E-Locus - Institutional Repository of the University of Crete - Μελέτη της πολυσυμπύκνωση του πυριτικού οξέος : πολυμερισμός του μονεμερούς ή ενσωμάτωση σε νανοσωματίδια διοξειδίου του πυριτίου απουσία και παρουσία χημικών προσθέτων

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Identifier

000422495

Title

Μελέτη της πολυσυμπύκνωση του πυριτικού οξέος : πολυμερισμός του μονεμερούς ή ενσωμάτωση σε νανοσωματίδια διοξειδίου του πυριτίου απουσία και παρουσία χημικών προσθέτων

Alternative Title

Study of polycondensation of silicic acid: polymerization of the monomer or incorporation into silicon dioxide nanoparticles in the absence and presence of chemical additives.

Author

Σκορδαλού, Γεωργία Ι.

Thesis advisor

Δημάδης, Κωνσταντίνος

Reviewer

Μήλιος, Κωνσταντίνος
Σπύρος, Απόστολος

Abstract

Diatoms constitute a fundamental class of unicellular algae that play a significant role in global silica biogenic cycle. They are capable of collecting and maintaining supersaturated solutions of soluble silicon (up to 340 mM) which they polymerize in order to form their cell wall using polymeric, amorphous silica. This research is focused on strategies to prevent the formation of amorphous silica in aqueous systems. Over the years a great deal of chemical additives have been studied (mostly polymers), either for their ability to enhance the polymerization process of silicic acid or to delay silica formation. In the latter, the additives seem to stabilize the extremely unstable silicic acidmonomer, Si(OH)₄, at levels significantly above the, in vitro, saturation concentration (~180 ppm, ~ 2 mM), in the absence of additives. The aim of this study is to shed further light on the complex mechanisms that govern the polycondencation process performed by diatoms, by using certain artificial polymers which contain functional groups of polyethyleneglycol (PEG) and pyridine rings. This project focuses on the effect of these polymers on the two aspects of silica chemistry (enhancement and inhibition), at different pH values and the interactions involved in these processes. In corporation of monomeric silicic acid species into silica nanoparticles is also studied in the absence and presence of artificial polymers under different pH conditions and temperatures.

Language

Greek

Subject

Catalysis

Diatoms

Inhibition

Polymerization

Silicicacid

Διάτομα

Κατάλυση

Παρεμπόδιση

Πολυμερισμός