Dissertations / Theses on the topic 'Heterogeneous membranes'

Solid oxide fuel cells and oxygen permeable membranes have received considerable attention during the last decade due to the increasing demand for electrical energy and easily transportable fuels combined with the requirement of low emission of CO₂. This work concentrates on the stability of ceramic interfaces in general, and more specifically to heterophase solid state interfaces related to solid oxide fuel cells and oxygen permeable membranes. Reaction mechanisms are discussed and requirements and properties of suitable materials are determined. This thesis consists of three parts: 1) Structure of Ca-substituted lanthanum manganite (Paper I), 2) Reactions between cathode and electrolyte for SOFC applications (Papers II-IV) and 3) Chemical and mechanical aspects of sealing dense oxygen permeable membranes (Papers V and VI).

Identifying the elastic properties of heterogeneous materials has long been a very challenging problem both theoretically and experimentally. When it comes to biological tissues, this task is even more difficult since biological tissues generally exhibit substantial anisotropic behavior. Moreover, identification is often required to be performed in the service condition of living human tissues and organs, i.e., in vivo. Presently, a method capable of performing such tasks is lacking. The primary goal of this study is to fill this gap by developing a novel experimental method, termed as pointwise identification method (PWIM), for delineating the elastic properties in nonlinear heterogeneous membranes. Fundamentally, the method hinges on a unique feature of membrane equilibrium problems, that is, wall stress can be determined from equilibrium consideration alone (static determinacy). Thanks to the static determinacy, membrane wall stress can be computed numerically by using finite element inverse elastostatics method (FEIEM), and depends minimally on the constitutive model. In PWIM, an inflation test is conducted for the target membrane with a series of tracking markers, and a series of deformed configurations are recorded by using appropriate motion tracking techniques. Subsequently, the pointwise stress distribution in each deformed configuration can be acquired independently by applying FEIEM, whereas the corresponding strain distribution can be determined from the deformation relative to the reference configuration which contains implicitly the elastic properties of the material. Consequently, the elastic properties at every material point can be extracted by fitting an appropriate constitutive model to the pointwise stress-strain data pairs. In this work, we have validated the method for nonlinear isotropic and anisotropic materials through numerical simulations on a patient-specific cerebral aneurysm model, developed an experimental system and validated the method experimentally by conducting an inflation test on a rubber balloon, and conducted a test on a rabbit urinary bladder. The situation of the global stress-free configuration being unknown was considered numerically by employing a concept of local stress-free configuration. In this regard, the method holds the promise of identifying in vivo the elastic properties of membrane-like living organs, e.g., cerebral aneurysms, using medical images upon the availability of powerful image registration techniques.

This thesis presents the application of k-space Image Correlation Spec- troscopy (kICS) to the analysis of fluorescence microscopy image time series for the measurement of particle diffusion in heterogeneous membranes, composed of micro- domains. The extension, testing and application of kICS for such measurements is developed both in silico with simulation and with in vivo cellular experiments.Connections between kICS analysis and other existing fluorescent microscopy techniques used in the study of heterogeneous membranes, such as single particle tracking (SPT) and spot vary Fluorescence Correlation Spectroscopy (FCS) are introduced. This is followed by the development of kICS theory of fluorescent particle diffusion within a heterogeneous two dimensional (2D) environment. Two possible membrane heterogeneities, isolated lipid micro-domains and actin proximal meshwork, are considered separately. The emergent models suggest that the kICS correlation function (CF) can be fit by a sum of two Gaussians in the case of particle diffusion in the presence of isolated micro-domains. These two fit components, called 'fast' and 'slow', with the fast associated with the rapid decay of the kICS CF at small spatial frequencies due to particle motion on large spatial scales outside domains while the slow component refers to the confined particle motion on large spatial frequencies or small spatial scales in domains. On the other hand, the meshwork confinement is well fit with a single Gaussian model for the analysis of kICS CF. These models suggest that the exponents and amplitudes of the fits embed the characteristic system parameters such as diffusion coefficients outside and inside domains, the partitioning rates, micro-domains radii and mesh pore size.Furthermore, systematic simulations to study different confinement scenarios were conducted and the calculated kICS correlation functions were fit and the output interpreted for recovery of self system parameters. The characterization of the simulated data suggests that kICS CFs exhibit various confinement dependent features, such as decays due to effective slow and fast dynamics populations and effective domain sizes. The in silico characterization of different confinement scenarios, suggests a connection between the apparent measured confinement properties, and the set system defining parameters. We explore the range and limits where confinement effects can be detected and accurately measured by kICS analysis. Possible systematic errors in the values of the fit extracted parameters due to background noise is discussed with possible alternative solutions.Finally, we apply this extension of kICS to the heterogeneous membrane en- vironment to explore the confinement dynamics of GPI-GFP anchored proteins in the basal plasma membrane of COS-7 cells. We employ a novel labelling approach of GPI-GFP using anti-GFP-Alexa594 and image the protein in COS-7 cell mem- branes with TIRF microscopy. Cells were exposed to enzymatic treatments, using the Cholesterol Oxidase (COase) and Sphingomyelinase (SMase), in order to dis- rupt membrane domains and change GPI-GFP confinement dynamics. We observe that GPI-GFP mobility and the effective domain size measured correlates with the enzymatic exposure time. We attribute it to the conversion of the membrane domain constituents, cholesterol and sphingomyelin, upon the enzymatic reactions, leading to membrane domain that are effectively larger and leakier. Finally, we conclude with possible improvements and future directions.
La thèse qui suit est a propos de l'adaptation de la technique de la spectroscopie par la corrélation des images dans l'espace de Fourier, appelle kICS. La nouveauté consiste en utilisation de kICS pour analyser les séries temporelles d'images fluorescentes afin de caractériser la diffusion des particules en présence des membranes hétérogénes, composées de micro-domaines.Tout d'abord, une parallèle est exposée entre l'analyse fondée sur kICS pro- posé ci-dessus et d'autres techniques de microscopie à fluorescence existantes et utilisées dans l'étude des membranes hétérogénes. Ensuite, on expose le développement de la théorie de kICS dans les cas de la diffusion des particules fluorescentes dans un espace hétérogène bidimensionnel (2D). Les deux hétérogénéités membranaires possibles, micro-domaines lipidiques isolés et le réseau de l'actine proximale, sont considérés séparément. Les modèles émergents suggèrent que la fonction de corrélation de kICS doit être caractérisé par une somme de deux Gaussiennes dans le cas de la dynamique des particules en présence de micro-domaines isolés. Ces deux éléments, appelés 'rapide' et 'lent', représentent les composantes dynamiques a deux échelles d'espace différentes. La rapide est associé à la décroissance rapide de la fonction de corrélation de kICS à petites fréquences spatiales dues au mouvement des particules sur de grandes échelles spatiales. La composante lente réfère au mouvement des particules confinées à des petites échelles spatiales, observées sur de grandes fréquences spatiales de kICS. D'autre part, la fonction de corrélation de kICS due au confinement par le réseau du cytosquelette peut être caractérise par unique décroissance Gaussienne. Ces modèles suggèrent que les exposants et les amplitudes obtenus par la caractérisation de la fonction kICS dépend des paramètres caractéristiques du système tels que les coefficients de diffusion à l'extérieur et à l'intérieur de domaines, les taux de migration de particules vers intérieur ou extérieur de micro-domaines ou des tailles de porosités du réseaux du cytosquelette.Les études systématiques par les simulations des scénarios différents de confinement et leurs effets sur la fonction de corrélation de kICS ont été explorés. La caractérisation des données simulées suggèrent que les fonctions de corrélation ont des caractéristiques qui dépendent de confinement et les propriétés spécifiques, tels que la dynamique des populations lents et rapides et la tailles effective de micro-domaines. La caractérisation des scénarios de confinement différents, représente les liens entre les propriétés apparentes mesurées de confinement, et un ensemble de paramètres définissant hétérogénéité. Nous explorons les limites pour lesquelles des effets de confinement ne sont pas observées dans la fonction de corrélation kICS. Les éventuelles erreurs systématiques dans les valeurs des paramètres extraits à cause du bruit de fond est discuté avec des possibles solutions. Finalement, nous utilisons l'analyse afin d'explorer la dynamique de confinement de la protéine ancrée à GPI-GFP dans la membrane plasmique basale des cellules COS-7. Nous explorons une approche nouvelle de la conjugaison entre le GPI-GFP et les anti-GFP-Alexa594 et imagé par la microscopie TIRF. Les cellules ont été exposées à des traitements enzymatiques, par Coase et SMase, afin de perturber domaines membranaires et changer la dynamique de confinement de GPI-GFP. Les réactions enzymatiques augmentent la mobilité et la taille effective des domaines de GPI-GFP. Nous attribuons cela à la conversion des constituants des domaines, le cholestérol et la sphingomyéline, par les réactions enzymatiques, ce qui conduit aux plus grandes et moins étanches domaines membranaires.

Les piles à combustible sont une technologie en pleine expansion dans le domaine du transport automobile.Les membranes polymères les plus utilisées actuellement dans ces systèmes sont celles à base de Nafion.Leur principal point faible se trouve dans leurs performances limitées au-delà de 80°C, où la membranedevient défaillante et l'eau ne peut plus assurer la conduction protonique. Le projet EUBECELL se proposede résoudre ce problème en mettant au point un système de pile à combustible fonctionnant à l'éthanol et àplus de 120°C. Cette thèse s'inscrit dans ce projet et se concentre sur l'élaboration de nouvelles membranespolymères conductrices de protons. Deux voies sont envisagées : l'amélioration des propriétés du Nafion àhaute température et le remplacement du Nafion par un polymère haute performance auquel on donne uneconductivité.L'amélioration du Nafion se fait par l'ajout de conducteurs liquides ioniques protiques (CLIPs), produitsayant donc une conductivité protonique venant s'ajouter à celle du Nafion. Un premier CLIP est synthétisé,caractérisé puis ajouté au Nafion et les performances des membranes obtenues mesurées. Les résultatsencourageants obtenus incitent à synthétiser d'autres CLIPs à partir de la même amine et en variant le contreion.D'autres mélanges Nafion-CLIPs sont ainsi synthétisés et caractérisés.Les polymères hautes performances étudiés ici pour remplacer le Nafion sont dans un premier temps despolysulfones sulfonées. Les polysulfones étant des polymères qui résistent aux températures élevées et lasulfonation leur donnant une conductivité. Pour conserver de meilleures propriétés après sulfonation, nousprocédons à une extrusion du film polymère suivi d'une sulfonation. Nous mettons donc au point unprotocole de sulfonation hétérogène. Les membranes obtenues sont ensuite caractérisées et leursperformances mesurées. Dans un deuxième temps nous travaillons sur des membranes macroporeuses, àforte tenue mécanique, que nous remplissons avec les CLIPs utilisés auparavant. Les membranes sont alorsaussi caractérisées et leurs performances mesurées
Fuel cells are an ever-expanding technology in the field of automotive transport. The polymer membranesthat are currently the most widely used are Nafion-based membranes. Their weakest point is their drastic lossof performances beyond the threshold of 80°C, where the membranes fails and water cannot ensure protonconduction anymore. The EUBECELLproject sets to achieve making a fuel cell system functioning above120°C and using ethanol as a fuel. This thesis is part of the project and focus on elaborating new protonconductingpolymer membranes. Two main ways are explored: improving the performances of Nafion athigh temperature and replacing Nafion with conductivity-added high-performance polymers.Improving Nafion's performances is achieved by adding proton conducting ionic liquids (PCILs), productsthat have a proton conductivity that adds to Nafion's own. A first PCIL is synthesized, characterized and thenadded to Nafion, the resulting membranes' performances then measured. The encouraging results that weobtain makes us synthesize more PCILs, from the same amine than the first, varying the counter-ion. OtherNafion-PCIL mixes are made and then characterized.The high-performance polymer investigated for replacing Nafion are, first, sulfonated polysulfones.Polysulfones are high-temperature resistant polymers and sulfonation gives them conductivity. To keep betterproperties after the sulfonation, we proceed to extrude the films before sulfonating them. We elaborate anheterogeneous sulfonation protocol for them. The resulting membranes are then characterized and theirperformances measured. Second, we work on macroporous membranes, with high mechanical strength,which we fill with the PCILs that we previously used. The membranes are then also characterized and theirperformances measured

Heterogeneously catalysed aerobic oxidation of alcohols has great potential in chemical synthesis, but its wide application is still limited by safety issues with the combination of gaseous oxygen and flammable organics. The aim of this thesis is to develop Teflon AF-2400 membrane reactors for the intrinsically safe use of oxygen in oxidation of alcohols. Initially, oxidation of benzyl alcohol and cinnamyl alcohol on Au-Pd/TiO2 catalyst was studied in a trickle bed microreactor. The catalyst deactivation in cinnamyl alcohol oxidation, rather than benzyl alcohol oxidation, was attributed to Pd leaching and a complex role of oxygen. Then, a Teflon AF-2400 packed tube-in-tube membrane microreactor was investigated for benzyl alcohol oxidation, which allowed continuous oxygen supply during the reaction and presented higher conversion and selectivity as compared to a reactor with oxygen pre-saturated feed. A novel approach using the tube-in-tube membrane contactor was demonstrated for measuring gas solubility in liquids. To simplify the reactor scale-up, a Teflon AF-2400 flat membrane microreactor was developed for benzyl alcohol oxidation, and the mass transfer and reaction in the reactor were experimentally and theoretically investigated with different catalysts. The oxygen transverse mass transfer in the catalyst bed, rather than oxygen permeation through membrane or oxygen internal/external transfer in the catalyst particles, was indicated to be the controlling process. An effectiveness factor analysis akin to internal/external mass transfer and reaction in a catalytic particle was provided to guide the catalyst choice and the membrane reactor design. For direct usage of small catalyst particles in continuous flow reactors, a stirred membrane reactor with a sintered metal filter and an external membrane contactor was experimentally demonstrated and mathematically simulated for benzyl alcohol oxidation. The reactant conversion and the catalyst utilization were indicated to be affected by various operation parameters, which were correlated to guide the reactor design and operation.

Les systèmes modèles (vésicules géantes unilamellaires) représentent un outil indispensable pour étudier la formation, la stabilité, la dynamique et les fonctions des rafts dans les membranes biologiques. L'originalité de notre étude réside : i) dans la visualisation du bourgeonnement et de la fission induits par des agents biologiques (sPLA2 ou Lyso PC) et ii) dans la visualisation directe de la solubilisation d'une membrane modèle de type Ld/Lo ainsi que le bourgeonnement et la fission des domaines Lo traitée avec des détergents (Triton X-100, Brij 98). Ces expériences appuient l'idée que l'isolement de DRM à partir des membranes cellulaires n'est probablement pas un artefact. Nous avons décrit un mécanisme possible pour l'expulsion d'une vésicule en phase Lo déclenché par des molécules d'asymétrie stérique positive. Enfin, les VGU hétérogènes peuvent présenter un modèle assez proche des phénomènes observés sur les membranes biologiques.

This work is focused on the preparation of heterogeneous bipolar membranes and studies the influence of different composition on mechanical and physical properties. The main feature of this approach is optimalization of composition following gained data. Theoretical part contains new piece of knowledge in the field of heterogeneous bipolar membranes. Experimental part engages preparation of bipolar ion-exchange membranes on one face cation-selective and on the other one anion-selective. In this case are used variant types of polyethylene.

Les matériaux « coeur-coquille » composés d’une nanoparticule métallique encapsulée à l'intérieur de coquilles inorganiques (oxydes, carbone …) attirent de plus en plus l'attention par leurs propriétés particulières, en particulier dans le domaine de la catalyse. Les particules métalliques sont protégées par la coquille, qui empêche entre autres le frittage et la croissance des particules à haute température. Cependant, les coquilles sont généralement méso à macroporeuses et elles ne peuvent pas jouer le rôle de tamis moléculaire pour les molécules de taille nanométrique. En revanche, les zéolithes sont des solides cristallins microporeux dont les pores bien définis permettent une forte discrimination des réactifs basée sur la taille, la forme ou leur coefficient de diffusion. L’objectif de cette thèse visait à la synthèse de catalyseurs de type coeur-coquille dans lesquels la coquille est une zéolite microporeuse de structure MFI (silicalite-1 et ZSM-5), le coeur étant soit une particule de métal noble (Au, Ag, Pt, Pd), soit des alliages de ces différents métaux, soit enfin un métal de transition (Co, Ni, Cu). Ces catalyseurs ont été appliqués dans des réactions d'hydrogénation sélective (aromatiques substitués) et l'oxydation sélective de CO en présence d'hydrocarbures. Nous avons ainsi montré que la coquille zéolithique, tout en protégeant les particules du frittage, modifie la sélectivité des réactions en interdisant aux réactifs volumineux d’atteindre les sites catalytiques
Nanostructured yolk-shell materials, which consist of metal nanoparticle cores encapsulated inside hollow shells, attract more and more attention in material science and catalyst applications during the last two decades. Metal particles are usually highly mono-dispersed in size and isolated from each other by the shell, which prevents growth by sintering at high temperature. Because they are generally made of meso/macroporous oxides or amorphous carbon, shells cannot carry out molecular sieve-type separation of molecules at the nanometric scale. The aim of the present thesis was to synthesize yolk-shell catalyst with microporous zeolite shells (silicalite-1 and ZSM-5), containing noble (Au, Pt, Pd) transition (Co, Ni, Cu) and alloy metal nanoparticles. Zeolites are crystalline microporous solids with well-defined pores capable of discriminating nanometric reactants on the basis of size, shape and diffusion rate. Zeolite-based yolk-shell catalysts have been applied in selective hydrogenation (toluene and mesitylene) and oxidation (CO) reactions in the presence of hydrocarbons. Zeolite shells not only plaid a key role as membranes, thus changing selectivities as compared to conventional supported catalysts, but they also protected metal nanoparticles from sintering under reaction conditions

Células a combustível de membrana polimérica têm cada vez mais se destacado como meio na obtenção de energia, pela sua alta eficiência e potencial para fazê-la de modo sustentável. Entretanto muitos ainda são os desafios para consolidá-la comercialmente. Dentre eles, a aglomeração e a perda de área ativa em catalisadores suportados em carbono recebem um destaque especial, principalmente em células PEM de temperatura elevada de operação. Eletrocatalisadores não suportados, baseados em nanoarquiteturas de geometria controlada, têm se tornado uma tendência em diversas frentes de pesquisa. Tal fato se deve à alta eficiência e estabilidade atingidas por sistemas nanométricos organizados, além da possibilidade em se criar superfícies funcionais adaptadas a reações específicas. O trabalho de pesquisa buscou o desenvolvimento de sistemas catalíticos não suportados, de alta área superficial, como alternativa a eletrocatalisadores nanoparticulados suportados em carbono, a fim de se reduzir a perda sobre a área ativa quando submetidos às condições de operação em células a combustível. O trabalho explorou dois conceitos, a confecção de nanotubos de platina e a confecção de nanofios nanoporosos à base de platina vítrea. Para este desenvolvimento foram estudados e caracterizados os efeitos da dissolução seletiva, em escala nanométrica, acoplados à conformabilidade de metais amorfos e à utilização da troca galvânica como ferramenta de síntese de superfícies. Tais estudos foram utilizados como base para o projeto de sistemas catalíticos não suportados. Os materiais propostos foram avaliados quanto a sua atividade e estabilidade frente a reações comuns em células a combustível. Tais sistemas demonstraram uma alta estabilidade em relação à sua área ativa, em ensaios de durabilidade, assim como uma alta utilização do metal nobre, tornando-os promissores para a tecnologia de células a combustível.
PEM Fuel cells have recently been excelled as energy conversion devices, due to their high efficiency and the potential of performing in a sustainable fashion. However, there are many issues still to be addressed before large scale commercialization. Among them, nanoparticle agglomeration and the loss over the active area in carbon supported catalysts, receive special attention, particularly in high temperature PEM fuel cells. Unsupported catalysts based on nanoarchitectures of controlled geometry, have became a new trend on several research lines. The reason underneath lies on the high efficiency and stability obtained by organized hierarchical nanostructures, furthermore, they have also the possibility of tailored made surfaces designed for specific reactions. This research work sought to develop unsupported catalytic systems, with high surface area, as an alternative to carbon supported nanoparticle catalysts, in order to overcome the loss over the active surface area when under the operational environment of fuel cells. The work explored two concepts; the synthesis of platinum nanotubes, and the synthesis of nanoporous nanowires on amorphous platinum alloys. For this development, the effects of selective dissolution, on nanometer scale, coupled with vitreous plastic conformation, were studied and characterized, as well as the employment of galvanic displacement as a tool on tailored made surfaces. Those studies provided a base for the design of unsupported catalytic systems. The proposed materials were evaluated according to their catalytic activity and stability towards common fuel cell reactions. The unsupported systems presented a high stability regarding its active surface area, on durability studies, as well as high noble metal utilization, making them promising materials for future electrode designs.

Cette thèse est consacrée à l'étude des coques minces élastiques constituées d'un matériau inhomogène et anisotrope. Dans la première partie, on considère les équations de l'élasticité linéarisée près d'un état naturel tandis que dans la seconde, on suppose que la coque est précontrainte et on considère les équations de l'élasticité linéarisée près de l'état précontraint. Dans le premier chapitre, un résultat de convergence vers un modèle couplant les effets de flexion et les effets membranaires est obtenu pour un matériau inhomogène et anisotrope. Nous exhibons une loi de comportement limite généralisant celle des milieux homogènes et isotropes. Les démonstrations sont menées en décomposant vecteurs et tenseurs sur des bases locales. Une étude asymptotique formelle est conduite dans le chapitre II en utilisant des outils de géométrie différentielle intrinsèque. Les vecteurs et tenseurs ne sont plus décomposés sur des bases comme dans le chapitre précédent. La représentation paramétrique de la coque est choisie en vue de son application au chapitre III et comprend les paramétrisations des coques à surface moyenne fixe, des coques à épaisseur variable et des coques faiblement courbées. Dans le chapitre III, après l'établissement des équations tridimensionnelles de l'élasticité linéarisée près d'un état précontraint, on met en œuvre la procédure asymptotique formelle et on trouve deux modèles limites suivant l'ordre de grandeur des précontraintes et des efforts appliquées : un premier modèle uniquement membranaire et un second couplant membrane et flexion. Le quatrième chapitre est la démonstration d'un résultat de convergence vers un modèle de déflexion membranaire pour une plaque étirée constituée d'un matériau homogène et isotrope

Design and synthesis of porous organic polymers have attracted considerable attentions during the past decade due to their wide range of applications in gas storage, gas separation, energy conversion, and catalysis. Porous organic polymers can be pre-synthetically and post-synthetically functionalized with a wide variety of functionalities for desirable applications. Along these pursuits, we introduced new synthetic strategies for preparation of porous organic polymers for selective CO2 capture. Porous azo-linked polymers (ALPs) were synthesized by an oxidative reaction of amine-based monomers using copper(I) as a catalyst which leads to azo-linkage formation. ALPs exhibit high surface areas of up to 1200 m2 g-1 and have high chemical and thermal stabilities. The nitrogen atoms of the azo group can act as Lewis bases and the carbon atom of CO2 can act as a Lewis acid. Therefore, ALPs show high CO2 uptake capacities due to this Lewis acid-based interaction. The potential applications of ALPs for selective CO2 capture from flue gas, natural gas, and landfill gas under pressure-swing and vacuum swing separation settings were studied. Due to their high CO2 uptake capacity, selectivity, regenerability, and working capacity, ALPs are among the best porous organic frameworks for selective CO2 capture. In our second project, a new bis(imino)pyridine-linked porous polymer (BIPLP-1) was synthesized and post-synthetically functionalized with Cu(BF4)2 for highly selective CO2 capture. BIPLP-1 was synthesized via a condensation reaction between 2,6-pyridinedicarboxaldehyde and 1,3,5-tris(4-aminophenyl)benzene, wherein the bis(imino)pyridine linkages are formed in-situ during polymerization. The functionalization of the polymer with Cu(BF4)2 was achieved by treatment of the polymer with a solution of Cu(BF4)2 via complexation of copper cations with bis(imino)pyridine moieties of the polymer. BF4- ions can act Lewis base and CO2 can act as a Lewis acid; and therefore, the functionalized polymer shows high binding affinity for CO2 due to this Lewis acid-based interaction. The functionalization of the pores with Cu(BF4)2 resulted in a significant enhancement in CO2 binding energy, CO2 uptake capacity, and CO2 selectivity values. Due to high reactivity of bis(imino)pyridines toward transitions metals, BIPLP-1 can be post-synthetically functionalized with a wide variety of inorganic species for CO2 separation and catalytic applications.

Dottorato di Ricerca in "Ingegneria Chimica e dei Materiali" Ciclo XXVI, a.a. 2013-2014
Questo elaborato finale del progetto di dottorato tratta lo studio del processo di cristallizzazione a membrana finalizzato alla produzione di composti farmaceutici in forma cristallina. Lo studio ha come obiettivo quello di dare una visione globale del processo di cristallizzazione a membrana andando oltre lo stato dell􀍛a􀆌te, bensì p􀆌opo􀅶e􀅶do l􀍛i􀅵ple􀅵e􀅶tazione della tecnica di cristallizzazione a membrana di base. A tal proposito il progetto è stato sviluppato seguendo in due diverse direzioni: da una parte la tecnica di 􀄐􀆌istallizzazio􀅶e a 􀅵e􀅵􀄏􀆌a􀅶a di 􀄏ase ha 􀇀isto l􀍛appli􀄐azio􀅶e ad u􀅶o spe􀄐ifi􀄐o settore dell􀍛i􀅶dust􀆌ia fa􀆌􀅵a􀄐euti􀄐a, dall􀍛alt􀆌a pa􀆌te lo studio è p􀆌oseguito investigando i meccanismi di cristallizzazione indotti dalla stessa membrana e successivamente ha visto una vera e propria progettazione di membrane opportunamente pensate per la cristallizzazione. Du􀅶􀆋ue, il 􀇀alo􀆌e aggiu􀅶to di tale studio 􀄐o􀅶siste 􀅶ell􀍛a􀇀e􀆌e di􀅵ost􀆌ato la possibilità di ampliare il campo di applicazione del processo a membrana, di aver esteso la conoscenza di base dei meccanismi di nucleazione eterogenea sottesi dalla membrana e di aver progettato, prodotto e caratterizzato delle membrane con differenti materiali e strutture appositamente per essere testati nella tecnica di cristallizzazione. In dettaglio, il lavoro presenta uno studio iniziale sul processo di nucleazione eterogenea che parte da particelle libere in soluzione per poi continuare studiando il processo di nucleazione eterogenea sullle membrane stesse. U􀅶a se􀄐o􀅶da sezio􀅶e t􀆌atta l􀍛appli􀄐azio􀅶e del processo a membrana alla cocristallizzazione farmaceutica. Successivamente inizia la parte di disegno e realizzazione di membrane eterogenee sia dal punto di vista chimico che strutturale: membrane fabbricate con tecniche e materiali differenti e membrane commerciali che sono state opportunamente funzionalizzate. Infine il lavoro si conclude con i tests di cristallizzazione condotti su tali membrane.
Università degli Studi della Calabria

Dissertação de mestrado integrado em Engenharia Civil
Os efeitos dos produtos farmacêuticos no ambiente e consequentemente nos seres vivos têm vindo a causar uma inquietação crescente quer na comunidade científica, quer nas entidades gestoras de sistemas de tratamento de águas. Tendo em conta que os mesmos são usados no tratamento e prevenção de doenças, o seu consumo e disseminação nos meios hídricos tem aumentado de forma preocupante. São constantemente desenvolvidas novas substâncias cujo ciclo de vida e efeitos no ambiente são muitas vezes ainda desconhecidos, sendo, por esse motivo, considerados como poluentes emergentes. Entre outros, os antibióticos são um dos grupos de compostos mais usados no tratamento veterinário e humano. Embora utilizados numa extensão semelhante, os fármacos veterinários, como a oxitetraciclina (OTC), não têm sido tão estudados no que respeita aos efeitos da sua emissão e presença nos ecossistemas aquáticos. Assim, na base desta dissertação estiveram presentes duas vertentes de estudo. A primeira vertente incidiu na avaliação da eficiência de degradação da OTC através da fotocatálise heterogénea, com dióxido de titânio (TiO2) e óxido de zinco (ZnO), em diferentes matrizes aquosas (água destilada e de abastecimento público) e condições de ensaio (concentração inicial do catalisador, tempo de exposição e fonte de radiação UV). A segunda vertente recaiu sobre a avaliação da permeabilidade de membranas fabricadas em laboratório, bem como a sua utilização na retenção de OTC em soluções aquosas. Nestes ensaios foram utilizadas membranas com e sem TiO2 na sua constituição, permitindo assim avaliar o efeito da presença desse fotocatalisador nesse processo de separação. Nesta dissertação foi também avaliada a toxicidade da concentração inicial do fármaco, bem como dos subprodutos resultantes da sua oxidação. A determinação das concentrações de OTC foram efetuadas com recurso à técnica laboratorial de espectrometria UV-visível. A melhor eficiência de remoção de OTC foi de 92% obtida nos ensaios de fotocatálise sob radiação da lâmpada UV, com uma concentração de 31 mg.L-1 de ZnO e para um tempo de exposição de 120 minutos. Os resultados dos ensaios de toxicidade realizados indiciam que a aplicaçao da fotocatálise com TiO2 e ZnO suspensos não induz o aparecimento de subprodutos tóxicos na água. Os valores mais satisfatórios em termos de permeabilidade hidráulica e de retenção de OTC foram obtidos com uma membrana com TiO2 na sua composição e podem considerar-se promissores.
The effects of pharmaceuticals in the environment and consequently in living beings have been causing an uneasiness growing in the scientific community and in managing bodies of water treatment systems. Given that they are used in the treatment and prevention of diseases, their consumption and dissipation in water resources has alarmingly increased. Constantly are developed new substances whose life cycle and effects on the environment are often still unknown, and, therefore, considered as emerging pollutants. Among others, antibiotics are one of the groups of compounds commonly used in veterinary and human treatment. Although used to a similar extent, veterinary drugs, such as oxytetracycline (OTC), haven’t been as studied with regard on the effects of their issue and presence in the ecosystems. So, on the basis of this dissertation were present two study sections. The first part focused on the evaluation of the OTC degradation efficiency by heterogeneous photocatalysis, with titanium dioxide (TiO2) and zinc oxide (ZnO), in different aqueous matrices (distilled water and public supply) and test conditions (initial concentration of catalyst, exposure time and UV radiation source). The second part has fallen on the evaluation of membrane permeability manufactured in laboratory as well as their use in OTC retention in aqueous solutions. The membranes used in these tests were with and without TiO2 in its composition, allowing to evaluate the effect of the presence of the photocatalyst in the separation process. On this thesis was also evaluated the toxicity of the initial drug concentration and of the by-products resulting from the oxidation. The determination of OTC concentrations were performed using the laboratory techniques of UV-visible spectroscopy. The OTC better removal efficiency of 92% was obtained in the photocatalysis tests under irradiation of UV light, at a concentration of 31 mg L-1 of ZnO and a time of 120 minutes exposure. The results of the toxicity tests indicate that the application of photocatalysis with TiO2 and ZnO suspended doesn't induce the appearance of toxic by-products in the water. The most satisfactory values in terms of hydraulic permeability and OTC retention, were obtained with a membrane with TiO2 in their composition and that can be regarded as promising.

The study of lateral heterogeneity on membrane surface has come a long way from the fluid mosaic model. Simulations and experimental studies have observed non-random mixing of lipids and proteins in the membrane. In this thesis, we have systematically addressed certain aspects of the current understanding of lateral organisation (summarised above). We believe there is scope for much work in this area. The forefront in investigations of lateral membrane organisation is to do with studying the effect of • membrane lipid and protein asymmetric distribution • cellular environment and physical factors such as presence of glycans, solvation of the membrane and • coupling of membrane lipids and proteins to cortical cytoskeleton on lateral organization in biological membranes. Generating an active model for the membrane which involves studying the coupling of cortical actin meshwork to the lipids and proteins on the membrane to control lateral organisation is a tough problem. With better understanding of physics of active non-equilibrium systems and experimental methods that can image lipid organisation in vivo, we believe we can gain better insights into functional importance of lateral organisation in biological membranes

In this project, nonlinear behavior of biomembrane are modeled as heterogeneous elastic biological systems. In addition to the static behavior of the membranes, their dynamic behavior are modeled to be able to investigate time-dependency of the variables of the systems. Some of the available models are used and some new ones are developed to study static and dynamic analysis of monolayer and bilayer membranes as well as circular axisymmetric biomembranes. The presented models are developed based on the Euler-Bernoulli constitutive law and employed to investigate buckling phenomena in the membranes as one of the most important physical phenomena in biological environment. Static and dynamic behavior of Buckling phenomenon in biological membranes are modeled. The static model results in nonlinear ordinary di erential equation for one-dimensional approximation. In order to extend the model for circular membranes, the criteria of constant length in one-dimensional membranes is changed to constant surface. Moreover, tension-compression and bending springs are added to the model and employed to study buckling of biomembranes. Similar to the procedure of obtaining the equations of static large deformation of the membrane, the equations of motion of the membrane is obtained using free body diagram of an in finitesimal element of the membrane and employing Euler- Bernoulli constitutive law. Hence, nonlinear integro partial di erential equations are obtained t model the dynamic behavior of the membrane. All of the equations, including static and dynamic ones, are changed to the dimensionless forms so that the results can be considered general and can be employed to analyze diff erent systems with diff erent properties. The nondimensional equations of each part of the project are solved using di erent iterative and time-dependent schemes. The schemes are used to obtain the discretized forms of the equations. The discretized equations of all nodes of the domain, with due attention to the considered boundary conditions, are gathered in a matrix and the matrix solved to obtain the solution of the variables at each node and time stage. The solutions obtained for diff erent problems investigated in this project are employed to illustrate variations of diff erent dependent variables of the models with respect to the independent variables and parameters of the problems. As the important step to analyze the problems, diff erent results of the problems investigated in the project are verifi ed using the available information in literature. Membrane pro le are obtained for di erent parameter values and external forces in the stationary condition. In addition, variation of maximum deflection and slope are studied with respect to the variation of diff erent dimensionless parameters of the system. As a verifi cation of the solution, the incompressibility of bilayer membrane is shown as well. Growth of di fferent variables is shown with respect to time employing the solution of dynamic modeling of the membrane. As one of the important parts of this project, e ects of heterogeneity on dynamic behavior of the membrane under buckling is investigated. The heterogeneous region is considered to have di fferent material properties and it position is changed to also study the geometrical e ffects.

Doctor of Philosophy
Department of Chemical Engineering
Mary E. Rezac
Characterizing a catalytic metal surface during heterogeneous hydrogenation is an enabling area of catalysis research. Available technology, however, often requires ultra-high vacuum or other limiting conditions which prohibit in operando research. Atomic force microscopy (AFM) can provide direct observations of fluid/solid interfaces at atmospheric conditions and in real time. Tapping-mode AFM can examine chemical and physical phenomena on surfaces in addition to topography. The work here describes using phase-angle information from tapping-mode AFM to observe liquid/solid interfaces in real time during the hydrogenation of styrene. Through optimized tuning and scanning procedures, it was possible to observe the onset of hydrogenation on the surface of palladium immersed in liquid in real time and with the topographic resolution inherent to AFM. This opens new avenues for in operando research on heterogeneous catalysis, a field that is of great fundamental and industrial importance. For reference, a catalytic membrane reactor (CMR) was used to observe the hydrogenation of phenylacetylene over a palladium layer as a batch process. It was determined that with a H2 diffusion rate of 3.7·10-9 mol/s and a theoretical, calculated H2 demand of at least 2.3·10-7 mol/s, the reaction would be hydrogen starved and would not progress at a realistic timescale for observation by AFM. By instead using either ethylbenzene (EB) or styrene (St) as the liquid in a solvent-free approach and injecting a small volume of the other liquid into the system mid-scan, the effects of changes in chemistry on tip-surface interactions were observable. EB injections in both EB and St-immersed scans showed no significant change in phase angle. Injecting St into an EB-immersed scan environment, however, caused an increase in phase which remained relatively constant for the remaining duration of the scan, demonstrating for the first time that a liquid-phase hydrogenation reaction can be observed in operando through the phase shift of tapping mode AFM.

Thesis (Ph. D.)--University of Alberta, 2009.
Title from PDF file main screen (viewed on Nov. 27, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy, Department of Mechanical Engineering, University of Alberta." Includes bibliographical references.

碩士
國立臺灣大學
環境工程學研究所
105
Capacitive deionization (CDI) has been developed as a promising electrochemical technology for removing ionic species. Recently, ion-exchange based materials have been widely introduced into the CDI, constituting a membrane capacitive deionization (MCDI) system to further enhance the ion removal efficiency. Many researchers have developed the high exchange capacity, low cost and environmental friendly ion-exchange electrodes. In this study, the heterogeneous anion-exchange composite electrodes were prepared to increase the phosphate removal from water. The heterogeneous anion-exchange carbon electrode (AE-AC) was integrated with anion-exchange resin (AE) and activated carbon (AC) via a facile approach. The surface analyses were implemented to characterize the physical and chemical behaviors of the electrodes, such as scanning electron microscope and X-ray photoelectron spectroscopy. Besides, as resulted by electrochemical measurements (e.g., cyclic voltammetry), the carbon electrode coated with anion-exchange layer has good capacitive properties for ion storage. The batch-mode desalination performance of MCDI using the AE-AC electrode as anode material showed superior phosphate electrosorption capacity of 0.0716 mmol/g-carbon. The optimal charging and discharging potentials were determined by the electrosorption-desorption cycling experiments. The effects of pH and competition with other ions on phosphate removal were also tested. Importantly, the phosphate electrosorption capacity of AE-AC electrode in the single-pass CDI experiment is 0.1235 mmol/g-carbon, which is about 3.5 times more than that of the activated carbon electrode. One can conclude that the heterogeneous anion-exchange layer coated carbon electrode has the great potential for enhanced phosphate removal in MCDI process.

In this thesis, two numerical modeling methods are used to investigate the thermal conductivity of the polymer electrolyte membrane (PEM) fuel cell gas diffusion layer (GDL). First, an analytical model is used to study the through-plane thermal conductivity from representative physical GDL models informed by microscale computed tomography imaging of four commercially available GDL materials. The effect of the heterogeneity of the through-plane porosity of the GDL and polytetrafluoroethylene (PTFE) treatment is studied and it is noted that the high porosity surface transition regions have a dominating effect over the addition of PTFE in impacting the overall thermal conductivity. Next, the lattice Boltzmann method (LBM) is employed to study both the in-plane and through-plane thermal conductivity of stochastic numerically generated GDL modeling domains. The effect of GDL compression, binder content, PTFE treatment, addition of a microporous layer (MPL), heterogeneous porosity distributions, and water saturation on the thermal conductivity are investigated.

碩士
國立中山大學
機械與機電工程學系研究所
93
A new type of heterogeneous carbon fiber bunch bipolar plate developed in our lab is applied to portable pure hydrogen proton exchange membrane fuel cell stacks. Several different types of bipolar plate structures have been designed, and the voltages and currents of these fuel cell stacks are measured to compare their performance. The new type of heterogeneous carbon fiber bunch bipolar plate is well in low contact resistance, weight low, small volume and the flexible geometry shape. Due to its flexible structure of carbon fiber bunch, the compressing pressure is small while assembling stack so that the electrode can not be over compressed and out of shape. Therefore the high porosity of diffusion layer can be keep and reaction gas can enter and distribute to all reaction areas easily. For using to portable equipments, a small 6-cell flat type of fuel cell stack are developed firstly. The total weight is about 75g and the total volume is about 68cm . The second stack is cylinder-type(I) fuel cell stack. The total weight is about 60g and the total volume is about 71cm . The third stack is cylinder-type (II). The total weight has been reduced to about 20g and the total volume has been reduced to about 30cm . Above three kinds of the 6-cell stacks the total electrode area is 13.5cm . Using Nafion, the catalyst content anode Pt 0.4mg/cm , cathode Pt 1.0mg/cm , On room temperature and inlet hydrogen gauge pressure 0.15atm air-breathing, total output power of the cylinder (II) can reach 1.85W, and the power density of unit area can reach about 137mW/cm^2.

This research work discusses the removal of organic pollutants specifically diclofenac and acid blue-25 using chalcogenide semiconductors. Semiconductors are materials that absorb light of specific energy and potentially degrade these organic pollutants into smaller compounds that are not toxic such as carbon dioxide and water.
Civil and Chemical Engineering