Master of Science / Department of Chemical Engineering / Larry A. Glasgow / The military is interested in stopping suspicious vehicles at checkpoints or security positions while minimizing noncombatant fatalities. Preliminary work has shown that decreasing the oxygen concentration in proximity to the automobile air intake system and blocking the air flow through an automotive induction system provides the greatest probability of success for the broadest possible array of internal combustion engines. A non-lethal foam deployment system was developed that satisfies the military’s needs to stop suspicious vehicles. The foam is discharged from a pressurized tank and engulfs the air intake system of the target vehicle. The foam is drawn into the air intake and the protein additive contained in the foam would occlude pores in the air filter medium. Once the air filter was blocked, the vehicle would become immobilized so that security personnel can secure the vehicle. The work carried out in this project consisted of development and refinement of surfactant solution composition, improvement in the rate of absorption of carbon dioxide for increased foam volume, and characterization of discharge for optimum foam volume. In addition, a half-scale model apparatus was developed to test the foam’s ability to be ingested in an automotive intake system. These experiments demonstrated that the foam deployment system would stop an automobile within six seconds.

<p>The company Kiviks Musteri AB produces a pear base wine that forms stable foam, which is problematic from a production perspective. The aim of this thesis was to investigate the factors underlying foam stability in the pear base wine and to find means for its reduction. This was done by foam testing wines and varying several variables, such as the fining agents normally used in the wine production (bentonite, gelatin, siliceous earth and activated carbon), enzyme treatment, and by changing the fermenting yeast species.</p><p>Results: The wine started to form stable foam during fermentation, and foam stability could be reduced by using more bentonite and carbon during the fining process. The other fining agents appeared to have only limited impact on foaming characteristics. No pectin was present according to the pectin test, but protein bands were evident from SDS PAGE analysis, though absent in samples treated with increased doses of bentonite.</p><p>In conclusion, pectin is not a major foaming agent in the wine, the yeast is most likely the producer of the foaming agents, carbon and bentonite have a reducing effect on foam stability, bentonite also reduces protein content. Proteins are likely to be involved in the foam stabilization but are not the sole contributors to stable foam.</p>

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The major part of this thesis concerns the development of catalytic methodologies based on palladium nanoparticles immobilized on aminopropyl-functionalized siliceous mesocellular foam (Pd0-AmP-MCF). The catalytic activity of the precursor to the nanocatalyst, PdII-AmP-MCF is also covered by this work. In the first part the application of Pd0-AmP-MCF in Suzuki-Miyaura cross-coupling reactions and transfer hydrogenation of alkenes under microwave irradiation is described. Excellent reactivity was observed and a broad range of substrates were tolerated for both transformations. The Pd0-AmP-MCF exhibited high recyclability as well as low metal leaching in both cases. The aim of the second part was to evaluate the catalytic efficiency of the closely related PdII-AmP-MCF for cycloisomerization of various acetylenic acids. The catalyst was able to promote formation of lactones under mild conditions using catalyst loadings of 0.3 - 0.5 mol% at temperatures of up to 50 oC in the presence of Et3N. By adding 1,4-benzoquinone to the reaction, the catalyst could be recycled four times without any observable decrease in the activity. The selective arylation of indoles at the C-2 position using Pd-AmP-MCF and symmetric diaryliodonium salts is presented in the third part. These studies revealed that Pd0-AmP-MCF was more effective than PdII-AmP-MCF for this transformation. Variously substituted indoles as well as diaryliodonium salts were tolerated, giving arylated indoles in high yields within 15 h at 20 - 50 oC in H2O. Only very small amounts of Pd leaching were observed and in this case the catalyst exhibited moderate recyclability. The final part of the thesis describes the selective hydrogenation of the C=C in different α,β-unsaturated systems. The double bond was efficiently hydrogenated in high yields both under batch and continuous-flow conditions. High recyclability and low metal leaching were observed in both cases. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 5: Submitted.</p><p> </p>

L’objet de cette thèse expérimentale est l’étude de la rhéologie des mousses de fluides complexes. L’utilisation de matériaux modèles permet de découpler les effets des bulles et du fluide complexe sur le comportement rhéologique des mousses. Nous caractérisons notamment le module élastique et la contrainte seuil des mousses de suspension de particules et des mousses d’émulsion. La rhéologie des mousses de particules est fortement dépendante du rapport entre la taille des particules et la taille du réseau interstitiel de la mousse (nœud et bords de Plateau). Lorsque les particules sont suffisamment petites pour être inclues dans le réseau de la mousse, elles peuvent former un squelette granulaire compact. Cette structure mise en place par le drainage de la suspension augmente sensiblement la valeur du module élastique des mousses de particules. En effet, le confinement exercé par les bulles sur le squelette granulaire est à l’origine de l’élasticité de la matrice granulaire. Lorsque taille des particules augmente, ces dernières sont exclues du réseau de la mousse et le module élastique des mousses de particules diminue avec la disparition de la matrice. Les mousses de particules avec un squelette granulaire possèdent l’avantage d’avoir deux sources d’élasticité distinctes : l’élasticité capillaire des bulles et élasticité du squelette granulaire. On peut sommer ces deux contributions pour modéliser le module élastique macroscopique de la mousse, ce n’est pas le cas des mousses d’émulsion. En effet, il existe un couplage entre bulles et la matrice d’émulsion. L’introduction des nombres capillaire élastique et capillaire de Bingham permet de décrire l’évolution respective du module élastique et de la contrainte seuil des mousses d’émulsion. Enfin, l’analyse de la contrainte seuil de ces deux types de mousses permet d’identifier la matrice de particules comme étant un fluide à seuil, et forme un parallèle intéressant entre ces deux mousses à priori dissemblables / The subject of this experimental thesis is the study of the rheology of complex fluid foams. The use of model materials allows decoupling the effects of the bubbles and the complex fluid on the rheological behavior of the foams. In particular, we characterize the elastic modulus and the yield stress of particle-loaded foams and emulsion foams. The rheology of particle-loaded foams is highly dependent on the size ratio between the particle and the interstitial foam network (node and the so called “Plateau borders”). When the particles are small enough to be included in the foam network, they can form a compact granular skeleton. This structure put in place by the drainage of the suspension substantially increases the value of the elastic modulus of the particle-loaded foams. Indeed, the confinement exerted by the bubbles on the granular skeleton is at the origin of the elasticity of the matrix (skeleton). As the size of the particles increases, they are excluded from the foam network and the elastic modulus of the foam particles decreases with the disappearance of the matrix. Particle foams with a granular skeleton have the advantage of having two distinct sources of elasticity: the capillary elasticity of the bubbles and the elasticity of the granular skeleton. These two contributions can be summed up to model the macroscopic elastic modulus of the foam, this is not the case for emulsion foams. Indeed, there is a coupling between bubbles and the emulsion matrix. The introduction of elastic capillary number and the Bingham number allows to describe the respective evolution of the elastic modulus and the yield stress of the emulsion foams. Finally, the analysis of the yield stress of these two types of foams enables to identify the matrix of particles as a yield stress fluid, and forms an interesting parallel between these two foams that are a priori dissimilar

Les mousses de ciment présentent d'intéressantes propriétés : une faible densité, une faible consommation de matière première et une bonne résistance thermique. Certaines propriétés finales de la mousse dépendent de sa morphologie. Pour mieux comprendre cette dépendance, on veut créer des échantillons de mousse de ciment avec une structure bien contrôlée. On crée des échantillons de mousses de ciment composés de bulles de même taille, en choisissant la quantité d'air, de ciment, d'eau et de tensioactif. Pour ce faire, on mélange d'une part une mousse aqueuse de morphologie contrôlée, stabilisée par des tensioactifs, et d'autre part une pâte de ciment. Le but de cette thèse est d'étudier comment conserver cette structure jusqu'à la prise du ciment. Tout d'abord, nous étudions d'interaction entre tensioactifs et pâte de ciment. Certains tensioactifs ne sont pas compatibles avec la solution alcaline présente dans la pâte de ciment et ne permettent pas de produire une mousse dans ces conditions. Parmi les tensioactifs compatibles avec la solution interstitielle de ciment, certains s'adsorbent sur les grains de ciment. Cette adsorption change les interactions entre grains de ciment et par conséquent, la contrainte seuil de la pâte. A faible concentration en tensioactif, la monocouche de molécules adsorbée rend les grains de ciment hydrophobes, ce qui produit une attraction hydrophobe entre grains et une augmentation de la contrainte seuil de la pâte. A forte concentration en tensioactif, les micelles adsorbées engendrent une répulsion stérique entre les grains de ciment et une chute de la contrainte seuil. Dans un deuxième temps, nous étudions l'effet des bulles d'air sur la contrainte seuil d'une pâte de ciment aérée, lorsque celle-ci contient moins de 40% d'air. Les mesures sont normalisées par la contrainte seuil de la pâte interstitielle afin d'être comparées à la littérature. Lorsque le tensioactif utilisé s'adorbe peu sur les grains de ciment, les résultats sont semblables à ceux de la littérature obtenus sur des fluides à seuil modèles. En revanche, lorsque le tensioactif utilisé a une grande affinité avec les grains de ciment, la contrainte seuil normalisée est bien au-dessus des prédictions. Notre hypothèse pour expliquer ce résultat est une modification des propriétés de surface des bulles à cause de l'adsorption des grains de ciment rendus partiellement hydrophobes par le tensioactif. Ensuite, nous nous focalisons sur la stabilité des mousses de ciment avant la prise, pour une fraction d'air de 83%. On s'intéresse tout d'abord à trois séries de mesures, en gardant pour chacune le rapport eau-sur-ciment et la taille des bulles constante. Pour chacune des trois séries, seule la contrainte seuil de la pâte de ciment est changée par l'addition de superplastifiant ou d'une grande quantité de tensioactif anionique. On obtient alors un résultat inattendu : la meilleure stabilité est observée pour des tailles de bulles relativement faibles. La comparaison avec les mesures des propriétés rhéologiques de la mousse fait penser que la bonne stabilité aux faibles contraintes seuil est due à la réorganisation des grains de ciment en un réseau granulaire plus dense. Pour aller plus loin sur l'étude de la stabilité des mousses, nous avons ensuite fait varier la taille des bulles, la rapport eau-sur-ciment et la quantité de tensioactif. Nous avons pu définir un critère de stabilité pour l'ensemble de ces mousses qui dépend de la contrainte seuil interstitielle de la pâte de ciment confinée par les bulles et de la taille des bulles. Pour finir, nous mesurons la résistance en compression de mousses de ciment et leur vitesse d'imbibition afin de corréler ces propriétés à leur structure / Cement foams advantages compared to normal concrete is their low density, low material need and thermal insulation properties. To better understand how the morphology of the cement foam affects its properties, we create solid cement foam with well controlled structure. This involves two steps: the creation of the fresh cement foam with chosen structure, and the stability of this structure up to cement hardening. Our cement foam fabrication protocol allows us to obtain fresh cement foams samples with very well controlled parameters. For each sample, all the bubbles have the same size, and we can select the content of air, water, cement and surfactant. This technique consists in mixing a well-controlled precursor aqueous foam stabilized by surfactant, with a cement paste prepared separately. First, we study the interaction of surfactants and cement paste. Some surfactants cannot stabilize foam in cement paste highly alkaline solution. Some others, mainly anionic surfactants, adsorb on cement grains surface, which modifies interactions between cement grains and consequently the yield stress of the cement paste. At low surfactant concentration, cement grain surface becomes hydrophobic and yield stress increases due to hydrophobic attraction between cement grains. At high surfactant concentration, adsorbed micelles create a steric repulsion between cement grains and make yield stress of cement paste drop. In a second chapter, we study the effect of bubbles on the yield stress of aerated cement paste. To compare the results with the literature, the measured yield stress is normalized by the yield stress of the suspending cement paste, i.e. taking into account the effect of surfactant. For a surfactant with low affinity to cement grains surface, results are consistent with literature, whereas reduced yield stress is much higher than expected when surfactant strongly adsorb on cement grain surface. This effect is attributed to the change of the bubble surface properties due to the adsorption of hydrophobic cement grains at the air-liquid interface. Then, we focus on cement foam stability, at air content 83%. We first study three series of experiments at given water-to-cement ratio and bubble size. For each series, the yield stress of the cement paste is changed by addition of superplasticizer or high amount of anionic surfactant. Unexpectedly, the best foam stability is obtained for relatively low yield stress. Rheological measurements on the fresh cement foams allowed us to understand this improved stability as a consequence of the reorganization of cement grains into denser packing. In a second part on stability, we study the influence of bubble size, water-to-cement ratio and surfactant content. A stability criterion is defined from the bubble size and the interstitial cement paste yield stress. Eventually, we observe that cement foam structure affects water imbibition velocity and mechanical resistance to compression of hardened cement foams

The aim of this thesis is to gain new insights into the physics underlying the long-term stability and instability of liquid foams and emulsions in the absence and presence of particles. By using Finite element based and mesoscopic Lattice Boltzmann techniques along with the microfluidic tools at our disposal, we tackled this question using two very different, yet complementary, approaches. In the first part, we went down to the smallest scale of foam, by observing a single bubble where the particle would straddle at interfaces of thin films. This brought a novel understanding to the observation that the torque on the particle is independent of film thickness and was mainly contributed by contact line stresses. We then precisely measured the hydrodynamic and dielectrophoretic interactions of a particle armored bubble treating the bubble as a flat surface and showed that its resistance to the motion was much less for hydrophobic particles compared to other wetting particles while the dielectrophoretic forces were more for hydrophobic particles as the latter protruded more in the oil phase. These findings are of utmost importance when designing particle-stabilized foams and dielectrophoresis-based particle separation techniques because they guide the choice of the particles to use for a particular application. In the second part, we studied the foam at a larger scale, by analyzing the evolution of a large population of identical bubbles produced in microfluidic geometries. This monodisperse foam destabilizes through Ostwald ripening or Coarsening toward a well-known self-similar state. However, we have shown that the transient regime leading to that state is not homogeneous in space. The microfluidic model that we develop predicts how the disorder grows in the foam, which is a valuable asset in applications where an ordered organization of the bubbles is required resisting foam coarsening. Furthermore, multiscale Lattice Boltzmann simulations of emulsion drainage based on frustrated long-range interactions are developed using the images from the microfluidic experiment as the initial phase thus providing a global understanding of emulsion stabilization and drainage dynamics. The key parameters investigated for particle-induced emulsion stabilization were solid particle concentration, particle size, wettability, heterogeneity and particle shape. The resulting emulsion droplets adopted pronounced non-spherical polyhedral shapes with time, indicating a high elasticity of the interface. The stability and the remarkable non-spherical shape of the emulsion droplets stabilized by the particles were features which bear resemblance with foam stabilization of bubbles using hydrophobic particles in flotation processes.

An experimental study has been carried out to investigate the effects of buoyancy on smoldering of polyurethane foam. The experiments are conducted with a high void fraction flexible polyurethane foam as fuel and air as oxidizer, in a geometry that approximately produces a one dimensional smolder propagation. The potential effect of buoyancy in the process is analyzed by comparing upward and downward smolder propagation through a series of normal gravity and variable gravity experiments. Both opposed and forward mixed (free and forced) flow smolder configurations are studied. In opposed smolder the oxidizer flow opposes the direction of smolder propagation, and in forward smolder both move in the same direction. Variable gravity free flow tests are also conducted in an aircraft flying a parabolic trajectories that provides low gravity periods of up to 25 sec. Measurements are performed of the smolder reaction propagation velocity and temperature as a function of the location in the sample interior, the foam and air initial temperature, the direction of propagation and the air flow velocity. This information is used in conjunction with previously developed smolder theoretical models to determine the smolder controlling mechanisms and the effect of gravity. Three zones in the fuel sample with clearly defined smolder characteristics are identified. A zone close to the igniter where smolder is affected by the external heat, a zone at the end of the sample where smolder is affected by the environment, and a zone at the end of the sample where smolder is affected by the environment, and a zone, in the middle of the foam, that is free from external effects. This last zone is the most characteristic of one dimensional, self-supported smolder, and the one that is studied in greater detail. In mixed flow convection buoyancy induced flows together with the forced flow are the primary mechanism of oxidizer transport to the reaction zone, while diffusion has a secondary importance. In natural convection, downward smoldering is of the opposed type while upward smoldering resembles more the forward type. For opposed flow smoldering, both natural and forced, the smolder propagation velocity is found to increase with the oxidizer mass flux reaching the reaction zone. This result confirms predictions from previously developed theoretical models that the smolder velocity is proportional to the oxygen mass flow. The experimental data is correlated in terms of a non-dimensional smolder velocity derived from these models, the results show very good agreement between theory and experiments for strong smolder. To implement the models, an analysis of the gas flow field is developed where the effect of significantly different permeabilities between char and foam is been Extinction is observed for very low and for very high flow rates, which shows that smolder is controlled by a sensitive competition between oxygen supply and heat losses to and from the reaction zone. Under these conditions the models do not describe the experiments well. The forward flow smolder experiments show that forward smoldering is controlled not only by the competition between oxygen supply and heat losses to and from the reaction zone but also by the competition between pyrolysis and oxidation. For low flow velocities a regime resembling the opposed flow is observed. As the air flow velocity is increased, foam pyrolysis followed by char oxidation is the controlling smolder mechanism. For both these conditions the theoretical models describe the experiments well. Increasing the flow velocity further results in a smolder propagation velocity controlled by total fuel consumption, in downward burining. For upward burning transition to flaming is observed for very high air flow velocities. This last regime is not well predicted by the theoretical models. The results from the experiments in variable gravity environment conducted in the KC-135A and Leajet airplanes confirm the normal gravity observations that the competition between heat losses and oxidizer transport is the major mechanism controlling smolder. The absence of convective flow in low gravity results in higher temperature in the unburnt fuel and char due to smaller heat losses to the surroundings. However, the oxidizer transport to the reaction zone also decreases and as a result the temperature at the reaction zone decreases indicating a weakening of the eaction, The presence of pyrolytic reactions in foward smolder and their capability to inhibit smoldering complicates the above described smolder mechanisms.

The spin-foam is a covariant path-integral style approaching to the quantization of the gravity. There exist several spin-foam models of which the most successful one is the Engle-Pereira-Rovelli-Levine/Freidel-Krasnov (EPRL-FK) model. Using the EPRLFK model people are able to calculate the transition amplitude and the n-point functions of 4D geometry (both Euclidean and Lorentzian) surrounding by a given triangulated 3D geometry. The semi-classical limit of the EPRL-FK amplitude reproduces discrete classical gravity under certain assumptions, which shows that the EPRLFK model can be understood as UV completion of general relativity. On the other hand, it is very hard to dene a continuum limit and couple a cosmological constant to the EPRL-FK model. In this dissertation, we addressed the problems about continuum limit and coupling a cosmological constant to the EPRL-FK model. Followed by chapter one as a brief introduction of the loop quantum gravity and EPRL-FK model, chapter two introduces our work about demonstrating (for the first time) that smooth curved spacetime geometries satisfying Einstein equation can emerge from discrete spin-foam models under an appropriate low energy limit, which corresponds to a semi-classical continuum limit of spin-foam models. In chapter three, we bring in the cosmological constant into the spin-foam model by coupling the SL(2, C) Chern-Simons action with the EPRL action, and find that the quantum simplicity constraint is realized as the 2d surface defect in SL(2, C)Chern-Simons theory in the construction of spin-foam amplitudes. In chapter four, we present a way to describe the twisted geometry with cosmological constant whose corresponding quantum states can forms the Hilbert space of the loop quantum gravity with cosmological constant. In chapter five, we introduced a new definition of the graviton propagator, and calculate its semi-classical limit in the contents of spin-foam model with the cosmological constant. Finally the chapter six will be a outlook for my future work. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection