Veronika OKRUHLICOVÁ alumni student
MSc. study 2021 - 2023
Supervisor: Karol Hensel Consultant: Richard Cimerman Title: Surface discharge in perforated ceramics Abstract: The diploma thesis describes the physical properties and chemical effects of a dielectric barrier discharge (DBD) generated in a perforated ceramic element and evaluates its potential for possible plasma treatment of gases polluted with low concentrations of pollutants. Experimental measurements were used to evaluate the physical properties of the investigated discharge under different operating conditions. We investigated the influence of the frequency of the applied high voltage (in the interval 0.5 - 2 kHz), the composition of the gas mixture containing nitrogen and oxygen (in gas ratios 80:20, 75:25 and 25:75) and the gas flow rate (in the interval 0.5 - 2 l/min). For all measurements, the discharge was generated at a fixed applied voltage of 6.7 kV. We investigated the influence of the above parameters on the discharge power, which was determined by the method of Lissaujous patterns, on the concentrations of generated ozone O3 and nitrous oxide N2O, which were measured by infrared absorption spectroscopy. The experimental results showed that the discharge exhibited maximum chemical activity at a frequency of 2 kHz, a flow rate of 0.5 l/min in a N2/O2 gas mixture of 25:275, where the measured O3 concentration was 4027 ± 227 ppm.
Bc. study 2020 - 2021
Supervisor: Karol Hensel Consultant: -- Title: Decontamination of respirators by surface dielectric barrier discharge Abstract: The bachelor thesis focuses on surface decontamination of respirators by means of surface dielectric barrier discharge (DBD). In the theoretical part of the work, we discussed the methods of plasma generation using electric discharges, and bio-decontamination effects of plasma in comparison to other conventional methods. We approached the issue of medical waste and focused on an excessive consumption of surgical respiratory masks as a consequence of the pandemic, as well as the impact of respirator waste on the environment and possibilities of its liquidation and decontamination. The main objective of the thesis is to present DBD decontamination of respirators as an effective method of reduction nonrecyclable waste in form of respirators. The experimental part describes series of preliminary tests to demonstrate a decontamination effect of DBD on E. coli bacteria deposited on the surface of the respirators. The DBD system consisted of a pair of electrodes encapsulated inside a dielectric material generating a plasma in a thin layer on the surface. The sample consisted of a piece of a contaminated mask and was repetitively moved trough the plasma zone. The decontamination effect of plasma was investigated at a constant value of applied voltage (2 kV, 30 kHz), while the variable factor was a processing time of the sample (15 – 300 s). After the plasma treatment, the samples were eluted in deionized water and spread on agar in Petri dish and for 20 h cultivated in an incubator. The results of the experiment were evaluated based on the number of bacterial colonies grown on Petri dishes. The results of the experiments showed that 60 s plasma treatment of a sample is sufficient to reduce the population of E. coli by 2,7 log. In case of 180 s plasma treatment 4 log reduction was achieved and we considered this effect and processing time as the optimal.
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Active
PhD students:
Jana KŠANOVÁ
Darina KUŽMOVÁ
Ramin MEHRABIFARD
Zuzana OKRUHLICOVÁ
Pankaj PAREEK
Gokul SELVARAJ
Sergei SMIRNOV
Peter TÓTH
MSc/Bc students:
Dominik DIŇA
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