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Influence of metallic atoms on nitrogen post-discharge
Bocková, Ivana ; Kudrle, Vít (referee) ; Krčma, František (advisor)
The aim of this master thesis is to study the influence of metallic atoms on nitrogen post-discharge. Pure nitrogen post-discharge is a subject study of many works dealing with kinetic processes in plasma. Unfortunately, there are only a few published works that present influence of various traces on nitrogen post-discharge kinetics. This master thesis deals with problems of nitrogen post-discharge containing mercury traces. All experimental data were obtained using optical emission spectroscopy of a DC discharge in a flowing mode, which can achieve appropriate temporal resolution in the order of milliseconds. Spectra emitted during the post-discharge were recorded in the range of 320-780 nm and the following molecular spectral systems were identified: • 1. positive system of nitrogen: N2(B) -> N2(A), • 2. positive system of nitrogen: N2(C) -> N2(B), • 1. negative system of nitrogen: N2+(C) -> N2+(X), • NO-beta system: NO(B) -> NO(X). Besides them we were able to record the mercury line at 254 nm, only (in the spectrum of the first as well as in the second order); no other mercury lines were observed. The mercury vapor was introduced into the system at selected post-discharge time. Dependence of selected molecular band head intensities as well as mercury line intensity on experimental conditions (pressure, discharge power, wall temperature, time of mercury vapor introduction) were observed in time evaluation. The data obtained in pure nitrogen were used as a reference. The obtained results showed very high sensitivity of kinetic processes on mercury atoms presence. If mercury was introduced into the post-discharge the mercury line was observable around the site where mercury vapor was introduced into the discharge. The experimental data showed that mercury line intensity was directly proportional to the mercury atoms concentration and saturation effect could be observed. The energy level diagram demonstrates that the observed mercury line can be excited by collisions with nitrogen ground state molecule excited to vibrational level 18. Thus the mercury can be used for the monitoring of population at this vibrational level. Finally we obtained the population profile at this nitrogen metastable level during the post-discharge. The presented work demonstrates possibility of mercury atoms application for the monitoring of one nitrogen metastable state. Unfortunately, the contemporary data are not sufficient for the measurement of metastable absolute concentration. However, complex understanding of nitrogen post-discharge kinetics is still an open problem. Therefore a lot of future work should be done although the presented work brings a good fundament for such research.
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Study of organosilicone fragmentation in plasma
Sahánková, Hana ; Studýnka, Jan (referee) ; Krčma, František (advisor)
This Bachelor Thesis deals on the study of organosilicone monomers in plasma. The dimethylphenylsilane (DMPS) was chosen as the organosilicone example. The theoretical part gives basic overview of plasmachemical processes and technologies used in present world. Some part is reserved for the description of plasma diagnostic basic methods as optical emission spectroscopy and mass spectroscopy. The experimental part is constituted from two different experiments. The first one was done as model experiment of DMPS fragmentation by electron beam of exact energy and it was completed at Faculty of Mathematics, Physics and Informatics in Bratislava. Results of these experiments brought a set of electron energies needed for the creation of various ionic fragments from the original molecule as well as the cross sections for their creation. The second part of the experiments was carried out under the inductively coupled RF low pressure plasma conditions during the deposition of DMPS based thin films. The plasma was monitored by optical emission spectroscopy at different discharge power. Various species were identified in the spectra. The calculation of plasma parameters and their comparision with the model experiment data will be subjects of the further work.
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Study of plasmachemical reduction of corrosive layers on bronze
Zemánek, Nikola ; Selucká, Alena (referee) ; Krčma, František (advisor)
The application of low-pressure low-temperature hydrogen plasma on artificial corrosion layers on bronze has been studied. For this purpose, three sets of bronze corroded samples were prepared. The first step of the model sample preparation was grinding of the bronze surface by using emery with 60, then 280 and finally by 600 grains density, in order to achieve the defined surface roughness. The next step of the work were optical and scanning electron microscopy observations with energy dispersive X-ray micro analysis (SEM-EDX) of the prepared bronze sample for purpose of surface structure characterization and element composition determination. Bronze samples with defined surface structure were corroded in different corrosion atmospheres. Three different model corrosion layers were formed by acidic atmospheres of hydrochloric acid, nitric acid and sulphuric acid. The element composition and structure of corrosion layer was determined by SEM-EDX again. The different amounts of oxygen, nitrogen, chlorine, sulfur, copper, tin and lead in the corrosion layer according to different types of corrosion atmospheres were determined. The next and also main part of the work was a plasma chemical reduction of corroded samples. The plasma reactor used the RF discharge (13.56 MHz) created in quartz tube with outer electrodes. The generation of capacitively coupled plasma in continuous or pulse mode by different supplied power was carried out. The plasma radiation emitted from the RF discharge during the sample treatment was measured by optical emission spectroscopy. The quantity of OH radical created in an active discharge by reactions of atomic hydrogen with the corrosion layer is a significant indicator of a reduction process. Therefore the OH radical band integral intensities observed as a function of the treatment time were used as a monitor for plasma chemical reduction process. The OH emission showed different behavior depending on corrosion layer composition during the plasma treatment. The transformations of the corrosion layer due to the plasma effect were investigated by means of SEM-EDX once again. Changes in the element composition of corrosion (or surface) layers in consequence of plasma chemical treatment are given. Generally, the element composition after the plasma chemical treatment showed explicitly that oxygen and chlorine content in the corrosion layer decreased, nitrogen was removed totally. Metal deposition on the reactor wall was observed occasionally. The SEM-EDX analyzes also showed that in some cases the tin content in sample surface layers was significantly decreased. For that reason, in case of bronze sample (artifacts) treatment, the sample and plasma temperature seem to be very important parameters for the process optimization. The acceptable conditions for plasma chemical treatment has been found in case of corrosion layer formed by nitric acid, only. The other corrosions will be a subject of further studies.
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Preparation and Plasmachemical Reduction of Model Corrosion Layers on Iron.
Sázavská, Věra ; Novák, Stanislav (referee) ; Zahoranová, Anna (referee) ; Krčma, František (advisor)
The plasmachemical removal process of corrosion layers is based on a reduction effect of RF hydrogen low-pressure plasma, and it is used for archaeological objects. Incrustation layers on artifact surface become brittle and porous due to plasma processing. The structure and composition of corrosion layers is changed. Therefore, it is much easier to recover the original surface of the plasma treated artifacts in contrary to those treated by conventional ways. Moreover, we can save time on invasive and thus dangerous mechanical removal of corrosion layers as for example sanding is. After plasma treatment, we can observe fine details of the original surface and memory of tools used during its manufacturing. These details are important information on the origin and manufacturing methods of the artifacts. The plasma reduction process leads to the removal of impurities from cavities as well, and a function of mechanical components of archaeological object can be restored. Moreover, chlorides can be easily removed from the corrosion layers and thus any significant post-corrosion is protected. Each archaeological object is original and it has its own “corrosion history”. First, the object had been exposed to the atmosphere for a long time. Then, it had been often placed in a tomb or grave or it otherwise got into the soil or sea. Thus, each archaeological object was exposed to different corrosion stress (humidity, composition of corrosive environment, etc.). Due to these facts, any universal way of a corroded object treatment is very difficult or even impossible to propose. In this work, the problem was solved using model samples of common metals which were treated at various plasma treatment conditions. Archaeological objects made of iron are the most common artifacts, and the typical corrosion products on iron are akaganeite, rokuhnite, and szomolnokite. These three corrosion products were created on the model samples in laboratory and then, the plasmachemical reduction was applied for their removal. The experiment was done in a Quartz cylindrical reactor with capacitive coupled RF plasma created using outer electrodes. We used discharge power from 100 W to 400 W in a continuous or pulsed regime (duty cycle of 75 %, 50 % and 25 %). Flowing plasma was created in pure hydrogen at pressure of 150200 Pa. Sample temperature was monitored by a thermocouple, and it did not exceed 200C during all these experiments. This temperature is regarded as a limit temperature for metallographic changes of archaeological iron. Higher temperature can cause destruction of archaeological iron objects. The optical emission spectroscopy of OH radical was used for the process monitoring. We focused on the monitoring of OH-radicals generated in the plasma, which are characteristic species formed by this process. Each corrosion product has a different time evaluation of generated OH-radicals, which is closely related to the degradation of a given corrosion product. Corrosion layers were analyzed before and after the plasmachemical reduction by SEM-EDX. We have found that the plasmachemical reduction is not very suitable for the szomolnokite corrosion product, which is degraded with difficulty and at high applied powers, only. However, very good removal efficiency was obtained for the rokuhnite and akaganeite corrosion.
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Preparation and Plasmachemical Reduction of Model Corrosion Layers on Iron.
Sázavská, Věra ; Novák, Stanislav (referee) ; Zahoranová, Anna (referee) ; Krčma, František (advisor)
The plasmachemical removal process of corrosion layers is based on a reduction effect of RF hydrogen low-pressure plasma, and it is used for archaeological objects. Incrustation layers on artifact surface become brittle and porous due to plasma processing. The structure and composition of corrosion layers is changed. Therefore, it is much easier to recover the original surface of the plasma treated artifacts in contrary to those treated by conventional ways. Moreover, we can save time on invasive and thus dangerous mechanical removal of corrosion layers as for example sanding is. After plasma treatment, we can observe fine details of the original surface and memory of tools used during its manufacturing. These details are important information on the origin and manufacturing methods of the artifacts. The plasma reduction process leads to the removal of impurities from cavities as well, and a function of mechanical components of archaeological object can be restored. Moreover, chlorides can be easily removed from the corrosion layers and thus any significant post-corrosion is protected. Each archaeological object is original and it has its own “corrosion history”. First, the object had been exposed to the atmosphere for a long time. Then, it had been often placed in a tomb or grave or it otherwise got into the soil or sea. Thus, each archaeological object was exposed to different corrosion stress (humidity, composition of corrosive environment, etc.). Due to these facts, any universal way of a corroded object treatment is very difficult or even impossible to propose. In this work, the problem was solved using model samples of common metals which were treated at various plasma treatment conditions. Archaeological objects made of iron are the most common artifacts, and the typical corrosion products on iron are akaganeite, rokuhnite, and szomolnokite. These three corrosion products were created on the model samples in laboratory and then, the plasmachemical reduction was applied for their removal. The experiment was done in a Quartz cylindrical reactor with capacitive coupled RF plasma created using outer electrodes. We used discharge power from 100 W to 400 W in a continuous or pulsed regime (duty cycle of 75 %, 50 % and 25 %). Flowing plasma was created in pure hydrogen at pressure of 150200 Pa. Sample temperature was monitored by a thermocouple, and it did not exceed 200C during all these experiments. This temperature is regarded as a limit temperature for metallographic changes of archaeological iron. Higher temperature can cause destruction of archaeological iron objects. The optical emission spectroscopy of OH radical was used for the process monitoring. We focused on the monitoring of OH-radicals generated in the plasma, which are characteristic species formed by this process. Each corrosion product has a different time evaluation of generated OH-radicals, which is closely related to the degradation of a given corrosion product. Corrosion layers were analyzed before and after the plasmachemical reduction by SEM-EDX. We have found that the plasmachemical reduction is not very suitable for the szomolnokite corrosion product, which is degraded with difficulty and at high applied powers, only. However, very good removal efficiency was obtained for the rokuhnite and akaganeite corrosion.
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Influence of metallic atoms on nitrogen post-discharge
Bocková, Ivana ; Kudrle, Vít (referee) ; Krčma, František (advisor)
The aim of this master thesis is to study the influence of metallic atoms on nitrogen post-discharge. Pure nitrogen post-discharge is a subject study of many works dealing with kinetic processes in plasma. Unfortunately, there are only a few published works that present influence of various traces on nitrogen post-discharge kinetics. This master thesis deals with problems of nitrogen post-discharge containing mercury traces. All experimental data were obtained using optical emission spectroscopy of a DC discharge in a flowing mode, which can achieve appropriate temporal resolution in the order of milliseconds. Spectra emitted during the post-discharge were recorded in the range of 320-780 nm and the following molecular spectral systems were identified: • 1. positive system of nitrogen: N2(B) -> N2(A), • 2. positive system of nitrogen: N2(C) -> N2(B), • 1. negative system of nitrogen: N2+(C) -> N2+(X), • NO-beta system: NO(B) -> NO(X). Besides them we were able to record the mercury line at 254 nm, only (in the spectrum of the first as well as in the second order); no other mercury lines were observed. The mercury vapor was introduced into the system at selected post-discharge time. Dependence of selected molecular band head intensities as well as mercury line intensity on experimental conditions (pressure, discharge power, wall temperature, time of mercury vapor introduction) were observed in time evaluation. The data obtained in pure nitrogen were used as a reference. The obtained results showed very high sensitivity of kinetic processes on mercury atoms presence. If mercury was introduced into the post-discharge the mercury line was observable around the site where mercury vapor was introduced into the discharge. The experimental data showed that mercury line intensity was directly proportional to the mercury atoms concentration and saturation effect could be observed. The energy level diagram demonstrates that the observed mercury line can be excited by collisions with nitrogen ground state molecule excited to vibrational level 18. Thus the mercury can be used for the monitoring of population at this vibrational level. Finally we obtained the population profile at this nitrogen metastable level during the post-discharge. The presented work demonstrates possibility of mercury atoms application for the monitoring of one nitrogen metastable state. Unfortunately, the contemporary data are not sufficient for the measurement of metastable absolute concentration. However, complex understanding of nitrogen post-discharge kinetics is still an open problem. Therefore a lot of future work should be done although the presented work brings a good fundament for such research.
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Study of plasmachemical reduction of corrosive layers on bronze
Zemánek, Nikola ; Selucká, Alena (referee) ; Krčma, František (advisor)
The application of low-pressure low-temperature hydrogen plasma on artificial corrosion layers on bronze has been studied. For this purpose, three sets of bronze corroded samples were prepared. The first step of the model sample preparation was grinding of the bronze surface by using emery with 60, then 280 and finally by 600 grains density, in order to achieve the defined surface roughness. The next step of the work were optical and scanning electron microscopy observations with energy dispersive X-ray micro analysis (SEM-EDX) of the prepared bronze sample for purpose of surface structure characterization and element composition determination. Bronze samples with defined surface structure were corroded in different corrosion atmospheres. Three different model corrosion layers were formed by acidic atmospheres of hydrochloric acid, nitric acid and sulphuric acid. The element composition and structure of corrosion layer was determined by SEM-EDX again. The different amounts of oxygen, nitrogen, chlorine, sulfur, copper, tin and lead in the corrosion layer according to different types of corrosion atmospheres were determined. The next and also main part of the work was a plasma chemical reduction of corroded samples. The plasma reactor used the RF discharge (13.56 MHz) created in quartz tube with outer electrodes. The generation of capacitively coupled plasma in continuous or pulse mode by different supplied power was carried out. The plasma radiation emitted from the RF discharge during the sample treatment was measured by optical emission spectroscopy. The quantity of OH radical created in an active discharge by reactions of atomic hydrogen with the corrosion layer is a significant indicator of a reduction process. Therefore the OH radical band integral intensities observed as a function of the treatment time were used as a monitor for plasma chemical reduction process. The OH emission showed different behavior depending on corrosion layer composition during the plasma treatment. The transformations of the corrosion layer due to the plasma effect were investigated by means of SEM-EDX once again. Changes in the element composition of corrosion (or surface) layers in consequence of plasma chemical treatment are given. Generally, the element composition after the plasma chemical treatment showed explicitly that oxygen and chlorine content in the corrosion layer decreased, nitrogen was removed totally. Metal deposition on the reactor wall was observed occasionally. The SEM-EDX analyzes also showed that in some cases the tin content in sample surface layers was significantly decreased. For that reason, in case of bronze sample (artifacts) treatment, the sample and plasma temperature seem to be very important parameters for the process optimization. The acceptable conditions for plasma chemical treatment has been found in case of corrosion layer formed by nitric acid, only. The other corrosions will be a subject of further studies.
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Study of organosilicone fragmentation in plasma
Sahánková, Hana ; Studýnka, Jan (referee) ; Krčma, František (advisor)
This Bachelor Thesis deals on the study of organosilicone monomers in plasma. The dimethylphenylsilane (DMPS) was chosen as the organosilicone example. The theoretical part gives basic overview of plasmachemical processes and technologies used in present world. Some part is reserved for the description of plasma diagnostic basic methods as optical emission spectroscopy and mass spectroscopy. The experimental part is constituted from two different experiments. The first one was done as model experiment of DMPS fragmentation by electron beam of exact energy and it was completed at Faculty of Mathematics, Physics and Informatics in Bratislava. Results of these experiments brought a set of electron energies needed for the creation of various ionic fragments from the original molecule as well as the cross sections for their creation. The second part of the experiments was carried out under the inductively coupled RF low pressure plasma conditions during the deposition of DMPS based thin films. The plasma was monitored by optical emission spectroscopy at different discharge power. Various species were identified in the spectra. The calculation of plasma parameters and their comparision with the model experiment data will be subjects of the further work.
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