Thesis (Ph.D.)--McMaster University, 2003. / Advisor: Daniel Yang. Includes bibliographical references (leaves 88-97). Also available via World Wide Web.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-10-17T12:26:13Z No. of bitstreams: 1 MARCÍLIO MÁXIMO DA SILVA - DISSERTAÇÃO (PPGEQ) 2018.pdf: 1518783 bytes, checksum: dfad1c1316712eda6e520bfdd752df58 (MD5) / Made available in DSpace on 2018-10-17T12:26:13Z (GMT). No. of bitstreams: 1 MARCÍLIO MÁXIMO DA SILVA - DISSERTAÇÃO (PPGEQ) 2018.pdf: 1518783 bytes, checksum: dfad1c1316712eda6e520bfdd752df58 (MD5) Previous issue date: 2018-04-16 / A análise de processos de cristalização utilizando uma abordagem entrópica é o objetivo principal deste trabalho. Embora a modelagem de processos de cristalização esteja bem estabelecida na literatura, a representação entrópica desses processos ainda precisa ser estudada. Diante disso, o objetivo principal deste trabalho foi desenvolver um modelo de processos de cristalização utilizando uma abordagem entrópica e avaliar os efeitos de variáveis do processo na taxa de produção de entropia do sistema. A modelagem considerando a segunda lei da termodinâmica resultou em um modelo que representa a taxa de geração de entropia de processos de cristalização. O modelo foi aplicado para um processo de cristalização em batelada por resfriamento de nitrato de potássio (KNO3). A avaliação da taxa de geração de entropia em função da temperatura foi analisada para diferentes perfis de temperatura. Os resultados indicam que o modelo entrópico do processo de cristalização em batelada possui conclusões interessantes, e o menor perfil de taxa de geração de entropia cumulativa corrobora com o maior tamanho médio dos cristais. Em conclusão, a relação entre a distribuição de tamanho de cristais e a taxa de geração de entropia pode ser aplicada em técnicas de otimização, em que a taxa de mínima geração de entropia é utilizada como um critério para melhorar a qualidade da distribuição de tamanho de cristal do produto final. / The analysis of crystallization processes considering an entropic perspective is the primary purpose of this paper. Although the modeling of crystallization processes is well established in the literature, the entropic representation of these processes still needs to be studied. The main goal of this paper was the development of a model of crystallization processes using an entropic perspective and the evaluation of the effect of the process variables in the production rate of entropy of the system. The modeling considering the second law of thermodynamics was investigated, which resulted in a model that represents the entropy generation rate of the crystallization process. The model was applied for a cooling batch crystallization process of potassium nitrate (KNO3). The evaluation of the entropy generation rate as function of temperature was analyzed for different temperature profiles. The results indicate that the model brings significant findings of the entropy of the batch crystallization process, and the lowest cumulative entropy generation rate profile corroborate with the highest crystal mean weight size. In conclusion, the relationship between the crystal size distribution and the entropy generation rate can be used in optimization techniques, where the minimum entropy generation rate is a criterion to improve the quality of the crystal size distribution of the final product.

Elastômeros termoplásticos têm sido largamente empregados como adesivos hot melt em diferentes setores da indústria. Neste trabalho foram estudados dois copolímeros em bloco de poliuretano na forma particulada, base poliéster (TPU1) e policaprolactona (TPU2), com o objetivo de avaliar o desempenho dos mesmos como adesivos particulados. Foram preparadas diferentes composições dos TPUs com aditivos de policarbodiimida (A), resina hidrocarbônica (B) e poliisocianato (C). Os TPUs aditivados em diferentes composições foram avaliados por termogravimetria (TGA) e calorimetria diferencial de varredura (DSC) e quanto à resistência da colagem. A cinética de cristalização dos TPUs particulados puros e aditivados em diferentes isotermas foi acompanhada por DSC. Os adesivos TPU1 apresentaram velocidade de cristalização mais lenta, com exceção do TPU1 contendo os aditivos A e B (TPU1AB). Os adesivos TPU2 apresentaram taxa de cristalização maior somente quando aditivado com mistura de aditivos (TPU2AB; TPU2BC; TPU2ABC; TPU2AC). O expoente de Avrami (n) foi inferior para os TPUs aditivados, o que sugere a ocorrência de alteração no tipo de nucleação e geometria de crescimento dos cristalitos. Os TPU1 (poliéster) e TPU2 (policaprolactona) apresentaram perfil de degradação térmica diferenciados devido a diferenças na estrutura química dos mesmos. Os adesivos TPU2 apresentaram valores de resistência mecânica mais elevados que os TPU1, em colagens de substratos de PVC. Os adesivos com maiores valores de resistência (TPU1A e TPU2A) foram extrusados e micronizados para uso como tal. O adesivo TPU1A micronizado apresentou aumento da resistência mecânica. As colagens com os adesivos TPU1 e TPU2 apresentaram falha coesiva e as composições TPU1B e TPU2AC demonstraram falha coesiva e adesiva em ensaio de tração. O processamento dos adesivos TPU1 por tratamento de plasma favoreceu um incremento dos valores de resistência de colagens em substratos de PVC. / Thermoplastic elastomers have widely been used as hot melt adhesives in different industry sectors. In this paper were studied two polyurethane block copolymers in particulate form, based polyester (TPU1) and polycaprolactone (TPU2), in order to evaluate their performance as adhesives. Different compositions of TPUs were prepared with polycarbodiimide (A), hydrocarbon resin (B) and polyisocyanate (C) additives. The TPUs with additives in different compositions were evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) and by the bond strength. The kinetics crystallization of pure and additivated TPUs at different isotherms were followed by DSC. The TPU1 adhesives showed lower crystallization rate, except the TPU1 with both A and B additives (TPU1AB). The TPU2 adhesives showed higher crystallization rate only when formulated with mixture of additives (TPU2AB; TPU2BC; TPU2ABC; TPU2AC). The Avrami exponent (n) was lower for the TPUs containing additives, which suggests changes in the nucleation type and crystallites growth geometry. The thermal degradation profile of both TPU1 (polyester) and TPU2 (polycaprolactone) adhesives were quite different due to chemical differences. The TPU2 adhesives showed higher strength values than TPU1s on PVC substrates. The adhesives with higher bond strength (TPU1A and TPU2A) were extruded and micronized, and the TPU1A adhesive showed improved bonding property. The TPU1 and TPU2 adhesives on PVC collages showed cohesive failure and the TPU1B and TPU2AC compositions showed cohesive and adhesive failure under tension test. The adhesive plasma treatment promoted a bonding increasing of TPU1 on PVC substrates.

L’altération des matériaux poreux est attribuée en grande partie aux sels présents en solution dans l’espace des pores. Ce phénomène d’altération est classiquement associé à la cristallisation des sels dissous via la notion de pression de cristallisation. Le phénomène de cristallisation est quant à lui souvent très directement lié aux écoulements ou aux variations de saturation dus à l’évaporation auquel est soumis le milieu poreux. Une meilleure compréhension des phénomènes d’altération passe donc par une compréhension du transport des ions lors de l’évaporation et notamment de l’évolution de leur concentration locale. Dans ce contexte, ce travail consiste à étudier expérimentalement et numériquement le transfert des ions en solution dans un milieu poreux hétérogène pour deux situations de référence : la situation de mèche et la situation de séchage. Dans le cas de la situation de mèche, le milieu poreux est alimenté de façon continue en solution saline au cours de l’évaporation. Le milieu poreux reste complètement saturé tout au long de l’évaporation. En revanche, la situation de séchage est caractérisée par la diminution progressive de la saturation en liquide au cours du temps. Le sel considéré est le chlorure de sodium, un sel très présent dans un grand nombre d’applications. L’accent est mis sur l’étude de l’effet d’hétérogénéités macroscopiques, c’est-à-dire des variations spatiales de porosité et/ou de perméabilité, sur la position et la dynamique des maximums de concentration en sel à la surface évaporative du milieu poreux pour les deux situations de référence précitées. Les maximums de concentration correspondent en effet aux lieux les plus probables de la cristallisation. La première partie de ce travail porte sur la situation de mèche. Les expériences et les simulations numériques montrent que les maximums de concentration en sel sont anticorrélés avec les maximums de porosité et/ou de perméabilité aux temps longs. Ainsi le sel se dépose à la surface du milieu le moins perméable et le moins poreux si l’évaporation est uniforme à la surface du milieu poreux. La deuxième partie de cette étude est dédiée à l’étude de la situation de séchage. On trouve l’inverse du cas de la situation de mèche, c’est-à-dire une corrélation directe des maximums de concentration avec les maximums de porosité et de perméabilités. Ceci s’explique par la désaturation préférentielle des zones à plus fortes porosités et à plus fortes perméabilités lors du séchage. Nous avons également étudié des situations où le flux d’évaporation était plus marqué en périphérie de l’échantillon, ce qui conduit notamment à l’apparition des efflorescences en forme d’anneau de fée. Notre étude a également mis en évidence un effet notable de sursaturation ainsi que la nécessité de prendre en compte dans l’analyse l’augmentation de la porosité près d’une paroi dans le cas des milieux poreux formés par des empilements de particules. / Alteration of porous media is often due to the salts solution present in the pore space. This phenomenon is typically associated with the crystallization process of dissolved salts in relation with the concept of crystallization pressure. The salt crystallization phenomenon is in turn very often directly related to the flows or the saturation variation resulting from evaporation. A better understanding of alteration process thus needs a better understanding of the ions transport during evaporation and of the local evolution of ions concentration. In this context, this work presents an experimental and numerical study of sodium chloride transport in heterogeneous porous media. Two basic situations are considered: namely drying and wicking-evaporation. In the evaporation-wicking situation the sample is in contact at its bottom with an aqueous solution and the medium remains fully saturated by the solution during evaporation. In drying the limiting surfaces of the porous sample are in contact with impervious walls or exposed to evaporation. Since there is no supply of liquid to compensate the evaporation in this case, the overall liquid saturation decreases during the drying process. The focus is on the impact of porosity and permeability heterogeneities on the ion concentration maxima at the evaporative surface of a porous medium for the two reference situations. The ion concentration maxima correspond to the incipient spots of crystallization. The first part is devoted to the evaporation-wicking situation. Experiments and numerical simulations show that the salt concentration maxima are anticorrelated with the maxima in porosity and / or permeability in the long time regime. As a result the salt crystallizes at the surface of the less permeable and less porous medium if the evaporation is uniform at the surface of porous medium. The second part is devoted to the study of the drying situation. The drying situation is markedly different from the evaporation-wicking situation. The ion concentration maxima correspond to regions of greatest porosity and / or permeability because of the preferential decrease in saturation in the region of largest porosity / permeability. This is exactly the contrary of the evaporation-wicking situation. We also studied situations where higher evaporation fluxes along the periphery of the evaporative surface lead to the formation of an efflorescence fairy ring. The study also reveals a quite significant supersaturation effect and the impact of porosity variations near the wall on the ion concentration distribution and the first time of crystallization when the porous medium is formed by a packing of particles.

Elastômeros termoplásticos têm sido largamente empregados como adesivos hot melt em diferentes setores da indústria. Neste trabalho foram estudados dois copolímeros em bloco de poliuretano na forma particulada, base poliéster (TPU1) e policaprolactona (TPU2), com o objetivo de avaliar o desempenho dos mesmos como adesivos particulados. Foram preparadas diferentes composições dos TPUs com aditivos de policarbodiimida (A), resina hidrocarbônica (B) e poliisocianato (C). Os TPUs aditivados em diferentes composições foram avaliados por termogravimetria (TGA) e calorimetria diferencial de varredura (DSC) e quanto à resistência da colagem. A cinética de cristalização dos TPUs particulados puros e aditivados em diferentes isotermas foi acompanhada por DSC. Os adesivos TPU1 apresentaram velocidade de cristalização mais lenta, com exceção do TPU1 contendo os aditivos A e B (TPU1AB). Os adesivos TPU2 apresentaram taxa de cristalização maior somente quando aditivado com mistura de aditivos (TPU2AB; TPU2BC; TPU2ABC; TPU2AC). O expoente de Avrami (n) foi inferior para os TPUs aditivados, o que sugere a ocorrência de alteração no tipo de nucleação e geometria de crescimento dos cristalitos. Os TPU1 (poliéster) e TPU2 (policaprolactona) apresentaram perfil de degradação térmica diferenciados devido a diferenças na estrutura química dos mesmos. Os adesivos TPU2 apresentaram valores de resistência mecânica mais elevados que os TPU1, em colagens de substratos de PVC. Os adesivos com maiores valores de resistência (TPU1A e TPU2A) foram extrusados e micronizados para uso como tal. O adesivo TPU1A micronizado apresentou aumento da resistência mecânica. As colagens com os adesivos TPU1 e TPU2 apresentaram falha coesiva e as composições TPU1B e TPU2AC demonstraram falha coesiva e adesiva em ensaio de tração. O processamento dos adesivos TPU1 por tratamento de plasma favoreceu um incremento dos valores de resistência de colagens em substratos de PVC. / Thermoplastic elastomers have widely been used as hot melt adhesives in different industry sectors. In this paper were studied two polyurethane block copolymers in particulate form, based polyester (TPU1) and polycaprolactone (TPU2), in order to evaluate their performance as adhesives. Different compositions of TPUs were prepared with polycarbodiimide (A), hydrocarbon resin (B) and polyisocyanate (C) additives. The TPUs with additives in different compositions were evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) and by the bond strength. The kinetics crystallization of pure and additivated TPUs at different isotherms were followed by DSC. The TPU1 adhesives showed lower crystallization rate, except the TPU1 with both A and B additives (TPU1AB). The TPU2 adhesives showed higher crystallization rate only when formulated with mixture of additives (TPU2AB; TPU2BC; TPU2ABC; TPU2AC). The Avrami exponent (n) was lower for the TPUs containing additives, which suggests changes in the nucleation type and crystallites growth geometry. The thermal degradation profile of both TPU1 (polyester) and TPU2 (polycaprolactone) adhesives were quite different due to chemical differences. The TPU2 adhesives showed higher strength values than TPU1s on PVC substrates. The adhesives with higher bond strength (TPU1A and TPU2A) were extruded and micronized, and the TPU1A adhesive showed improved bonding property. The TPU1 and TPU2 adhesives on PVC collages showed cohesive failure and the TPU1B and TPU2AC compositions showed cohesive and adhesive failure under tension test. The adhesive plasma treatment promoted a bonding increasing of TPU1 on PVC substrates.

abstract: X-ray crystallography is the most widely used method to determine the structure of proteins, providing an understanding of their functions in all aspects of life to advance applications in fields such as drug development and renewable energy. New techniques, namely serial femtosecond crystallography (SFX), have unlocked the ability to unravel the structures of complex proteins with vital biological functions. A key step and major bottleneck of structure determination is protein crystallization, which is very arduous due to the complexity of proteins and their natural environments. Furthermore, crystal characteristics govern data quality, thus need to be optimized to attain the most accurate reconstruction of the protein structure. Crystal size is one such characteristic in which narrowed distributions with a small modal size can significantly reduce the amount of protein needed for SFX. A novel microfluidic sorting platform was developed to isolate viable ~200 nm – ~600 nm photosystem I (PSI) membrane protein crystals from ~200 nm – ~20 μm crystal samples using dielectrophoresis, as confirmed by fluorescence microscopy, second-order nonlinear imaging of chiral crystals (SONICC), and dynamic light scattering. The platform was scaled-up to rapidly provide 100s of microliters of sorted crystals necessary for SFX, in which similar crystal size distributions were attained. Transmission electron microscopy was used to view the PSI crystal lattice, which remained well-ordered postsorting, and SFX diffraction data was obtained, confirming a high-quality, viable crystal sample. Simulations indicated sorted samples provided accurate, complete SFX datasets with 3500-fold less protein than unsorted samples. Microfluidic devices were also developed for versatile, rapid protein crystallization screening using nanovolumes of sample. Concentration gradients of protein and precipitant were generated to crystallize PSI, phycocyanin, and lysozyme using modified counterdiffusion. Additionally, a passive mixer was created to generate unique solution concentrations within isolated nanowells to crystallize phycocyanin and lysozyme. Crystal imaging with brightfield microscopy, UV fluorescence, and SONICC coupled with numerical modeling allowed quantification of crystal growth conditions for efficient phase diagram development. The developed microfluidic tools demonstrated the capability of improving samples for protein crystallography, offering a foundation for continued development of platforms to aid protein structure determination. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2016

abstract: Polycrystalline magnetite thin films were deposited on large area polymer substrates using aqueous solution based spin-spray deposition (SSD). This technique involved the hydrolysis of precursor salt solutions at low temperatures (70-100°C). The fundamental mechanisms and pathways in crystallization and evolution of the film microstructures were studied as a function of reactant chemistry and reactor conditions (rotation rate, flow rates etc.). A key feature of this method was the ability to constantly supply fresh solutions throughout deposition. Solution flow due to substrate rotation ensured that reactant depleted solutions were spun off. This imparted a limited volume, near two-dimensional restriction on the growth process. Film microstructure was studied as a function of process parameters such as liquid flow rate, nebulizer configuration, platen rotation rate and solution chemistry. It was found that operating in the micro-droplet regime of deposition was a crucial factor in controlling the microstructure. Film porosity and substrate adhesion were linked to the deposition rate, which in-turn depended on solution chemistry. Films exhibited a wide variety of hierarchically organized microstructures often spanning length scales from tens-of-nanometers to a few microns. These included anisotropic morphologies such as nanoplates and nanoblades, that were generally unexpected from magnetite (a high symmetry cubic solid). Time resolved studies showed that the reason for complex hierarchy in microstructure was the crystallization via non-classical pathways. SSD of magnetite films involved formation of precursor phases that subsequently underwent solid-state transformations and nanoparticle self-assembly. These precursor phases were identified and possible reaction mechanisms for the formation of magnetite were proposed. A qualitative description of the driving forces for self-assembly was presented. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2018

Les mémoires à changement de phase (PCRAM) sont l'un des candidats les plus prometteurs pour la prochaine génération de mémoires non-volatiles du fait de leurs excellentes vitesses de fonctionnement et endurance. Cependant, deux inconvénients majeurs nécessitent une amélioration afin de permettre leur percée sur le marché des mémoires, à savoir un temps de rétention court à hautes températures et une consommation électrique trop importante. Cette thèse s'intéresse au développement de nouveaux matériaux à changement de phase afin de remplacer le matériau standard Ge2Sb2Te5, inadapté aux applications mémoires embarquées fonctionnant à hautes températures. Le comportement des matériaux binaires GeTe et GeSb a ainsi été évalué et comparé au matériau référence lors de la cristallisation de l'amorphe 'tel que déposé' mais aussi de l'amorphe 'fondu trempé'. En effet, il est important d'étudier le matériau dans son état amorphe 'fondu trempé' pour être au plus près de l'état du matériau cyclé dans les dispositifs. Ainsi, le mécanisme de cristallisation du GeTe déterminé par l'étude de la cristallisation de l'amorphe 'fondu trempé' par recuit laser est en accord avec l'observation MET in situ (recuit thermique) de la cristallisation. L'incorporation d'éléments 'dopants' dans ces matériaux binaires a également été évaluée afin d'augmenter à nouveau la stabilité thermique des matériaux non dopés. Certains éléments 'dopants' permettent une diminution du courant de reset, ou un retard à la formation de 'voids' au cours des cycles. / Phase Change Memories are suitable for the next generation of non volatiles memories due to high programmation speed and endurance. However, two major improvements need to be made in order to enter memories market, the short retention time at high temperature, and the important electric consumption. This thesis focuses on the development of new phase change materials to replace the reference material, Ge2Sb2Te5, insuitable for embedded memories applications working at high temperatures. The behavior of binary compounds GeTe and GeSb has been investigated and compared to the reference material during both the crystallization of the « as deposited » amorphous and the « melt quenched » amorphous materials. Indeeed it is important to study the « melt quenched » amorphous state of the material to be as close as possible to the cycled material in the devices. So, the crystallization mechanism of GeTe checked by the crystallization study of the amorphous « melt quenched » by laser annealing is in agreement with the in situ TEM observation (thermal annealing) of the crystallization. The addition of “doping” elements in the binary compounds has also been performed to improve the thermal stability of amorphous undoped materials. These “doping” elements allow a current reset decrease, or a later formation of « voids » during cycling.

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