Πλοήγηση ανά Συγγραφέας "Vernardou, Dimitra"
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Τεκμήριο Electrochemical characterization and understanding of the basic Intercalation mechanisms in electrodes(ΕΛΜΕΠΑ, Σχολή Μηχανικών (ΣΜΗΧ), ΔΠΜΣ Νανοτεχνολογία για Ενεργειακές Εφαρμογές, 2026-04-02) Daskalakis, Stylianos; Δασκαλάκης, Στυλιανός; Vernardou, Dimitra; Βερνάρδου, ΔήμητραDespite the high potential impact of aqueous battery systems, fundamental characteristics such as cost, safety, and stability make them less feasible for large-scale energy storage systems. Si is an attractive electrode material due to its high specific capacity. Nevertheless, it exhibits volume expansion during the intercalation/de-intercalation processes, leading to poor stability performance. Furthermore, carbon nanotubes have superior electro-conductivity and mechanical robustness, and consequently, they are extensively utilized in semiconductor, hydrogen storage, and flexible device research. Even though lithium-ion batteries have dominated the market, there are growing concerns about the limited availability of resources, high costs, and limited safety. Multivalent ion batteries have emerged as potential candidates due to their low cost, safety, energy density, and material reserves. Among the different multivalent metals, Zn has gained interest due to its high Zn/Zn2+ reversibility in aqueous environments. Due to their affordability, greater stability, and increased electrochemical performances, aluminum-ion batteries as possible post-lithium ion batteries are also appealing for large-scale electrochemical energy storage applications, such as grid-scale electric energy storage and electric cars. Hence, the target of the particular master dissertation is related with a. the development of nanocomposites based on Si with carbon nanotubes, to act as both mechanical support and electrical conductor, and b. promote an industrially competitive technology of aerosol-assisted chemical vapor deposition for a new class of material based on phenethylammonium bismuth iodide on fluorine doped SnO2-precoated glass substrate. In particular, the Si/CNT electrodes probed in ZnSO4 and Al2(SO4)3 electrolyte demonstrated a high discharge capacity of 170 mAh gSi-1at a high discharge plateau of ≈1.6 V, improved coulombic efficiency, cycling life, and stability. The intercalation/de-intercalation of Zn ions is limited for plain CNT, while, the Si-loaded electrodes show a larger integration area, indicating a higher energy storage capacity. The Si/CNT electrodes exhibited a semi-infinite diffusion or fast faradaic performance, with pseudocapacitive-dominated behavior in Zn2+. The primary range of diffusivity values of electrodes were 10-10 ~ 10-11 cm2 s–1 and 10-11 ~ 10-13 cm2 s–1 for the oxidation and reduction process, respectively. In Al3+, the electrodes displayed more faradaic-dominated performance with pseudocapacitor behavior, opposing to the electrodes in Zn2+. The results of the diffusion coefficient were in the range of 10-10 ~ 10-12 cm2 s–1, thus, verifying better ion mobility for Al3+. The Si/CNT electrode with the highest Si loading suggested the fastest Zn2+ and Al3+ mobility during the anodic and cathodic processes. Regarding the phenethylammonium bismuth iodide electrodes, they were electrochemically investigated in Zn2+ aqueous electrolytes presenting a specific capacity of 220 mAh g-1 at 0.4 A g-1 with excellent stability after 50 scans, capacity retention of almost 100%, and diffusion coefficient of 10-15 cm2 s–1 both in cathodic and anodic processes.Τεκμήριο Evaluation of APCVD V2O5 for energy storage applications(ΕΛΜΕΠΑ, Σχολή Μηχανικών (ΣΜΗΧ), ΔΠΜΣ Νανοτεχνολογία για Ενεργειακές Εφαρμογές, 2024-07-08) Zogalis, Aristeidis-Konstantinos; Ζώγαλης, Αριστείδης-Κωνσταντίνος; Vernardou, Dimitra; Remediakis, Ioannis; Βερνάρδου, Δήμητρα; Ρεμεδιάκης, ΙωάννηςMy thesis revolves around the preparation, characterisation and then evaluation of thin films of Vanadium Pentoxide in three Electrolytes. These films were on a glass substrate with a thin FTO (Fluorine doped Tin Oxide) film, our precursor being Vanadium Acetylacetonate (ACAC). The method used to create our samples was APCVD (Atmospheric Pressure Chemical Vapour Deposition). Each sample was characterised using Raman Spectroscopy, Energy Dispersive Spectroscopy (EDS), Scanning Electron Microscope (SEM) and X-ray photo electron spectroscopy (XPS). The evaluation was performed through Cyclic Voltammetry, where we observed the behaviour of our samples in each separate electrolyte, namely Lithium, Aluminium and Zinc. Additionally, there is a guide to install GPAW, a simulation program that uses DFT theory which could assist in predicting and thus “perfecting” our experimental model to yield more favourable results. Finally, we of course discuss our findings and provide some advice moving forwardΤεκμήριο Evaluation of electrode materials derived from walnut biomass and their performance in sodium-Ion electrolyte systems for sustainable energy storage(ΕΛΜΕΠΑ, Σχολή Μηχανικών (ΣΜΗΧ), ΔΠΜΣ Νανοτεχνολογία για Ενεργειακές Εφαρμογές, 2026-06-07) Tsikritsaki, Eleftheria; Τσικριτσάκη, Ελευθερία; Vernardou, Dimitra; Βερνάρδου, ΔήμητραThe growing demand for sustainable energy-storage technologies has intensified research efforts toward environmentally benign electrode materials and low-cost electrochemical systems. Among emerging solutions, biomass-derived carbons have attracted increasing attention due to their renewability, scalability, and reduced environmental footprint. In this context, the present thesis investigates walnut-shell-derived biochar as a sustainable carbon electrode material for aqueous sodium-based supercapacitor systems, with particular emphasis on the role of electrolyte chemistry in governing electrochemical performance. Walnut shells were converted into carbon electrodes through a simple activation-free pyrolysis process at 800 °C, followed by pellet fabrication using a PTFE binder. The electrochemical behavior of the produced biochar was systematically evaluated using both three-electrode and symmetric two-electrode configurations in four aqueous sodium electrolytes (Na₂SO₄, NaNO₃, NaCl, and NaOH). Cyclic voltammetry and galvanostatic charge–discharge techniques were employed to investigate charge-storage mechanisms, ion transport kinetics, and device-level performance.Τεκμήριο Exploring composite metal oxide/carbon materials: growth mechanism and electrochemical performance for energy storage(ΕΛΜΕΠΑ, Σχολή Μηχανικών (ΣΜΗΧ), ΔΠΜΣ Νανοτεχνολογία για Ενεργειακές Εφαρμογές, 2025-07-15) Nikolidakis-Owens, David; Νικολιδάκης-΄Οουενς, Δαυίδ; Vernardou, Dimitra; Βερνάρδου, ΔήμητραIn recent years, the growing global interest in environmental protection and climate change has increased the demand for efficient storage energy. Lithium-ion batteries, due to their high energy density, excellent cycle performance, small size and long lifetime performance, have gained a prominent position in everyday life, finding applications in portable devices (laptops, smart phones). However, to address safety concerns associated with the flammable organic solvents in conventional lithium-ion batteries, aqueous lithium-ion batteries have been developed. These water based systems offer enhanced safety and lower production costs, making them a promising alternative. Transition Metal Oxides, like nickel oxide (NiO), have emerged as promising anode materials for aqueous lithium-ion batteries due to their ability to reach high capacity values (700-1200 mAh/g), surpassing those of commercial graphite anode. However, their low electronic conductivity limits the rate performance. To overcome this limitation, the incorporation of conductive materials such as graphene and graphene oxide (GO) has been explored. These carbon-based materials improve the structural stability of the electrode and enhance reaction kinetics. Graphene oxide, in particular, has attracted growing interest due to its solubility in various solvents, dielectric properties and tunable electrical characteristics. By integrating GO, the resulting NiO/GO anode material can facilitate rapid electron transfer in aqueous lithium-ion batteries. In this study, GO was synthesized using a modified Hummers method, while NiO suspension and NiO/GO composite solution were both used as electrolytes in the electrodeposition process. The processing parameters like electrodeposition time, Li2SO4 electrolyte concentration, NiO concentration, PVP K12 and GO addition on the NiO suspension were systematically investigated. All samples were characterized through morphological, structural and electrochemical measurements by scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), X-ray diffraction spectroscopy (XRD) and cyclic voltammetry (CV). In conclusion, this dissertation highlights the potential of NiO and NiO/GO anode electrodes synthesized via the electrodeposition technique as cost-effective and promising films for anode materials in energy devices.Τεκμήριο Exploring the growth mechanism of the electrodeposited carbon components as potential buffer layers for energy storage applications(ΕΛΜΕΠΑ, Σχολή Μηχανικών (ΣΜΗΧ), ΔΠΜΣ Νανοτεχνολογία για Ενεργειακές Εφαρμογές, 2024-07-09) Apostolopoulou, Maria; Αποστολοπούλου, Μαρία; Vernardou, Dimitra; Βερνάρδου, ΔήμητραIn recent years, the depletion of fossil fuels and environmental pollution has prompted both industry and the scientific community to seek alternative energy sources. Lithium-ion batteries, due to their high energy density, small size, long lifetime and low pollution, have gained a dominant position in everyday life, finding application in portable devices (laptops, smart phones), power tools and electric vehicles. Due to this rapid development of technology, there is growing demand for more efficient energy storage devices. This dissertation aims to investigate carbon-based materials, especially graphene oxide as a potential buffer layer for electrodes in lithium-ion batteries (LIBs) and electrochemical capacitors (ECs). The unique properties of carbon-based materials, such as high surface area, excellent electrical conductivity and tunable pore structures, have led to their widespread application as alternative materials to traditional graphite. The material synthesis procedure was carried out using a graphene oxide dispersion solution, which was prepared by the modified Hummer method. The dispersed solution was the electrolyte in the electrodeposition technique for the immobilization of graphene oxide on copper substrate. The growth mechanism of the material was studied for different deposition time and current. Additionally, the impact of the electrolyte concentration (Li2SO4) and the amount of graphene oxide on the electrochemical behavior of the synthesized materials was investigated. Then, the stability of the optimum material obtained (i.e. highest current and material’s adhesion) was tested in 600 continuous charge/discharge cycles with sufficiently satisfactory results. In all samples, structural, morphological and electrochemical measurements were carried out by Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). In conclusion, the dissertation highlights the potential of graphene oxide synthesized via the electrodeposition technique as a cost-effective, rapid, and promising buffer layer for anode materials in energy storage devices.Τεκμήριο LTO as a promising anode material for aqueous batteries: synthesis routes, properties and electrode preparation approaches(ΕΛΜΕΠΑ, Σχολή Μηχανικών (ΣΜΗΧ), ΔΠΜΣ Νανοτεχνολογία για Ενεργειακές Εφαρμογές, 2026-05-26) Pigounakis, Emmanouil; Πηγουνάκης, Εμμανουήλ; Vernardou, Dimitra; Βερνάρδου, ΔήμητραThe growing integration of renewable energy sources into modern electricity systems has significantly increased the need for energy-storage technologies that are safe, sustainable, and cost-effective. Among the various alternatives under investigation, aqueous lithium-ion batteries (ALIBs) have emerged as a promising option due to their intrinsic safety, high ionic conductivity, environmental compatibility, and the use of non-flammable electrolytes. Nevertheless, their broader deployment remains constrained by the narrow electrochemical stability window of water and by the complex interfacial reactions occurring at the electrode–electrolyte interface. Lithium titanate (Li₄Ti₅O₁₂, LTO) has attracted considerable attention as an anode material for aqueous systems because of its exceptional structural stability, negligible volume change during lithiation and delithiation, and relatively high operating potential, which helps mitigate hydrogen evolution. This thesis presents a comprehensive literature-based study of LTO in ALIB configurations, examining synthesis approaches, structural and electrochemical characteristics, electrolyte design strategies, and electrode fabrication techniques.Τεκμήριο Ενεργειακή αναβάθμιση μεμονωμένου διαμερίσματος Α’ ορόφου κατηγορίας «Η» σε διαμέρισμα σχεδόν μηδενικής ενεργειακής κατανάλωσης «Α+» με το πρόγραμμα «Εξοικονόμιση κατ΄ οίκον» στο Ηράκλειο Κρήτης(ΕΛΜΕΠΑ, Σχολή Μηχανικών (ΣΜΗΧ), Τμήμα Μηχανολόγων Μηχανικών, 2025-11-05) Αθανασίου, Ελένη; Athanasiou, Eleni; Βερνάρδου, Δήμητρα; Vernardou, DimitraΤα τελευταία χρόνια οι παγκόσμιες απαιτήσεις για ενέργεια αυξάνονται συνεχώς. Η εξοικονόμηση είναι πλέον απαραίτητη τόσο σε τοπικό όσο και σε παγκόσμιο επίπεδο. Προκειμένου να επιτευχθεί η αναβάθμιση των υφιστάμενων κτιρίων και να κατασκευαστούν τα νέα κτίρια με σχεδόν μηδενική κατανάλωση, ορίζεται ο Κανονισμός Ενεργειακής Απόδοσης Κτιρίων (Κ.Εν.Α.Κ). Το πρόγραμμα «Εξοικονομώ-Αυτονομώ» έχει στόχο τη βελτίωση της ενεργειακής κατάταξης των υφιστάμενων κτιρίων μέσα από μία σειρά παρεμβάσεων που μπορεί να επιλέξει ο ιδιοκτήτης ανάλογα τις ανάγκες του, ενώ παράλληλα του επιδοτεί ένα πολύ σημαντικό μέρος του κόστους υλοποίησής τους. Η παρούσα διπλωματική εργασία αφορά την ενεργειακή αναβάθμιση υφιστάμενου διαμερίσματος από κατηγορία «Η» σε κατηγορία «Α+». Πρόκειται για την υλοποίηση πραγματικού έργου. Γίνεται περιγραφή της σύνταξης και κατάθεσης των δικαιολογητικών εγγράφων που απαιτήθηκαν για την διαδικασία ένταξης του υφιστάμενου μεμονωμένου διαμερίσματος στο Πρόγραμμα «Εξοικονομώ Αυτονομώ», αναλύονται όλες οι δυνατές επιλέξιμες παρεμβάσεις, οι λύσεις για την αναβάθμιση του διαμερίσματος, οι τελικές επιλογές για την βέλτιστη ενεργειακή αναβάθμιση, ο προϋπολογισμός των παρεμβάσεων, όλες οι μελέτες οι οποίες εκπονήθηκαν από την έναρξη της διαδικασίας έως και την ολοκλήρωσή της. Επιπλέον, παρουσιάζεται μετά την ολοκλήρωση της δεύτερης ενεργειακής αναβάθμισης το αποτέλεσμα εξοικονόμησης ενέργειας για την ιδιοκτησία και ακολουθούν τα τελικά συμπεράσματα για την παρούσα επένδυση.