Computational thermodynamics is a powerful tool for solving practically important problems including the design of new materials and the analysis of their internal and external stability. This thesis contributes to computational thermodynamics by proposing several practical solutions to eliminate the so-called thermodynamic artifacts rather frequently found in thermodynamic assessments. First, a method is developed to eliminate the artifacts such as inverted miscibility gaps in the liquid phase at high-temperatures and reappearance of the liquid phase at low-temperatures or reappearance of a solid phase at elevated temperatures. This method is based on introducing a sufficiently dense mesh of knots (not related to experimental points utilized in the optimization) and ensuring that specific inequality conditions (topological constraints) governing the appearance of the phase diagram are satisfied in these knots. A feasibility of the approach proposed is exemplified by carrying out a re-optimization of the Mg-Sb system. Generally re-optimization of a system would take months to get the optimized results. Hence, to minimize time needed to get rid of artifacts, two different quick correction methods are developed to eliminate the unrealistic inverted miscibility gap in the liquid phase at elevated temperatures. Both methods employ optimization under topological constraints via controlling the sign of the second derivative of the Gibbs energy. Their applicability is exemplified on the Sn-Zr system. Also, a theoretical study was done on undulate phase boundaries. Usually, an inflection point on a phase boundary is considered as an unambiguous indication that one of the phases participating in the equilibrium is internally unstable, i.e., that it is prone to phase separation. It has been generally assumed that an inflection point may occur only if the thermodynamic model of this phase contains an excess Gibbs energy term. It is shown that in contrast to this assumption, inflection points on a phase boundary may appear when a pure solid component or a stoichiometric binary phase is in equilibrium with the ideal binary solution, which is internally stable. Finally, in addition to the theoretical analysis on undulate phase boundaries, a thermodynamic optimization is done on an imaginary A-B binary system subjected to topological constraints. Since, Thermo-Calc does not have the necessary tools to implement such topological constraints as d^2T/dx^2 >0 or d^2T/dx^2 <0. A Fortran 90 program was developed to make use of these constraints. / Thesis / Doctor of Philosophy (PhD)

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24400号 / 理博第4899号 / 新制||理||1700(附属図書館) / 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 佐々 真一, 教授 早川 尚男, 准教授 藤 定義 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

This thesis describes a Master of science research program of duration May, I960 to April, 1961 inclusive. It represents part of an extensive research program designed to investigate the thermodynamic aspects of phase transformations. A great deal of effort has been devoted to the application of multicomponent diffusion theory to (de)carburisation, pearlite, and segregation reactions; particularly in ferrous alloys. This fundamental research program is here extended to a general study of the morphological aspects of phase transformation interfaces. Substantially all industrial metallurgical phase transformations are accompanied by the development of non-planar morphologies with attendant segregation. Previous investigations have demonstrated that the factors controlling the type and degree of morphological development are varied and complex. It is apparent that the structural character of an interface is determined, to a large extent, by the system’s phasial constitution in terms of the concentration, temperature, and pressure variables. Therefore, an examination of the relation between these parameters and the structural form of non-planar interfaces was suggested as a potentially valuable field of endeavour. / Thesis / Master of Science (MSc)

This research is directed to the characterization of the thermodynamic properties and viscosity of lubricant base oils modified with polymeric additives. Several groups of mineral and synthetic base oils, including Ultra S4, Ultra S8, and poly alpha olefin PAO 4 have been studied. Among the various types of additives explored were viscosity index modifiers, polyisobutylene polymers (PIBs), and dispersants. The viscosity index modifiers are studied in terms of different polymer architectures, molecular weights, presence or absence of functional groups, and their concentrations. The dispersants are studied in terms of concentration, molecular weight, and presence of capping groups. Density data, as the basic thermodynamic data, are generated using a high-pressure variable-volume view-cell over a pressure range from 10 to 40 MPa and a range of temperatures from 298 to 398 K. The density data are then correlated with the Sanchez-Lacombe equation of state, from which key thermodynamic properties, namely isothermal compressibility, isobaric expansivity, and internal pressure are derived. These properties offer a rational approach to better understand molecular packing in lubricants under high pressure and temperature conditions which has direct impact on film formation. Viscosity determinations are carried out using a custom-designed high-pressure rotational viscometer. Data were generated in the pressure range from 10 to 40 MPa, but at temperatures ranging from 298 to 373 K as a function of shear rate up to 1270 s-1. Viscosity data were then correlated with density which provides interpretations in terms of free-volume and density scaling models. The molecular parameters produced from these correlations support the interpretation of molecular packing under high pressure and temperature conditions. The results of this study included several key findings. With regards to density, the addition of viscosity index modifiers to Ultra S4 base oil caused the density to increase, except for the addition of functionalized olefin copolymers (OCPs) which caused the density to decrease. This was true with both high and low molecular weight additives. In the case of Ultra S8 base oil, the addition of OCPs generally decreased the density, while the addition of polymethacrylates (PMAs) caused the density to increase. In terms of compressibility and expansivity, the addition of high molecular weight viscosity index modifiers to Ultra S4 base oil generally decreased both these properties. However, the compressibility increased with the addition of 5 wt % functionalized PMA and 2 wt % star styrene butadiene (SSB). Furthermore, there was less of a decrease in compressibility with the addition of functionalized additives. With the addition of low molecular weight viscosity index modifiers to Ultra S4 base oil, little change was observed in compressibility, and the expansivity decreased to a lesser degree than with the addition of high molecular weight viscosity index modifiers. Viscosity index modifiers did not alter the compressibility of Ultra S8 base oil. Compared to Ultra S4, expansivity in Ultra S8 decreased to a lesser extent. The internal pressure was observed to be lowered to a greater degree in either Ultra S4 or Ultra S8 base oil with the addition of additives with more rigid internal structures (PMA and SSB). The decrease occurred to a greater degree with the addition of the higher molecular weight versions of additives studied and/or with the incorporation of functional groups to the additives. Although density changes were often greater with the addition of additives to the Ultra S8 base oil, all other derived thermodynamic properties, including internal pressure, changed to a greater degree with the addition of additives to the lower molecular weight Ultra S4 base oil. The viscosity generally increased to varying degrees with the addition of different additives to either base oil. The addition of functionality and higher molecular weight additives led to more consistent viscosity increases at higher temperatures. At the highest viscosity isotherm tested, 373 K, the addition of viscosity index modifiers resulted in similar viscosity values in either base oil, even though the viscosity of Ultra S4 at 373 K is much lower than the viscosity of Ultra S8 at this temperature. However, at 298 K, the viscosity index modifiers increased the viscosity of the Ultra S8 base oil to much higher values than the viscosity of the Ultra S4 base oil. Model based correlations of viscosity showed that with addition of high molecular weight viscosity index modifiers to Ultra S4 base oil, the parameters that are linked to free-volume overlap and the density dependence were more sensitive to the addition of OCPs than with the addition of PMAs and SSBs. These changes were reflected in larger free-volume overlap parameters and larger density exponent values. However, with a low molecular weight addition, the resulting parameters changed more with the addition of PMAs than OCPs. Overall, the addition of polymers with more rigid architecture led to more similar changes in correlative parameters across molecular weights from that of the original base oil, while for the OCP addition, the molecular weight had more of an influence on the degree of change. With addition of viscosity index modifiers to the Ultra S8 base oil, the architecture of the additive had more of an influence on the viscosity correlation parameters as the addition of PMA led to more noticeable changes in the parameters (resulting in lower free-volume overlap parameters, and a lower density exponent) than the addition of OCP, irrespective of the molecular weight or functionality. In either base oil, the addition of PMA led to lower free-volume overlap parameters and density exponent values than the addition of OCP. In this study it was observed that the addition of functionality, or polar groups to viscosity index modifiers, led to more desirable thermodynamic and rheological property changes to the lubrication base oil. This change was more definitive with the addition of polymers with more rigid architecture, such as PMAs and SSBs in contrast to the OCPs. The study on the addition of PIBs and capped or uncapped dispersants showed little variation in the resulting density and viscosity values when added to Ultra S4 base oil. However, the compressibility in these systems generally increased while the expansivity decreased except with the addition of PIBs. The internal pressure decreased to similar levels for all additive additions, except for the lowest molecular weight PIB, in which there was little change. The study on the addition of PIBs to different base oils showed that low molecular weight PIBs had the potential to disrupt the packing of a more uniform PAO 4 base oil and change the thermodynamic properties and correlation parameters to a greater degree than with the addition of higher molecular weight PIBs. This resulted in higher compressibility and internal pressure values with the addition of low molecular weight PIB compared to the higher molecular weight PIBs. However, there was little variation in viscosity with any of the PIB additions, except for the highest molecular weight PIB. / Doctor of Philosophy / Several legislations have recently been passed which are aimed at improving the fuel efficiency in cars. One way to improve fuel efficiency is to reduce friction through improvements on the lubrication systems such as engine oils and transmission fluids. This applies to lubricants operating under cold start conditions and up to operating condition of approximately 100ºC. Additionally, the lubricants are subject to extreme pressure conditions when they are squeezed between contacts such as gears or clutch plates. Therefore, it is crucial to explore lubricant performance under high pressure and temperature conditions. The lubricants that are preferred are those that form a layer that completely protects metal contacts without causing the contacts difficulty in moving, causing a loss in efficiency. The desired film layer thickness under high pressure and temperature conditions can be improved using different additives. This thesis explores high pressure and temperature behavior of lubricant systems modified with different types of additives using uniquely designed lab instrumentation. The focus is on understanding their volumetric and flow properties, which directly influence the film layer and effectiveness of the lubricant. Volumetric properties are characterized by measurement of density as a function of temperature and pressure. Density data provides insights on molecular packing in lubricant systems. Flow properties, specifically, resistance to flow, can help analyze a potential loss in efficiency caused by the lubricant systems. The thesis is thus a comprehensive study on the volumetric and flow properties of lubricants at a wide range of temperatures ( from 298 to 398 K) and pressures (from 10 to 40 MPa) and how these properties are affected in the presence of additives that aim to improve lubricant performance.

Tubulin and elastin-like polypeptides (ELPs) both form large protein structures which can be thermodynamically evaluated using isothermal titration calorimetry and differential scanning calorimetry. ELPs are thermos-responsive biopolymers that undergo phase separation and form coacervates when heated. This project assesses the liquid-liquid phase separation of an ELP sequence derived from tropoelastin with a SynB1 cell-penetrating peptide attached to the N-terminus in conjunction with the chemotherapeutic drug doxorubicin. Microtubules (MTs) are a dynamic cellular structure formed of tubulin alpha/beta-heterodimers and are responsible for several important cellular processes, making them a viable target for anti-cancer drugs. There has been extensive research done to identify new ligands that show selective binding to microtubules. Ruthenium (II) polypyridyl complexes (RPCs) have been found to promote the polymerization of tubulin into microtubules. ITC has been used to determine the binding affinity of [Ru(II)(Ph2phen)3]2+ (RPC2).

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Universite de Lille, McMaster University / The main question of this thesis is: do we have today the tools to efficiently describe the structure, the bonding and the thermodynamics of actinide systems? This broad question is answered thanks to three studies. The first two are directly applied to the plastic industry and the nuclear plant safety. The last one, more fundamental, concerns the benchmarking of newly developed theoretical approach on f-element systems. First, actinides and transition metal arene-coordinated alkyl cations have been recently proven to be efficient catalysts for ethylene polymerizations. Interestingly, thorium, uranium and zirconium alkyl cations? catalytic activity depends on the solvent. To understand these behaviors and to confirm the tendency of these complexes to engage in unusual-arene coordination, relativistic DFT calculations combined with a characterization of the interaction thanks to the ETSNOCV method are used. Second, in accident scenario along the reprocessing of spent nuclear fuel, plutonium can be released in various volatile forms (PuO2, PuO3 or PuO2(OH)2, ...). The exploration of these scenarios by the use of simulations requires, among the various parameters, the knowledge of the thermodynamic properties of the possibly formed elements. Our insilico study focusses on the determination of the enthalpies of formation of the former two species for which experimental uncertainties remain, using multi-configurational relativistic wavefunction method. The last part of the thesis focusses on the benchmark of the B2-PLYP functional for f-element systems, which turns out quite accurate with respect to the experimental data and the gold-standard CCSD(T) method. La question générale traitée dans cette thèse est de déterminer si, aujourd’hui, nous disposons d óutils théoriques efficaces pour d’ écrire la structure, la liaison et les propriétés thermodynamiques de système comprenant un actinide. Cette large question va être abordée à láide de trois études différentes. Les deux premières sont directement liées à l?industrie plastique et à la sureté nucléaire. La dernière, plus fondamentale concerne une analyse comparative d?une approche théorique nouvellement développée sur des systèmes comprenant des éléments f. Tout dábord, les cations alkyles contenant un actinide (Th, U) ou un métal de transition (Zr) coordonné à un arène se sont révélés efficaces pour la catalyse de la synthèse du polyéthylène. étonnamment, les activités catalytiques des cations alkyles dépendent du solvant. Pour comprendre cela et confirmer la tendance quónt ces complexes à se lier à l?arène, une étude en DFT dans un contexte relativiste combinée à une caractérisation de liaison avec la méthode ETS-NOCV fut faite. La deuxième étude vise à étoffer les bases de données thermodynamiques qui servent à explorer numériquement les scénarios d?accidents. Notre étude in silico porte sur la détermination des enthalpies de formation des deux espèces pour lesquelles des incertitudes expérimentales subsistent (PuO3 ou PuO2(OH)2, ...), en utilisant une méthode quantique multiconfigurationnelle et relativiste. La dernière partie de la théorie se concentre sur l?estimation de la précision de la fonctionnelle B2-PLYP pour les éléments f, qui sávère assez précise en comparaison aux données expérimentales et à la méthode de référence CCSD(T). / Thesis / Doctor of Philosophy (PhD)