No / Using fugacity coefficient of a cubic equation of state, Henry’s law constant of a solute in a solvent isincorporated into binary interaction parameter of the classical attractive parameter mixing rule. Thedeveloped equation is a function of temperature. The binary interaction parameter is evaluated by purecomponent critical properties and acentric factors of the solute and the solvent and the Henry’s lawconstant of the solute in the solvent. The developed model accurately describes the solubility of gasesincluding methane, ethane, nitrogen, carbon dioxide and hydrogen sulphide in heavy n-alkanes from lowto high pressure for wide range of temperature. The solubility of methane and carbon dioxide in wateris also predicted adequately.

No description available.

Microbial cell disruption using pressurized gas is a promising approach to improve the lipid extraction yield directly from the wet biomass by eliminating the energy-intensive drying process, which is an integral part of traditional methods. As the process starts with the solubilization of the gas in lipid-rich microbial cells, it is important to understand the solubility of different potential gases in both lipid (triglyceride) and lipid-rich microbial cell culture to design efficient cell disruption processes. In this study, we determined the solubility of different gases (e.g., CO2, CH4, N2, and Ar) in canola oil (triglyceride) using a pressure drop gas apparatus developed in our laboratory. The solubility of different gases in triglyceride followed the trend CO2 > CH4 > Ar > N2. Since the solubility of CO2 was found to be higher compared to other gases, the solubility of CO2 in lipid rich cell culture, cell culture media, and spent media was also determined. It was found that CO2 is more soluble in triglycerides, but less soluble in lipid-rich cell culture compared to CO2 in water. From both thermodynamic models and Monte Carlo simulations, the correlated solubility was found to be in good agreement with the experimental results. CO2 was found to be the most suitable gas for microbial cell disruption because almost 100% cell death occurred when using CO2 whereas more than 85% cells were found to be active after treatment with CH4, N2, and Ar. The optimization of microbial cell disruption was conducted using the combination of Box-Behnken design of experiment (DOE) technique and response surface methodology. The optimized cell disruption conditions were found to be 3900 kPa, 296.5 K, 360 min, and 325 rpm where almost 100% cell death was predicted from the statistical modeling. Finally, it was found that 86% of the total lipid content can be recovered from the wet biomass after treatment with pressurized CO2 under optimized conditions compared to control where up to 74% of the total lipid content can be recovered resulting in 12% increase in the lipid extraction yield using pressurized CO2.

Experiments on the production of porous metallic materials were performed on Fe-base and Al-base alloys. The method involves dissolution of gases in the liquid state and solidification at various cooling rates. The alloy compositions were selected to induce solidification of primary particles intended to control the pore distribution. For the Fe-base alloys, nitrogen was introduced into the melt by dissolution of chromium nitride powder. Fe-Cr-Mn-Si-C alloys featuring M7C3 carbide particles were selected. For the Al-base alloys, hydrogen gas was dissolved into the melt by decomposition of water vapor. Al-Ti and Al-Fe alloys featuring primary Al3Ti and Al3Fe intermetallic particles, respectively, were considered. In the Fe-base alloys, a homogeneous distribution of gas pores through the specimens’ volume was obtained at high cooling rate (water quenching) and after introduction of external nucleating agents. In the case of the Al-base alloys, a good pore distribution was observed at all cooling rates and without addition of nucleating agents. Calculations of the variation of nitrogen (respectively hydrogen) solubility based on Wagner interaction parameters suggest that pore nucleation and growth occur during precipitation of the primary particles (M7C3 carbides, Al3Ti or Al3Fe intermetallics), due to composition changes in the melt and resultant supersaturation with gas atoms. Microscopic analyses revealed that the primary particles control the pore growth in the melt and act as barriers between adjacent pores, thereby preventing pore coalescence and promoting a fine pore distribution. Uniaxial compression testing of the porous Al-Ti and Al-Fe materials showed the typical compressive behavior of cellular metals. Further work is needed to improve the quality and reproducibility of the porous structures which can possibly be used in energy absorption or load-bearing applications. As a corollary result of the quenching of hypereutectic Fe-Cr-Mn-Si-C alloys in the experiments of synthesis of porous metals, a homogeneous featureless structure was observed in some parts of the samples, instead of the equilibrium structure of M7C3 and eutectic phases. Subsequent investigations on rapid solidification of Fe-base alloys at various alloy compositions and cooling rates led to the formation of a single-phase structure for the composition Fe-8Cr-6Mn-5Mo-5Si-3.2C (wt.%), at relatively low cooling rates (≈103 K/s) and for large sample dimensions (2.85 mm). The single phase, which is likely to be the hcp ɛ-phase, was found to decompose into a finely distributed structure of bainite and carbides at ≈600 °C. The annealed structure showed very high hardness values (850 to 1200 HV), which could be exploited in the development of high-strength Fe-base materials. / QC 20100809

Studying clathrate hydrates is, ideally, a simple task: one just have to keep water under a gas pressure. However, when trying to collect measurements in an accurate and repeatable way, things mess up. When, in particular, kinetic characterizations are required, not only pressure and temperature have to be measured: also particular parameters such as gas evolved/trapped during time, heat released/adsorbed during time, critical phenomena related to additive addition, etc, should be collected in a finer way. In the last years a growing interest has been devoted to investigations on the effects of a wide range of compounds capable to affect the thermodynamics and, in particular, kinetics of clathrate hydrate formation. The study of the effects of these compounds, called conditioners, requires an improvement of the performances of usual lab facilities by introducing a new strategy for the measurement of further characterizing parameters. Presently no standardization of the apparatus designed for clathrate hydrate studies exists, nor any commercial instrumentations are available. Generally, apparatus used are custom-made by the same research team according with the peculiar research requirements To do this we have designed, built, calibrated and tested a novel apparatus that, in addition to the ability of measuring usually unexplored parameters, is based on the idea of obtaining as many parameters as possible in a single formation batch. This in order to solve the problem of collecting a dataset that can be processed homogeneously, thus minimizing errors due stochastic behaviours. Using such an apparatus, several kinds of measurement are presented here, which are related directly to the clathrate hydrate investigation fields, but also more generally related to the study of equilibrium phases involving gaseous components.

Le fonctionnement des batteries lithium-ion, qu’il soit normal ou dans des conditions abusives, est accompagné d’une génération de gaz en particulier lors des premiers cycles. Celle-ci est intrinsèque au dispositif et est soumise à de nombreux paramètres tels que les matériaux d’électrodes utilisés, l’électrolyte ou encore les conditions opératoires. Cette génération de gaz est délétère : elle conduit à l’augmentation de la pression interne des batteries et pose donc des problèmes de sécurité. Cette étude vise à quantifier les volumes de gaz générés et à comprendre les mécanismes liés à la surpression dans les batteries. A cet effet, le format de batterie « pouch cell » a été adopté tout au long de ce travail de thèse. L’électrolyte choisi est le mélange EC:PC:3DMC + 1 mol.L-1 LiPF6. La première partie de ce travail est dédiée à la mise au point d’un protocole expérimental basé sur (i) l’analyse des matériaux d’électrodes (NMC, LFP, Gr, et LTO), (ii) la solubilité de gaz (O2, H2) comparées à (CO2, CH4) par PVT, et (iii) la quantification des volumes de gaz générés durant le cyclage en pouch cell, corrélée aux performances électrochimiques. Une analyse préalable en demi-piles et en dispositifs complets Gr//NMC et LTO//LFP a également été réalisée afin d’anticiper les performances attendues en pouch cells. Une analyse critique des données (de la littérature et de nos mesures) a permis de définir une procédure optimisée pour obtenir des résultats reproductibles et comparables lors des mesures de volume en pouch cells. La seconde partie de cette thèse consiste en la quantification du volume de gaz produit au cours du cyclage des pouch cells Gr//NMC, Gr//LFP, LTO//LFP et LTO//NMC. Ainsi, les tensions de fin de charge, l’effet du sel et de la température ont été discutés pour dégager les paramètres déterminants dans la génération de gaz en particulier lors de la formation de la SEI. Enfin, une analyse de la composition du gaz récupéré a été effectué par GC-MS et FTIR. A partir de résultats obtenus, des mécanismes ont été proposés et discutés. / The functioning of lithium-ion batteries, may it be under normal use or under abusive conditions, is accompanied by gas generation, especially during the first cycles. This extent of gas generation is dependent on the choice of electrode materials, the electrolyte, and the operating conditions. This gas generation is detrimental: the build-up of pressure leads to the over-pressure in the battery, raising serious concerns. This study is aimed at understanding the fundamental mechanisms governing these reactions. To do so, the « pouch cell » configuration was adopted throughout this thesis. The electrolyte we worked on is the mixture EC:PC:3DMC + 1 mol.L-1 LiPF6. The first chapter of this work is dedicated to development of an experimental protocol based on (i) the analysis of the electrodes materials (NMC, LFP, Gr and LTO), (ii) the gas solubilities (O2, H2) compared to (CO2, CH4) by PVT method, and (iii) the quantification of the volume of generated gases during the cycling of pouch cells which was correlated to the electrochemical performances. A preliminary analysis of half-cells and full cells Gr//NMC and LTO//LFP were also conducted to foresee the performances of the pouch cells. A critical analysis of data taken from the literature and from our own experiments enabled the optimization of a proper procedure to get reproducible and comparable results. The second part of this thesis consists in the quantification of the volume of gases generated during the cycling of Gr//NMC, Gr//LFP, LTO//LFP and LTO//NMC pouch cells. In that respect, the voltages of the end of charge and the effect of salt and of temperature were discussed to figure out the essential parameters in the gas generation and in particular during the formation of SEI. Lastly, a compositional analysis of gases was performed using GC-MS and FTIR. Based on those results, a mechanism is proposed and discussed herein.