PhD Thesis Defence Presentations - Christos Kostaras
Abstract (Περίληψη)
During the last years the electrothermal properties of graphene and carbon nanotubes have attracted researchers' interest towards their application anti-icing applications for wind generators and airplane wings. This works focuses on the electothermal response along with the mechanical properties of paper-like graphene/CNT hybrid structures (buckypapers). Two main methods were employed for the development of hybrid buckypapers. The first method involved the filtration of surfactant aided graphene/MWCNT suspensions (inks). The second method involved the filtration of graphene oxide/oxidized MWCNT inks followed by the chemical reduction of the modified nanomaterial-based buckypaper. Mechanical characterization via tensile tests along with temperature measurements of samples under constant electrical voltage showed that buckypapers that were developed via the second method greatly surpassed the buckypapers that were formed by the first method both in terms of mechanical properties and electrothermal response. Graphene oxide was produced via the chemical exfoliation of large graphite flakes ensure larger lateral sizes than pristine graphene used in the first method. Concurrently, oxidized MWCNTs displayed a truncated size after chemical modification. As a result, buckypapers that included chemically modified nanomaterials and their chemically reduced counterparts displayed a compact structure that translated to superior mechanical and electrical properties. Furthermore, by comparing the mechanical properties of modified and reduced buckypapers an increase of toughness was observed after reduction and was more pronounced for higher reduced graphene oxide content, due to material plasticity having been enhanced by the removal of chemical groups. Finally, the mechanical testing of hybrid composite buckypapers that exhibited small polymer weight fractions (10 wt. %) were also conducted. Testing revealed a general increase of mechanical properties except for strain at failure, between composite and neat buckypapers
Speakers Short CV (Σύντομο Βιογραφικό Ομιλητή)
Christos Kostaras is a graduate of the Physics Department of the University of Patras (2014) and the post-graduate program for Master's Diploma of the same department with Material Physics as a specialty (2016). At the end of the Master's program he presented his Master's Thesis titled (trans.) "Adsorption of Diblock Copolymers within Cylindrical Nanopores". He enrolled in 2017 in the post-graduate studies for acquiring a PHD of the Chemical Engineering Dpt. of University of Patras where he joined the research group of the Nanotechnology and Advanced Materials Laboratory with the aim of completing his thesis over nanocomposites based on graphene; under the initial guidance of Professor Costas Galioitis and later on under Assistant Professor Konstantinos Dassios. During his stay in the program he has worked on two research projects under funding from the general secretariat for research and innovation and the european comission. His reasearch intersts revolve around the study of intrinsic properties of two- and one-dimensional materials and transfer of said properties to the macroscale.
Publications
- Christos Kostaras, Dimitra Patroni, Nikolaos Spiliopoulos, Dimitrios L. Anastassopoulos, Alexandros Vradis, and Chris Toprakcioglu "Flow through Alumina Nanopores Bearing Responsive Polymer Brushes" Macromolecules 2022, 55, 14, 6231–6237
- Christos Kostaras, Spilios Dellis, Anastasia Christoulaki, Dimitrios L. Anastassopoulos, Nikolaos Spiliopoulos, Alexandros Vradis, Chris Toprakcioglu, and George D. Priftis "Flow through polydisperse pores in an anodic alumina membrane: A new method to measure the mean pore diameter" J. Appl. Phys. 124, 204307 (2018)
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Marinos Dimitropoulos, George Trakakis, Nikolaus Meyerbröker, Raphael Dalpke, Polina Angelova, Albert Schnieders, Christos Pavlou, Christos Kostaras, Costas Galiotis, Konstantinos Dassios "Nanomechanics of ultrathin carbon nanomembranes for water separation" accepted for publication
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Christos Kostaras, Christos Pavlou, Koutroumanis Nikolaos, George Paterakis, George Trakakis, Costas Galiotis, Konstantinos G. Dassios, "Rapid Resistive Heating in Graphene/Carbon Nanotube Hybrid Films for De-Icing Applications" accepted for publication
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Christos Kostaras, George Trakakis, Christos Pavlou, Konstantinos G.Dassios "CNT Sheets and Graphene Sheets: Fabrication Methods and State of the Art Applications" submitted for publication
Conferences and workshops
- 26 - 30/06/2022 20th European Conference on Composite Materials Lausanne, Switzerland: Poster title "Robust and Flexible Resistive Heating Graphene and MWCNT Heaters - Ultra-Fast Resistive Heating Response and High Temperature Performance"
- 08 - 10/12/2021 Smartfan Conference and Workshop Lavrion, Greece: Poster tittle "Flexible graphene and MWCNT Joule heaters: Towards the design and integration of fast and thin heating elements"
- 26 - 27/01/2021 Grpahene Industrial Forum 2021 (Online conference): Poster title "Micromechanical Characterisation of Oxidized Carbon Nanotube and Graphene Oxide Papers"
- 01/10/2018 4th Workshop of Graduates and Post-Docs in Chemical Engineering Sciences (CES-WGP4): Poster title "Production of Graphene via Shear Induced Exfoliation of Graphite in Aqueous Media"
- 04 - 06/06/2015 10th Panhellenic Scientific Conference of Chemical Engineering Presentation Title: "Stimuli Responsive Polymer Brushes into Nanoconfined Geometry"