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.

<p>The microphase segregation behavior, which exhibits periodic patterns on a mesoscale, has been found in many systems where it has demonstrated its extreme industrial usefulness in the diblock copolymer system. When studying more general isotropic colloidal systems, periodic microphases should ubiquitously emerge in systems for which short-range inter-particle attraction is frustrated by long-range repulsion~(SALR). The morphological richness of these phases makes them desirable material targets, but our relatively coarse understanding of even simple models hinders controlling their assembly both from thermodynamic and dynamic points of view. The thermodynamic question is what should be the appropriate potential to stabilize microphases, such as cluster crystal, cylindrical, double gyroid and lamellar, while the dynamic question is whether the current experiments are long enough for these phases to appear. This dissertation will focus on solving these two parts of problems and hopefully guide the experiments to discover a simple material that can have microphase segregation behavior. In order to answer the thermodynamic problem of the stability of the microphases, we use a novel thermodynamic integration method as well as density functional methods in comparing the free energy of the microphases with uniform liquids. With the thermodynamic integration, we locate FCC-cluster, cylindrical, double gyroid and lamellar phases as well as nontrivial interplay between cluster, gel and microphase formation for a model microphase former. We also extended the methods to the model with a shorter and longer repulsion region where we found that the shorter region of the system may be in the Wigner glass of clusters of different sizes rather than the microphases. We also compare our simulation results with that from the density functional theory where we demonstrate that the classical density functional theory is qualitatively right but the simple improvement of the radial distribution functional by assuming the system is the same as Percus-Yevick hard sphere does not make a quantitatively difference. Our finding confirms that if the colloidal system has proper SALR potential as well as the right regime of area fraction and temperature, the microphase will be found in these systems. We then answer the second question which is whether the slow dynamics hinders the formation of microphases. We study the modeled microphase former and track the change of the first peak in the structure factor as well as the structural correlation time. We found that the system has a very complex dynamical regimes, including homogeneous fluid, void micelle, liquid gel and solid gel. The system becomes extreme slow in the solid gel regime but if in the regime that density and temperature are near the order-disorder transition, the lamellar self-assembly is much faster than the relaxation time of the solid gel which may explain why in the experimental system, the colloids seem stuck forever. We have collaborated with an experimental group to realize the SALR self-assemble behavior in a well controlled system. We have calibrated the system using a high precision thermodynamic integration by determining and matching the critical point and triple point of the experiments when the system is set up in the purely attractive regime. The system, however, becomes unpredictable when it goes into the SALR system where both higher body and other interactions become dominant. Finally, we try to extend our system to a spherocylinder model, which is an anisotropic particles with SALR. We have developed a novel cell list method here to accelerate the simulation. By determining the percolation transition and the order parameter, we find that the simple anisotropic interaction will introduce a much complex phase behavior of the system even in the disordered regime. We have identified several disordered phases, including homogeneous liquid, micellar liquid, free rotator gel, nematic gel and smectic gel.</p> / Dissertation

No description available.

The purpose of this research was to develop the pseudo-ternary phase diagrams for a model drug delivery system consisting of vitamin E (model drug) + soybean oil + surfactant + co-surfactant (anhydrous glycerol) + water. The model drug (vitamin E) was loaded in the oil phase. The effects of different surfactants (pure and mixed) on the phase diagram, especially the microemulsion region, were investigated. The influence of drug loading level on the phase diagram was also determined. The surfactants studied were Tween 20, Tween 80, Cremopher EL, and their mixtures. The size (area) of the microemulsion region of the phase diagram was found to be dependent on the type of surfactant used and the loading level of drug (vitamin E). The phenomenon of phase inversion from W/O microemulsion to O/W microemulsion was also investigated for the drug delivery system consisting of soybean oil (0% w/w Vitamin E loading or 30% w/w Vitamin E loading) + Tween 80 + anhydrous glycerol + water. The inversion of phases was detected by observing changes in the viscosity of the system.

The purpose of this research was to develop the pseudo-ternary phase diagrams for a model drug delivery system consisting of vitamin E (model drug) + soybean oil + surfactant + co-surfactant (anhydrous glycerol) + water. The model drug (vitamin E) was loaded in the oil phase. The effects of different surfactants (pure and mixed) on the phase diagram, especially the microemulsion region, were investigated. The influence of drug loading level on the phase diagram was also determined. The surfactants studied were Tween 20, Tween 80, Cremopher EL, and their mixtures. The size (area) of the microemulsion region of the phase diagram was found to be dependent on the type of surfactant used and the loading level of drug (vitamin E). The phenomenon of phase inversion from W/O microemulsion to O/W microemulsion was also investigated for the drug delivery system consisting of soybean oil (0% w/w Vitamin E loading or 30% w/w Vitamin E loading) + Tween 80 + anhydrous glycerol + water. The inversion of phases was detected by observing changes in the viscosity of the system.

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In addition to their potential use at low to moderate temperatures in mobile fuel cell technologies, metal hydrides may also find application as high temperature tritium getterers in the U.S. DOE Next Generation Nuclear Plant (NGNP). We use Density Functional Theory to identify metal hydrides capable of sequestering tritium at temperatures in excess of 1000 K. First we establish the minimum level of theory required to accurately capture the thermodynamics of highly stable metal hydrides and determine that isotope effects can be neglected for material screening. Binary hydride thermodynamics are largely well established, and ternary and higher hydrides typically either do not form or decompose at lower temperatures. In this thesis we investigate anomalous systems with enhanced stability in order to identify candidates for the NGNP application beyond the binary hydrides. Methods implemented in this work are particularly useful for deriving finite temperature phase stability behavior in condensed systems. We use grand potential minimization methods to predict the interstitial Th−Zr−H phase diagram and apply high throughput, semi-automated screening methodologies to identify candidate complex transition metal hydrides (CTMHs) from a diverse library of all known, simulation ready ternary and quaternary CTMHs (102 materials) and 149 hypothetical ternary CTMHs based on existing prototype structures. Our calculations significantly expand both the thermodynamic data available for known CTMHs and the potential composition space over which previously unobserved CTMHs may be thermodynamically stable. Initial calculations indicate that the overall economic viability of the tritium sequestration system for the NGNP will largely depend on the amount of protium rather than tritium in the metal hydride gettering bed feed stream.

Made available in DSpace on 2014-06-11T19:25:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-12-15Bitstream added on 2014-06-13T19:12:25Z : No. of bitstreams: 1 paes_c_me_ilha.pdf: 1124164 bytes, checksum: b30843e958a40bb7c8b7ff4142f19d31 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente trabalho tem como objetivo estudar, através de investigações de espectros no infravermelho (FTIR), as transições de fases estruturais do sistema ferroelétrico titanato zirconato de chumbo, PbZr1-xTixO3 (PZT) no Contorno de Fase Morfotrópico (Morphotropic Phase Boundary, conhecido como MPB), região em que as propriedades elétricas desse material são máximas. Foram analisadas as soluções sólidas PbZr0,53Ti0,47O3 e PbZr0,54Ti0,46O3, que à temperatura ambiente encontram-se no interior do MPB e PbZr0,55Ti0,45O3, composição no limite da região do MPB, entre a fase monoclínica e a fase romboédrica, região ainda não bem definida e sob intensa investigação. Estudos estão centrados na freqüência e na meia largura dos modos stretching nos octaedros (BO6) da estrutura perovskita (ABO3) em função da temperatura. Anomalias encontradas para amostras com 47 e 46 mol % de PbTiO3 sugerem as transições da fase monoclínica de baixa para alta temperatura ( LT M F ? HT M F ), da fase monoclínica de alta temperatura para a coexistência da fase monoclínica com a fase tetragonal ( M F ? M F + T F ), e da coexistência da fase monoclínica com a tetragonal para a fase cúbica ( M F + T F ? C F ). Na amostra com 45 mol % de PbTiO3 foram encontradas anomalias que podem também estar associadas às transições de fases, mas que não foram possíveis de serem identificadas nas fases envolvidas. / The present work studies, through investigations of the spectra in infrared (FTIR), the transitions of structural phases of the ferroelectric system lead zirconate titanate, PbZr1- xTixO3 (PZT), in the Morphotropic Phase Boundary (MPB), region where the electrical properties of this material are at its maxiumun. We analyzed the solid solutions PbZr0,53Ti0,47O3 and PbZr0,54Ti0,46O3, which at room temperature are found within the MPB and also the composition PbZr0,55Ti0,45O3, that is located on the limit of the MPB - between the monoclinic and the rhombohedral phases - a not-yet defined region under intense investigation. Studies are concentrating on frequency and half width of the stretching modes in octahedrons (BO6) of the perovskite structure (ABO3) regarding temperature. Anomalies found in samples with 47 and 46 mol % of PbTiO3 suggest transitions in the monoclinic phase from low to high temperature ( LT M F ? HT M F ), from monoclinic phase of high temperature to the coexistence between the monoclinic phase with the tetragonal phase ( M F ? M F + T F ), and the coexistence between the monoclinic phase with tetragonal for the cubic phase ( M F + T F ? C F ). In the sample with 45 % mol of PbTiO3 we have found anomalies that can also be associated with phase transitions. Such transitions have not been possible to identify during the stages of this work.

Orientador: Eudes Borges de Araújo / Banca: Victor Ciro Solano Reynoso / Banca: Sebastião William da Silva / Resumo: O presente trabalho tem como objetivo estudar, através de investigações de espectros no infravermelho (FTIR), as transições de fases estruturais do sistema ferroelétrico titanato zirconato de chumbo, PbZr1-xTixO3 (PZT) no Contorno de Fase Morfotrópico (Morphotropic Phase Boundary, conhecido como MPB), região em que as propriedades elétricas desse material são máximas. Foram analisadas as soluções sólidas PbZr0,53Ti0,47O3 e PbZr0,54Ti0,46O3, que à temperatura ambiente encontram-se no interior do MPB e PbZr0,55Ti0,45O3, composição no limite da região do MPB, entre a fase monoclínica e a fase romboédrica, região ainda não bem definida e sob intensa investigação. Estudos estão centrados na freqüência e na meia largura dos modos stretching nos octaedros (BO6) da estrutura perovskita (ABO3) em função da temperatura. Anomalias encontradas para amostras com 47 e 46 mol % de PbTiO3 sugerem as transições da fase monoclínica de baixa para alta temperatura ( LT M F ? HT M F ), da fase monoclínica de alta temperatura para a coexistência da fase monoclínica com a fase tetragonal ( M F ? M F + T F ), e da coexistência da fase monoclínica com a tetragonal para a fase cúbica ( M F + T F ? C F ). Na amostra com 45 mol % de PbTiO3 foram encontradas anomalias que podem também estar associadas às transições de fases, mas que não foram possíveis de serem identificadas nas fases envolvidas. / Abstract: The present work studies, through investigations of the spectra in infrared (FTIR), the transitions of structural phases of the ferroelectric system lead zirconate titanate, PbZr1- xTixO3 (PZT), in the Morphotropic Phase Boundary (MPB), region where the electrical properties of this material are at its maxiumun. We analyzed the solid solutions PbZr0,53Ti0,47O3 and PbZr0,54Ti0,46O3, which at room temperature are found within the MPB and also the composition PbZr0,55Ti0,45O3, that is located on the limit of the MPB - between the monoclinic and the rhombohedral phases - a not-yet defined region under intense investigation. Studies are concentrating on frequency and half width of the stretching modes in octahedrons (BO6) of the perovskite structure (ABO3) regarding temperature. Anomalies found in samples with 47 and 46 mol % of PbTiO3 suggest transitions in the monoclinic phase from low to high temperature ( LT M F ? HT M F ), from monoclinic phase of high temperature to the coexistence between the monoclinic phase with the tetragonal phase ( M F ? M F + T F ), and the coexistence between the monoclinic phase with tetragonal for the cubic phase ( M F + T F ? C F ). In the sample with 45 % mol of PbTiO3 we have found anomalies that can also be associated with phase transitions. Such transitions have not been possible to identify during the stages of this work. / Mestre