|
|
Plasma chemical removal of bronze corrosion layers
Miková, Petra ; Slavíček, Pavel (referee) ; Tiňo, Jozef (referee) ; Krčma, František (advisor)
The thesis deal with applying low-pressure low-temperature plasma to corrosion products layers on bronze. Layers of corrosion products on samples were artificially prepared. As a result, they had the same composition and could be irreversibly destroyed during experiments, which would not be possible with real archeological artifacts. Bronze, copper and tin alloy, samples were cut with respect to the size of the plasma-chemical device. XRF was used to determine the bronze composition. Before being corroded by the active medium, each sample was washed with ethanol and dried with a hot air stream. Until now, the procedure was the same for all samples. During formation of corrosion products layers, two factors have to be taken into account: the time consumption and the corrosiveness of the active environment. By focusing on one or the other factor, several groups of samples with differently degraded surfaces were created. The fastest way was to place samples in a corrosion chamber where sodium chloride solution was applied at the elevated temperature. The samples were corroded within a few days there. Longer, but in terms of corrosion products layers compactness better way proved procedure where the samples were sealed in the desiccator. At the desiccator bottom the Petri dish with an inorganic acid was placed, in our case, with hydrochloric acid inside. This method corroded the samples within one month. The longest but the most closed to the real live method was the burial of samples into soil or compost. However, this method corroded the samples within two years. Final step after the samples were removed from any corrosive environment, were dried under low pressure and were placed in a barrier film made bag together with moisture and oxygen absorbers. So prepared samples with layers of corrosion products have been treated in a low-pressure low-temperature plasma. Treatment was carried out in the apparatus which is based on the reactor: cylinder of quartz glass having a diameter of 100 mm and a length of 900 mm. The reactor was supplied with a working gas or a mixture of working gases with a total flow rate of 50 sccm. In our case, one is pure hydrogen or a combination with argon. A rotary oil pump was used to provide vacuum. The reactor base pressure was 10 Pa before treatment, while during the treatment it was 150 Pa. High-frequency generator (13.54 MHz) was used for supply the system with energy through two copper electrodes located outside the reactor. According to the energy delivery method, the treatment was carried out in a continuous or pulse mode. The sample temperature was monitored during the experiment and were evaluated the emission spectra from OES. The sample temperature was one of the key factors. The measurement was first done with a thermocouple, later switched to a thermocouple with optical data transmission. A safe temperature was set and then the whole process was controlled through it. In addition, the effect of the energy delivery method, value of the delivered power, sample size, presence of incrusted layers and composition of working gas were studied. After application of plasma, samples were analyzed by SEM – EDX and XRD. After the evaluation of the acquired knowledge and experience, a real artifact - a bronze chisel from the site of Boskovice - was treated. This documentation lacked the artifact, so it could be used to verify the lessons learned about plasma chemical reduction.
|
|
|
Use of plasma jet for biomedical application
Doubravová, Anna ; Márová, Ivana (referee) ; Skoumalová, Petra (advisor)
This master´s thesis is focused on the utilization of the sterilization effects of low temperature plasma towards the bacterial microorganisms that occur mainly on the human skin. The plasma sterilization process is fast efficient, non-toxic, environmentally friendly, cost-effective and safe for the operating staff as well as for the patient. Another advantage of using low temperature plasma is to support cell proliferation and wound healing. By combining these advantages, an effective method can be obtained, which would sterilize the wounds sparingly with regard to the surrounding healthy tissue and support the regeneration of the damaged tissue at the same time. In the experimental part, gram positive and gram negative bacteria were used to prove the sterilization effects with respect to different cell wall structure. Staphylococcus epidermidis and Propionibacterium acnes, which cause purulent skin inflammations, were used as gram-positive microorganisms. Serratia marcescens and Escherichia coli were selected from gram positive bacteria. These model organisms were inoculated at various concentrations on culture broths and treated by plasma at a distance of 1 mm from the agar surface. The microwave discharge was generated in argon at a power of 9 W, a gas flow rate of 5 l / min and water cooling to avoid thermal effects on the treated surface. Subsequently, model skin cells of HaCaT were exposed to low temperature plasma and tested for plasma cytotoxicity to demonstrate its healing effects. The obtained results make it possible to state that the sterilizing effects of low-temperature plasma in all tested gram-positive and gram-negative bacterial strains are verified in this work. Finally, tests were demonstrated using a suitable method of the treatment on human skin cells, where the safety and usefulness of the tested low-temperature plasma was demonstrated when applied to shorten the healing process.
|
|
|
Comparison of organic dye decomposition in various plasma systems
Dotsenko, Anastasia ; Králová, Marcela (referee) ; Kozáková, Zdenka (advisor)
This bachelor thesis deals with the comparison of the degradation of organic dyes (namely: Saturn Red L4B (Direct Red 79) and Indigo Carmine (Acid Blue 74)) in different plasma systems and the general characteristics of the optical emission spectrometry of a microwave plasma nozzle. It briefly summarizes basic information about plasmas and the processes involved. The theoretical part focuses on basic information about plasmas and their processes, basic information about dyes and their degradation methods. Plasma contains a number of active particles such as hydroxyl radicals, nitrogen oxide radicals, excited nitrogen molecules, atomic nitrogen, argon and oxygen. All these particles, together with photons generated by the plasma, are useful in environmental applications. The experimental part focuses on treating a sample of model dyes in selected plasma systems generating plasma above the liquid surface (microwave surface wave discharge, dielectric barrier discharge with liquid electrode) or below it (plasma nozzle in liquid) and evaluating their decomposition rate. Characterization of the distribution of active particles along the plasma axis of a high frequency plasma jet in argon and determination of the conditions in the plasma with respect to the environmental applicability of the system.
|
|
|
Optimization of distribution of active particles generated by low temperature plasma on biopolymer surfaces
Krupičková, Lucie ; Kozáková, Zdenka (referee) ; Krčma, František (advisor)
This thesis is focused on the optimization of the distribution of active particles (RONS), generated by the low temperature plasma, on the biopolymer surfaces. The theoretical part characterizes plasma and its active particles. Furthermore, this chapter summarizes its applications in medicine and food industry, also a review of different skin models is listed here. The last section is focused on the skin anatomy and the characterization of selected microorganisms C. glabrata, E. coli and S. epidermidis. In the experimental part, selected biopolymers with specific dyes for detection of active particles were prepared. Furthermore biopolymers were spot treated under different conditions leading to color changes in all biopolymers. This test confirmed a presence of active particles in the plasma. After that, the optimal parameters for active particles distribution over the entire surface were found. Also an experiment, which allowed the UV light to pass through but prohibited the passage of active particles, was made. In this experiment, no color change was noticed, which means, that the reaction of active particles with the colored biopolymer is responsible for the color change. The optimized parameters were used for treatment of agar plates with monoculture of C. glabrata, E. coli, S. epidermidis and with mixed culture C. glabrata + E. coli. Two different plasma torches were used – unipolar microwave discharge torch and surface wave microwave discharge jet. Treated samples were photographed after incubation. Software Aurora then calculated the surface area which was covered by the microbial culture. Based on the data, the microbial reducion was evaluated in comparison with untreated samples. The unipolar microwave discharge torch achieved higher efficiency than the surface wave microwave discharge jet, for all tested microorganisms.
|
|
|
Application of plasma and plasma activates water for wound healing
Šrámková, Sarah ; Janda,, Mário (referee) ; Kozáková, Zdenka (advisor)
This work is focused on the study of plasma interactions with liquids and selected microorganisms, Staphylococcus epidermidis and Escherichia coli. The use of the cold atmospheric pressure plasma in the biomedical field has been a hot topic in the last decade, due to its decontamination properties applicable not only in the biomedical field but also in the food industry and agriculture. Recently, the plasma treated (activated) liquids (PTLs) have also been a subject of a great interest due to the relatively simple preparation, the possibility of optimizing the composition of PTLs to achieve the desired effect, their non-toxic nature and their environmental friendliness. The purpose of this work is to study the inhibitory effects of the plasma discharges and the plasma treated liquids for the purpose of decontamination and stimulation of wound healing. To study the effect of a direct plasma application on selected microorganisms, two types of discharges, the unipolar microwave torch and the microwave surface wave jet, were selected. For both selected discharges, the dependence of the inhibitory effects on the treatment time, the power, the closure of the treated area and the bacterial species (gramnegative/grampositive) was studied. Comparable results in the inhibition efficiency were obtained for both discharges. The effect of indirect treatment using plasma-treated water was studied next. A decent microbial reduction occurred for all three studied PTLs. The PTL prepared using a plasma jet with a direct current (DC) source was found to be the most efficient. The last stated goal of this diploma thesis was to study the effect of treatment combinig both the indirect treatment with PTL and the direct plasma treatment. Based on the results of previous treatments, a bacterial culture of Staphylococcus epidermidis was treated with PTL prepared with a direct current (DC) plasma jet. The unipolar microwave torch with a power of 12 W was selected for the direct treatment. By combining both types of treatments, higher inhibition effeciency was achieved. The inhibition efficiency was demonstrated for all types of treatments, with the combined treatment aspiring to be the most effective, as it targets both grampositive and gramnegative bacteria.
|
|
|
Microbial contamination of raw food and cereal products
VENGLOVIČOVÁ, Kristýna
Plasma has been increasingly used in recent years due to its lethal effect on microorganisms. Foods treated in this way are not a risk to humans in terms of chemical substance. The literature search is focused on raw foods. Description of pathogenic microorganisms frequently occurring on seeds and methods of disposal feasible in accordance with the rules of the raw diet. The aim of this bachelor thesis was to evaluate the effect of low-temperature plasma on seeds. Seed groups were exposed to plasma for 4, 5, 6, 7 and 8 minutes. Seeds of mung beans, broccoli, watercress, radish and barley were treated with the plasma generated in the vacuum chamber. First of all was evaluated the inhibitory effect of plasma treatment on microorganisms occurring on seeds. Furthermore was monitored the impact on the growth of sprouts and roots. Could not be demonstrated the inhibitory effect of plasma on microorganisms present on seeds. The treated seeds compared to the untreated control group were contaminated with a similar amount of microorganisms. The effect on seed development was different for each species.
|
|
|
Detection of crop pathogens by metagenomic analysis
KOLÁŘOVÁ, Johana
Microorganisms colonizing seed of wheat (Triticum aestivum L.) and oilseed rape (Brassica napus L.) were identified by sequencing analysis of genes encoding rRNA in this thesis. Bacteria were identified according to the sequence of part of gene for 16S rRNA and fungi were identified according to the sequence of part of gene for 28S rRNA. Subsequently, the effect of low-temperature plasma seed treatment on the viability of the detected microorganisms was assessed.
|
|
|
Study of low-temperature plasma products using mass spectrometry and their relation to thin film chemistry
Maršálek, Blahoslav ; Bránecký, Martin (referee) ; Čech, Vladimír (advisor)
The aim of this thesis was to analyse and interpret the spectra of tetravinylsilane as a function of plasma discharge power in order to find a relationship between plasma products, layer deposition and thin film chemistry. Another objective was to carry out a literature search in the field of plasma-enhanced chemical vapour deposition (PECVD) and mass spectrometry. Low temperature organosilicate-based plasma technology enables the synthesis of specific materials with controlled chemical and physical properties. The targeted synthesis of surfaces with controlled properties is determined by the atomic and molecular processes in the plasma, which are responsible for building the chemical structure and the resulting material in the form of a thin film. In this work, mass spectrometry has been used to detect and quantify the particles produced in the PECVD process, which is one of the methods that allow the characterization and identification of plasma products. Analysis of the mass spectra revealed that the molecules responsible for the growth of the layer contain carbon and silicon. The deposition rate determined by in situ spectroscopic ellipsometry correlates quantitatively with the flux of carbon and silicon particles that are chemisorbed on the film surface. The ratio of carbon and silicon deposited on the surface also correlates strongly with the C/Si flux ratio of the power driven plasmas. The contribution of silicon-containing particles as building blocks to the film growth decreases with increasing power and accounts for 20% (2 W), 5% (10 W) and only 1% (75 W) of the total chemisorbed fraction. This ratio between bound silicon containing particles and carbon particles affects the elemental composition and chemical structure of the deposited layers. The relationships between plasmachemical processes and particle adhesion on the surface are quite complex. The adhesion of silicon particles first increases sharply to a maximum at 25 W and then gradually decreases, which is characteristic of the so-called precursor-deficient PECVD. Similarly, the concentration of vinyl groups incorporated into the deposited layer and the fraction of sp2 hybridization of carbon correlate with the particle fluxes of the corresponding plasma. This work has demonstrated that mass spectroscopy is a suitable method for the study of plasmachemical deposition from the gas phase (PECVD). PECVD technology is promising for the deposition of silicon-containing layers, which is technologically applicable in many directions of materials research.
|
|
|
Application of methods of computational physics for the study of plasma-solid interaction
Hromádka, Jakub ; Hrach, Rudolf (advisor) ; Novák, Stanislav (referee)
Low-temperature plasma and its interaction with immersed solids is studied in this work. The research of the physical processes on this interface is performed by two-dimensional particle computer model. The model uses molecular dynamic method. Mutual forces between particles are computed by Particle- in-Cell method. The main application of the model is in the area of the probe diagnostic of plasma. Simple problems are compared with theory and two dimensional effects are discused. Contribution of particle modeling to plasma research is showed on the problem of interaction of sheaths around cylidrical probes. We deal with question whether we are able to get some information about unevennesses at the surface of solid immersed in plasma by measuring probe characteristics in its surroundings. We also studied the influence of plasma electronegativity on the parameters of sheaths around cylidrical probes. Powered by TCPDF (www.tcpdf.org)
|
|
|
Study of plasma interaction with bacteria for wound healing
Šrámková, Sarah ; Krčma, František (referee) ; Kozáková, Zdenka (advisor)
This thesis focuses on the study of the interaction of plasma with bacteria to enhance the promotion of wound healing. Firstly, the wound healing process is described, followed by low temperature plasma, its effect on bacterial cells and its use in biomedicine. The experimental part deals with the application of low-temperature plasma generated by microwave jet on selected microorganisms and the influence of experimental conditions on the antimicrobial effect of the plasma. One representative of the microorganisms occurring in the wounds was selected as representatives of Gram-positive bacteria and Gram-negative bacteria, namely Staphylococcus epidermidis and Escherichia coli. Using the results obtained, the antimicrobial effect of plasma generated by microwave jet in argon was confirmed. The degree of antimicrobial effect is related to the concentration of the microorganisms, the time of treatment and whether the bacteria are Gram-positive or Gram-negative.
|
guest ::
