Determinar o conteúdo dos lipídeos presentes nos tecidos animais nem sempre resulta em uma resposta com precisão, devido á pouca disponibilidade de métodos adequados para a extração e determinação quantitativa destes lipídeos. A extração de lipídeos de matrizes complexas, como o pescado, por meio dos métodos tradicionais de Bligh & Dyer e Folch normalmente utilizam solventes com elevada toxicidade, cujos resíduos podem gerar um elevado impacto ambiental. A chamada segurança química está diretamente ligada à qualidade de vida e alerta para as questões de controle e prevenção dos efeitos adversos dos solventes ao ser humano e ao ambiente, compreendendo desde a extração, uso e descarte desses e seus resíduos. Portanto, o objetivo deste trabalho foi estudar as condições de extração de lipídeos totais de resíduos do processamento de tilápias, visando à proposição de um método alternativo que garanta uma eficiência tão satisfatória quanto as obtidas pelos métodos tradicionais de extração. Ademais, foi desenvolvido um método de extração mais seguro ao ambiente utilizando solventes menos tóxicos que os propostos pelo método de Bligh &Dyer, por meio da aplicação experimental de um diagrama de fases hexano- etanol- água. Após a identificação da melhor combinação de solventes, os extratos obtidos com hexano- etanol apresentaram rendimento eficiente em lipídeos totais e capacidade de extrair os componentes lipídicos polares e apolares das amostras analisadas. O melhor aproveitamento dos lipídeos a serem extraídos da matriz resíduos de peixes na proporção em massa de solvente hexano: etanol: água, foram da solução 1 (1: 7: 1,375) para a carcaça, da solução 2 (1: 2,5: 1,1875) para a cabeça e da solução 4 (4: 1: 4,375) para as vísceras totalizando 14,13%, 14,69 e 47,63% de teor de lipídeos, respectivamente. Logo, ao buscar sistemas de solventes alternativos ao clorofórmio - metanol, para extrair lipídeos de resíduos do processamento de tilápias, foi possível identificar as melhores proporções de hexano: etanol: água como substituição do método tradicional proposto por Bligh & Dyer (1959). / The total lipid content of animal tissues is not always accurately measured due to the lack of adequate methods for lipid extraction and quantitative determination of tissue fat. The extraction of lipids from complex matrices, such as fish, using the traditional methods proposed by Bligh &Dyer and Folch usually, employs solvents with high toxicity, whose residues can generate a high environmental impact. The chemical safety concern nowadays is directly linked to quality of life involving control and prevention of adverse effects of solvents to humans and the environment, ranging from the extraction, use and disposal of these and their residues. Moreover, the procedures of sample preparation, the sample: solvent ratio, the proportion of solvents applied, and the order of addition of solvents during the experiment are not standardized in these methods. Therefore, the present study aimed to assess the extraction conditions of total lipids from fish processing residues, and thus propose a standardized method which ensures a maximum efficiency in lipid extraction. Furthermore, a more environmental-friendly oil extraction method using less toxic solvents than those proposed by the Bligh & Dyer method (i.e. using the hexane-ethanol-water phase diagram) was developed. After identifying the best combination of solvents, the extracts obtained with hexane- ethanol showed effective yield on total lipids and the ability to extract the polar lipid components and nonpolar of the samples. The best use of lipids to be extracted from fish waste matrix, were the solution 1 (1: 7: 1,375) for the carcass of solution 2 (1: 2,5: 1,1875) for the head and the solution 4 (4: 1: 4,375) for the viscera totaling 14,13%, 14,69% and 47,63%(4: 1: 4,375) respectively. Therefore, to seek alternative solvent systems chloroform - methanol to extract lipids of tilapia processing waste, it was possible to identify the best proportions of hexane: ethanol: water as replacing the traditional method proposed by Bligh & Dyer (1959).

Heusler compounds form a large class of intermetallic materials, which attracted a lot of interest in recent years. The reason is their enormous flexibility, which makes it possible to observe almost every physical effect in one of the 1000 members known nowadays. Especially many magnetic Heusler compounds display promising properties, which offer potential application in fields like rare-earth free permanent magnets, magnetocalorics, spin transfer torque devices and tunnel junctions. Apart from that, magnetic Heusler systems are also interesting for fundamental research since some members host skyrmion lattices and other magnetically complex orders. The search for new Heusler compounds is therefore fruitful in many ways. Accordingly, the present thesis followed the approach of synthesizing and characterizing such Heusler compounds that were either entirely new or had unexplored magnetic properties. Exactly this second approach was demonstrated in Chapter 3, namely for IrMnGa. With help of combined neutron and x-ray diffraction experiments it was possible to correct the structural model from literature and show that the compound crystallizes indeed within the half-Heusler space group but with a substantial degree of Y -disorder. In contrast to older suggestions, the subsequent magnetic characterization revealed a robust canonical spin glass state instead of antiferromagnetic order. The magnetic phase diagram was found to be similar to Au1−xFex and thus hinted on a Heisenberg-like spin glass with considerable anisotropy. Contrary to synthesis route and heat treatment, changing the composition allowed to tune the spin glass state extensively. Increasing the Mn content caused a transition from spin to cluster glass behavior and for Mn contents above 40 at%, it was even possible to introduce ferrimagnetic order. Notably, the composition dependence of spin glasses was only studied for binary systems before. It turned out that many trends are quite similar for the Ir-Mn-Ga ternary scenario with the exception of magnetic behavior near the percolation limit being more complex. Generally, spin glass order is rather rare in Heusler compounds and especially for half-Heusler systems a report remained elusive up to IrMnGa. Chapter 4 then summarized investigations on the Heusler series Fe3−xMnxSi, which features a spin reorientation transition at low temperatures. Despite being one of the most studied Heusler systems, the magnetotransport properties were not yet covered systematically in literature. The presented investigations unveiled that the mechanisms of longitudinal as well as Hall resistivity change upon cooling through the spin reorientation transition. For the Hall effect, skew scattering dominates above TR whereas it is the intrinsic mechanism below. The finding emphasizes the dependency of the intrinsic Hall contribution on the magnetic structure and it should be possible to generalize this change of the Hall mechanism to all magnetic transitions, where the intrinsic contribution is affected. The subsequent Chapter 5 provided a reevaluation of the Fe-Mn-Si phase diagram. The approach seemed well justified since the obtained phase boundaries agreed better with theory than the old experimental studies. Furthermore, it was found that those compounds, which were previously identified as β-Mn, actually crystallize in a superstructure. The ordered version has a Mn3IrSi as prototype and derives from β-Mn by splitting of the 8c site into two 4a sites. Due to the close relation of both structures, this phase was named β’-Mn. Moreover, it turned out that the ’mysterious’ secondary phase, which was mentioned for Mn-rich Fe3−xMnxSi Heusler compounds but never specified, is given exactly by β’-Mn. The investigations of its magnetic properties indicated a transition to a canonical spin glass state at low temperatures. β’-Mn thus adds a further type of magnetic ordering to the Fe-Mn-Si system. Indeed, the latter comprised all kinds of solid state magnetism but no spin glass order was reported before. Finally, the spin glass state was demonstrated to exhibit a similar composition dependence as in Ir-Mn-Ga, which illustrated nicely the universal character of the spin glass concept. The last chapter dealt with the difficult search for entirely new Heusler compounds. It was explained that high-throughput studies struggle to predict phase stabilities, which is why they have to be treated with care. To overcome these issues, some design rules were suggested to evaluate whether a Heusler compound is likely to be experimentally stable or not. Usually, there are no reports for systems, which do not form as single phase. Since this is a highly inefficient habit, 26 multi-phase ’Heusler compounds’ were listed. In the end of the chapter, the successful synthesis of three new compounds was presented, namely Ru2CrAl, Ru2CrGa and Ru2CrSb. Ru2CrGa was identified as Pauli paramagnet whereas Ru2CrSb exhibited an antiferromagnetic transition around 100 K. A second transition at 40 K was accompanied by a small increase of magnetization, which hinted on some more complex magnetic structure at low temperatures.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22777号 / 工博第4776号 / 新制||工||1747(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 乾 晴行, 教授 安田 秀幸, 教授 辻 伸泰 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

The main focus in the present work concerns calculations on steel/slag equilibria. Thermodynamic software and databases are now powerful and accurate enough to give reliable results when applied to complex metallurgical processes. One example is the decarburization process of high alloyed steels. It is shown that using advanced thermodynamic models, without a complicated kinetic description of the system, reasonable agreement with experimental data is obtained. The calculations are performed using the Thermo-Calc software. Within this work a Java interface for Thermo-Calc has been implemented. Java gives graphical possibilities and a graphical interface has been created that facilitates calculations that involve both metallic phases as well as oxides and make them feasible also for an industrial user. / QC 20101118

Wir untersuchen die Phasenbildung von Festkörperlösungen von (InxGa1-x)2O3 experimentell mittels Transmissionselektronenmikroskopie und stützen uns bei der Modellierung auf die Clusterexpansion. Epitaktische (InxGa1-x)2O3 Schichten auf kristallinen Substrate sind durch ausgeprägte Ordnung auf den Kationenuntergittern gekennzeichnet, bei welchem In und Ga sich auf Gitterplätze einbauen auf denen sie die energetisch günstigste Koordination zum Sauerstoff einnehmen. Ausgehend von diesem Befund, modifizieren wir das Modells der idealen Mischung so dass wir die Konfigurationsentropie auf den kationischen Untergittern mit spezifischer Koordinations getrennt betrachten um diese realistisch zu berechnen. Das resultierende Phasendiagramm ist durch enge thermodynamisch Stabilitätsbereiche für die jeweiligen Phasen gekennzeichnet, weil sich gleichzeitig große metastabile Zusammensetzungsbereiche ergeben bei Temperaturen die typisch für epitaktisches Wachstum sind: so ist die monokline Phase im Zusammensetzungsbereich x<0.5 metastabil, die hexagonale Phase für 0.55<x<0.7 und die kubische Bixbyit-Phase für x>0.91. Wird amorphes (InxGa1-x)2O3 kristallisiert in-situ im TEM, bildet sich im Zusammensetzungbereich bis x<0.22 die Spinellphase, die als ungeordnete Variante der monoklinen Phase beschrieben wird. Oberhalb dieser Zusammensetzung ist die kubische Phase stabil. Ursache hierfür ist der Einfluss der maximale Menge an Konfiguartionsentropie auf die Bildungsenthalpie in Strukturen mit vielfältigem Koordinationsumgebungen der Kationen. Der letzte Teil der Arbeit befasst sich mit dem Einflusses der Gitterordnung auf den Materialkontrast bei der Abbildung mittels HAADF (High Angle Annular Dark Field) STEM. Hier wird gezeigt, dass die Anregung des 2s-Bloch-Wellen-Zustands zu langperiodsichen Kontrastoszillationen führt, die die quantitaive Bestimmung der Zusammensetzung mittels Z-Kontrast erschwert es aber erlaubt den Ordnungsparameter bei bekaannter Zusammensetzung zu messen. / We investigate the phase formation in (InxGa1-x)2O3 solid solutions experimentally by means of transmission electron microscopy (TEM) and with computational support using cluster expansion. In the case of epitaxial growth on crystalline substrates, we find strong ordering on the cation sublattices of (InxGa1-x)2O3, energetically driven by the tendency of In and Ga to each assume their preferred coordination environment. Based on this experimental finding, we modify the model of the ideal mixture by considering the configurational entropy on the respective cation sublattices with different coordination separately in order to calculate it realistically. The resulting phase diagram is characterized by narrow thermodynamically stable ranges for each phase, while wide composition ranges of metastable compounds are predicted, which can be achieved at temperatures typical for epitaxy: the monoclinic phase is metastable in the composition range x<0.5, the hexagonal phase for 0.55<x<0.7, and the cubic bixbyite phase for x>0.91. If amorphous (InxGa1-x)2O3 is crystallized in-situ in the TEM, the spinel phase, which is described as a disordered variant of the monoclinic phase, is formed in the composition range up to x<0.22, while above this composition, the bixbyite phase is stable. This shift in stability is explained by the maximum amount of configurational entropy present during crystallization, which strongly influences the formation enthalpy in structures with diverse coordination environments of the cations. The last part of the work deals with the influence of the lattice order on the material contrast when imaging by HAADF (High Angle Annular Dark Field) STEM. It is shown that the excitation of the 2s-Bloch wave state leads to long-period contrast oscillations, which complicate the quantitative determination of the composition by Z-contrast but allows to quantify the order parameter for a given composition.

<p>  </p> <p>Metallic uranium-zirconium (U-Zr) nuclear fuel is a primary candidate for future fast reactors. The U-Zr system has been studied for decades with thousands of fuel pins being irradiated, yet the phase boundaries and lattice evolution with respect to temperature and composition remain poorly quantified. Historic engineering scale testing has resulted in empirical models for fuel evolution and subsequent fuel performance. However, these historic tests are on a convoluted system, consisting of dynamic temperatures, evolving thermal gradients, varying irradiation damage and damage rates, evolving compositions via fission and redistribution of primary constituents, and morphological evolution. This system proves exceedingly difficult to describe mechanistically due to the coexistence of various intertwined thermodynamic driving forces (e.g., temperature, composition, fluence, and fission rate which all vary concurrently). The driving forces influence the manifestation of the primary life-limiting phenomena present within the U-Zr system, specifically fuel-cladding mechanical interaction, fuel-cladding chemical interaction, fuel swelling, and fuel constituent redistribution. Although the phenomena present in the U-Zr system are known and qualitatively described, they are lacking in fundamental descriptions due to the historic inability to deconvolve the effects of temperature, composition, and fission rate. This study evaluates the current understanding of U-Zr fuel swelling and constituent redistribution in a uniquely quantified manner using Phenomena Identification and Ranking Tables. </p> <p><br></p> <p>In response to these findings, a novel separate effects irradiation test vehicle, housing uniquely fabricated U-Zr alloys, was proposed, developed, and successfully fabricated to provide the community with a means to decouple temperature, composition, initial microstructure, and fission rate from one-another. Initial out-of-pile characterization was conducted with scanning electron microscopy, transmission electron microscopy, and neutron diffraction with in-situ heating on various U-Zr alloys (U- 6, 10, 20, and 30 wt.% Zr). This work quantifies the initial microstructure throughout the fabrication process and the thermal response of the material. Results include the phase morphology, phase boundaries, absolute lattice parameters, and lattice specific coefficients of thermal expansion. The phase boundaries identified in this study were then used to develop a new U-Zr phase diagram. The isolation of thermal and compositional dependencies furthers the understanding of the fuel system and can be used to increase fuel longevity.</p>

Le biogaz, constitué essentiellement de méthane et de dioxyde de carbone, représente une voie alternative aux sources d’énergies fossiles. Pour être valorisé le mélange doit être séparé dans un procédé de séparation de gaz. Ces dernières années, un nouveau procédé basé sur la formation d'hydrates de gaz (GSHF) a suscité une attention particulière dans la communauté scientifique. Basé sur une transition de phase hydrate – liquide – vapeur conduite en présence de promoteurs thermodynamiques, la purification est supposée demander moins d’énergie et moins de réactifs dangereux pour l’environnement que les procédés chimiques traditionnels comme l’absorption dans des solutions d’amines. Une connaissance des équilibres de phase dans les systèmes eau + gaz + additifs est essentielle à la validation du procédé. Dans ce projet, nous avons étudié quatre promoteurs, le bromure de trétrabutylammonium (TBAB), le bromure de tétrabutylphosphonium (TBPB), l’oxyde de tributylphosphine (TBPO) et le tétrahydropyrane (THP), qui ont pour buts d’abaisser la consommation d'énergie et d’améliorer la cinétique et la sélectivité du procédé. Une partie de ce projet a été consacrée à déterminer les conditions d'équilibre d'hydrates de gaz en présence de ces promoteurs et différentes phases gaz (CO2, CH4 et biogaz simulé). Les méthodes de calorimétrie différentielle à balayage (DSC) ont été appliquées pour mesurer les températures de transition de phase. De nouvelles données d'équilibre de phases ont été déterminées pour les systèmes hydrates de gaz + promoteurs. Dans la deuxième partie du projet, nous avons effectué des mesures quantitatives dans un réacteur instrumenté afin d'évaluer le procédé GSFH pour la valorisation du biogaz. Chaque promoteur a été évalué tant sur le plan de la cinétique (temps, d’induction, vitesse de croissance cristalline) que sur celui de la thermodynamique (quantité de gaz piégé, sélectivité). L'optimisation du programme de formation / dissociation des hydrates a montré d'excellents résultats en termes de cinétique. / Biogas represents an alternative path to fossil energies. It is composed mainly by methane and carbon dioxide. This couple must be separated in a gas separation process. In recent years, the new process based on gas hydrate formation (GSHF) has taken special attention in academic community. Besides, the use of thermodynamic promoters can increase the efficiency of the process. Since GSFH is based on phase transition phenomenon, knowledge about phase equilibria is essential. In this project, we have selected and studied four thermodynamic promoters (tretrabutylammonium bromide / TBAB; tetrabutylphosphonium bromide / TBPB; tributylphosphine oxide / TBPO; tetrahydropyran / THP) that have potential to improve GSFH process of biogas in terms of stability gain (less energy consumption), kinetics and selectivity. One part of this project consisted in determining the gas hydrate equilibrium conditions involving these promoters and the different gas phases (CO2, CH4 and simulated biogas). Differential scanning calorimetry (DSC) methods were applied to measure the phase transition temperatures. Therefore, new phase equilibrium data were determined for the promoter/gas hydrate systems. In the second part of the project, we carried out quantitative measurements in an instrumented reactor in order to evaluate the GSFH process for upgrading biogas. Each promoter was evaluated in kinetics and thermodynamics aspects, such as crystal growth rate, amount of gas trapped into the hydrate phase, and selectivity. The optimization of the hydrate formation / dissociation cycle showed excellent results in terms of kinetics improvement.

No description available.

The work presented has the ultimate aim to increase dynamic mechanical properties by improvements in density and optimisation of microstructure of ultra high carbon PM steels by careful selection of processes, i.e. mixing, binding, alloying, heating profile and intelligent heat treatment. ThermoCalc modelling was employed to predict liquid phase amounts for two different powder grades, Astaloy 85Mo or Astaloy CrL with additive elements such as (0.4-0.6wt%)Si, (1.2-1.4wt%)C and (1-1.5wt%)Mn, in the sintering temperature range 1285-1300ºC and such powder mixes were pressed and liquid phase sintered. In high-C steels carbide networks form at the prior particle boundaries, leading to brittleness, unless the steel is heat-treated. To assist the breaking up of these continuous carbide networks, 0.4-0.6% silicon, in the form of silicon carbide, was added. The water gas shift reaction (C + H2O = CO + H2, start from ~500ºC) and Boudouard reaction (from ~500ºC complete ~930ºC) form CO gas in the early part of sintering and can lead to large porosity, which lowers mechanical properties. With the use of careful powder drying, low dew point atmospheres and optimisation of heating profiles, densities in excess of 7.70g/cm3 were attained. The brittle microstructure, containing carbide networks and free of cracks, is transformed by intelligent heat treatment to a tougher one of ferrite plus sub-micron spheroidised carbides. This gives the potential for production of components, which are both tough and suitable for sizing to improve dimensional tolerance. Yield strengths up to 410 MPa, fracture strengths up to 950 MPa and strains of up to 16 % were attained. Forging experiments were subsequently carried out for spheroidised specimens of Fe-0.85Mo+06Si+1.4C, for different strain rates of 10-3, 10-2, 10-1 and 1sec-1 and heated in argon to 700¿C, density ~7.8g/cm3 and 769 MPa yield strength were obtained. / Libyan Education Ministry Office

Biological systems are composed of complex materials which are responsible for performing various functions, such as providing structural support, mobility, functional adaptation to the environment, damage repair, and self-healing. These complex materials display excellent mechanical properties and can rapidly adapt to external stimuli. Thus, nature inspires in terms of source materials, functions, and designs to develop new-generation structural and functional materials. Polymers (natural or synthetic) are excellent sources of developing materials to mimic the functions of soft segments in biological systems. This dissertation focuses on synthesizing and characterizing two different materials with tunable structures and properties: complexes from natural polysaccharides or polyelectrolytes and bioinspired hydrogels from synthetic polymers. Oppositely charged polyelectrolytes can form polyelectrolyte complexes (PECs) due to the electrostatic interactions. The structure and properties of PECs can be tuned by varying the salt concentration, as the addition of salt can facilitate associative phase separation. PECs were prepared from two biopolymers, positively charged chitosan and negatively charged alginate. Rheological experiments for the complexes displayed a tunable shear modulus with changing salt concentrations. The microstructural study conducted using small-angle X-ray scattering provided insights regarding the length scales of these complexes, and the results follow the observed rheological and phase behavior. Elastic biopolymers such as resilin display remarkable mechanical properties, including high stretchability and resilience, which many species exploit in nature for mechanical energy storage to facilitate their movement. Such properties of resilin have been attributed to the balanced combination of hydrophilic and hydrophobic segments present in the chain. In this work, we synthesized hydrogels with hydrophilic and hydrophobic components to mimic the properties of resilin. With this system, we determined the tensile, retraction (ability to revert to the original state after stretching), and swelling properties when (i) the concentration of the hydrophobic polymer was varied and (ii) additional hydrophobic components were included. The stretchability, stiffness, and strength of the gels varied as the compositions were altered. The fundamental understanding of the structure-property-function relationship for materials presented in this work provides insights into engineering materials for applications such as tissue engineering, drug delivery, wound healing, artificial muscles, soft robotics, and power amplification.