussi à une surstructure fluorine. Elle cristallise dans un système cubique (a = 11.22 Å) avec le groupe d'espace rare Pn n. Ce composé est prometteur puisqu'il présente une conductivité par les ions oxyde proche de celle de La2Mo2O9 à basse température. / La2Mo2O9, the first compound in the LAMOX family, is interesting for its applications as electrolytes in fuel cells because it presents a high ionic conductivity. It was discovered during the investigation of La2O3 - MoO3phase diagram. That shows the important role of phase diagram study in the discovery of new materials which has become a major objective of many solid chemists.In this concept, two ternary phase diagrams of La2O3-Nb2O5-WO3 and La2O3-Nb2O5-MoO3 were explored and analyzed for the first time using the solid-state synthesis. The structures of the obtained samples were characterized by the powder X-ray and neutron diffraction and by the transmission electronic microscopy. Besides, their electric properties were tested by the complex impedance spectroscopy onsintered pellets.As results, most of the mono-, bi-, tri-phase zones in the title phase diagrams have been defined. Particularly, during the phase-diagram investigation, the structures of two new phases La3NbWO10 and La5NbMo2O16 were ab-initio resolved. Firstly, the La3NbWO10 cell is asuperstructure of a fluorine (2aF*2aF*2aF) with the lengthened c axis. Considering the La18Nb6W62O604(Z = 6) formulation, we can easily note that the structure presents 2 types of defaults: cationic and anionic vacancies. Secondly, the La5NbMo2O16 phase is isotype of Pr5Mo3O16 compound. Its cell is also a fluorine superstruture. It crystallized in a cubic system (a = 11.22Å) with the space group Pn n. The compound is promising because it presents an oxygen conductivity comparable to that of La2Mo2O9 at low temperature.

Climate change is no longer imminent but eminent. To combat climate change, effective, efficient and smart energy use is imperative. Thermal energy storage (TES) with phase change materials (PCMs) is one attractive choice to realize this. Besides suitable phase change temperatures and enthalpies, the PCMs should also be robust, non-toxic, environmental-friendly and cost-effective. Cost-effective PCMs can be realized in bulk blends. Blends however do not have robust phase change unless chosen articulately. This thesis links bulk blends and robust, cost-effective PCMs via the systematic design of blends as PCMs involving phase equilibrium evaluations. The key fundamental phase equilibrium knowledge vital to accurately select robust PCMs within blends is established here. A congruent melting composition is the most PCM-ideal among blends. Eutectics are nearly ideal if supercooling is absent. Any incongruent melting composition, including peritectics, are unsuitable as PCMs. A comprehensive state-of-the-art evaluation of the phase equilibrium-based PCM design exposed the underinvestigated categories: congruent melting compositions, metal alloys, polyols and fats. Here the methods and conditions essential for a comprehensive and transparent phase equilibrium assessment for designing PCMs in blends are specified. The phase diagrams of the systems erythritol-xylitol and dodecane-tridecane with PCM potential are comprehensively evaluated. The erythritol-xylitol system contains a eutectic in a partially isomorphous system unlike in a non-isomorphous system as previous literature proposed. The dodecane-tridecane system forms a probable congruent minimum-melting solid solution, but not a maximum-melting liquidus or a eutectic as was previously proposed. The sustainability aspects of a PCM-based TES system are also investigated. Erythritol becomes cost-effective if produced using glycerol from bio-diesel production. Olive oil is cost-effective and has potential PCM compositions for cold storage. A critical need exists in the standardization of methods and transparent results reporting of the phase equilibrium investigations in the PCM-context. This can be achieved e.g. through international TES collaboration platforms. / Energi är en integrerad del av samhället men energiprocesser leder till miljöbelastning, och klimatförändringar. Därför är effektiv energianvändning, ökad energieffektivitet och smart energihantering nödvändigt. Värmeenergilagring (TES) är ett attraktivt val för att bemöta detta behov, där ett lagringsalternativ med hög densitet är s.k. fasomvandlingsmaterial (PCM). Ett exempel på ett billigt, vanligt förekommande PCM är systemet vatten-is, vilket har använts av människor i tusentals år. För att tillgodose de många värme- och kylbehov som idag uppstår inom ett brett temperaturintervall, är det viktigt med innovativ design av PCM. Förutom lämplig fasförändringstemperaturer, entalpi och andra termofysikaliska egenskaper, bör PCM också ha robust fasändring, vara miljövänlig och kostnadseffektiv. För att förverkliga storskaliga TES system med PCM, är måste kostnadseffektivitet och robust funktion under många cykler bland de viktigaste utmaningarna. Kostnadseffektiva PCM kan bäst erhållas från naturliga eller industriella material i bulkskala, vilket i huvudsak leder till materialblandningar, snarare än rena ämnen. Blandningar uppvisar dock komplexa fasförändringsförlopp, underkylning och/eller inkongruent smältprocess som leder till fasseparation. Denna doktorsavhandling ger ny kunskap som möjliggör att bulkblandningar kan bli kostnadseffektiva och robusta PCM-material, med hjälp av den systematiskutvärdering av fasjämvikt och fasdiagram. Arbetet visar att detta kräver förståelse av relevanta grundläggande fasjämviktsteorier, omfattande termiska och fysikalisk-kemiska karakteriseringar, och allmänt tillämpliga teoretiska utvärderingar. Denna avhandling specificerar befintlig fasjämviktsteori för PCM-sammanhang, men sikte på att kunna välja robusta PCM blandningar med specifika egenskaper, beroende på tillämpning. Analysen visar att blandningar med en sammansättning som leder till kongruent smältande, där faser i jämvikt har samma sammansättning, är ideala bland PCM-blandningar. Kongruent smältande fasta faser som utgör föreningar eller fasta lösningar av ingående komponenter är därför ideala. Eutektiska blandningar är nästan lika bra som PCM, så länge underkylning inte förekommer. Därmed finns en stor potential för att finna och karakterisera PCM-ideala blandningar som bildar kongruent smältande föreningar eller fasta lösningar. Därigenom kan blandningar med en skarp, reversibel fasändring och utan fasseparation erhållas – egenskaper som liknar rena materialens fasändringsprocess. Vidare kan man, via fasdiagram, påvisa de blandningar som är inkongruent smältande, inklusive peritektiska blandningar, som är direkt olämpliga som PCM. Denna avhandling ger grundläggande kunskap som är en förutsättning för att designa PCM i blandningar. Genom en omfattande state-of-the-art utvärdering av fas-jämviktsbaserad PCM-design lyfter arbetet de PCM-idealiska blandningarna som hittills inte fått någon uppmärksamhet, såsom kongruenta smältande blandningar, och materialkategorierna metallegeringar, polyoler och fetter. Resultatet av arbetet visar dessutom att vissa PCM-material som ibland föreslås är direkt olämpliga då fasdiagram undersöks, bl a pga underkylning och även peritektiska system med fasseparation och degradering av kapaciteten (t ex Glauber-salt och natriumacetat-trihydrat). Denna avhandling specificerar och upprättar grundläggande teori samt tekniker, tillvägagångssätt och förhållanden som är nödvändiga för en omfattande och genomsynlig fasjämviktsbedömning, för utformning av PCM från blandningar för energilagering. Med detta som bas har följande fasdiagramtagits fram fullständigt: för erytritol-xylitol och för dodekan-tridekan, med PCM-potential för låg temperaturuppvärmning (60-120 °C) respektive frysning (-10 °C till -20 °C) utvärderas fullständigt. Erytritol-xylitol systemet har funnits vara eutektiskt i ett delvis isomorft system, snarare än ett icke-isomorft system vilket har föreslagits tidigare litteratur. Dodekan-tridekan systemet bildar ett system med kongruent smältande fast lösning (idealisk som en PCM) vid en minimumtemperatur, till skillnad från tidigare litteratur som föreslagt en maximumtemperatur, eller ett eutektiskt system. Teoretisk modellering av fasjämvikt har också genomförts för att komplettera det experimentella fasdiagrammet för systemet erytritol-xylitol. Efter granskning av de metoder som använts tidigare i PCM-litteraturen har här valts ett generiskt tillvägagångssätt (CALPHAD-metoden). Denna generiska metod kan bedöma vilken typ av material och fasändring som helst, till skillnad från en tidigare använda metoder som är specifika för materialtyper eller kemiska egenskaper. Denna teoretiska studie bekräftar termodynamiskt solvus, solidus, eutektisk punkt och erytritol-xylitol fasdiagrammet i sin helhet. Vad gäller hållbarhetsaspekter med PCM-baserad TES, lyfter denna avhandling fokus på förnybara och kostnadseffektiva material (t.ex. polyoler och fetter) som PCM. Som exempel har här undersökts erytritol och olivolja, med förnybart ursprung. Erytritol skulle kunna bli ett kostnadseffektivt PCM (163 USD/kWh), om det produceras av glycerol vilket är en biprodukt från biodiesel/bioetanolframställning. Olivolja är ännu ett kostnadseffektivt material (144 USD/kWh), och som här har påvisats innehålla potentiella PCM sammansättningar med lämpliga fasändringsegenskaper för kylatillämpningar. En övergripande slutsats från denna avhandling är att det finns ett behov av att standardisera tekniker, metoder och transparent resultatrapportering när det gäller undersökningar av fasjämvikt och fasdiagram i PCM-sammanhang. Internationella samarbetsplattformar för TES är en väg att koordinera arbetet. / <p>QC 20170830</p>

Ce travail de thèse repose sur deux axes d'étude : (i) l'influence des éléments légers solides, B et C sur la stabilité des phases binaires U-Si, et (ii) la recherche de nouvelles phases et leurs caractérisations physiques dans le système ternaire U-Pt-Si. Des ajouts mineurs de carbone ou de bore au sein d'échantillons U-Si ont montré que la formation de la phase de composition U₅Si₄ était corrélée à la présence de ces éléments légers, conduisant à mettre en doute son existence au sein du système binaire U-Si. Afin d'étudier le potentiel du bore comme simulant des non-métaux de la seconde période (C, N, O), la section isotherme à 927 °C du diagramme de phases ternaire U-Si-B a été tracée, révélant des équilibres entre les axes U-B et U-Si majoritairement et l'existence d'une nouvelle phase U₂₀Si₁₆B₃ isotype du composé ternaire au carbone. Ces résultats tendent à montrer les spécificités physico-chimiques de chacun de ces éléments légers sur le diagramme de phase U-Si. L'étude du diagramme de phases ternaire U-Pt-Si a été effectuée pour la section isotherme à 900 °C. Elle a abouti à la découverte de 14 nouvelles phases, dont U₃Pt₆Si₄ et U₃Pt7Si, présentant des arrangements structuraux inédits. Au préalable de cette étude, un examen du système U-Pt a été entrepris pour la zone de composition 30-70 at.% Pt, conduisant à une nouvelle évaluation du diagramme de phases binaire, intégrant le nouveau composé U₃Pt₄. La température des transformations a été mesurée par ATD. Nos résultats couplés aux données de la littérature ont permis une modélisation par la méthode Calphad. Les caractérisations physiques du nouveau composé binaire U₃Pt₄, indique un comportement de fermion lourd ordonné ferromagnétiquement en dessous de Tc = 7(1)K. En parallèle de ces travaux, l'étude de la famille U₃TGe₅ de type structural anti-Hf₅CuSn₃ a permis la découverte de neuf nouveaux composés pour T = V, Cr, Mn, Zr, Nb, Mo, Hf, Ta et W en plus du composé U₃TiGe₅ déjà répertorié. Leurs propriétés magnétiques et électroniques ont été évaluées, révélant des composés aux corrélations électroniques modérés avec des comportements évoluant en fonction du nombre d'électrons de valence du métal de transition d. Pour les composés avec T = Ti et V des corrélations entre ondes de densités de spin et de charge sont suspectées en dessous de la température d'ordre magnétique. / Two main research axes were defined for this Ph-D work : (i) studying the effect of light elements (B, C) on the stability of U-Si compounds, and (ii) identifying and physically characterizing new phases in the U-Pt-Si system. Minor additions of carbon and boron in U-Si samples revealed that the formation of U₅Si₄ would be correlated to the presence of these light elements, questioning its existence in the U-Si system. To evaluate the boron potential as a stimulant for non-metallic light elements of the second period (C, N, O), the isothermal section of the ternary phase diagram U-Si-B has been drawn at 927 °C, disclosing solid equilibrium mainly between the U-B and U-Si binary axes and the existence of the novel compound U₂₀Si₁₆B₃, isostructural to the carbon equivalent one. These results suggest a specific behavior for a given light element on the U-Si phase relations. The isothermal section at 900 °C of the U-Pt-Si ternary system was experimentally determined, leading to the discovery of 14 new phases, among which U₃Pt₄Si₆, U₃Pt₆Si₄ and U₃Pt7Si crystallized in their own structural type. As a prerequisite for this study, the phase relations in the U-Pt binary phase diagram were re-examined for the composition range 30 at.% and 70 at.% Pt, leading to a new assessment of the phase diagram which comprises the new U₃Pt₄ compound . The temperature of the transformations has been measured by DTA. By coupling our experimental results to the literature data, a modeling of the phase diagram by the Calphad method was performed. Physical characterizations of the new U₃Pt₄ compound revealed a moderate heavy fermion behavior, with ferromagnetic ordering below Tc = 7(1) K. As a side project, a study of the U₃TGe₅ family with the anti-Hf₅CuSn₃ structural type lead to the discovery of nine new compounds for T = V, Cr, Mn, Zr, Nb, Mo, Hf, Ta and W in addition to the previously reported U₃TiGe₅. Their magnetic and electronic properties were evaluated, disclosing moderate heavy-fermion compounds, with behavior evolving with valence electron count of the transition metal. For T = Ti, V compounds, correlation between spin and charge density waves are suspected below the magnetic ordering temperature.

Nous nous proposons d'explorer les propriétés structurales et vibrationnelles de la glace d'ammoniac en présence de fluor et d'eau sur une large gamme de pression et de température. Ces solides moléculaires et ioniques sont des idéaux afin d'étudier les quatre liaisons hydrogène les plus importantes O-H...O, N-H...N, O-H...N et N-H...F et le mécanisme de transfert de proton le long de ces liaisons. Bien que ces mélanges soient composés de molécules simples, ils sont omniprésents dans l'univers et en particulier à l'intérieur des planètes géantes glacées (Neptune, Uranus) et de leurs satellites (Titan, Ganymède), ce qui a motivé leur exploration sous haute condition de pression et de température. Nous utilisons plusieurs méthodes ab initio afin d'étudier le diagramme de phase de deux cristaux, le fluorure d'ammonium (NH4F) et l'ammoniac monohydraté (NH3.H2O). Après avoir prédit plusieurs structures cristallographiques à 0 K, nous avons pu nous consacrer aux calculs de spectres Raman et infrarouge ainsi qu'à la prise en compte des effets de désordre et dynamique en utilisant la méthode de la dynamique moléculaire ab initio. Nos résultats ont ensuite été comparés à ceux issus des expériences sous enclumes de diamant. Nous avons découvert une transition de type ordre-désordre au sein de NH4F et un diagramme de phase très similaire au diagramme de phase de l'eau. Enfin, nous avons démontré que des conditions thermodynamiques relativement douces étaient suffisantes afin de transformer le mélange NH3.H2O en un cristal exotique où coexiste des molécules d'ammoniac et d'eau avec des ions hydroxyde et ammonium. / In this thesis, we explore the structural and vibrational properties of fluorinated and hydrated ammonia ices over a wide range of pressure and temperature. These crystals are considered as models to study the four main hydrogen bonds O-H…O, N-H…N, O-H…N, N-H…F and proton hopping mechanisms along these bonds. Although these mixtures are composed of simple molecules they are considered to be the major components of the interior of the giant icy planets (Neptune, Uranus) and their satellites (Titan, Ganymede), which has motivated their exploration under high pressure-temperature conditions. Here we investigate the phase diagram of two crystals, ammonium fluoride (NH4F) and ammonia monohydrate (NH3.H2O) by using several ab initio methods. Firstly, we have performed random structural search calculations in order to predict the lowest enthalpy structures at 0 K. On the other hand, we have calculated Raman and infrared spectra of the most promising structures and ab initio molecular dynamics simulations were performed for the understanding of disorder and dynamic effects. Then, our results have been compared to experimental evidence. We have discovered an order-disorder transition in NH4F with a phase diagram surprisingly similar to that of water. Finally, we have demonstrated that relatively mild pressure conditions were sufficient to transform NH3.H2O into an exotic phase where the standard molecular forms of water and ammonia coexist with their ionic counterparts, hydroxide and ammonium ions.

Transition metals (Ti, Zr, Hf, Mo, W, V, Nb, Ta, Pd, Pt, Cu, Ag, and Au) are essential building units of many materials and have important industrial applications. Therefore, it is important to understand their thermal and physical behavior when they are subjected to extreme conditions of pressure and temperature. This dissertation presents: An improved experimental technique to use lasers for the measurement of thermal conductivity of materials under conditions of very high pressure (P, up to 50 GPa) and temperature (T up to 2500 K). An experimental study of the phase relationship and physical properties of selected transition metals, which revealed new and unexpected physical effects of thermal conductivity in Zr, and Hf under high P-T. New phase diagrams created for Hf, Ti and Zr from experimental data. P-T dependence of the lattice parameters in α-hafnium. Contrary to prior reports, the α-ω phase transition in hafnium has a negative dT/dP slope. New data on thermodynamic and physical properties of several transition metals and their respective high P-T phase diagrams. First complete thermodynamic database for solid phases of 13 common transition metals was created. This database has: All the thermochemical data on these elements in their standard state (mostly available and compiled). All the equations of state (EoS) formulated from pressure-volume-temperature data (measured as a part of this study and from literature). Complete thermodynamic data for selected elements from standard to extreme conditions. The thermodynamic database provided by this study can be used with available thermodynamic software to calculate all thermophysical properties and phase diagrams at high P-T conditions. For readers who do not have access to this software, tabulated values of all thermodynamic and volume data for the 13 metals at high P-T are included in the APPENDIX. In the APPENDIX, a description of several other high-pressure studies of selected oxide systems is also included. Thermophysical properties (Cp, H, S, G) of the high P-T ω-phase of Ti, Zr and Hf were determined during the optimization of the EoS parameters and are presented in this study for the first time. These results should have important implications in understanding hexagonal-close-packed to simple-hexagonal phase transitions in transition metals and other materials.