This study addresses the critical need for effective thermal management in hypersonic vehicles facing intense heat at their leading edge due to high enthalpy flow. The objective is to propose an active impingement cooling system that ensures the structural stability and performance of these vehicles. This dissertation presents an in-depth exploration of the numerical simulations conducted on the hypersonic leading edge, focusing on a 3mm radius with active cooling utilizing supercritical carbon dioxide (sCO2) as the coolant. The research incorporates conjugate simulations that merge external hypersonic flow and sCO2 active cooling. Utilizing a thermodynamic non-equilibrium two-temperature model and various chemical models, including the 5-species Park's model and the 11-species Gupta's model, separate validations for the external hypersonic flow and internal sCO2 coolant flow were conducted. These validations facilitated combined simulations, underscoring the potential of maintaining metal temperatures within operational limits using sCO2 coolant. A comparative study of the 5- 5-species Park model and 11-species Gupta model demonstrated the former's effectiveness in predicting flow fields at Mach 7. Furthermore, this study shows the effect of varying the coolant tube-to-leading-edge distance (H/D), Thermal barrier coating thickness, and impingement angles, demonstrating improved heat transfer performance through these variations. A key aspect of this work is the exploration of converting hypersonic vehicle heat flux to power using the sCO2 cycle. The conceptual study, illustrated through the Mach 7 case, confirms the feasibility of harnessing power from aerodynamic heat flux, marking a significant progression in the field. This research contributes to the field by offering a detailed analysis of active impingement cooling for hypersonic leading edges, integrating real gas effects and multiple chemical models. The study adds novelty by investigating heat transfer enhancements through iv geometric variations and evaluating sCO2's potential as a coolant, addressing key facets of hypersonic vehicle thermal management.

Ce travail de thèse vise à comprendre les propriétés thermodynamiques et les mécanismes réactionnels engendrés dans les réactions de cycloaddition d'époxydes en milieu CO2 supercritique catalysées par des liquides ioniques pour la synthèse de carbonates cycliques. Les propriétés thermodynamiques (solubilité, gonflement, diagramme de phase) des mélanges binaires époxyde/CO2 ont été déterminées pour des époxydes modèles et des époxydes dérivées d'huiles végétales. Des suivis cinétiques in-situ par spectroscopie IR-TF et Raman ont été effectués pour déterminer l'influence de la nature des liquides ioniques étudiés et des paramètres température-pression sur les cinétiques de réaction. Des modélisations moléculaires de type DFT nous ont permis de proposer un mécanisme réactionnel en accord avec les résultats expérimentaux et de bien comprendre quels sont les rôles respectifs de l'anion et du cation du liquide ionique dans la réaction. / This thesis aims to understand the thermodynamic properties and reaction mechanisms generated in the cycloaddition reaction of epoxides in supercritical CO2 medium catalyzed by ionic liquids for the green synthesis of cyclic carbonates. Thermodynamic properties (solubility, swelling, phase diagram) of epoxide/CO2 binary mixtures were determined for commercial mono-epoxides and vegetable based epoxidized oils. Kinetics study in-situ by FTIR and Raman spectroscopy were performed to determine the influence of the nature of the ionic liquids studied and of different parameters such as temperature and pressure on the reaction. Molecular modeling using DFT method has helped us to propose a reaction mechanism consistent with the experimental results and to understand what are the respective roles of the anion and cation of the ionic liquid in the reaction.

La synthèse de particules polyuréthane par organo-catalyse dans le dioxyde de carbone supercritique a été étudiée. Des réactions modèles ont été préalablement conduites et suivies par spectroscopie infrarouge in situ dans le CO2 supercritique afin d'identifier les catalyseurs organiques de réaction d'uréthanisation les plus efficients. Une série de polymères siliconés CO2-phile, porteurs de la fonction organo-catalytique en bout de chaîne (organo-catasurfs), a ensuite été préparée et testée dans le CO2 supercritique pour la polymérisation en dispersion de polyuréthane. / The organocatalysed synthesis of polyurethane particles in supercritical carbon dioxide has been studied. Model reactions were first carried out in supercritical CO2 and monitored by in situ infrared spectroscopy in order to indentify the most efficient catalysts for the urethanisation reaction. A series of CO2-philic silicone polymers, end-functionalised with the organocatalytic group (organocatasurfs), were then synthesised and tested in supercritical CO2 for the dispersion polymerisation of polyurethane.

Porous metal oxides formed by supercritical carbon dioxide (SCCO2) treatments at low temperature were used for displays, solar cells, and light emitting diodes (LEDs) applications. The SCCO2 fluid, also known as green solvents, exhibits low viscosity, low surface tension and high diffusivity as gases, and high density and solubility same with liquids. In this thesis, we successfully fabricated porous antimony-doped tin oxide (ATO) and porous indium tin oxide (ITO) by the SCCO2 treatments. In addition, the treatment can also be used to improve the work function and surface energy of ITO anode of an organic LED (OLED). The performance of the OLEDs was drastically enhanced in comparison with that of the devices without any ITO surface treatments. First, the porous ATO films were formed by the SCCO2 treatment for absorption of silver molecules in silver electro deposition devices. The porosity, resistivity and average optical transmittance of the porous ATO film in visible wavelength were 43.1%, 3 £[-cm and 90.4%, respectively. For the silver electro deposition devices with the porous ATO film, the transmittance contrast ratio of larger than 12 in visible spectrum was obtained at an operating voltage of 1.5 V. Furthermore, for the 0.25 cm2 device, the switching time of 4.5 seconds was achieved by applying a square-wave voltage ranging from 1.5 to -0.2 V between the electrodes. On the other hand, the porous ITO with low refractive index was prepared by SCCO2/IPA treatment on gel-coated ITO thin films. The high refractive index of the ITO film was achieved by long-throw radio-frequency magnetron sputtering technique at room temperature. The index contrast (£Gn) was higher than 0.6 between porous ITO and sputtered ITO films. The large £Gn is useful for fabricating conductive anti-reflection (AR) and high reflection (HR) structures using the porous ITO on sputtered ITO bilayers. The weighted average reflectance and transmittance of 4.3% and 83.1% were achieved for the double-layer ITO AR electrode with a sheet resistance of 1.1 K£[/¡E. For HR structures, the reflectance and sheet resistance were 87.9% and 35 £[/¡E with 4 periods ITO bilayers. Finally, the SCCO2 treatments with strong oxidizer H2O2 were proposed to modify surface property of ITO anode of a fluorescent OLED. The highest work function and surface energy of 5.5 eV and 74.8 mJ/m2 was achieved by the SCCO2/H2O2 treatment. For the OLED with 15 min SCCO2 treatment at 4000 psi, the turn-on voltage and maximum power efficiency of 6.5 V and 1.94 lm/W were obtained. The power efficiency was 19.3% and 33.8% higher than those of the OLEDs with oxygen plasma treated and as-cleaned ITO anodes.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The use of chemicals, in excessive doses or inadequately, in the control of pests and diseases in agriculture, has promoted environmental damage, contamination of animals, intoxication of farmers, among others. Looking for less aggressive control alternatives, plant extracts have been successfully used and are a differentiated and a promising option for the integrated management in plant protection. These products are considered an alternative for the control of phytopathogens. They do not cause harm to the environment and to living beings. One of the techniques for extracting plant extracts is the extraction wiyh supercritical/pressurized fluids. This thechnology appears as a great option which is economically viable and ecologically correct. Therefore, the main objective of this work was to investigate the potential of extraction of extracts from flowers, leaves, stalks and roots of Lupinus albescens, using pressurized fluids as liquefied petroleum gas (LPG) or supercritical carbon dioxide (CO2). Furthermore, the objective was to evaluate the kinetic parameters, adjusting to a mathematical spline model. Characterization of extracts and evaluation of their potential in biological control, was performed. In the supercritical fluid extraction with CO2 (SFE-CO2) pressure ranged between 150 to 250 bar and temperature ranged between 40 and 60ºC. In the extraction with compressed LPG, these parameters were fixed between 15 and 35 bar and 25 and 45ºC, respectively. The yield of extraction, kinetic parameters, chemical profile and antifungal effect were evaluated. Maximum yield of extract obtained from different matrices was 1.28% in leaves with solvent LPG under 45°C and 15 bar. The chemical profiles were similar for all matrices and solvents investigated, highlighting stigmasterol. With respect to minimum inhibitory concentration, it rang ed from 29.248 to 192.965 μg mL-1. For antifungal tests, all extracts showed inhibitory powers for Fusarium oxysporum and Fusarium verticillioides. Plant extract obtained from roots showed superior inhibition power, as 70.12% (CO2) and 65.12% (LPG) for Fusarium oxysporum, and 67.76% CO2) anda 61.15% (LPG) for Fusarium verticillioides. From the results obtained in this work, it is possible confirm that the supercritical extraction or using pressurized fluid is a promising methodology for obtaining bioactive compounds from Lupinus albescens, which presented antifungal potential for both fungi investigated in this work. / A utilização de produtos químicos, em doses excessivas ou de forma inadequada, no controle de pragas e doenças na agricultura, tem promovido grandes danos ambientais, contaminação de animais, intoxicação de agricultores, entre outros. Buscando alternativas de controle menos agressivas, extratos vegetais têm sido utilizados com sucesso e ressurgem como uma opção diferenciada e promissora para o manejo integrado em proteção de plantas. Estes produtos são considerados uma alternativa de controle de fitopatógenos, demonstrando prósperos resultados, não causando malefícios ao meio ambiente e aos seres vivos. Uma das técnicas de obtenção dos extratos vegetais é a extração por fluidos supercríticos/pressurizados que também aparece como ótima opção de tecnologia economicamente viável e ecologicamente correta. Portanto, o objetivo principal deste trabalho foi investigar o potencial da extração das flores, folhas, caules e raízes de Lupinus albescens, a partir da técnica da extração por fluidos pressurizados ou em condições supercríticas utilizando gás liquefeito de petróleo (GLP) e dióxido de carbono (CO2) como solventes, bem como avaliar os parâmetros cinéticos, adequando ao ajuste matemático. Realizou-se também a caracterização dos extratos obtidos e avaliação do seu potencial no controle biológico. Na extração supercrítica foram utilizados dióxido de carbono no estado supercrítico (EFS-CO2) e gás liquefeito de petróleo pressurizado. Na EFS-CO2 os valores de pressão investigadas foram fixados entre 150 a 250 bar e os valores da temperatura entre 40 e 60ºC; já para a extração com GLP pressurizado, estes parâmetros foram fixados entre 15 e 35 bar e 25 e 45ºC, respectivamente, sendo avaliados o rendimento de extração, os parâmetros cinéticos, o perfil químico e efeito antifúngico. O rendimento máximo de extrato obtido nas diferentes matrizes foi de 1,28% na folha com o solvente GLP nas condições de 45°C e 15 bar. Os perfis químicos foram semelhantes para todas as matrizes e solventes investigados, destacando-se o composto estigmasterol, em relação à concentração inibitória mínima que variou de 29,248 à 192,965 μg/ml-1. Para os testes antifúngicos, todos os extratos apresentaram poderes inibitórios para Fusarium oxysporum e Fusarium verticillioides. O extrato vegetal obtido a partir da raiz apresentou poder de inibição superior, para Fusarium oxysporum de 70,12% (CO2) e 65,12% (GLP) de inibição, e para Fusarium verticillioides de 67,76% (CO2) e 61,15% (GLP). A partir dos resultados obtidos neste trabalho, os mesmos confirmam que a extração supercrítica ou utilizando fluido pressurizado é uma metodologia promissora na obtenção de compostos bioativos de Lupinus albescens, sendo que o extrato apresentou potencial antifúngico para ambos os fungos investigados neste trabalho.

Recently, the supercritical carbon dioxide (s-CO2) Brayton cycle has been identified as a promising candidate for solar-thermal energy conversion due to its potentially high thermal efficiency (50%, for turbine inlet temperatures of ~ 1000 K). Realization of such a system requires development of solar receivers which can raise the temperature of s-CO2 by over 200 K, to a receiver outlet temperature of 1000 K. Volumetric receivers are an attractive alternative to tubular receivers due to their geometry, functionality and reduced thermal losses. A concept of a ceramic pressurized volumetric receiver for s-CO2 has been developed in this work. Computational Fluid Dynamics (CFD) analysis along with a Discrete Ordinate method (DOM) radiation heat transfer model has been carried out, and the results for temperature distribution in the receiver and the resulting thermal efficiency are presented. Issues regarding material selection for the absorber structure, window, coating, receiver body and insulation are also addressed. A modular small scale prototype with 0.5 kWth solar heat input has been designed. The design of a small scale s-CO2 loop for testing this receiver module is also presented in this work. There is a lot of ongoing investigation for design and simulation of different configurations of heat exchangers and solar receivers using s-CO2 as the working fluid, in which wall temperatures up to 1000 K are encountered. While CO2 is considered to be transparent as far as solar radiation spectrum is concerned, there may be considerable absorption of radiation in the longer wavelength range associated with radiation emission from the heated cavity walls and tubes inside the receivers. An attempt has been made, in this study, to include radiation modelling to capture the effect of absorption bands of s-CO2 and the radiative heat transfer among the equipment surfaces. As a case study, a numerical study has been performed to evaluate the contribution of radiative heat transfer as compared to convection and conduction, for s-CO2 flow through a circular pipe. The intent is to provide a guideline for future research to determine the conditions for which radiation heat transfer modelling inside the pipe can be significant, and what errors can be expected otherwise. The effect of parameters such as Reynolds number, pipe diameter, length to diameter ratio, wall emissivity and total wall heat flux has been studied. The effect of radiation modelling on wall temperatures attained for certain amount of heat flux to be transferred to s-CO2 is also studied. The resulting temperature distribution, in turn, affects the estimation of heat loss to the environment

La méthode microgravimétrique statique a permis d’observer que la pulpe de l’aiélé est plus hygroscopique que l’amande de karité à 25°C. A l’inverse, on fait l’observation contraire entre 35 et 55°C. Le modèle d’Oswin décrit le mieux les données de sorption des deux produits sur toute la gamme d’activité de l’eau. Les isothermes de l’amande de karité et de la pulpe de l’aiélé présentent le phénomène d’hystérésis entre 25 et 55°C. La conservation de ces oléagineux doit s’effectuer dans une atmosphère d’humidité relative comprise entre 40 et 60% afin d’obtenir des teneurs en eau recommandées. Un modèle adapté de prédiction des isothermes de sorption de ces oléagineux en deçà de 25°C et au delà de 55°C a été obtenu. L’extraction de la matière grasse au CO2 supercritique donne des rendements inférieurs à ceux obtenus de l’extraction à l’hexane. L’indice d’acide des matières grasses extraites au CO2 est supérieur à celui des lipides extraits à l’hexane. Ces indices, pour les lipides extraits des produits stockés à 18°C, sont les plus élevés. Quelque soient le mode de stockage et le solvant d’extraction, l’indice d’iode baisse avec le stockage. Le CO2 présente une sélectivité vis-à-vis de l’acide linolénique. Les lipides extraits au CO2 présentent les taux d’acides gras libres les plus élevés. Il ressort des résultats que le stockage -33°C est le meilleur. Toutefois, il ne doit pas dépasser 5 mois. L’extraction des lipides au CO2 supercritique doit utiliser les fruits frais ou stockés à -33°C. Les produits stockés à 18°C sont les plus durs et la dureté est corrélée négativement à la teneur en eau, mais positivement à l’indice d’acide des matières grasses extraites / The static microgravimetric method permitted to observe that the Canarium pulp was more hygroscopic at 25°C than the sheanut kernels. On the other hand, sheanut kernel was more hygrocopic in the temperature range 35°C-55°C. The Oswin model best described the sorption data of the two products in the whole water activity range. Hysteresis was observed in the entire temperature range 25-55°C for sheanut kernel and Canarium pulp. It is suggested that these products should be stored in an environment with a relative humidity of 40-60%, in order to attain the recommended moisture content for storage. A model was adapted to predict the sorption isotherms of shea and Canarium below 25°C and above 55°C. The oil yields obtained with supercritical CO2 were lower than those obtained with hexane. The acid values of butter and oil extracted with carbon dioxide were greater than those of lipids extracted using hexane. The acid values of samples stored at 18°C were the largest. The iodine value of the oils decreased with an increase of the storage period, irrespective of the storage temperature and the solvent used for extraction. The extraction with CO2 did not extract linolenic acid. The proportion of free fatty acids increased when carbon dioxide was used for extraction. From the foregoing, it is suggested that storage at -33°C for up to 5 months presents the best means of preserving these products. Only fresh or fruits stored at -33°C should be used for the extraction of lipids using carbon dioxide. The products stored at 18°C were the most hard and the hardness was correlated negatively to the water content, but positively to the acid value of fatty material extracted

Background: As a company it is more important than ever to consider the environmental sustainability aspect within the whole supply chain and all the stakeholders. Studies show that people's concerns about environmental sustainability increases and will continue to grow in the future. The wet dyeing process is the part of the textile production that consists of liquor and contains three main steps which are pretreatment, coloration and finishing. This process is presented as the most water, energy and chemicals consuming process within the textile industry and because of that, it is important to investigate it to be able to improve the environmental sustainability.  Purpose: The purpose of the thesis is to increase the understanding of IKEA’s suppliers' current usage of water, energy and chemicals within the wet dyeing process. Followed by an identification of opportunities for improvements in the wet dyeing process, aiming to become more environmentally sustainable.  Method: Through interviews with two suppliers, information regarding IKEA’s current wet dyeing processes will be collected. After that, data from relevant theoretical sources will be collected to analyze possible improvements of methods and colorants that can be relevant for IKEA as well as other companies within the textile industry to implement.  Conclusion: For research question 1, the researchers reach the conclusion that IKEA’s supplier number one has a more environmentally sustainable wet dyeing process compared to the second supplier.. A conclusion is nevertheless drawn that improvements within both suppliers wet dyeing processes should be considered to become more environmentally sustainable. For research question 2, the researchers come to the conclusion that Spray dyeing is the best alternative method to implement for improving environmental sustainability within the wet dyeing process. The researchers also recommend companies to actively become a part of the development of bacterial colorants, the future of coloration.

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La vaste gamme de combinaisons possibles de cations et anions, ainsi que les excellentes propriétés intrinsèques des liquides ioniques (LIs) peuvent être considérées comme les principaux facteurs qui ont conduit au développement d’une recherche utilisant des LIs comme additifs des matériaux polymère. Ainsi, l'objectif principal de ce travail est d'explorer le rôle de la nature du cation et/ou du anion du LI sur les propriétés des matériaux basées de poly (méthacrylate de méthyle) (PMMA). Dans une première partie, des LIs de type imidazolium et ammonium ont été incorporés au PMMA et des caractérisations morphologiques et structurales ont été effectuées afin de comprendre leur impact sur les propriétés thermiques, viscoélastiques et mécaniques des matériaux résultants. Dans la section suivante, la capacité de ces LIs à base d'imidazolium et d'ammonium en tant qu’agents interfaciaux à la surface de la silice a été évaluée. Sub-micro et nanoparticules de silice, ainsi que les LIs, ont été incorporées dans une matrice de PMMA afin de préparer des composites. L'amélioration des propriétés des matériaux ont été discutées en fonction du degré auquel chaque LI influence la compatibilité entre les particules et la matrice polymère. De plus, ces composites ont été exposés au dioxyde de carbone en état supercritique (scCO2) pour utiliser celui-ci comme agent moussant et ainsi produire des matériaux expansés. Le rôle du LI et des particules de silice pour structurer les matériaux expansés a été analysé. Dans la dernière partie de cette étude, le scCO2 est utilisé comme milieu de réaction pour la modification chimique par greffage de la surface des nanoparticules de silice par des LIs de type imidazolium, contenant également des groupes hydrolysables et différentes chaînes alkyles. Le rôle de la pression et la quantité de LI ajoutées au milieu de réaction, ainsi que la longueur de la chaîne alkyle des LIs se sont avérées essentielles pour contrôler le degré de fonctionnalisation des nanoparticules. Enfin, ces nanoparticules modifiées ont été incorporées dans une matrice PMMA. Des analyses de morphologie ont été utilisées pour évaluer la dispersion des particules dans la matrice et les propriétés physico-chimiques de ces matériaux ont été également étudiées. / The large array of cation/anion combinations, and the excellent intrinsic properties of ionic liquids (ILs) open a large range of possibilities in their use as additives to polymer materials. Thus, the main objective of this work is to explore the role of both the cation and anion of a series of ILs on the properties of poly(methyl methacrylate) (PMMA)-based materials. In a first approach, low amounts of imidazolium and ammonium-based ILs were incorporated as additives to PMMA in the molten state. Morphological and structural characterizations were developed in order to understand the impact of the presence of such ILs on the thermal and mechanical properties of the resulting materials. Then, in the following section, the ability of the same imidazolium and ammonium-based ILs as physical modifiers of silica surface was evaluated. In such an approach, ILs were supposed to act as interfacial agents. Sub-micron and nanosize silica particles were used to prepare PMMA composites. Thus, the extents of each IL improve the interfacial interaction between PMMA and silica particles were discussed. In addition, supercritical carbon dioxide (scCO2) was used as foaming agent to produce foamed PMMA-based composites. In such a case, the combined effect of the presence of ILs and silica particles was analyzed regarding the morphology of the foamed structures. In the last section, scCO2 was used as reaction medium, in an environmental friendly approach, to chemically modify silica nanoparticles using a series of imidazolium IL-functionalized silanes (with different alkyl chain lengths). Thermogravimetric analysis (TGA) was used to highlight the effect of the working pressure and the content of such ILs in the reaction medium. The effect of the alkyl chain length on the grafting density of the resulting nanoparticles was also discussed. Finally, novel PMMA-based nanocomposites were prepared by the incorporation of such grafted nanoparticles. Transmission electron microscopy (TEM) and small-angle neutron scattering (SANS) analyses were used to evaluate the state of dispersion of the particles into the polymer matrix. Moreover, the thermal, rheological and mechanical properties of the materials were studied.