Submitted by Celso Magalhaes (celsomagalhaes@ufrrj.br) on 2017-05-09T11:39:47Z No. of bitstreams: 1 2012 - Filipe Arantes Furtado.pdf: 4817236 bytes, checksum: 027c11b973e31fc0617693a998446e3e (MD5) / Made available in DSpace on 2017-05-09T11:39:47Z (GMT). No. of bitstreams: 1 2012 - Filipe Arantes Furtado.pdf: 4817236 bytes, checksum: 027c11b973e31fc0617693a998446e3e (MD5) Previous issue date: 2012-07-26 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPq / The main objective of this work was the development of a methodoly using the Solid Phase Microextraction (SPME) on determinations of thermodynamic equilibrium data of liquid and polymeric mixtures. Three methodologies were proposed for determination of infinite dilution activity coefficient of solutes in liquid mixtures (??). The ?? values were determined for 9 hydrocarbons in the solvent furfural at temperatures of 25, 35 and 45 ?C. The liquid-gas partition coefficients were also determined in each studied temperature. On the experiments involving liquid mixtures, high sorption of solvent was observed, which may lead to swelling the polymer coating phase. Statistical tests were conducted after each experiments to measure possible damages on fiber coatings. There was also proposed a methodology using the SPME to determine the Flory Huggins parameter of the nine hydrocarbons used as solutes in polydimethylsiloxane (PDMS) and polyacrylate (PA). The Flory parameter were determined at temperature range of 25 to 80 ?C for the PDMS and 50 to 90 ?C for the PA. The proposed methodologies were evaluated through comparison of the obtained data with literature. All the results agreed with literature data. The Hildebrandt solubility parameter for PA was not available on literature and was determined on these experiments for the first time / O principal objetivo deste trabalho foi o desenvolvimento de uma nova metodologia para determina??o de dados de equil?brio termodin?mico em misturas l?quidas e polim?ricas. Tr?s metodologias foram propostas utilizando a Microextra??o em Fase S?lida (SPME) para determina??o dos coeficientes de atividade em dilui??o infinita (??) de sistemas l?quidos. Os valores de ?? de 9 hidrocarbonetos foram determinados em furfural nas temperaturas de 25, 35 e 45 ?C. Foram determinados valores de coeficiente de parti??o l?quid-g?s (KLg) em cada uma das temperaturas estudadas. Nos experimentos envolvendo as misturas l?quidas, foi observada uma alta taxa de sor??o de solvente podendo ocasionar o inchamento e poss?vel quebramento das fibras de SPME. Para verificar o poss?vel inchamento, foram conduzidos testes estat?sticos antes e depois de cada amostragem. Foi proposto ainda uma metodologia para determinar os par?metros de Flory em polidimetilsiloxano (PDMS) e poliacrilato (PA) utilizando a SPME. Nesse caso, os mesmos 9 hidrocarbonetos tiveram seus par?metros de Flory determinados na faixa de temperatura 25 a 80 ?C para o PDMS e de 50 a 90 ?C para o PA. As metodologias foram avaliadas atrav?s da compara??o dos dados obtidos com dados da literatura. Todos os resultados foram satisfat?rios, sendo ainda obtidos os valores dos par?metros de solubilidade de Hildebrandt, que para o poliacrilato, eram inexistentes na literatura

Wave energy is one of the most promising renewable energy sources for future exploitation. This thesis focuses on thermodynamic effects within Oscillating Water Column (OWC) devices equipped withWells turbines, particularly humidity effects. Previous theoretical studies of the operation of OWCs have resulted in expressions for the oscillation of the water surface in the chamber of an OWC based on linear wave theory, and the air expansion{compression cycle inside the air chamber based on ideal gas theory. Although in practice high humidity levels occur in OWC devices open to the sea, the influence of atmospheric conditions such as temperature and moisture on the performance of Wells turbines has not yet been studied in the field of ocean energy. Researchers have reported substantial differences between predicted and measured power output, and performance rates of OWCs presently coming into operation. The effect of moisture in the air chamber of the OWC causes variations on the atmospheric conditions near the turbine, modifying its performance and efficiency. Discrepancies in available power to the turbine are believed to be due to the humid air conditions, which had not been modelled previously. This thesis presents a study of the influence of humid air on the performance of an idealised Wells turbine in the chamber of an OWC using a real gas model. A new formulation is presented, including a modified adiabatic index, and subsequent modified thermodynamic state variables such as enthalpy, entropy and specific heat. The formulation is validated against experimental data, and found to exhibit better agreement than the ideal approach. The analysis indicates that the real gas behaviour can be explained by a non{dimensional number which depends on the local pressure and temperature in the OWC chamber. A first approach to the OWC formulation through the calculation of real air flow in the OWC is given, which predicts a 6% decrease in efficiency with respect to the ideal case when it is tested with a hypothetical pulse of pressure. This is important because accurate prediction of efficiency is essential for the optimal design and management of OWC converters. A numerical model has also been developed using computational fluid dynamics (CFD) to simulate the OWC characteristics in open sea. The performance of an OWC turbine is studied through the implementation of an actuator disk model in Fluent®. A set of different regular wave tests is developed in a 2D numerical wave flume. The model is tested using information obtained from experimental tests on a Wells{type turbine located in a wind tunnel. Linear response is achieved in terms of pressure drop and air flow in all cases, proving effectively the applicability of the actuator disk model to OWC devices. The numerical model is applied first to an OWC chamber containing dry air, and then to an OWC chamber containing humid air. Results from both cases are compared, and it is found that the results are sensitive to the degree of humidity of the air. Power decreases when humidity increases. Finally, results from the analytical real gas and numerical ideal gas models are compared. Very satisfactory agreement is obtained between the analytical and the numerical models when humidity is inserted in the gaseous phase. Both analytical and numerical models with humid air show considerable differences with the numerical model when dry air is considered. However, at the resonance frequency, results are independent of the gas model used. At every other frequency analysed, the real gas model predicts reduced values of power that can fall to 50% of the ideal power value when coupled to the radiation-diffraction model for regular waves. It is recommended that real gas should be considered in future analyses of Wells turbines in order to calculate accurately the efficiency and expected power of OWC devices.

O pó de aciaria elétrica é um importante subproduto da indústria siderúrgica devido ao seu alto teor de zinco. Assim, tecnologias vêm sendo desenvolvidas visando seu aproveitamento, sendo o forno Waelz a mais difundida delas atualmente. No entanto, sua operação, por contar com um forno rotativo de grandes dimensões que abriga uma infinidade de fenômenos físico-químicos, apresenta difícil previsibilidade ab initio. Por essa razão, este trabalho faz uso de uma ferramenta avançada da termodinâmica computacional, destinada à modelagem de processos, chamada SimuSage, a fim de modelar o seu comportamento. Para a criação do modelo utilizou-se também uma base de dados termodinâmicos advinda do software FactSage e a plataforma de desenvolvimento Lazarus. Com base em dados e resultados operacionais da literatura, foi possível realizar simulações nos modos adiabático e isotérmico, comparando os resultados com os da prática industrial. Constatou-se uma grande capacidade do modelo de reproduzir os resultados da literatura, mesmo quando não há muita informação para aferição dos parâmetros, gerando boa concordância com a composição química relatada dos produtos Óxido Waelz e Escória Waelz. / The electric arc furnace dust is an important by-product of the steel industry due to its high content of zinc. Thus, technologies have been developed aiming for its use, and the Waelz Kiln is the most widespread of them today. However, counting on a very large rotary kiln that houses an infinity of physico-chemical phenomena, its operation is difficult to predict ab initio. For this reason, in order to model its behaviour this work uses an advanced tool of computational thermodynamics designed to process modelling, called SimuSage. To create the model, a thermodynamic database, provided by the FactSage software, as well as a development platform, Lazarus IDE, were also used. Based on operational data and results from de literature, it was possible to perform simulations on both adiabatic and isothermal modes comparing its results with the industrial practice. A great capability of the model to reproduce results from the literature was found, even when there is not much information for the parameters calibration, generating good agreement regarding the reported chemical composition for the products, Waelz Oxide and Waelz Slag.

Nesta dissertação, apresentamos estudos preliminares envolvendo a Termodinâmica de átomos aprisionados por potenciais inomogêneos. Estes estudos foram realizados em dois sistemas experimentais distintos, a partir da definição de novas variáveis globais propostas por V. Romero-Rochín, as quais, chamaremos parâmetro de volume e parâmetro de pressão. O primeiro sistema, consiste no experimento desenvolvido em nosso laboratório e envolve a Condensação de Bose-Einstein em átomos de 87Rb aprisionados em uma armadilha óptico-magnética. Este sistema é descrito em detalhe ao longo da dissertação. O segundo sistema consiste no sistema experimental do professor R. G. Hulet, na Universidade Rice, e envolve a Condensação de Bose-Einstein em átomos7 Li aprisionados em uma armadilha óptica. Neste segundo experimento é possível variar a interação da amostra atômica estudando a sua influência no parâmetro de pressão. Ainda, nesta dissertação, realizamos uma análise teórica da transição de fase para a fase condensada a partir dessas novas variáveis. / In this master thesis we present some preliminary studies on the Thermodynamics of ultracold gases in inhomogeneous potentials. These studies were performed in two different experimental setups using the new global variables proposed by V. Romero-Rochín, which we call volume parameter and pressure parameter. The first system is the experiment built in our laboratory in which we produce a Bose-Einstein Condensation (BEC) of 87Rb atoms in a hybrid trap. The second experiment is the Prof. Hulet´s setup at Rice University in which a BEC of 7Li is produced in an optical trap. At this second experiment it was possible to vary the interaction between the atoms in such a way that we were able to characterize its influence on the pressure parameter. In addition we present a theoretical analysis of the BEC phase transition in terms of these new variables.

As ligações entre a termodinâmica e a mecânica quântica mostram-se interessantes tópicos de pesquisa desde os anos 50 e tem atraído cada vez mais atenção nos últimos anos, tanto por suas possíveis aplicações tecnológicas, quanto pelo aspecto teórico - como, por exemplo, as relações de sistemas quânticos com a segunda lei da termodinâmica. Para sistemas quânticos mesoscópicos, restritos apenas a um número relativamente pequeno de estados energéticos, torna-se necessária uma generalização da termodinâmica usual. Neste trabalho mostramos como construir uma máquina de Stirling no contexto de íons aprisionados. Para isso, faz-se necessária a engenharia de frequências dependentes do tempo do modo vibracional do íon, além da engenharia de reservatórios térmicos com temperaturas controladas. Após a construção da máquina de Stirling e do cálculo do trabalho e da eficiência associados apresentamos um protocolo para a medida da função de distribuição do trabalho que recorre às medidas dos níveis de energia eletrônicos do íon para, a partir dessas, extrair-se informação sobre o seu estado vibracional. / The connections between quantum mechanics and thermodynamics have been an interesting research topic since the 1950´s and began attracting more and more attention recently, not only for the technological applications, but also from a theoretical point of view - as, for instance, when dealing with the relations between quantum systems and the second law of thermodynamics. For mesoscopic (or even macroscopic) quantum systems, restricted to relatively few energy states, a generalization of the usual thermodynamics becomes necessary. In the present work we show how to engeneer a Stirling engine in an ionic trap. To achieve this we have to engeneer an ionic vibrational mode with a time dependent frequency, and simutaneously engeneer a thermal reservoir with controled temperatures. After the construction of the Stirling machine and the calculation of the associated work and efficiency, we show a protocol that allows the measurement of the work distribution function which call on the measurement of the electronic energy levels of the ion and, from them, extract information about the vibrational state of the trap.

abstract: The seasonal deposition of CO2 on the polar caps is one of the most dynamic processes on Mars and is a dominant driver of the global climate. Remote sensing temperature and albedo data were used to estimate the subliming mass of CO2 ice on south polar gullies near Sisyphi Cavi. Results showed that column mass abundances range from 400 - 1000 kg.m2 in an area less than 60 km2 in late winter. Complete sublimation of the seasonal caps may occur later than estimated by large-scale studies and is geographically dependent. Seasonal ice depth estimates suggested variations of up to 1.5 m in depth or 75% in porosity at any one time. Interannual variations in these data appeared to correlate with dust activity in the southern hemisphere. Correlation coefficients were used to investigate the relationship between frost-free surface properties and the evolution of the seasonal ice in this region. Ice on high thermal inertia units was found to disappear before any other ice, likely caused by inhibited deposition during fall. Seasonal ice springtime albedo appeared to be predominantly controlled by orientation, with north-facing slopes undergoing brightening initially in spring, then subliming before south-facing slopes. Overall, the state of seasonal ice is far more complex than globally and regionally averaged studies can identify. The discovery of cryovolcanic features on Charon and the presence of ammonia hydrates on the surfaces of other medium-sized Kuiper Belt Objects suggests that cryovolcanism may be important to their evolution. A two-dimensional, center-point finite difference, thermal hydraulic model was developed to explore the behavior of cryovolcanic conduits on midsized KBOs. Conduits on a Charon-surrogate were shown to maintain flow through over 200 km of crust and mantle down to radii of R = 0.20 m. Radii higher than this became turbulent due to high viscous dissipation and low thermal conductivity. This model was adapted to explore the emplacement of Kubrik Mons. Steady state flow was achieved with a conduit of radius R = 0.02 m for a source chamber at 2.3 km depth. Effusion rates computed from this estimated a 122 - 163 Myr upper limit formation timescale. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2019

Low-temperature heat capacity data contain information on the physical properties of materials, and new models continue to be developed to aid in the analysis and interpretation of heat capacity data into physically meaningful properties. This work presents the development of two such models and their application to real material systems. Equations describing low-energy vibrational modes with a gap in the density of states (DOS) have been derived and tested on several material systems with known gaps in the DOS, and the origins of such gaps in the DOS are presented. Lattice vacancies have been shown to produce a two-level system that can be modeled with a sum of low-energy Schottky anomalies that produce an overall linear dependence on temperature in the low-temperature heat capacity data. These two models for gaps in the vibrational DOS and the relationship between a linear heat capacity and lattice vacancies and many well-known models have been applied to several systems of materials to test their validity and applicability as well as provide greater information on the systems themselves. A series of bulk and nanoscale Mn-Fe and Co-Fe spinel solid solutions were analyzed using the entropies derived from heat capacity data, and excess entropies of mixing were determined. These entropies show that changes in valence, cation distribution, bonding, and the microstructure between the mixing ions is non-ideal, especially in the nanoparticles. The heat capacity data of ten Al doped TiO2 anatase nanoparticle samples have also been analyzed to show that the Al3+ dopant ions form small regions of short-range order, similar to a glass, within the TiO2 particles, while the overall structure of TiO2 remains unchanged. This has been supported by X-ray diffraction (XRD) and electron energy-loss spectroscopy and provides new insights to the synthesis and characterization of doped materials. The final investigation examines nanocrystalline CuO using heat capacities, magnetization, XRD, and electron microscopy and compares the findings to the known properties of bulk CuO. All of these measurements show transitions between antiferromagnetic and paramagnetic states in the temperature range of about 150-350 K that are greater in number and higher in temperature than the transitions in bulk CuO. These changes are shown to cause an increase in the temperature range of multiferroicity in CuO nanoparticles.

<div> <div> <div> <p>Since their commercialization in the early 1990’s, rechargeable lithium ion batteries (LIBs) have become ever-present in consumer electronics, and the share of electric vehicles within the transportation sector has become much more significant. <i>Ab initio</i> modeling techniques - namely density functional theory (DFT) - have played a signifcant role in describing the atomic scale nature of Li+ insertion and removal chemistry in LIB electrode materials, and have been pivotal in accelerating the design of energy dense battery materials based on their bulk properties. Despite these advances, there remains a knowledge gap with respect to understanding the many complex reactions that occur at the surfaces and interfaces of rechargeable battery materials. This work considers several case studies of surface and interfacial reactions in energy storage materials, using DFT modeling techniques to develop strategies that can rationally control the interfacial chemistry for optimal electrochemical performance. </p><p><br></p><p> </p><div> <div> <div> <p>The first portion of this thesis aims to understand the role of interfacial modification strategies toward mitigating Mn dissolution from the spinel LiMn2O4 (LMO) surface. First, a thermodynamic characterization of LMO surface structures is performed in order to develop models of LMO substrates for subsequent computational surface science studies. A subset of these surface models are then used analyze interfacial degradation processes through delithiation-driven stress buildup and crack formation, as well as reaction mechanisms for ethylene carbonate and hydrofluoric acid to form surface Mn2+ ions that are susceptible to dissolution. Surface passivation mechanisms using protective oxide and metallic coatings are then analyzed, which elucidate an electronic structure-based descriptor for structure-sensitive atomic layer growth mechanisms and describe the changes in lithiation reactions of coated electrodes through electronic band alignment at the solid-solid interface. These studies of protective coatings describe previously overlooked physics at the electrode-coating interface that can aid in further development of coated electrode materials. Using the LMO substrate models, a thermodynamic framework for evaluating the solubility limits and surface segregation tendencies of cationic dopants is described in the context of stabilizing LMO surfaces against Mn loss. </p><p><br></p><p> </p><div> <div> <div> <p>Next, solid-solid interfacial models are developed to evaluate the role of nanostructure in catalyzing the lithiation of NiO to form reduced Ni and Li2O as concurrent discharge products. Applying a Ni/NiO multilayer morphology, interfacial energies are evaluated using DFT and implemented into a classical nucleation model at a heterogeneous interface. These calculations, alongside <i>operando</i> X-ray scattering measurements, are used to explain atomic scale mechanisms that reduce voltage hysteresis in metal oxide LIB conversion chemistry. </p><p><br></p><p> </p><div> <div> <div> <p>The structure between a Li metal anode and the lithium lanthanum titanate solid electrolyte are subsequently analyzed as a model system to understand potential inter- facial stabilization mechanisms in solid-state batteries. This analysis combines bulk, surface, and interfacial thermodynamics with <i>ab initio</i> molecular dynamics simulations to monitor the evolution of the interfacial structure over short time scales, which provides insights into the onset of degradation mechanisms. It is shown that the reductive instability of Ti4+ is the primary driving force for interfacial decomposition reactions, and that a lanthanum oxide interlayer coating is expected to stabilize the interface based on both thermodynamic and electronic band alignment arguments. </p><p><br></p><p> </p><div> <div> <div> <p>In the last part of this thesis, charge transfer kinetics are studied for several applications using constrained DFT (cDFT) to account for electronic coupling and reorganization energies between donor and acceptor states. Charge hopping mechanisms to and from dichalcogenide-based electrocatalysts during O2 and CO2 reduction/evolution reactions in Li-O2 and Li-CO2 battery systems are first evaluated. Then, the role of the spatial separation Li+ vacancies and interstitials on hole and electron polaron hopping in the prototypical LixCoO2 cathode is analzyed. The results demonstrate that Marcus rate theories using cDFT-derived parameters can reproduce experimentally observed anisotropies in electronic conductivity, whereas conventional transition state theory analyses of polaron hopping do not. Overall, this proof-of-concept study provides a framework to understand how charged species are transported in battery electrodes and are dependent on charge compensating defects.</p><p><br></p> <p>Finally, the key insights from these studies are discussed in the context of future directions related to the understanding and design of materials for electrochemical energy conversion and storage. </p> </div> </div> </div> </div> </div> </div> </div> </div> </div> </div> </div> </div> </div> </div> </div>

The biodesulfurization 4S-pathway is a promising complementary enzymatic approach to remove sulfur from recalcitrant thiophenic derivatives in petroleum products that remain from conventional hydrodesulfurization method without diminishing the calorific value of oil. The final step of this pathway involves the carbon-sulfur bond cleavage from HBPS, and the production of the final products 2-hydroxybiphenyl (HBP) and sulfite, has been recognized as the rate-limiting step, partially as a result of product inhibition. However, the mechanisms and factors responsible for product inhibition in the last step have not been fully understood. In this work, we proposed a computational investigation using molecular dynamic simulations and free energy calculations on 2’-hydroxybiphenyl-2-sulfinate (HBPS) desulfinase (DszB) with different bound ligands as well as different solvent conditions to develop a fundamental understanding of the molecular-level mechanism responsible for product inhibition. Based on available crystal structures of DszB and biochemical characterization, we proposed a “gate” area close to substrate binding site of DszB is responsible for ligand egress and plays a role in product inhibition. We have conducted biphasic molecular dynamic simulations to evaluate the proposed gate area functionality. Non-bonded interaction energy analysis shows that hydrophobic residues around the gate area produce van der Waals interactions inhibiting translocation through the gate channel, and therefore, the molecules are easily trapped inside the binding site. Umbrella sampling molecular dynamics was performed to obtain the energy penalty associated with gate conformational change from open to close, which was 2.4 kcal/mol independent of solvent conditions as well as bound ligands. Free energy perturbation calculations were conducted for a group of six selected molecules bound to DszB. The selections were based on functional group representation and to calculate binding free energies that were directly comparable to experimental inhibition constants, KI. Our work provides a fundamental molecular-level analysis on product inhibition for the biodesulfurization 4S-pathway.

Spontaneous combustion of coal has historically been a major problem for the coal industry, predominantly during storage and transportation. Various methods have been used in the laboratory for evaluating the propensity of different coal sources to self-heat. However, the heterogeneity of coal and the complexity of the system has resulted in inconsistencies and sometimes conflicting results as indicated by the findings reported in several publications. The primary objective of the current study was to build a laboratory scale apparatus that simulates the condition of a coal stockpile to evaluate the events leading to spontaneous combustion and develop potential remedies. As such, the influential factors can be identified with confidence, thereby providing an improved understanding of the spontaneous combustion. An adiabatic heating apparatus was designed and constructed which included instrumentation to closely monitor the oxidation process and the stages leading to spontaneous combustion under various conditions. The device was equipped with thermocouples which measured the temperature rise as a function of time leading to the determination of an index value that indicated the propensity of a given coal source to spontaneously combustion. The index was referred to as the R70 value which was measured as the temperature was increased during the period of rapid oxidation. The units for the index was degrees Celsius per hour. As such, a high index value reflected the likelihood of spontaneous combustion for a given coal source. To standardize the test procedure, a detailed three-level statistical experimental design was conducted involving three critical parameters, i.e., particle size, oxygen flow rate and the duration of the drying period prior to feeding oxygen to the system. Using empirical models describing the R70 value as a function of the parameter values developed from the test data, it was determined that R70 was sensitive to the sample particle size and drying time. A decrease in particle size and drying time significantly increased the R70 value while the oxygen rate did not have a significant impact over the range of values tested. Based on the results of the test program, a standard test procedure was established to evaluate various coal sources and identify chemicals that could be used to remediate the spontaneous combustion issue. Several sub-bituminous coal sources collected from the Powder River Basin were tested in the apparatus and found to be prone to spontaneous combustion as indicated by R70 values that approached 50oC per hour. Several chemicals were evaluated as a means of eliminating or slowing the spontaneous combustion process. These agents included anti-oxidants, binders and humectants. Organic binders were used to agglomerate the fine coal particles which limited surface area exposure. The effect significantly reduced the oxidation rate as indicated by a reduction in the R70 index from 44.07oC/hr to 5.71oC/hr. However, after entering the latent heat stage, the temperature increased rapidly at a rate of 27.58oC/hr. Humectants were evaluated which contained several hydrophilic groups, mainly hydroxyl groups, and thus have an affinity for water. As a result, when the coals were treated with humectant, the latent heat rate was reduced to 4.24oC/hr although the R70 remained relatively high. By using a combination of humectant and binder, the optimum result was obtained with an R70 value of 5.04oC/hr and a latent heat rate of 11.06oC/hr. These findings were successfully implemented into industrial practice for significantly delaying the spontaneous combustion event.