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1
Butt, M. Taqi Zahid. "Study of gold-based alloy phase diagrams". Thesis, Brunel University, 1990. http://bura.brunel.ac.uk/handle/2438/7389.
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The partial constitutions of the Au-Ge-X and Au-Pb-X ternary alloys have been investigated, where X is a metallic element, selected from the sub-groups period 1m and rrm of the periodic table (In, Ga, Zn, or Cd), which forms one or more stable compounds with gold, but which forms no stable compound with Ge and Pb. The Smith Thermal Analysis Method, supplemented by metallographic and X-ray techniques, was used to determine the constitutions of the ternary systems. Eutectiferous, pseudobinary systems were found between Ge and the stable congruent intermediate compounds, AuIn, Auln2' AuGa, AuGa2' AuZn and AuCd. The solubility of Ge in the AuX compounds was not determined directly. However, it was 1.3 at.% Ge for Zn and Cd containing alloys and less than 1.0 at. % Ge for In and Ga containing alloys at the eutectic temperatures, which is in accordance with the Hume-Rothery rule. Ternary eutectic points were also determined in the Auln-AuIn2-Ge, Auln2-In-Ge and AuGa-AuGa2-Ge partial ternary systems. No evidence of liquid immiscibility was found in any of these ternary systems. The experimental results obtained were in good agreement with computed features of the diagrams. However, pseudobinary systems were not found between Pb and the stable congruent melting intermediate compounds, AuGa, AuGa2, AuZn and AuCd (the AuIn-Pb and AuIn2-Pb sections had already been investigated). The evidence of an extensive liquid immiscibility was found in each of these systems. The miscibility in the liquid state was found to decrease progressively down group IV when the elements of this group react with AuX compounds, which can be attributed to the progressive increase of the atomic size and decrease in electronegativities and solubility parameters of the elements, down this group. Two rules were derived to relate the liquid immiscibility/miscibility of ternary systems. One of the rules based upon the atomic sizes and melting points of the constituent elements showed a fair agreement with many systems. However, the other rule based upon the solubility parameter and electronegativities of the constituent elements showed good agreement with immiscible systems, but gave a poor predictability for miscible systems. The lower temperature equilibria of the Au-rich portion of the Au-Sn binary phase diagram are not well defined. So, long term heat treatment of samples at appropriate temperatures and compositions was carried out. Optical microscopy and SEMIEDAX techniques were employed and hence the low temperature equilibria of the Au-Sn binary system have been amended.
2
Wu, Yang. "Azimuthal anisotropy in gold-gold collisions at 4.5 GeV center-of-mass energy per nucleon pair using fixed-target mode at the Relativistic Heavy-Ion Collider". Kent State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=kent1562355001935965.
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Hajiw, Stéphanie. "Des interactions entre nanoparticules d’or hydrophobes à leur auto-assemblage". Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS080/document.
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Comme de nombreux colloïdes, des nanoparticules métalliques recouvertes de ligands en suspension s’organisent au-delà d’une fraction volumique seuil et forment ce que l’on appelle un « supracristal ». Ce sont ainsi des systèmes modèles, déjà largement étudiés à partir de suspensions dans des solvants volatils, qui permettent de mieux comprendre l’auto-assemblage de sphères déformables. Les interactions qui conduisent à l’auto-assemblage sont couramment décrites par une compétition entre une attraction de van der Waals entre les cœurs métalliques et une répulsion entre les ligands qui va dépendre de l’affinité entre les ligands et le solvant. Un effet du solvant a déjà été observé sur l’auto-organisation de nano-objets. En mesurant par diffusion de rayons X aux petits angles le facteur de structure de suspensions de nanoparticules d’or greffées, j’ai pu sonder de façon systématique les interactions entre des nanoparticules en suspension avec plusieurs tailles de cœur, des ligands alcane-thiols de longueur différente et dans différents solvants à la fois volatils et non volatils. J’ai ainsi pu mettre en évidence une interaction attractive inattendue dans des alcanes linéaires flexibles et dont l’intensité augmente avec la longueur de l’alcane. Pour corréler les interactions entre particules à leur diagramme de phase, j’ai suivi le processus de cristallisation dans des suspensions en solvant volatil ou partiellement volatil ainsi qu’en émulsion, techniques qui permettent d’augmenter lentement la concentration en nanoparticules. Les interactions attractives induites par le solvant contribuent ainsi à la formation de supracristaux à de très faibles fractions volumiques. A de fortes concentrations, la structure des supracristaux ne dépend pas du solvant utilisé mais, à forte densité de greffage, du rapport R entre la longueur des ligands et le diamètre du cœur d’or. Pour un rapport R voisin de 0.7, la structure finale observée est cubique centrée, la structure à concentration intermédiaire étant cubique à faces centrées. Pour un rapport R deux fois plus petit, une structure originale a été mise en évidence. Il s’agit d’une structure hexagonale de grand paramètre de maille, analysée comme une phase de Frank et Kasper de type MgZn2 ou C14. C’est la première fois qu’une telle phase à empilement local tétraédrique est observée dans un système de sphères monodisperses molles. L’existence de cette phase ainsi que le rôle du rapport R a pu être interprétée en estimant quantitativement la compétition entre l’attraction de van der Waals forte et l’entropie des ligandsAs many colloids, metallic nanoparticles grafted with hydrophobic ligands self-assemble above a volume fraction threshold and thus build superlattices. These model systems, which are widely studied when suspended in volatile oils, enable a better understanding of soft spheres self-assembly.Interactions which lead to self-assembly are commonly described by the combination of van der Waals attraction with interaction between the ligand shells. The shell behavior is controlled by the ligand affinity with the solvent. An effect of the solvent on the self-assembly of nanoparticles has already been observed. Using a small angle X-ray scattering, I measured, through the structure factor, the interactions between gold nanoparticles grafted with alkanethiols in different oils, at various concentrations, for different lengths of ligands and core diameters. I noticed an attractive interaction when using flexible linear alkanes as solvent. It has also been shown that the attraction intensity increases with the solvent length.In order to correlate the interactions between particles to their phase diagram, I studied the crystallization process by concentrating nanoparticles using evaporation in capillaries or Ostwald ripening in emulsions. I showed that attractive interactions induced by the solvent lead to superlattices formation at very low volume fractions.At high concentrations, the superlattice structure depends on the ratio of the ligand length over the gold core diameter. For a ratio around 0.7, the final structure observed is body centered cubic, whereas at lower concentration, it is face centered cubic. When this ratio is halved, an unexpected structure is observed. It is a hexagonal structure with a large lattice parameter. It has been analyzed as a Frank and Kasper’s phase named MgZn2 or C14. It is the first time that this topologically close-packed structure is observed for monodisperse soft spheres. The existence of this phase and the role of the ratio R have been interpreted by considering quantitatively the competition between ligands entropy and the strong van der Waals attraction
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Richard, Pauline. "Exploration ab initio du diagramme de phases de l'or à haute pression et haute température". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF040.
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Cette thèse est consacrée à l'exploration du diagramme de phases de l'or à haute pression et haute température. Pour cela, le calcul de l'énergie libre est fondamental afin de comparer la stabilité relative des phases dans des conditions thermodynamiques spécifiques. Cependant, cette grandeur dépend explicitement de la fonction de partition, ce qui la rend difficile à calculer en simulation atomistique. Elle est souvent décomposée en contributions froide et thermique. Parmi ces contributions, les vibrations du réseau cristallin, les phonons, jouent un rôle crucial. En effet, les températures explorées induisent l'apparition d'effets anharmoniques, nécessitant l'emploi de la dynamique moléculaire ab initio, ici basée sur la théorie de la fonctionnelle de la densité (DFT). Cette méthode est la plus appropriée pour prendre en compte ces effets, que les potentiels interatomiques phénoménologiques existants ne parviennent pas à reproduire. Couplée à l'intégration thermodynamique, cette approche constitue une méthode de référence pour le calcul de l'énergie libre. Toutefois, elle reste très coûteuse en temps de calcul et est donc prohibitive pour construire le diagramme de phase complet de l'or. Des méthodes alternatives existent, comme l'approximation quasi-harmonique, mais leur validité à haute température est difficile à évaluer. L'objectif de cette thèse est donc de proposer une méthode efficace pour calculer l'énergie libre tout en conservant la précision de la DFT. Pour ce faire, une procédure d'échantillonnage accélérée par apprentissage automatique est employée. Elle permet d'entraîner des potentiels numériques de substitution, mobilisés a posteriori pour extraire les énergies libres de Gibbs des structures considérées via un calcul d'intégration thermodynamique hors équilibre. Les résultats obtenus ont été validés par comparaison avec ceux du potentiel effectif dépendant de la température. Dans une première partie, cette approche a été appliquée pour construire le diagramme de phases de l'or solide de 0 à 1 TPa et jusqu'à 10 000 K. Elle montre la stabilisation d'une phase cubique centrée (bcc) à haute température, autour de 200 GPa. Une explication de la transition cubique faces centrées (fcc)-bcc avant la fusion a été proposée, se basant sur les effets des constantes de forces interatomiques. Par ailleurs, les domaines de stabilité des phases fcc et hexagonale compacte (hcp) prédits par cette étude sont en bon accord avec la plupart des résultats expérimentaux récents. Dans la seconde partie, cette procédure a été étendue au calcul de la courbe de fusion de l'orThis thesis is dedicated to exploring the phase diagram of gold under high pressure and high temperature. Calculating the free energy is fundamental for comparing the relative stability of phases under specific thermodynamic conditions. However, this quantity explicitly depends on the partition function, making it challenging to calculate in atomistic simulations. It is often decomposed into cold and thermal contributions. Among these contributions, the lattice dynamics, or phonons, play a crucial role. The temperatures explored induce indeed anharmonic effects, necessitating the use of expensive ab initio methods, based on density functional theory (DFT) which are the most appropriate method to account for these effects that existing empirical potentials cannot reproduce. Coupled with thermodynamic integration, it is the reference method for calculating free energy. However, this method remains very time-consuming and is thus prohibitive to explore the whole phase diagram of gold. Alternative methods exist, such as the quasi-harmonic approximation, but its validity at high temperature is difficult to assess. The goal of this thesis is to propose a method that maintains DFT accuracy while reducing computation time. To achieve this, an accelerated sampling procedure using machine learning is employed. This procedure allows for the training of surrogate potentials, which are then used a posteriori to extract the Gibbs free energies of the considered structures via a non-equilibrium thermodynamic integration calculation. The results obtained have been validated by comparison with those from the temperature-dependent effective potential. In the first part, this approach was applied to construct the phase diagram of solid gold from 0 to 1 TPa and up to 10,000 K. It shows the stabilization of a body-centered cubic (bcc) phase at high temperatures, around 200 GPa. An explanation for the cubic face-centered (fcc)-bcc transition before melting was proposed, based on the effects of interatomic force constants. Furthermore, the stability domains of the fcc and hexagonal close-packed (hcp) phases predicted by this study are in good agreement with most recent experimental results. In the second part, this procedure was extended to calculate the melting curve of gold
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Park, Heung-Shik. "Self-assembly of lyotropic chromonic liquid crystals: Effects of additives and applications". Kent State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=kent1291043533.
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Fallas, Chinchilla Juan Carlos. "Pressure-temperature phase diagram of LiA1H₄". abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1464434.
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Azevedo, Cesar R. de Farias. "Phase diagram and phase transformations in Ti-Al-Si system". Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/1278.
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Prins, Sara Natalia. "The AI-Pt-Ru ternary phase diagram". Diss., Pretoria : [s.n.], 2003. http://upetd.up.ac.za/thesis/available/etd-09192005-163724/.
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Attwood, Brian Christopher. "Global phase diagram for monomer/dimer mixtures". NCSU, 2001. http://www.lib.ncsu.edu/theses/available/etd-20011012-113555.
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The objective of this thesis is to calculate the global phase diagram predicted by the Generalized Flory Dimer equation of state for mixtures of square-well monomers and dimers. Towards that goal, we first extend the Generalized Flory Dimer (GFD) theory for hard sphere monomer/dimer mixtures to square-well monomer/dimer mixtures. Theoretical predictions for the compressibility factor as a function of volume fraction are compared to discontinuous molecular dynamic simulation results on monomer/dimer mixtures at well depth ratios 0.5 - 1.5 and dimer mole fractions 0.111 - 0.667 and on monomers/8-mer mixtures at well depth ratios 0.5 - 1.5. Agreement is found generally to be good and consistent with the agreement obtained when the GFD theory is applied to other square-well systems. Next we calculate the GFD predicted global phase diagram for square-well monomer/dimer mixtures using a brute force method. The locus of critical points in the direction implies that monomer/dimer systems have a greater tendency towards liquid-liquid immiscibility in our system than in monomer/monomer systems.
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Huang, Gang 1971. "Phase diagram for liquid crystalline polymerpolycarbonate blends". Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33973.
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Blends containing a thermotropic liquid crystalline polymer and an engineering thermoplastic polymer have recently received considerable attention, because liquid crystalline polymers display low melt viscosity, excellent chemical resistance, thermal stability and mechanical performance. A novel mechanism to form binary polymer blends is through phase separation by spinodal decomposition in the unstable region of the phase diagram. The overall objective of this work is to investigate the effects of thermally induced phase separation by spinodal decomposition on the morphology development of liquid crystalline polymer/polycarbonate blends and to obtain a thermodynamic binary phase diagram. The blends were obtained using a twin-screw extruder at various processing melt temperatures. To study miscibility of the blends and the resulting morphology, techniques such as differential scanning calorimetry and scanning electron microscopy were used. The liquid crystalline polymer/polycarbonate blend undergoes phase separation during thermally induced spinodal decomposition exhibiting a miscibility window reminiscent of a lower critical solution temperature. The blend is found to be miscible, when blend Tg slightly decreases. On the other hand, the blend is found to be immiscible as blend Tg increases. A thermodynamic two-phase transition curve phase diagram was obtained using an innovative practical experimental technique in conjunction with twin screw extrusion and scanning electron microscopy.
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Duncan, Graham Kirk. "Phase diagram studies of the beta-aluminas". Thesis, University of Aberdeen, 1985. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=201758.
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Chang, Fwu-Ranq. "Optimal Growth and Impatience: A Phase Diagram Analysis". 名古屋大学大学院経済学研究科附属国際経済政策研究センター, 2004. http://hdl.handle.net/2237/11954.
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Assawasunthonnet, Wathid. "Second order critical point in QCD phase diagram". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/51611.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2009.Includes bibliographical references (p. 57).
In this thesis I explore the theoretical model based on Asakawa and Nonaka's idea[l]. I start by arguing that the critical point of the QCD phase diagram is second order and belongs to the three dimensional Ising model universality class. Then the singular part of the equation of state is derived. The singular part and non-singular part equation of state are glued together to find the general form of the equation of state. This equation of state includes the critical point. With this equation of state, we construct the isentropic trajectories. The pathology of these trajectories is discussed. Moreover the validation of the signature of the critical point suggested by Asakawa and Nonaka is also discussed.
by Wathid Assawasunthonnet.
S.B.
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Mikula, Hynek. "Fázový diagram chladiva LiF-NaF-KF". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-374735.
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In introduction this graduation theses discource about phase diagrams and thein fission. Next part is about concrete phase diagrams NaF – KF, NaF – LiF, KF – LiF. Their determination trough use of cooling surves and their specification trough use of numerical method. Conclusion contains proposal of method for concrete phase diagram of NaF – KF – LiF.
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Yamamoto, Masahiro, Hiromichi Ohta y Kunihito Koumoto. "Thermoelectric phase diagram in a CaTiO3- SrTiO3 - BaTiO3 system". American Institute of Physics, 2007. http://hdl.handle.net/2237/8769.
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Günther, Jana [Verfasser]. "Lattice investigations of the QCD phase diagram / Jana Günther". Wuppertal : Universitätsbibliothek Wuppertal, 2017. http://d-nb.info/1128844818/34.
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Steinert, Thorsten [Verfasser]. "The QCD phase diagram within effective models / Thorsten Steinert". Gießen : Universitätsbibliothek, 2018. http://d-nb.info/116167036X/34.
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Ubbens, Menke Ubbo Heert. "The superconducting phase diagram of the t-J model". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/32130.
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Epifano, Enrica. "Study of the U-Am-O ternary phase diagram". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX084/document.
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Les isotopes de l’Américium sont les principaux contributeurs à la radioactivité des déchets nucléaires. Parmi les scénarios pour diminuer la toxicité des déchets, la transmutation dans les réacteurs à neutrons rapides utilisant des pastilles d’oxyde mixte (U,Am)O2 est une voie prometteuse. Dans ce cadre, la connaissance des propriétés thermodynamiques du système U-Am-O est essentielle pour prédire le comportement des pastilles (U,Am)O2 en conditions nominale et accidentelle. Cette thèse est dédiée à l’étude expérimentale d’oxydes mixtes (U,Am)O2 dans une large gamme de composition (7,5 % at. ≤ Am/(Am+U) ≤ 70 % at.). L’objectif est d’acquérir des données pour développer un modèle thermodynamique avec la méthode semi-empirique CALPHAD. Les résultats peuvent être classés en trois catégories : données structurales, données de diagramme de phase et données thermodynamiques. Pour la modélisation thermodynamique d’un système ternaire, l’optimisation des sous-systèmes binaires est nécessaire. Comme des questions restaient en suspens sur le système Am-O, le diagramme de phase Am-O a tout d’abord été étudié par diffraction des rayons X à haute température. L’existence d’un domaine de composition de la phase bcc AmO1.61 a été mis en évidence et la lacune de miscibilité dans la phase fluorite, proposée dans la littérature, n’a pas été confirmée. Grâce à ces nouveaux résultats, le modèle CALPHAD de Gotcu et al a été modifié. Dans une deuxième étape, des analyses structurales des dioxydes (U,Am)O2±x ont été effectuées par DRX, XAS et spectroscopie RAMAN. La DRX a permis de confirmer que tous les échantillons sont constitués d’une seule phase de structure fluorite. Le rapport O/M (avec M=U+Am) mesuré à température ambiante est inférieur à 2 ; la stabilité de l’Américium trivalent Am3+ a été mise en évidence. Celle-ci induit l’oxydation partielle de l’U4+ en U5+. Cette distribution de charge s’accompagne par la formation de défauts de l’oxygène complexes dans la structure fluorite. Lors de l’étude par DRX HT des oxydes mixtes sous air, il a été montré que la présence d’Am3+ stabilise la phase fluorite par rapport aux oxydes plus riches en oxygène (U4O9, U3O8). De nouvelles données de diagramme de phase ont été obtenues : des conodes dans les domaines biphasés M4O9-M3O8 and MO2+x-M3O8 et la solubilité de l’Américium dans les oxydes M4O9 et M3O8. L’étude du diagramme de phase U-Am-O a été poursuivie par la détermination des températures de solidus/liquidus des oxydes mixtes par une technique de chauffage laser, sous argon et sous air, et par la caractérisation des échantillons après fusion par SEM et XAS. La température de fusion des oxydes mixtes diminue avec une teneur croissante d’Américium (Am/(Am+U)) et d’oxygène (O/(Am+U)). Finalement, les propriétés thermodynamiques des oxydes (U,Am)O2±x ont été mesurées : les incréments enthalpiques par calorimétrie de chute et les pressions partielles des espèces gazeuses par Spectrométrie de Masse couplée à une cellule de Knudsen (KEMS). Une contribution d’excès de la capacité calorifique a été observée à haute température, attribuée à la réduction des oxydes (avec formation de lacunes d’oxygène). Les résultats de KEMS ont permis de déterminer une composition congruente de vaporisation à 2300 K, pour un rapport Am/(Am+U) de 0,6 et un rapport O/(U+Am) inférieur à 1,9. Finalement, la modélisation thermodynamique du système U-Am-O par la méthode CALPHAD a été abordée par la description de la phase fluorite. Un bon accord est obtenu entre le modèle et les données de potentiel d’oxygène pour l’oxyde (U0.5Am0.5)O2±x et de distribution des cations. De plus, le modèle permet de reproduire de façon satisfaisante les données de KEMS. En perspective de ce travail, la modélisation thermodynamique du ternaire sera étendue à la description des équilibres de phase mettant en jeu les oxydes M4O9, M3O8 et la phase liquideAmericium isotopes are the main contributors to the long-term radiotoxicity of the nuclear wastes, after the plutonium extraction. Among the reprocessing scenarios, the transmutation in fast neutron reactors using uranium-americium mixed oxide (U,Am)O2±x pellets seems promising. In this frame, the knowledge of the thermodynamics of the U-Am-O ternary system is of essential for the prediction of the behavior of (U,Am)O2 pellets and their possible interaction with the cladding, under normal and accidental conditions. This thesis is dedicated to the experimental investigation of U-Am mixed oxides on a wide range of Am contents (7.5 at.% ≤ Am/(Am+U) ≤ 70 at.%), with the aim to collect data for developing a thermodynamic model based on the semi-empirical CALPHAD method. The obtained results can be classified in three categories: structural, phase diagram and thermodynamic data. For the thermodynamic modeling of the ternary system, the assessment of the binary sub-systems is first required. As open questions still existed on the Am-O system, a first part of the work was dedicated to the study of the Am-O phase diagram by high-temperature (HT) XRD. The existence of a composition range of the bcc AmO1.61 phase was highlighted and the miscibility gap in the fluorite phase, proposed in the literature, was not found. Thanks to the new experimental data, the existing CALPHAD model of Gotcu et al. was modified. In a second step, structural investigations were performed on synthesized (U,Am)O2±x dioxides by coupling XRD, XAS and Raman spectroscopy. For all the compositions, the XRD confirmed the formation of a single fluorite structure. The O/M ratio (with M=U+Am) at room temperature was determined to be lower than 2; the stability of trivalent americium Am3+ in the dioxide solid solution was highlighted, which induces a partial oxidation of uranium from U4+ to U5+. This charge distribution, peculiar for a dioxide, is accompanied by the formation of complex oxygen defects in the fluorite structure. By a HT-XRD investigation of the mixed oxides under air combined with XAS characterization of the oxidized samples, it was shown that the presence of Am3+ leads to a stabilization of the dioxide fluorite phase toward the formation of oxides richer in oxygen, in comparison to the U-O system. New phase diagram data were obtained in the oxygen rich region at 1470 K: tie-lines in the M4O9-M3O8 and MO2+x-M3O8 domains were determined and the solubility of americium in the M4O9 and M3O8 oxides was estimated. The investigation of the U-Am-O phase diagram continued at higher temperature with the study of the solidus/liquidus transitions using a laser-heating technique, under argon and air, and post-melting characterizations conducted by SEM and XAS. The melting temperature of Am-U dioxides decreases with the increase of both the Am/(Am+U) and O/M ratios. Finally, thermodynamic properties of the U1-yAmyO2±x oxides were measured: enthalpy increments using drop calorimetry, partial vapor pressures by Knudsen cell effusion mass spectrometry (KEMS). An excess contribution to the heat capacity at high temperature was observed and this was attributed to the reduction of the dioxides at high temperature (formation of oxygen vacancies). The KEMS results lead to determine the congruent vaporization composition at 2300 K, for a Am/(Am+U) ratio of 0.6 and an O/M ratio lower than 1.9. Finally, the CALPHAD thermodynamic assessment of the U-Am-O system was started, by focusing the attention on the modelling of the fluorite phase. A good agreement between the model and the oxygen potential data for (U0.5Am0.5O2±x) and the cation distribution was achieved. Furthermore, the model is able to satisfactorily reproduce the KEMS data and hence the equilibrium between the dioxide and gas phase. For the perspectives of this work, the optimization of the thermodynamic model should be extended to describe the phase equilibria involving the M4O9, M3O8 oxides and the liquid phase
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Maelger, Jan. "Perturbative perspectives on the Phase diagram of Quantum ChromoDynamics". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLX050/document.
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L'étude du diagramme des phases de la Chromodynamique Quantique (QCD) et des transitons associées (déconfinement et restoration de la symétrie chirale) représentent des défis majeurs de la Physique moderne et nombreuses sont les approches théoriques qui visent à en sonder les multiples facettes. Du fait de l'intensité de l'interaction forte dans les régimes d’énergie pertinents pour les transitions susmentionnées, ces approches sont en général de nature non-perturbative, la théorie des perturbations étant réputée inapplicable à ces échelles. Il est, cependant, bien établi que le point de départ de la théorie usuelle des perturbations, basée sur la procédure de fixation de jauge de Faddeev-Popov, est ambigu à ces échelles (ambiguïté de Gribov). Dans ce contexte, une approche perturbative modifiée, basée sur le Lagrangien de Curci et Ferrari, a été proposée, via l’ajout phénoménologique d'un terme de masse effectif pour le gluon en jauge de Landau. Cette approche a été testée avec succès, notamment dans sa capacité à reproduire les fonctions de corrélation de la théorie Yang-Mills (et QCD dans la limite de quarks lourds) et la thermodynamique à temperature et potentiel chimique non nuls.Dans cette thèse, nous avons testé la robustesse de ces résultats en évaluant la structure de phase de la QCD avec quarks lourds au deuxième ordre de la théorie des perturbations dans le modèle de Curci-Ferrari et en comparant nos résultats à ceux d'approches nonperturbatives. Nos résultats indiquent que, dans ce régime de quarks lourds, le diagramme de phases est contrôlée perturbativement. Nous avons égalementétendu notre étude au cas de la QCD avec quarks légers en utilisant un schéma de resommation qui exploite la présence de petits paramètres dans le régime infrarouge de la QCD. Dans le secteur des quarks, cette démarche donne lieu à la resommation des fameux diagrammes dits "arc-en-ciel”. Ici, nous généralisons ce formalisme à temperature et densité non nulles et en presence d'un champ de fond gluonique. Nous réalisons une toute première étude qualitative des prédictions du modèle CF concernant l’existence possible d’un point critique dans le diagramme de phases de QCD sur la base d’une version simplifiée des équations générales ainsi obtenuesUnravelling the structure of the QCD phase diagram and its many aspects such as (de)confinementand chiral symmetry breaking, is one of the big challenges of modern theoretical physics, and manyapproaches have been devised to this aim. Since perturbation theory is believed to cease feasibilityat low energy scales, these approaches treat the relevant order parameters, the quark condensate andthe Polyakov loop, non-perturbatively. However, it is also well-established that the starting point forperturbation theory, the Fadeev-Popov gauge-fixing procedure, is inherently ill-defined in the infrareddue to the presence of Gribov ambiguities. In this context, a modified perturbative approach based onthe Curci-Ferrari Lagrangian has been introduced, where a phenomenologically motivated effective gluonmass term is added to the Landau gauge-fixed action. Prior to the beginning of the thesis, this approach hasproven extremely fruitful in its descriptions of (unquenched) Yang-Mills correlation functions and thermodynamics at (non)zero temperature and density.Throughout the thesis we extend this analysis to the entire phase structure of QCD and QCD-liketheories and test the validity of the model in various regimes of interest. For instance, to further aprevious one-loop study in the regime of heavy quark masses, we have computed the two-loop quarksunset diagram in the presence of a non-trivial gluon background in a finite temperature and densitysetting. We come to the conclusion that the physics underlying center symmetry is well-described by our perturbative model with a seemingly robust weak-coupling expansion scheme. Furthermore, we study the regime of light quarks by means of a recently proposed resummation scheme which exploits the presence of actual small parameters in the Curci-Ferrari description of infrared QCD. In the quark sector, this leads to the renown rainbow equations. We extend this first-principle setup to nonzero temperature, chemical potential, and gluon background. We perform a first qualitative analysis of the prediction of the model concerning the possible existence of a critical endpoint in the QCD phase diagram by using a simplified version of these general equations
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Pandiyan, Manoj Soundhira. "Phase diagram and control of thermoelectric properties of sodium cobaltate". Thesis, University of London, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603508.
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The temperature-composition phase diagram of sodium cobaltate, NaxCo02, was determined over the range 0.32 < x < 0.85 and 90 < T < 500K. Sodium de-intercalation was achieved using Brz/CI-hCN as an oxidising agent, and the superstructures were determined using X-ray diffraction. A kaleidoscope of Na+ ion patterns were found, including both commensurate and incommensurate structures. The sodium ion patterning of some of the superstructures was solved via a model independent approach using Reverse Monte Carlo. Diffuse scattering was observed above the sodium ordering temperature. For high x, it was possible to reproduce the data using Monte Carlo simulations of short-range ordered 8lTangements of multi-vacancy clusters. For x :::: 0.5, the ordering consists of small regions of the superstructure confined to a single sodium plane. Old samples of sodium cobaltate are found to have de-intercalated so that the surface layer has a superstructure corresponding to a lower value of x than the bulk. The thermoelectric and magnetic properties change dramatically when the superstructures change from di-vacancies to tri-vacancies. In the case of x = 0.5 we are able to understand the resonant X-ray scattering from the electronic ordering directly from the superstructure.
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Gagliardi, Giuseppe [Verfasser]. "The QCD Phase Diagram from Strong Coupling Expansion / Giuseppe Gagliardi". Bielefeld : Universitätsbibliothek Bielefeld, 2020. http://d-nb.info/1211474089/34.
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Skellern, Matthew G. "Structural and electronic properties of barium lanthanum vanadates". Thesis, University of Aberdeen, 2003. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU167989.
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A study of the subsolidus region of the BaO-La2O3-V 2O5 phase diagram has been carried out. Four ternary phases can be prepared, one of which has not been previously identified. The four ternary phases are a palmierite solid solution Ba3-3xLa2x V2O8, Ba2LaV3O11, BaLa10V4O26 (new phase) and Ba3La 40V12O93. Addition of BaLa10V 4O26 and the previously omitted phase La1.42V 0.58)3.58 to the ternary system has resulted n a re-determination of the complete phase diagram. A comprehensive study of the Ba3-3xLa 2xV2O8 solid solution has been carried out, employing a number of techniques including x-ray diffraction, infra-red spectroscopy, thermogravemetric analysis, impedance spectroscopy, electron paramagenetic resonance spectroscopy, inductively coupled plasma mass spectroscopy and x-ray absorption near edge structure spectroscopy. Conductivity measurements show the end-member Ba3V2O8 to be an oxide ion conductor, with the conduction mechanism being facilitated by the ease of transformation of the BaO3 layers to BaO2 and vice versa. The La-doped members show an increase in conductivity, with electrons becoming the dominant conducting species. The crystal structure of Ba2LaV 3O11 was confirmed to be isostructural with Ba2BiV 3O11. A full refinement of the structural parameters has been performed. The unit cell is primitive monoclinic, a = 12.44510(3)A, b = 7.78854(12)A, c = 11.26245(21)A and beta = 103.134(4)°, space group P21/c. Preliminary structural studies have begun on the new phase BaLa10V4O26. The x-ray powder pattern has been fully indexed and a possible monoclinic unit cell of a = 20.2939A, b = 5.886A, c = 12.6234A and beta = 118.05° is proposed. The serendipitous synthesis of a barium-deficient celsian phase, Ba0.8A11.6 Si2.4O8, is reported; the structure was solved using Patterson methods. The phase has a monoclinic unit cell with, a = 8.6090(8)A, b = 13.0858(12)A, c = 7.2047(7)A and beta = 115.418(2)°, space group C2/m.
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Bourov, Geuorgui Kostadinov. "SIMULATION STUDIES OF SELF-ASSEMBLY AND PHASE DIAGRAM OF AMPHIPHILIC MOLECULES". Doctoral diss., University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3486.
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The aim of this dissertation is to investigate self-assembled structures and the phase diagram of amphiphilic molecules of diverse geometric shapes using a number of different computer simulation methods. The semi-realistic coarse-grained model, used extensively for simulation of polymers and surfactant molecules, is adopted in an off-lattice approach to study how the geometric structure of amphiphiles affects the aggregation properties. The results of simulations show that the model system behavior is consistent with theoretical predictions, experiments and lattice simulation models. We demonstrate that by modifying the geometry of the molecules, self-assembled aggregates are altered in a way close to theoretical predictions. In several two and three dimensional off-lattice Brownian Dynamics simulations, the influence of the shape of the amphiphilic molecules on the size and form of the aggregates is studied systematically. Model phospholipid molecules, with two hydrophobic chains connected to one hydrophilic head group, are simulated and the formation of stable bilayers is observed. In addition, (practically very important) mixtures of amphiphiles with diverse structures are studied under different mixing ratios and molecular structures. We find that in several systems, with Poisson distributed chain lengths, the effect on the aggregation distribution is negligible compared to that of the pure amphiphilic system with the mean length of the Poisson distribution. The phase diagrams of different amphiphilic molecular structures are investigated in separate simulations by employing the Gibbs Ensemble Monte Carlo method with an implemented configurational-bias technique. The computer simulations of the above mentioned amphiphilic systems are done in an area where physics, biology and chemistry are closely connected and advances in applications require the use of new theoretical, experimental and simulation methods for a better understanding of their self-assembling properties. Obtained simulation results demonstrate the connection between the structure of amphiphilic molecules and the properties of their thermodynamically stable aggregates and thus build a foundation for many applications of the remarkable phenomena of amphiphilic self-assembly in the area of nanotechnology.Ph.D.
Department of Physics
Arts and Sciences
Physics
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Huang, Gang. "Synthesis and study of crystalline hydrogels, guided by a phase diagram". Thesis, University of North Texas, 2004. https://digital.library.unt.edu/ark:/67531/metadc4698/.
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Monodispersed nanoparticles of poly-N-isopropylacrylamide-co-allylamine (PNIPAM-co-allylamine) and PNIPAM-co-acrylic acid (AA) have been synthesized and used as building blocks for creating three-dimensional networks. The close-packed PNIPAM-co-allylamine and PNIPAM-co-AA nanoparticles were stabilized by covalently bonding neighboring particles at room temperature and at neutral pH; factors which make these networks amicable for drug loading and release. Controlled release studies have been performed on the networks using dextran markers of various molecular weights as model macromolecular drugs. Drug release was quantified under various physical conditions including a range of temperature and molecular weight. These nanoparticle networks have several advantages over the conventional bulk gels for controlling the release of biomolecules with large molecular weights. Monodispersed nanoparticles of poly-N-isopropylacrylamide-co-allylamine (PNIPAM-co-allylamine) can self-assemble into crystals with a lattice spacing on the order of the wavelength of visible light. By initiating the crystallization process near the colloidal crystal melting temperature, while subsequently bonding the PNIPAM-co-allylamine particles below the glass transition temperature, a nanostructured hydrogel has been created. The crystalline hydrogels exhibit iridescent patterns that are tunable by the change of temperature, pH value or even protein concentration. This kind of soft and wet hydrogel with periodic structures may lead to new sensors, devices, and displays operating in aqueous solutions, where most biological and biomedical systems reside. The volume-transition equilibrium and the interaction potential between neutral PINPAM particles dispersed in pure water were investigated by using static and dynamic light-scattering experiments. From the temperature-dependent size and energy parameters, the Sutherland-like potential provides a reasonable representation of the inter-particle potential for PNIPAM particles in swollen and in collapsed phases. An aqueous dispersion of PNIPAM particles can freeze at both high and low temperatures. At low temperatures, the freezing occurs at a large particle volume fraction, similar to that in a hard-sphere system; while at high temperature, the freezing occurs at low particle concentrations, driven by the strong van der Waals attraction due to the collapsed microgel particles. The calculated phase diagram has been confirmed semi-quantitatively by experiments.
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Patel, Keyurkumar S. "Automatic generation of global phase equilibrium diagram from equation of state". [Tampa, Fla] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002327.
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Sevelev, Maxime. "Phase diagram, jamming and glass transitions in the non-convex perceptron". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS331.
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Cette thèse de doctorat traite du « modèle de perceptron sphérique », un modèle simple et exactement soluble qui présente un comportement visqueux et d'encombrement qui a été généralisé aux valeurs négatives du paramètre de produit scalaire κ. Le problème classique d'apprentissage par machine qui consiste en la classification des motifs aléatoires par le perceptron fait partie des problèmes de satisfaction des contraintes (PSC) convexes. Même quand le « paramètre de stabilité » du modèle κ devient négatif, le problème reste toujours correctement posé et peut être interprété comme le problème de placement des particules sur une sphère N-dimensionnelle en évitant les obstacles placés au hasard. Dans ce cas, le PSC correspondant n'est pas convexe. Cette thèse étudie le problème en détail dans le domaine non convexe. Une étude systématique est rendue possible en faisant correspondre à un problème de satisfaction de contraintes un problème d'optimisation sur le même support, mais doté d'un Hamiltonien (fonction de coût) qui mesure les violations des contraintes en fonction de la configuration du système. Le lien entre le PSC aléatoire et la phénoménologie vitreuse en physique est bien connue et a été explorée en détail pour les modèles à variables discrètes. La présence de variables continues dans le modèle de perceptron (sphérique) nous permet de dévoiler, en PSC aléatoire, la transition caractéristique SAT/UNSAT où le système subit une transition du régime satisfaisable (dans lequel l'état fondamental possède une énergie nulle) à celui insatisfaisable (dans lequel l'état fondamental possède une énergie positive). Cette transition de phase peut également être interprétée comme une transition d'encombrement similaire à celles démontrées par les modèles des sphères sans friction. La simplicité du modèle étudié permet de trouver exactement son diagramme de phase à température zéro en fonction des deux paramètres de contrôle: la densité des obstacles et leur taille. Ainsi identifiée, la transition d'encombrement est complètement caractérisée dans le présent document. Sont également étudiées en détail de diverses phases vitreuses de caractère stable et marginalThis thesis treats the «spherical perceptron model», a simple exactly solvable model for glassy behavior and jamming suitably generalized to negative values of scalar product parameter κ. The classical machine-learning problem of random pattern classification by the perceptron is a convex constraint satisfaction problem (CSP). Even when the «stability parameter» κ of the model becomes negative, the problem still make sense and can be interpreted as the problem of particles on an N-dimensional sphere trying to avoid randomly placed obstacles. In this case, the corresponding CSP is non-convex. This thesis studies the problem in detail in the non-convex domain. Systematic study is made possible by assigning to a constraint satisfaction problem its corresponding optimization version endowed with a Hamiltonian function (cost function) quantifying the violations of the constraints, as a function of the system's configuration. The connection between random CSP and glassy phenomenology in physics is well known and has been explored in detail for models with discrete variables. The presence of continuous variables in the (spherical) perceptron model enables us to unveil, in random CSP, the characteristic SAT/UNSAT transition where the system transits from the satisfiable regime (where the ground state has zero energy) to the unsatisfiable one (where the ground state energy is positive). This phase transition can also be interpreted as a jamming transition similar to the one that exhibit models with frictionless spheres. The simplicity of the considered model allows the exact determination of the zero temperature phase diagram as a function of the control parameters: the density of obstacles and their size. In the present thesis, the jamming transition thus identified is completely characterized and several glass phases of stable and marginal character are studied in detail
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Kismarahardja, Ade Wijaya. "The Deformation-Induced Phase Transformation in Gold Nanoribbons". Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23034.
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The tensile experiment for nanomaterials in a transmission electron microscope (TEM) has become a very important tool to study the atomic deformation of material at nanoscale. An enormous amount of effort has been spent to perform the tensile experiments on nanomaterials. They revealed new discoveries that have never been observed in bulk materials and eventually lead to further applications. In this thesis, experimental reports of tensile test on gold nanoribbons in TEM were reported. The gold nanoribbons have 4H structure but the FCC structure could coexist in some areas. Gold nanoparticles have been studied intensively in the past decades due to their extraordinary properties and promising applications. The rise of chemical syntheses technology has stimulated further exploration of gold nanoparticles in recent years. The wet chemical technique has successfully created more closed-packing structures that have never been discovered before, including 4H gold nanoribbons. Even though the latest syntheses techniques have created many interesting structures, the investigation of their mechanical properties seems to be very difficult to perform. The tensile experiment on gold nanoribbons has never been performed. This thesis reports the first investigation of the mechanical properties of gold nanoribbons by using tensile test in TEM. Phase transformation from 4H to FCC or vice versa were observed. The dislocation in the structures leads to the phase transformation. Furthermore, necking has also been observed during tensile test, particularly in the FCC structure which eventually lead to ductile fracture. However, necking was also observed in 4H structure. In addition to this, coalescence between two nanoribbons was also observed during tensile.
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Ikoma, Daisaku, Hiroki Tsuchiura y Jun-ichiro Inoue. "Magnetic phase diagram of metallic pyrochlore lattice in the double-exchange model". The American Physical Society, 2003. http://hdl.handle.net/2237/7114.
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Gräfe, Uwe. "Investigation of the Superconducting and Magnetic Phase Diagram of Off-Stoichiometric LiFeAs". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-233972.
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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.
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Horrocks, P. J. "Phase diagram and thermodynamics of the Ag-Cd-In ternary alloy system". Thesis, University of Manchester, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508170.
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Steinberg, Aman. "The Functional Renormalisation Group and the Phase Diagram of Strongly Interacting Matter". Thesis, Uppsala universitet, Kärnfysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-213291.
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Jacobs, Thorsten. "Unraveling the cuprate superconductor phase diagram : Intrinsic tunneling spectroscopy and electrical doping". Doctoral thesis, Stockholms universitet, Fysikum, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-129270.
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High-temperature superconductors belong to the group of strongly correlated materials. In these compounds, complex repulsive electron interactions and a large number of degrees of freedom lead to a rich variety of states of matter. Exotic phases like the pseudogap, charge-, spin- and pair-density waves, but also the remarkable phenomenon of superconductivity emerge, depending on doping level and temperature. However, up to now it is unclear what exactly causes these states, to what extent they are coexisting or competing, and where their borders in the phase diagram lie. A better understanding could help in finding the mechanism behind high-temperature superconductivity, but would also provide a better insight into the puzzling behavior of strongly correlated materials. This thesis tries to resolve some of these questions with focus on the underdoped pseudogap regime. Mesa structures of bismuth-based cuprate superconductors were studied using intrinsic tunneling, which allows spectroscopic characterizations of electronic density of states inside the material. A micro/nano fabrication method was developed to further reduce mesa areas into the sub square-micrometer range, in order to minimize the effect of crystal defects and measurement artifacts caused by heating induced by the measurement current. The comparison of energy scales in Bi-2201 and Bi-2212 cuprates shows that the pseudogap phenomenon is not connected to superconductivity, but possibly represents a competing spin-singlet order that is universal to all cuprates. The analysis of the upper critical field in Bi-2201 reveals a low anisotropy, which gives evidence of paramagnetically limited superconductivity. Furthermore, a new electrical doping method is demonstrated, which enables the reversible tuning the doping level of Bi-2212 and study a broad doping range upon a single sample. Using this method, two distinct critical points were observed under the superconducting dome in the phase diagram: one at the overdoped side, associated with the onset of the pseudogap and a metal to insulator transition, and one at optimal doping, associated with an enhanced "dressed" electron energy. Finally, a novel angular-dependent magnetotunneling technique is introduced, which allows for the separation of the superconducting and non-superconducting contributions to the pseudogap phenomenon. The method reveals that after an abrupt decay of the energy gap for T→Tc, weak superconducting correlations persist up to several tens of degrees above Tc.
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Anzellini, Simone. "Phase diagram of iron under extreme conditions measured with time resolved methods". Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066155/document.
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Cette thèse concerne l'étude du diagramme de phase du fer en conditions extrêmes de pression et température. La Terre possède un noyau interne solide et un noyau externe liquide, qui sont principalement composés de fer. Une détermination fiable de la température de fusion du fer à 330 GPa, pression au-delà de laquelle le noyau terrestre est solide, permet de contraindre la température du noyau, ce qui est essentiel pour comprendre la dynamique terrestre. Le diagramme de phase du fer a été étudié jusqu'à 200 GPa en cellule à enclumes de diamant chauffée par laser utilisant la diffraction par rayon X comme diagnostic de l¿apparition de la fusion. Les températures obtenues sont en accord avec celles mesurées par compression dynamique, aux incertitudes expérimentales près, et sont plus élevées que celles obtenues lors de précédentes expériences statiques utilisant un critère de fusion différent. L'appareil, les méthodes et la métrologie utilisés pour les expériences en cellule à enclume de diamant chauffée par laser sont présentées ainsi que les problèmes rencontrés dans les expériences statiques à de telles conditions extrêmes. La possibilité d'utiliser le signal de diffraction des rayons X du joint en Re à des fins d'étalonnage de la pression pour l'expérimentation dans le domaine du multi-Mbar est aussi abordée. Dans ce but, l'équation d¿état du Re a été mesurée à 144 GPa. En fin, un test préliminaire a été effectué pour vérifier la possibilité d'utiliser la spectroscopie d'absorption des rayons X en dispersion d'énergie comme une technique complémentaire à la diffraction des rayons X pour la détermination de la courbe de fusion du ferThis thesis concerns the study of the phase diagram of iron at extreme conditions of pressure and temperature. Iron is the main constituent of the terrestrial planetary cores. In particular, the Earth has a solid inner core and a liquid outer core which are mainly composed of iron. The accurate determination of the melting temperature of iron at the inner core boundary pressure, 330 GPa, would provide an important constraint on the temperature of the core, which is essential to understand how the dynamic Earth works. The phase diagram of iron has been investigated in laser-heated diamond anvil cell experiments up to 200 GPa using synchrotron-based fast X-ray Diffraction as a primary melting diagnostic. The obtained melting temperatures agree within the experimental uncertainties with the ones obtained from shock wave experiments and are higher than those reported by previous static experiments, where a different melting criterion was used. The apparatus, methods and metrology used in the static laser heated diamond anvil cell are discussed together with the issues encountered in static experiments at such extreme conditions. The possibility of using the X-ray diffraction signal of Re gasket for pressure calibration purpose for experiment in the multi-Mbar range is also discussed. For this purpose, Re equation of state has been measured up to 144 GPa. Finally, a preliminary test has been performed to check the possibility of using energy dispersive X-ray absorption spectroscopy as a technique complementary to fast X-ray diffraction in the investigation of the melting curve of iron
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Sterpetti, Edoardo. "Phase diagram and fluctuations in two dimensional space charge doped Bi2Sr2CaCu2O8+x". Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS100.
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Le diagramme de phase des supraconducteurs à haute température critique en fonction du dopage et de la température a été étudié de manière intensive avec une variation chimique du dopage. Le dopage chimique peut provoquer des changements structurels et du désordre, masquant les effets intrinsèques. Alternativement, des échantillons ultra-minces dopés électrostatiquement peuvent être utilisés à travers des dispositifs de type transistors à effet de champ (FET). Cependant, nombreux défis technologiques sont à affronter lorsque des supraconducteurs à haute température sont concernés. Dans cette thèse nous surmontons ces obstacles en utilisant des techniques développées dans notre laboratoire et nous nous concentrons sur le supraconducteur à haute température BSCCO-2212 dont le diagramme de phase n'a jamais été étudié par effet électrostatique. Notamment, nous fabriquons des dispositifs supraconducteurs de BSCCO-2212 de haute qualité et utilisons une méthode électrostatique originale appelée dopage de charge d'espace, et mesurons les caractéristiques de transport de 330~K à basse température. Nous extrayons les paramètres et les températures caractéristiques sur une grande plage de dopage et établissons un diagramme de phase complet pour les échantillons BSCCO-2212 d'épaisseur 1~u.c. en fonction du dopage, de la température et du désordre. Nous identifions aussi la plage critique de dopage où une transition de phase quantique est prédite. Enfin, nous examinons de près la transition supraconductrice dans la limite de la bi-dimensionnalité. Les dispositifs BSCCO-2212 à 1 maille cristalline d'épaisseur. Les fluctuations et les effets extrinsèques sont décrits par des formalismes théoriques appropriés et le caractère bidimensionnel de la transition supraconductrice de BSCCO-2212 est analyséThe phase diagram of hole-doped high critical temperature superconductors as a function of doping and temperature has been intensively studied with chemical variation of doping. Chemical doping can provoke structural changes and disorder, masking intrinsic effects. Alternatively, electrostatically doped ultra-thin samples can be used through Field-Effect Transistor (FET) devices. The electrostatic modulation of charge carrier density in 2D materials is an elegant and clean approach that presents many technological challenges when high temperature superconductors are concerned. In this thesis we overcome these technological obstacles by using proprietary techniques developed in our laboratory for the study of 2D materials, and we focus on the high temperature superconductor BSCCO-2212, whose phase diagram has so far never been studied via electrostatic effect. Notably we fabricate ultra-thin high quality superconducting BSCCO-2212 devices and use an original electrostatic method called space charge doping to measure transport characteristics from 330~K to low temperature. We extract parameters and characteristic temperatures over a large doping range and establish a comprehensive phase diagram for one-unit-cell-thick BSCCO-2212 samples as a function of doping, temperature and disorder. We also identify the critical doping range where a quantum phase transition is predicted. Finally we take a closer look at the superconducting transition in the two dimensional limit. Fluctuations and extrinsic effects are accounted for using appropriate theoretical formalism and the two dimensional character of the superconducting transition of BSCCO-2212 is analysed
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Gaiassi, A. "Gold-catalyzed liquid phase oxidations for the organic synthesis". Doctoral thesis, Università degli Studi di Milano, 2008. http://hdl.handle.net/2434/155291.
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Gold catalysts prepared by sol immobilisation and deposition-precipitation were tested in aminoalcohol oxidation for direct preparation of aminoacids. Nitrogen substitution appeared to be crucial for avoiding parallel reaction pathway, but also the reaction conditions play an important role. Basic conditions and moderate temperature (40°C) represent a good compromise for enhancing selectivity to aminoacids. Generally sol-prepared catalysts resulted more resistant to deactivation than DP-prepared catalysts, even not always the most active.
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Ichihara, Terukazu. "Fluctuations in QCD phase diagram in the strong coupling limit of lattice QCD". 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215301.
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権利表示を行うこと, 出典表示を行うこと, 出版社版へのリンクを表示することKyoto University (京都大学)
0048
新制・課程博士
博士(理学)
甲第19488号
理博第4148号
新制||理||1596(附属図書館)
32524
京都大学大学院理学研究科物理学・宇宙物理学専攻
(主査)教授 大西 明, 准教授 菅沼 秀夫, 教授 田中 貴浩
学位規則第4条第1項該当
38
Welzbacher, Christian Andreas [Verfasser]. "Quarks and gluons in the phase diagram of quantum chromodynamics / Christian Andreas Welzbacher". Gießen : Universitätsbibliothek, 2016. http://d-nb.info/1112909974/34.
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Haas, Lisa Marie [Verfasser] y Jan Martin [Akademischer Betreuer] Pawlowski. "On the phase diagram of QCD / Lisa Marie Haas ; Betreuer: Jan Martin Pawlowski". Heidelberg : Universitätsbibliothek Heidelberg, 2012. http://d-nb.info/117703963X/34.
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Yin, Yan. "The thermodynamics and phase diagram data for the system Zr02[subscript]-CaO-MgO". Thesis, University of Sheffield, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.579724.
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Michnick, Robin Beth. "Phase diagram determination and relative dielectric constant measurements of the butyronitrile-chloroethane system". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/32168.
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Lyman, Edward. "Phase Diagram of a Driven Lattice Gas of Two Species with Attractive Interactions". Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/27513.
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We study the phase diagram of an interacting lattice gas of two species of particles and holes, driven out of equilibrium by a local hopping bias (denoted by `E').
Particles interact by excluded volume and nearest-neighbor attractions. We present a detailed Monte Carlo investigation of the phase diagram. Three phases are found, with a homogenous phase at high temperatures and two distinct ordered phases at lower temperatures. Which ordered phase is observed depends on the parameter f, which controls the ratio of the two types of particles. At small f, there is nearly a single species, and a transition is observed into a KLS-type ordered phase. At larger f, the minority species are sufficiently dense to form a transverse blockage, and a sequence of two transitions are observed as the temperature is lowered.
First, a continuous boundary is crossed into an SHZ-type ordered phase, then at a lower temperature a first-order boundary is crossed into the KLS-type ordered phase. At some critical value of f is a bicritical point, where the first-order line branches from the two continuous boundaries. We also consider correlations in the homogenous phase, by constructing a continuum description and comparing to the results of simulations. Long range correlations are present in both the theoretical results and the simulations, though certain details of the theory do not fit the observations very well. Finally, we examine the beahvior of three-point correlations in the single-species (KLS) limit. Nontrivial three-point correlations are directly related to the nonzero bias E. We therefore consider the behavior of the three-point correlations as a function of E. We find that the three-point signal saturates very rapidly with E. There are some difficulties interpreting the data at small E.Ph. D.
43
Parks, Michael Lawrence. "Efficient Numeric Computation of a Phase Diagram in Biased Diffusion of Two Species". Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/32896.
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A lattice gas with equal numbers of oppositely charged particles, diffusing under the influence of a uniform electric field and an excluded volume condition undergoes an order-disorder phase transition, controlled by the particle density and the field strength. This transition may be continuous (second order) or continuous (first order). Results from previous discrete simulations are shown, and a theoretical continuum model is developed. As this is a nonequilibrium system, there is no associated free energy to determine the location of a first order transition. Instead, the model equations for this system are evolved in time numerically, and the locus of this transition is determined via the presence of a stable state with coexisting regions of order and disorder. The Crank-Nicholson, nonlinear Gauss-Seidel, and GMRES algorithms used to solve the model equations are discussed. Performance enhancements and limits on convergence are considered.Master of Science
44
Sun, Chia-Chun y 孫家駿. "ECG Analysis by Phase Diagram". Thesis, 1998. http://ndltd.ncl.edu.tw/handle/92642355871288147489.
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Boniface, Tracy Diane. "The ruthenium-aluminium phase diagram". Thesis, 2016. http://hdl.handle.net/10539/20874.
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A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand)
in partial fulfilment of the requirements for the degree of Master of Science in Engjneering
Johannesburg, 1994Recent international investigations into new advanced materials have shown that the intennetallic compound, RuA1, possesses prormising characteristics for high-temperature use in corrosive environments. In order to optimise production of this alloy, an understanding of the Ru-A1 system is necessary. [Abbreviated Abstract. Open document to view full version]
46
Chen, Ta-Yuan y 陳大元. "Phase Diagram of Dusty Plasma". Thesis, 1996. http://ndltd.ncl.edu.tw/handle/57684432082505895383.
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Chen, Dai-Yuan y 陳大元. "Phase Diagram of Dusty Plasma". Thesis, 1996. http://ndltd.ncl.edu.tw/handle/62236262387051663526.
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Xiao, Xuhui y 蕭旭暉. "Phase diagram of colloid-rod system". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/5834ac.
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碩士國立中央大學
物理研究所
97
The semi-grand ensemble theory [H.N.W. Lekkerkerker, Europhys. Lett. 20, 559 (1992)] in conjunction with the fundamental measure density functional theory [V.B. Warshavsky and Xueyu Song, Phys. Rev. E 69, 061113 (2004)] are used to construct the Helmholtz free energy density for both the solid and liquid phases. Given these free energy density functions, we apply the free energy density minimization method [G.F. Wang, S.K. Lai, Phys. Rev. E 70, 051402 (2004)] to crosshatch the coexistence regions of a mixture of uncharged colloidal hard spheres and colloidal rods. The calculated results show that the triangular area bounded by gas-liquid, gas-solid and liquid-solid coexisting phases which has been called coexistence region of gas-liquid-solid corresponds in fact to sets of two phases in coexistence. The phase boundaries which are delimitations of our calculated coexistence domains compare very well with previous theoretical calculations. The relevance of the phase-diagram domains to three phases in coexistence will be discussed.
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Liu, Chih-Hua y 柳智華. "Zr-Cu-Ni Phase Diagram at 800℃". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/35921417714601195951.
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碩士國立中山大學
材料科學研究所
92
Zirconium base alloys have very good metallic glass forming ability. In this study,the Zr-Cu-Ni ternary isotherm at 800℃ were determined by using metallography,electron-probe microanalysis and X-ray diffraction.The main objective is to provide the necessary information for alloy design to form new Zr-base with better glass forming ability.
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Weng, Ying Che y 翁穎哲. "The Phase Diagram Analysis for YBCO Material". Thesis, 1993. http://ndltd.ncl.edu.tw/handle/60295305652900591890.
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