Neste trabalho estudamos o efeito da temperatura T e do campo magnético externo H sobre o modelo de Ising de spin 1/2 com interações competitivas J1 e J2 = -pJ1 entre primeiros e segundos vizinhos, respectivamente, numa direção axial (modelo ANNNI), e o efeito do campo de anisotropia cristalina D sobre o estado fundamental de um modelo ANNNI de spin maior que 1/2. No primeiro modelo levantamos os diagramas de fases p-T e H-T na aproximação de campo médio. Nestes diagramas encontramos diversos tipos de transições de fases tais como transições quase-contínuas e transições singular-contínuas. Encontramos também evidências da existência de pontos ípsilon () e pontos superdegenerados até então só encontrados nos diagramas de fases do estado fundamental de modelos do tipo Frenkel-Kontorova. No segundo modelo levantamos os diagramas p-D a T=0 para os dez primeiros valores de spin S. Estudamos a evolução das fronteiras de fases e de pontos de encontro de mais que duas fases sobre estas fronteiras conforme S é variado. Constatamos que as diferenças entre diagramas com S inteiro e diagramas com S semi-inteiro tendem a desaparecer com o crescimento de S. / In this work we studied the effect of the temperature T and external magnetic field H on the spin 1/2 lsing model with competing interactions J1 and J2 = -pJ1 between the first- and second-neighbors, respectively, along an axial direction (ANNNl model), and the effect of the crystal field anisotropy D on the ground state of the ANNNl model with spins greater than 1/2. In the first model we built the p-T and H-T phase diagrams in the mean-field approximation. In these phase diagrams we found various types of phase transitions such as quasi-continuous and singular-continuous phase transitions. We also found evidences for the upsilon point (1) and superdegenerate points, which have previously been found only on the groundstate phase diagrams of Frenkel-I<ontorova type models.

O principal programa de pesquisa do Grupo de Diagrama de Fases e Termodinâmica Computacional do DEMAR/EEL-USP é o estudo de estabilidade de fases em ligas dos sistemas Me-Si-B (Me = Metal Refratário), os quais apresentam um interesse crescente na área de ligas com potencial para aplicações em altas temperaturas. Destes estudos, este Grupo está construindo uma base de informações termodinâmicas com a finalidade de extrapolá-las para sistemas de ordem superior. Diversos sistemas já foram ou estão sendo estudados. Dando continuidade a este programa, os objetivos principais deste trabalho são a avaliação experimental do sistema ternário Ta-Si-B em sua região rica em Ta e a modelagem termodinâmica dessa mesma região. A projeção liquidus e a seção isotérmica a 1900 ºC, ambas na região rica em Ta, de Ramos (2005), são as únicas informações experimentais para o sistema ternário Ta-Si-B encontradas na literatura. Ramos (2005) identifica em várias de suas amostras a presença de uma nova fase ternária, denominada &#966;, de estrutura ainda não determinada. A pesquisa de Ramos (2005) foi realizada sempre com amostras produzidas por fusão em forno a arco, a partir de pedaços de Ta, Si e B puros. Nessa condição de preparação das amostras, houve dificuldade em se alcançar o equilíbrio termodinâmico, mesmo após tratamentos térmicos prolongados (1900 oC por 48 horas). Já, neste trabalho, as amostras foram, em sua maioria, produzidas por tratamento térmico de pastilhas prensadas a partir de pós de Ta, Ta5Si3 e TaB. Com essa mudança na forma de confeccionar os experimentos conseguiu-se maior facilidade na obtenção da condição de equilíbrio termodinâmico das amostras durante os tratamentos térmicos, embora ainda com resultados não totalmente satisfatórios. De uma forma geral, os resultados de Ramos (2005) são confirmados no presente trabalho. Uma proposta de relação de fases a 2000 ºC é apresentada para a região envolvendo as fases TaSS, Ta2B, T2, Ta3B4 e TaB. A estabilidade da fase D88, proposta por Nowotny, Lux e Kudielka (1956), também é confirmada e os resultados sugerem que sua estequiometria seja Ta5Si3B. Nenhuma modelagem termodinâmica para este sistema ternário é encontrada na literatura. A otimização do sistema binário Ta-B é realizada por Kaufman (1991) e Chad (2003). A otimização do sistema binário Ta-Si é realizada por Vahlas, Chevalier e Blanquet (1989) e Kaufman (1991). A otimização do sistema binário Si-B é realizada por Fries e Lukas (1991), Zaitsev e Kodentsov (2001) e Fiorani e Coelho (2006). A única otimização adotada completamente é a de Fiorani e Coelho para o sistema binário Si-B. Para o sistema binário Ta-B é adotada a otimização de Chad (2003) com a inclusão de uma nova fase, denominada &#966;, de alta temperatura, a mesma do sistema ternário, que teria sua origem nesse sistema binário. Já, para o sistema binário Ta-Si é necessária uma nova otimização, por haver algumas inconsistências termodinâmicas nas otimizações anteriores, que poderiam levar a uma descrição inadequada das relações de fases no sistema ternário Ta-Si-B e em sistemas de ordem superior. Neste trabalho é apresentada uma proposta para a modelagem termodinâmica do sistema ternário, que reproduz satisfatoriamente os resultados experimentais disponíveis. / Currently, the main research program of the Phase Diagram and Computational Thermodynamics Group of DEMAR/EEL-USP is the study of phase stability in ternary Me-Si-B systems (Me = Refractory Metal), which presents an increasing interest in the area of alloys with potential for applications at high temperatures. It includes the development of a thermodynamic database to evaluate systems of higher order. Several systems have already been studied. Giving continuity to this program, the main objectives of this work are the experimental evaluation of the ternary Ta-Si-B system in the Ta-rich region and the thermodynamic modeling of this system. The liquidus projection and an isothermal section at 1900 ºC from Ramos (2005), both in the Ta-rich region, are the only experimental information found in literature. Ramos (2005) identifies in several of her samples the presence of a new ternary phase, named as &#966;, of structure not yet determined. The research of Ramos (2005) is carried out with samples produced from pure Ta, Si and B via arc melting. In this method of sample preparation, it is difficult to obtain thermodynamic equilibrium conditions during heat treatments at 1900 ºC for 48 h. In the present work, the majority of samples were produced via sintering of pressed pellets from Ta, Ta5Si3 and TaB powders. With this method of sample preparation, the attainment of equilibrium conditions was easier during the heat treatments, even though not completely satisfactory. In general, the results of Ramos (2005) were confirmed. A proposal for the phase relations at 2000 ºC is presented for the region involving the phases TaSS, Ta2B, T2, Ta3B4 and TaB. The stability of the D88 phase, proposed by Nowotny, Lux and Kudielka (1956), is also confirmed and the results suggest that its stoichiometry is near Ta5Si3B.No thermodynamic modeling for this ternary system is found in literature. The optimization of the binary Ta-B system is carried out by Kaufman (1991) and Chad (2003). The optimization of the binary Ta-Si system is carried out by Vahlas, Chevalier and Blanquet (1989) and Kaufman (1991). The optimization of the Si-B binary system is carried out by Fries and Lukas (1991), Zaitsev and Kodentsov (2001) and Fiorani and Coelho (2006). In this work the thermodynamic data from Fiorani and Coelho (2006) is used for the Si-B system. For the binary Ta-B system it was adopted the optimization from Chad (2003) with the inclusion of the high temperature &#966; phase, the same one of the ternary system, which has its origin in this binary system. In addition, for the binary system Ta-Si a new optimization is necessary, since some thermodynamic inconsistencies in the previous optimizations would lead to an inadequate description of the phase relations in the Ta-Si-B and systems of higher order. Thus, in this work presents for the first time a thermodynamic modeling for the Ta-Si-B system, which reproduces the available experimental results satisfactorily.

Orientador: Everson Alves Miranda / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-04T07:13:28Z (GMT). No. of bitstreams: 1 Barros_GeorgiadeOliveiraFigueiredo_M.pdf: 2282903 bytes, checksum: b104323f697a813ec6af57b15ba7b95b (MD5) Previous issue date: 2005 / Resumo: A separação de enantiômetros em altos níveis de pureza enantiomérica é atualmente um requerimento da industria farmacêutica. No entanto, altas purezas estão sendo alcançadas neste sistema com comprometimento da produtividade. O acoplamento do leito móvel simulado (LSM) a uma etapa de cristalização pode resultar num processo de maior produtividade global . A escolha do método de cristalização para a resolução de misturas racêmicas por cristalização é dependente do tipo de cristal (conglomerado ou composto racêmico) e da localização do ponto eutético no diagrama de solubilidade. O ponto eutético difine a mínima puraza enantiomérica que deve ser fornecida pelo LMS para assegurar que a cristalização irá produzir somente um dos enantiômeros puros. A cetamina é um anstésico que possui um isômero R com indesejáveis efeitos colaterais. O objetivo deste trabalho é trabalho é o desenvolvimento de conhecimento básico (identificação do tipo de racemato e seu ponto eutético no diagrama de solubilidade) para o acolplamento do LMS a uma etapa de cristalização a fim de produzir o isômero S da cetamina em pureza enantiomérica e produtividade alta. Para caracterizar a natureza cristalina da cetamina, diração de raios-X e espectroscopia de infravermelho da mistura racêmica e dos enantilômero puros foram realizados e as curvas de solubilidade em função da temperatura foram determinadas...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital / Abstract: The resolution of enantiomers to high levels of enantiomeric purity is presntly a requeriment in the pharmaceutical industry. However, high, purities are reached with this system at the expenses of productivity. Coupling of simulated moving bed (SMB) to a crystallization step can result in a process whith a overall higher productivity. The choise ofcristallization method for the resolution of racemic mixtures is dependent on the eutetic point on the solubility diagram. Eutetic point is the minimum enantiomeric purity that has to be delivered by the SMB to assure that crystallization will produce just one pure isomer. Ketamine is a anesthetic that has a R-isomer with undesirable side-effect. The objective of this work was development of basic knowlwdge for a process (identification of the type of racemate and its eutetic point in the solubility diagram) coupling the SMB to a crystallization step in order to produce the S-isomer of ketamine at high enantiomeric purity and productivity. To characterize the crystalline nature of ketamine, X-ray diffraction and infrared spectroscopy of the racemic mixture and pure enantiomers were performed between powder x-ray pattems, infrared spectra, and solubility curve slopes of the pure enantiomers and racemic mixture indicated racemic compound formation...Note: The complete abstract is available with the full electronic digital thesis or dissertations / Mestrado / Desenvolvimento de Processos Biotecnologicos / Mestre em Engenharia Química

The power of thermodynamics in the calculation of complex chemical and metallurgical equilibria of importance to industry has, over the last 15 years, been considerably enhanced by the availability of computers. It has resulted in the storage of data in databanks, the use of physical but complex models to represent thermodynamic data, the vast effort spent in the generation of critically assessed data and the development of sophisticated software for their application in equilibrium calculations. This thesis is concerned with the generation and application of metallurgical thermodynamic data in which the computer plays a central and essential role. A very wide range of topics have been covered from the generation of data by experiment and critical assessment through to the application of these data in calculations of importance to industry. Particular emphasis is placed on the need for reliable models and expressions which can represent the molar Gibbs energy as a function of temperature and composition. In addition a new computer program is described and used for the automatic calculation of phase diagrams for binary systems. Measurements of the enthalpies of formation of alloys in the Fe-Ti system are reported. All data for this system have been critically assessed to provide a dataset consistent with the published phase diagram. Critically assessed data for a number of binary alloy systems have been combined in order to perform quantitative calculations in two types of steel system. Firstly data for the Cr-Fe-Ni-Si-Ti system have been used to provide information about the long term stability of alloys used in fast breeder nuclear reactors. Secondly very complex calculations involving nine elements have been made to predict the distribution of carbon and various impurities between competing phases in low alloy steels on the addition of Mischmetall. Finally a new model is developed to represent the thermodynamic data for sulphide liquids and is used in the critical assessment and calculation of data for the Cu-Fe-Ni-S system. The phase diagram and thermodynamic data calculated from the assessed data are in excellent agreement with those observed experimentally. The work reported in this thesis, whilst successful, has also indicated areas which will benefit from further study particularly the development of reliable data and models for pure elements, ordered solid phases and liquid phases for high affinity systems.

L’émulsifiant est une matière première largement utilisée dans les systèmes formulés de type émulsion. Grâce à sa structure chimique amphiphile, cette molécule diminue la tension interfaciale entre les deux liquides non miscibles qui composent une émulsion, ce qui augmente la stabilité du système dans le temps. En plus, à cause de sa structure, il peut former des cristaux liquides dans les systèmes formulés, ce qui impacte considérablement les propriétés physico-chimiques et applicatives des émulsions. Ce projet vise l’étude d’un tensioactif mixte naturel alkyl polyglucoside/alcool gras. Les propriétés de celui-ci ont été d’abord investiguées via la construction du diagramme de phase. Ainsi, il a été démontré que la variation de la concentration et du ratio alkyl polyglucoside/alcool gras dans l’émulsifiant mixte favorise le passage de solutions micellaires vers les cristaux liquides de types lamellaire ou hexagonale dans les systèmes étudiés. La maitrise des propriétés des systèmes binaires a permis, par la suite, de comprendre les métamorphoses subies par le système lorsqu’une phase grasse est incorporée. La structure chimique des émollients (présence des hétéroatomes) affecte l’organisation des cristaux liquides formés par les molécules amphiphiles. Par conséquent, en fonction de l’émollient utilisé, les propriétés microscopiques et macroscopiques des systèmes changent (taille et distribution des gouttelettes, profil rhéologique, thermique et de texture). Finalement, les propriétés applicatives des émulsions sont aussi affectées, comme cela a été montré via l’analyse sensorielle et les mesures biométriques in-vivo. / Emulsifier is a raw material widely used in formulated systems of emulsion type. Due to its amphiphilic chemical structure, this molecule decreases the interfacial tension between two immiscible liquids that form an emulsion, which increases the stability of the system over time. In addition, it can form liquid crystals in the formulated systems because of its structure and this has a considerable impact on the physicochemical and applicative properties of emulsions. The objective of this project is to study a natural alkyl polyglucoside/fatty alcohol mixed surfactant. Its properties were first investigated via the construction of the phase diagram. Thus, it has been shown that the variation of the concentration and of the ratio of alkyl polyglucoside/fatty alcohol in the mixed emulsifier favors the transition between the micellar solutions towards liquid crystals of lamellar or hexagonal type in the studied systems. Next, the mastering of the binary systems properties allowed understanding the metamorphoses undergone by the system when an oil phase is incorporated into it. The chemical structure of emollients (presence of heteroatoms) affects the organization of liquid crystals formed by the amphiphilic molecules. Therefore, depending on the emollient type, the microscopic and macroscopic properties of the systems change (droplet sizes and distribution, rheological, thermal and texture profile). Finally, the applicative properties of emulsions are also affected, as shown by sensory analysis and in-vivo biometric measurements.

Orientador: Mário Noboru Tamashiro / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-31T00:17:06Z (GMT). No. of bitstreams: 1 Ercule_Adinei_M.pdf: 1649654 bytes, checksum: a32bd621f02831c6f06d0618847ad1a9 (MD5) Previous issue date: 2016 / Resumo: Estudamos através da solução do modelo de Blume¿Emery¿Griffiths na rede de Bethe, o efeito da coordenação da rede no comportamento multicrítico do modelo ferromagnético (J > 0) na região de acoplamentos biquadráticos repulsivos, analisando o caso particular K/J = ?3,5. O estudo foi feito para duas coordenações diferentes (z = 4, 6) e a campo nulo (H = 0). Durante a análise do mapeamento surgiram órbitas de período 2 e por esse motivo foi feita uma divisão da rede em duas sub-redes interpenetrantes. Nesta região o diagrama de fases apresentou quatro fases termodinâmicas distintas: paramagnética, ferromagnética, quadrupolar alternada (ou antiquadrupolar) e ferrimagnética. Além disso, o diagrama de fases apresentou regiões de coestabilidade numérica que foram investigadas pelo cálculo da energia livre. A expressão analítica da energia livre foi obtida através do engenhoso método de Gujrati. Para a coordenação z = 4 a transição entre as fases ferrimagnética e quadrupolar alternada é sempre contínua, enquanto a transição das fases ferromagnética e ferrimagnética é descontínua a baixas temperaturas, tornando-se contínua para temperaturas acima do ponto tricrítico. Por outro lado, para a coordenação z = 6 a transição entre as fases ferromagnética e ferrimagnética é sempre contínua. No entanto, a transição entre as fases ferrimagnética e quadrupolar alternada é descontínua para temperaturas abaixo do ponto tricrítico e contínua para temperaturas maiores, em concordância com os diagramas de fases obtidos na aproximação de campo médio / Abstract: We studied through the solution of the Blume¿Emery¿Griffiths model on the Bethe lattice, the effect of the lattice coordination on the multicritical behavior of the ferromagnetic model (J > 0) in the region of repulsive biquadratic couplings, analyzing the particular case K/J = ?3,5. The study was performed for two different lattice coordinations (z = 4, 6) and zero magnetic field (H = 0). During the mapping analysis, 2-cicle orbits arose and therefore a division of the lattice into two interpenetrating sublattices was implemented. In this region the phase diagram displayed four distinct thermodynamic phases: paramagnetic, ferromagnetic, staggered quadrupolar and ferrimagnetic. In addition, the phase diagram displayed regions of numerical co-stability, that were investigated by calculating the free energy. The analytical free-energy expression was obtained by the inventive Gujrati¿s method. For coordination z = 4 the transition between the ferrimagnetic and the stag- gered quadrupolar phases is always continuous, while the transition of the ferromagnetic and ferrimagnetic phases is discontinuous at low temperatures, turning into continuous for temperatures above the tricritical point. On the other hand, for coordination z = 6 the transition between the ferromagnetic and the ferrimagnetic phases is always continuous. However, the transition between the ferrimagnetic and the staggered quadrupolar phases is discontinuous for temperatures below the tricritical point and continuous for higher temperatures, in agreement with the phase diagrams obtained in the mean-field approximation / Mestrado / Física / Mestre em Física / 132988/2014-3 / CNPQ

Orientador: Maurice de Koning / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-31T00:11:25Z (GMT). No. of bitstreams: 1 SantosFlorez_PedroAntonio_M.pdf: 3560756 bytes, checksum: 596fa8433415493ec218ee7c185319ea (MD5) Previous issue date: 2016 / Resumo: O modelo de Uhlenbeck-Ford, que é um sistema artificial caracterizado por um potencial interatômico logarítmico e repulsivo, foi definido originalmente para o estudo teórico de gases imperfeitos, baseado no fato de que todas as integrais de muitos corpos, envolvidas no cálculo de coeficientes viriais, podem ser calculadas analiticamente. Assim, este modelo possui uma expressão exata para a equação de estado e a energia livre de Helmholtz na fase fluida. Um potencial escalonado deste modelo já foi proposto como sistema de referência na implementação de métodos de simulação atomística, para cálculos de energia livre de sistemas na fase fluida. Neste trabalho, é construído o diagrama de fase do modelo de Uhlenbeck-Ford dependente deste fator de escalonamento, delimitando as fases fluida e sólida, com estruturas cristalinas (BCC e FCC). A estabilidade das diferentes fases foi estudada analisando as curvas de energia livre, que foram obtidas utilizando a técnica de simulação atomística da Dinâmica Molecular a partir de processos fora do equilíbrio. Nossos resultados mostraram que existem regiões para qualquer densidade onde a fase fluida é a mais estável, e portanto, o modelo de Uhlenbeck-Ford pode ser usado como sistema de referência para cálculos de energia livre de sistemas na fase fluida / Abstract: The Uhlenbeck-Ford model, which is an artificial system characterized by a logarithmic and repulsive interatomic potential, was originally defined for the theoretical study of imperfect gases, based on the fact that all the many-body integrals, involved in calculating virial coefficients, can be calculated analytically. Thus, this model has an exact expression for the equation of state and the Helmholtz free energy in the fluid phase. A modified potential by a scale factor of this model was proposed as a reference system in the implementation of atomistic simulation methods for free energy calculation in the fluid phase. In this paper, we construct the phase diagram of the Uhlenbeck-Ford model dependent on a scale factor, finding the coexistence lines between fluid and solid phases, with crystalline structures (BCC and FCC). The stability of the different phases was studied by analyzing the free energy curves, which were obtained using the atomistic simulation technique of Molecular Dynamics, using nonequilibrium processes. Our results show that for any density, there exist regions in which the fluid phase is the most stable and therefore the Uhlenbeck-Ford model can be used as a reference system for free energy calculations of systems in the fluid phase / Mestrado / Física / Mestre em Física / 1370441/2014 / CAPES

京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第22546号 / 人博第949号 / 新制||人||226(附属図書館) / 2019||人博||949(吉田南総合図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)准教授 木下 俊哉, 教授 吉田 鉄平, 教授 森成 隆夫 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DGAM

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23017号 / 理博第4694号 / 新制||理||1673(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)准教授 成瀬 元, 准教授 堤 昭人, 教授 生形 貴男 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Le besoin d’accès aux énantiomères purs a largement augmenté depuis les années 90. Les procédés ayant recours à la cristallisation sont souvent moins cher mais tout aussi efficace que les autres procédés. Deux études ont été réalisées dans cette thèse : -La première concerne l’amélioration d’un procédé déjà établi. En effet, l’efficacité de la Cristallisation Préférentielle (PC) de conglomérat est connue. Néanmoins, son application à des solutions solides images l’une de l’autre dans un miroir est plus complexe. Est présenté le premier exemple de PC réalisée sur un système à solution solide complète démixant à basse température : le sel d’hydrogénomaléate de baclofène (un API). De plus, il s’agit de la première preuve expérimentale d’un tel équilibre de phases et de PC de solutions solides dont les résultats sont comparables à la cristallisation préférentielle traditionnelle. -Le second sujet ne traite pas directement de la séparation d’énantiomère mais de prometteuses discriminations chirales ont été obtenues. Le diagramme d’équilibre de phases entre les compositions racémiques de deux couples d’atropoisomères a été étudié. Deux résultats en lien avec la discrimination chirale ont été établis : le premier est la possibilité de déracémiser un composé A initialement non-discriminé (composé racémique) à l’intérieur de la matrice d’un composé B discriminé (conglomérat). Le second est l’observation d’un nouveau type de chiralité : Chiralité Induite par Dissymmétrie de Distribution (CIDD). / The need for access to pure enantiomers has largely increased since the nineties. Processes using crystallization are often cheaper and as efficient as other processes. Thus, the improvement of existing techniques and the need for new processes are attractive for scientist and industry. Two studies have been performed in this thesis:The first one concerns the improvement of an existing technique. Indeed, conglomerate Preferential Crystallization efficiency is well known. Nonetheless, its application to mirror image partial solid solutions is more difficult. Here is presented the first example of PC performed on a complete solid solution at high temperature which shows a solid solutions demixion at low temperature: the baclofen hydrogenomaleate salt (an API). Moreover, it is the first experimental observation of such phase equilibria and PC of mirror image solid solutions whose results are comparable to classical PC. -The second topic did not involve directly enantiomer separation but promising chiral discriminations have been obtained. The phase diagram between the racemic composition of two couples of atropisomers has been defined. Beside multiples equilibria observed, two results concerning the chiral discrimination can be highlighted: the first one is the possibility to deracemize a compound A initially not discriminated (racemic compound) inside the matrix of a compound B (which forms a stable conglomerate). The second is the observation of a new kind of chirality: Chirality Induced by Dissymmetric Distribution (CIDD).