Publications by authors named "Christos Argirusis"

10 Publications

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Study on the influence of advanced treatment processes on the surface properties of polylactic acid for a bio-based circular economy for plastics.

Ultrason Sonochem 2021 Jun 10;76:105627. Epub 2021 Jun 10.

Clausthal Centre for Materials Technology (CZM), Clausthal University of Technology, Leibnizstr. 9, 38678 Clausthal-Zellerfeld, Germany; School of Chemical Engineering, National Technical University of Athens, 9 Heroon Polytechneiou St., Zografou Campus, 15780 Athens, Greece. Electronic address:

New biotechnological processes using microorganisms and/or enzymes to convert carbonaceous resources, either biomass or depolymerized plastics into a broad range of different bioproducts are recognized for their high potential for reduced energy consumption and reduced GHG emissions. However, the hydrophobicity, high molecular weight, chemical and structural composition of most of them hinders their biodegradation. A solution to reduce the impact of non-biodegradable polymers spread in the environment would be to make them biodegradable. Different approaches are evaluated for enhancing their biodegradation. The aim of this work is to develop and optimize the ultrasonication (US) and UV photodegradation and their combination as well as dielectric barrier discharge (DBD) plasma as pre-treatment technologies, which change surface properties and enhance the biodegradation of plastic by surface oxidation and thus helping bacteria to dock on them. Polylactic acid (PLA) has been chosen as a model polymer to investigate its surface degradation by US, UV, and DBD plasma using surface characterization methods like X-ray Photoelectron Spectroscopy (XPS) and Confocal Laser Microscopy (CLSM), Atomic Force Microscopy (AFM) as well as FT-IR and drop contour analysis. Both US and UV affect the surface properties substantially by eliminating the oxygen content of the polymer but in a different way, while plasma oxidizes the surface.
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http://dx.doi.org/10.1016/j.ultsonch.2021.105627DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8209739PMC
June 2021

Synergetic decolorization of azo dyes using ultrasounds, photocatalysis and photo-fenton reaction.

Ultrason Sonochem 2021 Mar 20;71:105367. Epub 2020 Oct 20.

School of Chemical Engineering, National Technical University of Athens, 9 Heroon Polytechneiou St., Zografou Campus, 15780 Athens, Greece; Clausthal Centre for Materials Technology (CZM), Clausthal University of Technology, Leibnizstr. 9, 38678 Clausthal-Zellerfeld, Germany. Electronic address:

In the present work, ultrasound irradiation, photocatalysis with TiO, Fenton/Photo-Fenton reaction, and the combination of those techniques were investigated for the decolorization of industrial dyes in order to study their synergy. Three azo dyes were selected from the weaving industry. Their degradation was examined via UV illumination, Fenton and Photo-Fenton reaction as well as ultrasound irradiation at low (20 kHz) and high frequencies (860 kHz). In these experiments, we investigated the simultaneous action of the ultrasound and UV irradiation by varying parameters like the duration of photocatalysis and ultrasound irradiation frequency. At the same time, US power, temperature, amount of TiO photocatalyst and amount of Fenton reagent remained constant. Due to their diverse structure, each azo dye showed different degradation levels using different combinations of the above-mentioned Advanced Oxidation Processes (AOPs). The Photo-Fenton reagent is more effective with US 20 kHz and US 860 kHz for the azo dyes originated from the weaving industry at pH = 3 as compared to pH = 6.8. The combination of the Photo-Fenton reaction with 860 kHz ultrasound irradiation for the same dye gave an 80% conversion at the same time. Experiments have shown a high activity during the first two hours. After that threshold, the reaction rate is decreased. FT-IR and TOC measurements prove the decolorization due to the destruction of the chromophore groups but not complete mineralization of the dyes.
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http://dx.doi.org/10.1016/j.ultsonch.2020.105367DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7786534PMC
March 2021

Rhenium oxide nanoparticles - Sonochemical synthesis and integration on anode powders for solid oxide fuel cells.

Ultrason Sonochem 2020 Dec 8;69:105250. Epub 2020 Jul 8.

National Technical University of Athens, School of Chemical Engineering, Laboratory of Inorganic Materials Technology, I. Polytechniou 9, 15773 Zografou, Athens, Greece; Technische Universität Clausthal, Clausthal Research Center for Materials Technology (CZM), Leibnizstr. 9, 38678 Clausthal-Zellerfeld, Germany. Electronic address:

Rhenium oxide nanoparticles have been prepared using ultrasonication at 20 kHz. Samples characterization was committed via SEM-EDX, TEM, XRD, and Raman spectroscopy. Various experimental parameters were examined, including precursor/substrate amounts, ultrasonication intensity, and type of solvent used. Insights to the agglomeration of the prepared nanoparticles depending on the preparation parameters are given. As ultrasonic source we used either an ultrasonic probe by Sonics & Materials Inc. (20 kHz, 750 W net output) or a Bandelin SONOPULS HD 3200 ultrasound generator (20 kHz, 200 W net output) at intensities between 30 and 100 W/cm. The rhenium oxide nanoparticles haven been decorated on state-of-the-art anode materials (NiO/GDC) for solid oxide fuel cells (SOFCs) in order to prepare catalytically more active anode powders. These experiments revealed that ultrasonication intensity and solvents used are able to affect final nanoparticles size distribution and morphology. At the same time, ratio of precursor and substrate compounds amounts as well as ultrasonication intensity and duration were all found to affect the decoration loading extend of nanoformations on substrate powders. The results showing the influence of the above-mentioned parameters allowed for the quantification of the effects on the loading and the preferable sites of the decoration.
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http://dx.doi.org/10.1016/j.ultsonch.2020.105250DOI Listing
December 2020

A study on the synchronous decoration of molybdenum oxide or tungsten oxide nanoparticles on anode materials for natural gas fed solid oxide fuel cells using ultrasounds.

Ultrason Sonochem 2019 Dec 1;59:104715. Epub 2019 Aug 1.

National Technical University of Athens, School of Chemical Engineering, Laboratory of Inorganic Materials Technology, I. Polytechniou 9, 15773 Zografou/Athens, Greece; Technische Universität Clausthal, Clausthal Research Centre for Materials Technology (CZM), Leibnizstr. 9, 38678 Clausthal-Zellerfeld, Germany. Electronic address:

Sonochemistry was used for the metal oxides nanoparticle synthesis. All experiments were run using a BANDELIN Sonopuls HD 3200 ultrasonic generator (20 kHz, 200 W net output) with a ultrasonic probe in thermostated environment of 80 °C under ambient air. At the same time, ultrasonication activity achieved their decoration on state-of-the-art fuel cell anode powders. These modified powders shall be used in solid oxide and ceramic proton exchange membrane fuel cells anode sites. Metal oxide nanoformations synthesized were those of tungsten and molybdenum. In case of sonochemical synthesis, organometallic compounds dissolved in organic solvents played the role of precursors. Experiments of metal oxides synthesis revealed that ultrasonication intensity and solvents are able to affect final nanoparticles size distribution and morphology. At the same time, ratio of precursor and substrate compounds amounts as well as ultrasonication intensity and duration were all found to affect the decoration loading extent of nanoformations on substrates. Transmission electron microscopy was mainly used for identifying the final product of each synthesis attempt. Moreover, selected area diffraction of characteristic formations examined, gave important information about the nanocrystallinity and stoichiometry of all materials synthesized.
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http://dx.doi.org/10.1016/j.ultsonch.2019.104715DOI Listing
December 2019

Metal Organic Frameworks (MOFs) and ultrasound: A review.

Ultrason Sonochem 2019 Apr 9;52:106-119. Epub 2018 Nov 9.

National Technical University of Athens, School of Chemical Engineering, 9 Heroon Polytechniou, 15773 Zografou, Athens, Greece; Clausthal Centre of Materials Technology, Leibnizstr. 9, 38678 Clausthal-Zell., Germany; Institute of Energy Research and Phys. Technologies, Clausthal University of Technology, Leibnizstr. 4, 38678 Clausthal-Zell., Germany. Electronic address:

Metal-organic frameworks (MOFs) have received a lot of attention due to their unique properties and abundant functionalities. Permanent porosity and high surface area are just a few traits that have made them attractive to researchers. They can be prepared as task-specific materials by exploiting the functional group variety and tuning their size and geometry. The main purpose of this review is to present an alternative method of preparing MOF crystals and underline the advantages of ultrasound assisted (sonochemical) synthesis. State of the art ultrasound assisted techniques for the preparation of MOFs in nanoscale are presented. Optimization of morphology and particle size is highlighted throughout this work, as we discuss the effects of various factors, such as energy input, reagent concentration, adequate solvents, reaction time and more.
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http://dx.doi.org/10.1016/j.ultsonch.2018.11.004DOI Listing
April 2019

Sonoelectrochemical one-pot synthesis of Pt - Carbon black nanocomposite PEMFC electrocatalyst.

Ultrason Sonochem 2017 Mar 13;35(Pt B):591-597. Epub 2016 May 13.

National Technical University of Athens, School of Chemical Engineering, Zografou Campus, 9 Heroon Polytechneiou St., 15773 Zografou-Athens, Greece; Institut für Energieforschung und Physikalische Technologien, Clausthal University of Technology, Leibnizstr. 4, 38678 Clausthal-Zell., Germany; Clausthaler Zentrum für Materialforschung (CZM), Agricola Str. 2, 38678 Clausthal-Zellerfeld, Germany. Electronic address:

Simultaneous electrocatalytic Pt-nanoparticle synthesis and decoration of Vulcan XC-72 carbon black substrate was achieved in a novel one-step-process, combining galvanostatic pulsed electrodeposition and pulsed ultrasonication with high power, low-frequency (20kHz) ultrasound. Aqueous chloroplatinic acid precursor baths, as well as carbon black suspensions in the former, were examined and decoration was proven by a combination of characterization methods, namely: dynamic light scattering, transmission electron microscopy, scanning electron microscopy with EDX-analysis and cyclic voltammetry. In particular, PVP was shown to have a beneficial stabilizing effect against free nanoparticle aggregation, ensuring narrow size distributions of the nanoparticles synthesized, but is also postulated to prevent the establishment of a strong metal-substrate interaction. Current pulse amplitude was identified as the most critical nanoparticle size-determining parameters, while only small size particles, under 10nm, appeared to be attached to carbon black.
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http://dx.doi.org/10.1016/j.ultsonch.2016.05.023DOI Listing
March 2017

Copper NPs decorated titania: A novel synthesis by high energy US with a study of the photocatalytic activity under visible light.

Ultrason Sonochem 2016 Jul 15;31:295-301. Epub 2016 Jan 15.

GranitiFiandre SpA, Castellarano (MO), Italy.

The most important drawback of the use of TiO2 as photocatalyst is its lack of activity under visible light. To overcome this problem, the surface modification of commercial micro-sized TiO2 by means of high-energy ultrasound (US), employing CuCl2 as precursor molecule to obtain both metallic copper as well as copper oxides species at the TiO2 surface, is here. We have prepared samples with different copper content, in order to evaluate its impact on the photocatalytic performances of the semiconductor, and studied in particular the photodegradation in the gas phase of some volatile organic molecules (VOCs), namely acetone and acetaldehyde. We used a LED lamp in order to have only the contribution of the visible wavelengths to the TiO2 activation (typical LED lights have no emission in the UV region). We employed several techniques (i.e., HR-TEM, XRD, FT-IR and UV-Vis) in order to characterize the prepared samples, thus evidencing different sample morphologies as a function of the various copper content, with a coherent correlation between them and the photocatalytic results. Firstly, we demonstrated the possibility to use US to modify the TiO2, even when it is commercial and micro-sized as well; secondly, by avoiding completely the UV irradiation, we confirmed that pure TiO2 is not activated by visible light. On the other hand, we showed that copper metal and metal oxides nanoparticles strongly and positively affect its photocatalytic activity.
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http://dx.doi.org/10.1016/j.ultsonch.2016.01.015DOI Listing
July 2016

Sonochemistry in the service of SOFC research.

Ultrason Sonochem 2014 Nov 8;21(6):1939-47. Epub 2014 Feb 8.

School of Chemical Engineering, National Technical University of Athens, 15780 Zografou Campus, Greece. Electronic address:

Decoration of SOFC anode cermets with metal nanoparticles (NPs) enchance their ability and stability in natural gas to hydrogen reform. A novel sonoelectrochemical approach of Au-NPs synthesis (mean 12.31±2.69nm) is suggested, according to which the sonication is held constant while the electrochemical activity is either pulsed or continuous. The gold colloidal solution is cosonicated with state of the art cermet powder to yield particles decorated with Au-NPs. Nevertheless sonochemical routes of mixed molybdenum, rhenium or tungsten mixed oxides synthesis are utilized in order to decorate SOFC anode cermets. The decoration loading achieved spanned from 0.1 to 10.0wt.%.
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http://dx.doi.org/10.1016/j.ultsonch.2014.02.001DOI Listing
November 2014

Enhancement of oxygen surface exchange kinetics of SrTiO(3) by alkaline earth metal oxides.

Phys Chem Chem Phys 2005 Oct 8;7(20):3523-5. Epub 2005 Sep 8.

TU Clausthal, Institut für Metallurgie, Robert-Koch-Str. 42, 38678, Clausthal-Zell., Germany.

The oxygen incorporation reaction in undoped SrTiO(3) was investigated by electrical measurements (pressure modulation technique) in the temperature range from 650-920 degrees C and by means of tracer exchange experiments in the temperature range from 458-600 degrees C. The surface of the undoped SrTiO(3) single crystals was modified by alkaline earth metal compounds leading to a tremendous enhancement of the effective surface exchange rate for oxygen incorporation as compared to the uncoated surface.
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http://dx.doi.org/10.1039/b510834aDOI Listing
October 2005

Lanthanide transport in stabilized zirconias: interrelation between ionic radius and diffusion coefficient.

J Chem Phys 2004 Sep;121(11):5482-7

TU Clausthal, Institut für Metallurgie, Robert-Koch-Strasse 42, D-38678 Clausthal-Zellerfeld, Germany.

The diffusion of all stable lanthanides was measured both in calcia stabilized zirconia (CSZ) and in yttria stabilized zirconia (YSZ) in the temperature range between 1,286 and 1,600 degrees C. The lanthanide diffusion coefficients obtained increase with increasing ionic radius. The experimental activation enthalpy of diffusion is near 6 eV for CSZ and between 4 and 5 eV for YSZ and is not strongly affected by the type of lanthanide. The results were correlated with defect energy calculations of the lanthanide diffusion enthalpy using the Mott-Littleton approach. An association enthalpy of cation vacancies with oxygen vacancies of about 1 eV (96 kJ/mol) was deduced in the case of CSZ, while there is no association in the case of YSZ. Furthermore, the change in diffusion coefficients can be correlated to the interaction parameter for the interaction between the lanthanide oxide with zirconia: The higher the interaction parameter, the higher the lanthanide diffusion coefficient.
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http://dx.doi.org/10.1063/1.1784439DOI Listing
September 2004