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Identifier 000457409
Title Development and evaluation of nanocomposite membranes for proton conduction and gas separations
Alternative Title Ανάπτυξη και αποτίμηση νανοσύνθετων μεμβρανών για αγωγή πρωτονίων και διαχωρισμούς αερίων
Author Μπούτσικα, Λαμπρινή Γ.
Thesis advisor Τρικαλίτης, Παντελής
Reviewer Χαραλαμποπούλου, Γεωργία
Στεριώτης, Θεόδωρος
Φρουδάκης, Γεώργιος
Γουρνής, Δημήτριος
Μήλιος, Κωνσταντίνος
Τριανταφυλλίδης, Κωνσταντίνος
Abstract Membrane processes are nowadays well-established technologies, which have been extensively used in different fields from gas separation to fuel cells. The aim of the present Thesis was the development and thorough study of new nanocomposite dense polymeric membranes with improved properties in order to examine their suitability for energy and environmental applications with an emphasis on polymer electrolyte membrane fuel cells (PEMFCs) and mixed matrix membrane (MMM) systems for gas separation applications. In this context, as a first step, the possibility of improving the most widespread polymer electrolyte membrane for fuel cells, “Nafion®”, was investigated. This was pursued by combining Nafion with new or suitably modified nanoparticles. PEMFCs are considered very promising next generation power sources for portable/vehicular applications, due to their highenergy efficiency and power density. However, PEMFC operation also faces particular challenges, associated e.g. with the durability of its key components (such as membranes) and the need for complex and expensive heat and water management systems. An appealing strategy to improve the PEMFCs performance at operating temperatures up to 120–130 °C is the development of nanocomposite membranes by incorporating hydrophilic inorganic particles into Nafion®, in order to impart higher proton conductivity and higher thermal stability. In this respect, the present Thesis particularly focused on the development of spherical colloidal silica nanoscale ionic materials (NIMs), and 2D - organosilica layered materials bearing different functional groups. Hybrid nanocomposite membranes (1, 3, 5 wt% loadings) were prepared by solvent casting methods. The initial nanoparticles and the final nanocomposite membranes were characterized by a combination of experimental techniques (XRD, IR, TGA, SEM, TEM), the mechanical properties of the polymer films as well as their proton conductivity were tested by dynamic mechanical analysis (DMA) over a wide temperature range, while the water dynamics which is an important factor for the efficiency of the fuel cells, was examined by pulsed field gradient NMR spectroscopy. On the other hand, membrane technology has gained particular interest over the last decades also for the separation of gaseous mixtures, as it can lead to more efficient processes in industrial, energy and environmental applications (e.g. biogas upgrade, CO2 capture, etc.). In particular polymeric membranes have been extensively studied for gas separation processes mainly due to their low cost and facile fabrication. However, they also have a range of important disadvantages. In this respect, significant efforts have been devoted towards producing membrane systems with higher thermal stability, tolerance to contaminants, resistance to plasticization, and ability to compete with other well-established technologies. One of the most widespread approaches is the development of mixed matrix membranes (MMMs) that combine an organic phase (polymer) with inorganic particles and exploit the synergistic advantages from each phase such as, the separation potential of the dispersed fillers with the facile processability of the polymers. On this basis, one of the main objectives of the Thesis was to develop and evaluate specific types of MMMs focusing on CO2 gas separation processes. More specifically, two different types of polymeric materials (the rubbery Pebax® MH1657 and glassy 6FDA-DAM), that are widely used in applications involving the removal of CO2 from gas mixtures, were combined with metal organic framework (MOF) particles. Pebax® MH1657 is a PA/PEO copolymer (PA/PEO = 40/60, where PA: polyamide and PE: polyethylene; 6FDA-DAM is a high-performance glassy polyimide with high free volume and thermal stability that satisfies most gas separations, including CO2 /CH4, even under high pressures. The choice of MOFs, which are a special class of hybrid microporous crystalline materials, was based on their with excellent adsorption properties that can be controlled by tailoring their topology and porous structure. More specifically, focus was placed on the use of materials from the UiO and ZIF families in different percentages (from 5 to 20 wt%), as they also offer increased stability when they are incorporated in Pebax® MH1657 and 6FDA-DAM polymers. The performance of all membranes was evaluated experimentally with adsorption measurements at various pressure and temperature conditions to assess the corresponding CO2 solubility, as well as single gas (CO2, CH4, H2) permeability measurements to enable the calculation of the ideal selectivity for CO2 / CH4 and CO2 /H2. In all cases, along with the evaluation of the performance of the membranes, their physicochemical characterization (XRD, FT-IR, SEM, TGA/DSC) was performed to evaluate their properties before and after the incorporation of MOFs. Overall, the above work confirmed that with an appropriate synthetic procedure and inorganic filler selection, it is possible to obtain nanocomposite membranes with significantly improved properties that can be used in a range of environmental and energy applications.
Language English, Greek
Subject 6FDA-DAM
Gas separation,
Layered organosilica
MMMs
MOFs
NIMs
Nafion®
PEMFCs
Pebax
ZIFs
Διαχωρισμός αερίων
Διδιάστατη πυριτία
Κελιά καυσίμου πολυμερικής μεμβράνης αγωγής πρωτονίων
Μεταλλό- οργανικά πλέγματα συναρμογής
Νανοσύνθετες μεμβράνες μικτής μήτρας
Issue date 2023-07-28
Collection   School/Department--School of Sciences and Engineering--Department of Chemistry--Doctoral theses
  Type of Work--Doctoral theses
Permanent Link https://elocus.lib.uoc.gr//dlib/c/9/2/metadata-dlib-1689834820-70985-17787.tkl Bookmark and Share
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