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Diagnostic of nitrogen post-discharge by optical emission spectroscopy
Kabeláčová, Kateřina ; Slavíček,, Pavel (referee) ; Mazánková, Věra (advisor)
The aim of this thesis is diagnose post-discharge nitrogen plasma with optical emission spectroscopy. There is long interest of investigated of nitrogen post-discharge plasma and study how to use it in theory as well as in practice. All results were measured with method of optical emission spectroscopy of post-discharge plasma. Discharge was generated by direct-current voltage generator with flowing regime. In this thesis was used for different series of experiments. First experiment was performed with adding water vapour into argon plasma. Measuring was processed at constant current 140 mA, voltage 1.5 V and pressure 1 000 Pa. It was changed flow rate and for each individual flow rate was measured in range 1–25 cm from end of active discharge. Second experiment was with adding nitrogen into argon plasma. Measuring was processed at constant current 140 mA, voltage 1.5 V and pressure 1 000 Pa. We were changing flow rate of nitrogen (0,2 sccm, 0,4 sccm and 0,8 sccm). For each individual flow rate was same experiment with changing distance from active discharge. Third experiment was about adding mercury vapour into nitrogen post-discharge. Measuring was processed at constant current 120 mA, voltage 3.5 V and pressure 1 000 Pa. Measuring was performed with two configuration: with diaphragm and without it. Last experiment was about adding air into argon plasma. Measuring was processed at constant current 140 mA, voltage 1.0 V and pressure 1 000 Pa. Temperature of outer face of tube was measured by thermocouple and infrared thermometer, was measured for last two experiments (argon – air and nitrogen). During experiments with pure nitrogen was visible phenomenon called pink afterglow which is manifested by noticeable increase pink coloration. Optical emission spectrums post-discharge was take at various range of wavelength. At argon with water vapour was 280–600 nm and at adding nitrogen into argon was at range 320–500 nm. At added mercury vapour into nitrogen was 320–600 nm. For experiment argon – air was wavelength range 320–600 nm. From results of experiments were designed dependencies of calculated intensity from measured spectra on distance from active discharge. Also were constructed dependencies of measured temperature on distance from active discharge.
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Generation of ozone by photochemical processes in CO2
Kucserová, Aneta ; Salyk, Ota (referee) ; Mazánková, Věra (advisor)
The bachelor thesis deals with the measurement of ozone concentration, which was produced by dielectric barrier discharge, corona discharge and UV lamp. The concentration of ozone in the air was also measured. The theoretical part deals with the basic properties of ozone, its use and determination of concentration by various methods. In the experimental part, ozone generation is described by the above-mentioned discharges.
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Study of chemical processes in the gliding arc discharge by optical emission spectroscopy
Maďarová, Štefánia ; Töröková, Lucie (referee) ; Mazánková, Věra (advisor)
The aim of the bachelor thesis is to study the chemical processes of the glow discharge and the sliding arc under the post discharge conditions. The post discharge or afterglow plasma means that the external source of energy is removed from the system and the relaxation process can start. The experiments in bachelor work were performed under the different experimental conditions, for various pressures and gas mixtures. The theoretical part briefly describes term plasma and kinetic processes occurring in plasma generated by electrical discharges. Also there is described the problem of Titan’s atmosphere and possibility of mimic it by the gliding arc discharge. In the experiments, pure nitrogen and a gaseous mixture of nitrogen and methane were used at the same flow rate and different pressures. Optical Emission Spectroscopy (OES) and Gas Chromatography-Mass Spectrometry (GC-MS) were used to analyze chemical reaction products. The glow discharge was generated by a DC voltage source and the measurement was in flow mode. The total gas pressure ranged from 1 000-4 000 Pa at a nitrogen flow rate of 400 ml / min and methane of 0.025 ml / min. The current was in the range of 85-150 mA. In all experimental conditions, a well-known phenomenon called “pink afterglow” was observed. This phenomenon corresponds to the maximum intensity of radiation in a stagnant discharge, exhibiting a significant increase in characteristic pink radiation. The optical emission spectra of the discharging discharge were scanned in the wavelength range 540-640 nm. Three spectral nitrogen systems (the first and the second positive and the first negative ones) have been identified in the measured spectra, they have maximum values in the so-called " "Pink-afterglow". These maxims dropped with increasing pressure and shifted to a later decay time.
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Diagnostics of electric discharges in liquids
Vašíček, Michal ; Mazánková, Věra (referee) ; Kozáková, Zdenka (advisor)
The main scope of this thesis is to measure electrical characteristics of a DC discharge in an electrolyte solution in order to evaluate individual discharge parameters (voltage, current, emitted light and sound). As a result of these parameters, a comparison between a diaphragm and capillary configuration has been realized using static and dynamic characteristics. Next part of this thesis is finding mutual differences and to set an approximate transition of individual configurations. For the study of the pin-hole discharge a polycarbonate reactor with total volume of 110 ml was used. It was divided by a changeable polyacetal insulating wall. The Shapal ceramic discs (thickness of 0.3–1.5 mm and diameter of the central pin-hole of 0.3 mm) were mounted in the centre of the insulating wall. This wall divided the reactor into two approximately equal spaces with one stainless steel electrode in each part. A DC high voltage source providing constant power supply up to 500 W was applied on the electrodes. The water solution of NaCl with initial conductivity of 570 S/cm was used as electrolyte. Time resolved electrical characteristics were recorded by a four channel oscilloscope Tektronix TDS 2024B. Measured parameters were as follows: voltage (by a HV probe Tektronix P6015A), current at ballast resistor of 5.13 , sound detected by a piezzo-microphone mounted under the reactor, and light emitted by the discharge was detected by an optical fiber in vicinity of the orifice. Measuring and processing of time resolved electrical characteristics present an accurate description of behavior of the diaphragm and capillary configuration. Voltage differences during the phase of bubble formation as well as around the breakdown point were discussed. This thesis contains a description of bubble cavitation and sets transition ratio between the diaphragm and capillary configuration approximately to l/d= 3 (where l is thickness of the wall and d is diameter of the pin-hole).
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Characterization of microwave plasma jet generated in argon-nitrogen mixtures
Truchlá, Darina ; Mazánková, Věra (referee) ; Krčma, František (advisor)
This thesis is concerned with influence of nitrogen admixture to non-thermal microwave plasma jet generated in argon flow at atmospheric pressure. Non-thermal plasma can be used in more biomedical applications such cancer treatment, blood coagulation, sterilization etc. It is necessary to know the changes of plasma composition and its parameters in dependence nitrogen concentration to avoid potentional damages of the treated tissue. Plasma jet was characterized by optical emission spectroscopy along its axis. Electron, vibrational and rotational temperatures were calculated from intensities of the selected spectral lines and bands emitted by particles generated in plasma. The results show increase of the nitric oxide concentration followed by the increase UVC radiation. Temperature of the neutral gas increase too, but not so much and thus jet with nitrogen addition can be still used for the treatment of thermosensitive materials such as human tissue. Study of the sterilization effect of microwave plasma generated in argon-nitrogen mixtures is still under progress. Some of the results obtained during this thesis were included in the paper submitted into Journal of Physics D: Applied Physics.
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Study of ozone reactions with the surface of metallic materials
Krzyžanková, Anežka ; Kozáková, Zdenka (referee) ; Mazánková, Věra (advisor)
This bachelor thesis is focused on the study of ozone and oxygen reactions with the surface of metallic materials. Ozone undergoes spontaneous decomposition, which is, for example, influenced by increased temperature or reactions with other substances. The aim is to find out how fast heterogeneous decomposition or ozone formation takes place on different metal surfaces. The theoretical part describes the properties of ozone, possibilities of its use, generation of ozone, methods of determination of concentration and relation of ozone to solid surfaces. The experimental part examines how the ozone concentration changes depending on the reaction time at room temperature, the change in oxygen and argon flow during blowing, and the decomposition itself on the steel, copper, and aluminum surfaces. The ozone generated from the oxygen was enclosed in a metal material tube and allowed to react for a certain period of time. After this time, the ozone was blown out by various oxygen flow rates. Ozone concentration was monitored by absorption spectrometry. The dependence obtained shows that ozone concentration decreases. In further experiments, ozone was allowed to flow through the tubes for 5 min. After this time, pure oxygen was fed into the tube and ozone formed by heterogeneous surface reactions. The influence of the reaction time on the formation and disappearance of ozone on the surfaces was investigated. Finally, surface analysis was performed using a scanning electron microscope with elemental analysis.
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Polymer layers prepared on the basis of 2-methyl-2-oxazoline by plasmachemical method and their diagnostics
Podzemná, Daniela ; Kozáková, Zdenka (referee) ; Mazánková, Věra (advisor)
The main topic of this bachelor thesis was preparation of 2-methyl-2-oxazoline-based thin polymer layers. These layers were prepared by plasma polymerization in a dielectric barrier discharge in an inert nitrogen atmosphere. In experimental part polyoxazoline layers were characterized using several diagnostic methods. The first one was study of layers surface using scanning electron microscopy, next was determination of contact angles and subsequent determination of free surface energy. Antibacterial properties were also investigated by antibacterial tests using a bacterial culture of Staphylococcus epidermidis.
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Optical emission spectroscopy of the nitrogen post-discharge plasma with metal trace impurity
Bocková, Ivana ; Mazánková, Věra (referee) ; Krčma, František (advisor)
The bachelor´s thesis deals with the optical emission spectroscopy of the nitrogen post-discharge with metal trace impurity. The analysed sample introduced to the low-temperature plasma was zinc vapor and stannic chloride. As a diagnostic method was choosen optical emission spectroscopy as one of the simplest plasma diagnostic methods. The teoretical part is aimed to information about plasma and processes in the plasma. The special focus is deald for post-discharged plasma and the optical emission spectroscopy. Measurement itself is implemented in flowing regime of DC post-discharge under low pressure. The intensities of selected nitrogen bands and atomic lines are observed as a function of metal vapor presence. The simplified mechanism of the observed phenomen is presented. The possible excitation mechanisms are shown of metallic atoms during the post-discharge.
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Study of post-discharge in N2-H2 mixtures
Zedníčková, Petra ; Mazánková, Věra (referee) ; Krčma, František (advisor)
The presented Thesis deals on the nitrogen-hydrogen DC post-discharge observations by optical emission spectroscopy. The plasma was generated in Pyrex tube in flowing regime at pressure of 1 kPa at discharge current of 100 mA. The optical emission spectra were recovered at discharge times up to 50 ms in nitrogen containing 0 – 92 % of hydrogen; the gas mixture volume, i.e. the gas speed in the system was conserved for all mixtures. The experiments were carried out at two reactor wall temperatures at the spectra collecting point – at ambient temperature and at the wall temperature of liquid nitrogen (temperature in plasma was about 150 K). The nitrogen first and second positive and first negative spectral systems were identified in the spectra, the hydrogen atomic Balmer series lines were recorded, too. No molecular hydrogen emission was determined during the post-discharge. Some non-identified bands (but with high probability bands of nitrogen Herman infrared system) at 690 and 780 nm were detected, too, mainly at low temperature. The intensities of all determined radiating species decreased exponentially or more than exponentially with the decay time. The experimental data showed strong quenching of all nitrogen radiative states even at very a few percent hydrogen additions. The shape of the selected intensity dependencies on both hydrogen concentration, and the decay time are nearly the same for N2(C) and N2+(B) states, dependencies for N2(B) levels differs of them. The hydrogen line emission was nearly independent on the hydrogen content in the gas mixture up to about 50%, at highest hydrogen concentrations it slightly increased. The results obtained at the decreased wall temperature were very similar, only intensities of all nitrogen spectra increased by the factor about 3, the intensities of levels populated by the recombination of nitrogen atoms increased by factor about five. The atomic hydrogen alpha line (at 656 nm) was the most sensitive on temperature decrease; its intensity increased over one order in whole observed time interval. The obtained results will be confronted with numeric model of kinetic processes in the near future. After that, the specific conditions applicable for the technological applications of nitrogen-hydrogen gas mixtures under post-discharge conditions will be proposed.
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