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Study of oxygen and ozone reactions on the surface of construction materials
Krzyžanková, Anežka ; Brablec,, Antonín (referee) ; Mazánková, Věra (advisor)
This master's thesis deals with the study of the reactions of the ozone and oxygen with various construction materials. Ozone as an unstable gas tends to decompose spontaneously and this process can be accelerated by reaction with other substances. The aim of this work is to determine the course of ozone's formation and its depletion in after the contact with various substances. Ozone is widely used mainly due to its disinfecting effects. Therefore, the monitoring of these reactions is beneficial for the choosing of ozonizer's material or its accessories. The theoretical part of this work describes the important properties of the ozone, the possibilities of using this gas, various methods of its generation, the influence of gas admixtures and a temperature on its generation and decomposition, the methods of determining the concentration and surface reaction. The dependence of ozone's formation on the size of the reaction space was monitored for either the silicone and Teflon material in the experimental part of the thesis. The length of the hoses was 20-50 cm and the diameter of the inner space was 6 mm for Teflon and 7,99 mm for a silicone. Furthermore, other experiments were performed for the silicone material, where the formation of the ozone was monitored while the oxygen and argon were being used as working gases. The formation and the depletion of the ozone depending on the changes of reaction time were investigated in the third series of experiments. We worked with a ceramic material with two different inner diameters and also with a brass and a stainless steel material in this experiment. The materials were constructed as the tubes of the same length of 54 cm. The ozone generated from the oxygen was enclosed into the reaction tube and the depletion was monitored. The last experiment was focused on the monitoring of the course of ozone's formation in a quartz cuvette influenced by the reaction time and the composition of the working gas. The amount of generated ozone was determined by absorption spectrometry in the all studied cases. The ozone flowing through the system was adsorbed by the surface of the material during the discharge. A mixture of gases (the adsorbed ozone, the oxygen and the argon in various ratios) was present in the sealed reaction space. The Ozone was formed on the surface of the material. The adsorbed ozone decomposed into a molecular and an atomic oxygen. The atomic oxygen reacted with the oxygen molecule occurring in the reaction space. The reaction time leading to the biggest obtained concentration of generated ozone was determined by the experimental data. For most of the materials, the reaction time was about 6 minutes.
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Barier films based on polyparaxylylene and their properties
Horák, Jakub ; Mazánková, Věra (referee) ; Přikryl, Radek (advisor)
This diploma thesis is focused on preparation and characterization of parylene C barrier properties. The layers were prepared by chemical vapour deposition (CVD). The interest in characterization of those layers is huge mainly because of their possible use in museology for the protection of the museum archives against the corrosion. Chlorinated dimer of para-xylylene was used as a precursor. Polypropylene foils, metal sheets and silica wafers were used as tested substrates for thin film preparation. Polypropylene foils were used for oxygen transmission rate measurements, metal sheets were used for corrosion tests and silica wafers were used for Fourier transform infrared spectroscopy (FTIR), confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM) and stylus profilometry.
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Measure of atomic nitrogen concentration in the nitrogen post-discharge
Josiek, Stanislav ; doc.Mgr.Pavel Slavíček, Ph.D. (referee) ; Mazánková, Věra (advisor)
Clean post-discharge nitrogen plasma and nitrogen plasma with different traces have been focus of scientists for more than 50 years and there were published many articles on theme active discharge, post-discharge, processes and reactions. It is possible to create kinetic models from all these information and then calculate concentrations of elements in atomic form. This diploma thesis is focused on measuring of concentration of atomic nitrogen for different conditions (decay time, pressure, admixture). The titration method by nitric oxide in post-discharge was used to determinate of concentration of atomic nitrogen. All experimental results were obtained by the optical emission spectroscopy. Optical emission spectra were taken in the range of 300-600 nm. DC discharge was created in a quartz tube in a flowing regime. The flowing regime was chosen for this experiment because of better time resolution of decay time, order in milliseconds. Decay time was in the range of 16 – 82 ms for individual experiments. Nitrogen flow was 400 mln/min. Nitrogen oxide flow was in the range of 0-10 mln/min and it was added at the selected post-discharge time. Trace of methane was 0,006 % of the whole volume. Total gas pressure was set on values from 500 to 4000 Pa. The output of discharge was set on constant value of current 150 mA and the output has changed according to the amount of pressure. Nitrogen first positive, second positive and first negative spectral systems, NO spectral system and NO2* spectral system were recognized in all measured spectra. Absolute concentration of atomic nitrogen was specified by the method of titration of NO. Traces of methane increase dissociation of molecular nitrogen and therefore increase the concentration of atomic nitrogen. This thesis brings new results into longtime research of moon Titan and new results into study of processes in nitrogen-methane plasma.
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Plazmachemical reduction of corrosion layers on copper samples
Kujawa, Adam ; Slavíček,, Pavel (referee) ; Mazánková, Věra (advisor)
The object of study in present diploma thesis is the plasmachemical reduction of corrosion layers on copper. This process is based on reductive properties of low pressure hydrogen plasma. In this case three series of copper samples were prepared and corroded in different corrosion environments in order to create three kinds of artificial corrosion layers. In the first step the copper coupons were properly grinded in order to achieve a defined surface roughness. In the next step the coupons corroded for 12 days in vapours of three concentrated acids – HCl, HNO3, and H2SO4. SEM/EDX analysis was carried out in order to characterise the grown corrosion layers on copper coupons, which showed us the presence of nitrogen, oxygen, chlorine and sulphur in different chemical forms in corrosion layers. The most significant part of this work was the plasmachemical treatment of corroded copper samples. Pure hydrogen was used as a reaction gas under the pressure of about 200 Pa and 50scc/m flow rate. The discharge was generated in quartz-glass reactor by using RF generator under the different power and mode settings. Optical emission spectroscopy was used to detect the intensity of plasma radiation. The value of integral intensity of OH radicals represented quantitative ablation of oxygen from a corrosion layer. OH radicals were the main products of reaction between hydrogen radicals (from plasma) and oxygen in corrosion layer. Time of increasing of OH radicals intensity was different for coupons from different corrosion environment and was also related to used power of generator and mode. The process was finished when the OH radicals intensity decreased to 10% of reached maximum. Sample temperature was an important indicator of sample protection against metallographic changes. The analyses XRD and SEM/EDX on corroded and treatment samples were performed. The analyses show that the decrease of main corrosion agents as chlorine and oxygen was achieved by hydrogen plasma treatment. The corrosions as well as their removal are a very complex problem and the plasmachemical treatment of metal objects is an efficient method for the removal of corrosion layers as compared to conventional conservations methods mainly due to a significant reduction of treatment time.
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Spectroscopic Study of Post-Discharges in Nitrogen and its Mixtures
Mazánková, Věra ; Kapička, Vratislav (referee) ; Hrachová,, Věra (referee) ; Krčma, František (advisor)
Presented thesis gives results obtained during the spectroscopic observations of post –discharges of the pure nitrogen plasma with small oxygen admixture and in the nitrogen – argon mixture and the effect of the pink afterglow in it. The DC discharge in the flowing regime has been used for the plasma generation. The decaying plasma was study by optical emission spectroscopy, mainly in the range of 300–800 nm. The first positive, second positive, first negative nitrogen spectral system and NO spectral systems were observed in measured spectra. The band head intensities of these bands have been studied in the dependencies on experimental conditions. Simultaneously, the relative vibrational populations on the given nitrogen states have been calculated. Two discharge tubes made from different materials (PYREX glass and QUARTZ glass) were used in the case of nitrogen plasma containing low oxygen traces (up to 0.2 %). These experiments have been carried out at two wall temperatures for the determination of the temperature effect on the post-discharge. The discharge tube around the observation point was kept at the ambient temperature (300 K) or it was cooled down to 77 K by liquid nitrogen vapor. The total gas pressure of 1 000 Pa and the discharge current of 200 mA were conserved for all these experiments. The relative populations of electronic states were calculated in the dependence on the post-discharge time. The dependencies on oxygen concentration were given, too. The results showed no simple dependence of vibrational populations on oxygen concentration. Generally, slight increase of neutral nitrogen states populations was observed with the increase of oxygen concentration. These observations were well visible due to the intensity of nitrogen pink afterglow effect that was well visible at all oxygen concentrations. The pink afterglow maximal intensity was reached at about 5–10 ms at the wall temperature of 300 K in the PYREX tube. The molecular ion emission was strongly quenched by the oxygen and as this was dominant process for the pink afterglow emission the pink afterglow effect disappears at oxygen concentration of about 2000 ppm. The temperature and wall material influences were observed, too. The post-discharge in nitrogen argon mixtures was studied only in the PYREX tube at the ambient wall temperature of 300 K. The power dissipated in an active discharge was constant of 290 kW. The experimental studies had two new parameters – total gas pressure (500 Pa – 5 000 Pa) and the argon concentrations that were varied in the range of 0–83 %. Also in this case the dependencies of relative intensities of the bands given above were obtained and further the relative populations of electronic states as a function of decay time, total gas pressure and on argon concentration were obtained. The pink afterglow effect was observed at all applied discharge powers and total gas pressures. At the highest argon concentrations, especially at lower pressure, the pink afterglow effect disappeared. The presented experimental work is one of the hugest sets of experiments in the nitrogen with oxygen traces and in nitrogen-argon mixtures. These data can be used as a very good fundament for the further studies using wide numeric modeling of the post-discharge kinetic processes.
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Hydrogen peroxide generation by the microwave plasma jet
Staškovanová, Denisa ; Mazánková, Věra (referee) ; Kozáková, Zdenka (advisor)
This Bachelor thesis deals with the generation of hydrogen peroxide by the microwave plasma jet in distilled and tap water. The main goal was to characterize the amount of generated hydrogen peroxide depending on various experimental conditions and to determine its stability. A titanium reagent was used to determine if hydrogen peroxide was present in the sample. The method for determination of hydrogen peroxide concentration was spectrophotometry. In conclusion, differences in the concentration of hydrogen peroxide are formulated according to the change in experimental conditions, its stability in plasma activated water and stability in complex with the titanium reagent. Differences between the generation in distilled and tap water are also described.
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Multilayer barrier coatings
Sedláček, Ondřej ; Mazánková, Věra (referee) ; Přikryl, Radek (advisor)
The theme of this work is the preparation and characterization of multilayer barrier coatings to polymer and metal substrates based on SiOx and organic molecules. It deals with the determination of their properties in terms of oxygen permeability and corrosion protection. The starting materials for the preparation of these layers are hexamethyldisiloxane, octafluorocyclobutane and 4,12-dichloro[2.2]paracyclophane. These layers have been prepared with regard to their use as barrier coatings for use in archeology, with the focus on corrosion protection of coated items and other specific requirements museums. For these samples was realized characteristic of both in terms of their physical properties – the ability to resist permeation of oxygen and in terms of their chemical composition. The fourier transformation infrared spectroscopy (FTIR), scanning elektron microscopy (SEM), oxygen transmission rate (OTR), contac angle measurement and corrosion testing were used for the above-mentioned characterisations.
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Generation of ozone by photochemical processes in O2 and admixtures
Tomečková, Klára ; Blahová, Lucie (referee) ; Mazánková, Věra (advisor)
Ozone is a toxic gas with the fatal impact to living organisms at high concentrations. Therefore, this gas is useful in sterilization in many cases. The subject of this work is the generation of ozone using various methods and determination of its concentration. Then the generated ozone can be used in ozone therapy. The theoretical part deals with properties and use of ozone. In addition, information gathering connected to ozone was performed. It was about methods of ozone generation and subsequently about the diagnostics determine of ozone concentration. In the experimental part the ozone generation and determination of its concentration was performed using spectrophotometric method and iodometric titration. The ozone concentration in the air was also measured over the long term using the Schönbein method.
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Deposition and characterization of polymer layers prepared from 2-Methyl-2-oxazoline
Tomečková, Klára ; Čech,, Jan (referee) ; Mazánková, Věra (advisor)
Polyoxazolines are class of polymers which are suitable for medical applications because they have many interesting properties. These polymers are characterized by antibacterial properties so they can stop bacterial colonization of medical devices and significantly reduce the risk of infection. Furthermore, polyoxazolines are interesting for good biocompatibility. Basic topic of this diploma work is preparation of oxazoline-based thin films by plasma polymerization. Thin films were prepared by plasma polymerization from 2-methyl-2-oxazoline vapors in a nitrogen atmosphere in a dielectric barrier discharge. During the deposition was increased the substrate temperature. Polyoxazoline films were analyzed by several diagnostic methods. Physical and chemical properties of thin films were studied by SEM, AFM, FTIR by measuring contact angles and nanoindentation method. The films were found to be homogeneous, hydrophilic and have a higher nitrogen content. Furthermore, films showed viscoelastic properties. Polyoxazoline films were subjected to antibacterial and biocompatibility tests and the result showed, that films have antibacterial properties and support of viability cells viability.
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Plasmachemical preparation of polymer layers based on 2-ethyl-2-oxazoline and their diagnostics
Podzemná, Erika ; Menčík, Přemysl (referee) ; Mazánková, Věra (advisor)
The bachelor’s thesis deals with deposition of thin polymer layers on 2-ethyl-2-oxazolin basis in a dielectric barrier discharge in a nitrogen atmosphere. Polyoxazolines are characterized by good antibacterial effects in general, which make them a suitable material for medical applications. After preparing of the layers. Their properties were studied using three methods. The first were antibacterial tests, which unfortunately did not confirm the above written properties. Furthermore, the free surface energy of the layers, from which it could be inferred that the surfaces were hydrophilic, was determined by measuring contact angles. The scanning electron microscopy showed the surface of the layers as well as the elemental composition thanks to the connected X-ray detector.
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