|
|
Surface cleaning of archaeological objects by plasma generated in water solutions
Tihonová, Jitka ; Grossmannová, Hana (referee) ; Krčma, František (advisor)
This bachelor thesis is focused on the plasma surface treatment of historical ceramics by low temperature electrical discharges in water solution. Four samples were chosen - two of the Lusatian Urnfields Culture and two of Anabaptist Faience. The treatment was done at minimum power of the power supply. Stainless steel electrode and a specially designed electrode system with wolfram wire in the quartz glass capillary were used for generation of discharge using an audio frequency power supply. Elemental analysis by scanning electron microscopy (SEM) was done before and after the treatment and values were compared with the elemental analysis of material’s core. Samples of the Lusatian Urnfields Culture were successfully treated without any surface damage. The first one of samples of Anabaptist Faience was damaged. The experiment was repeated on the glass to determine the cause. It was find out that damage was probably caused by thermal stress. The second one of Anabaptist Faience was already treated without damage. Next research will be focused on determining specific conditions of the power supply, modification of water solution and modification of sample’s surface for the most efficient ancient ceramics cleaning.
|
|
|
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.
|
|
|
Plasma Chemical Surface Treatment of Polymeric Materials for Biomedical Applications
Mikušková, Radka ; Kozáková, Zdenka (referee) ; Krčma, František (advisor)
The theoretical part of bacalor thesis summarizes a plasma application for surface modification of materials used for biomedical applications. The main focus is on polymeric materials. Practical part focuses on specific surface modifications. An aim is to obtain from the initially hydrophobic surface hydrophilic by plasma chemical surface treatment and to optimize the method. Hydrophilicity is achieved by treating the sample in low temperature low pressure plasma generated in air based gaseous mixtures. The surface treatment efficiency is characterizad by water leak through the material. Structural changes of material surface are confirmed by X-ray photoelectron spectroscopy.
|
|
|
Fibre reinforcement with plasma in cement composites
Žižková, Lucie ; Hela,, Rudofl (referee) ; Bodnárová, Lenka (advisor)
The usage of polymer fibres can be increased by the new progressive method of the plasma treatment. This thesis is focused on verification of the influence of the low-temperature treatment on polymer fibres´ surface used in concrete. The treatment of polypropylene fibres in low-temperature plasma is described in the theoretical part. The impact of the treatment on the volume differences of cement composites is also evaluated. The influence of the addition of commercially available fibres and plasma treated fibres on the volume differences of cement composites is also experimentally verified.
|
|
|
Use of plasma jet for wound healing
Dvořáková, Eva ; Márová, Ivana (referee) ; Skoumalová, Petra (advisor)
This diploma thesis was focused on the possibility of using a plasma nozzle to accelerate the wound healing process. The benefits of using low-temperature plasma in medicine or biomedical applications are known from many studies, and low-temperature plasma is already used to sterilize medical devices, materials or surgical instruments. Some studies also report a high potential of usinh plasma nozzle in the treatment of skin wounds. In the experimental part of this work, an in vitro wound healing test was performed using two different low-temperature plasma sources. Source No. 1 was a surface wave microwave discharge and source No. 2 was a torch microwave discharge. An in vitro scratch healing test was performed on a monolayer of HaCaT keratinocytes and testing was performed using various parameters. The influence of the plasma treatment time was monitored, as well as the influence of the plasma discharge power and also the influence of the argon working gas flow. Especially when using a torch microwave discharge, faster wound healing was recorded at most of the parameters used compared to the control. Thus, it can be said that this source appears to be potentially suitable for faster wound healing. Furthermore, in the work using the MTT cytotoxicity test, the viability of skin cells after their plasmination was also monitored using the same conditions as in the in vitro wound healing test. When performed in the standard MTT assay, none of the settings or sources used showed any cytotoxic effects on keratinocytes. LDH cytotoxicity tests were also performed concurrently to verify the accuracy of the MTT assays. The results of both tests agreed and the use of low-temperature plasma in skin treatment can be considered as safe. Overall, the results show that the plasma nozzle can find use in medicine in the healing of skin wounds and chronic defects as a potentially fast, inexpensive and effective method.
|
|
|
Study of the properties of cement composites with polypropylene fiber modified low-temperature plasma
Žižková, Lucie ; Herka, Petr (referee) ; Bodnárová, Lenka (advisor)
Plasma treatment of polypropylene fibers presents a new progressive method, how to increase the utility properties of these fibers. The thesis is focused on verifying the effect of surface treatment of polypropylene fibers in concrete with low-temperature plasma discharge in the normal atmosphere. The paper describes the procedure for treatment of polypropylene fibers with low-temperature plasma and evaluate the impact of this adjustment on the volume changes of cement composites. It should also be emphasized that the thesis is focused on the initial volume changes, ie volume changes in the early stages of solidification and only for your own mixture, which is not considered an external load. Subsequently, the experimental verification of the effect of the addition made commercially available fibers and fibers treated plasma volume changes to a selected physico-mechanical properties of the test compounds.
|
|
|
Monitoring of vitamin E content in the samples of cereals
Cibulcová, Pavla ; Borkovcová,, Ivana (referee) ; Benešová, Karolína (advisor)
Thesis deals with the analysis of vitamin E in cereal samples, namely barley and wheat and malt produced from them. Selected samples were treated with low-temperature plasma, fungicide and biological treatment to elimination fungus and mycotoxins. The aim of the thesis was to find out the influence of the treatment, the combination of several types of treatment on vitamin E content in grain and malt. If the content of health-positive substances is not reduced and grain can be used for food, malt, or for feed purposes. The theoretical part focuses on the properties, occurrence, biochemistry and importance of vitamin E for living organisms. It also focuses on the properties of cereals that are a significant source of vitamin E. Malt production and sample treatment are also described. The experimental part describes the field experiment, individual types of treatment, extraction of vitamin E from the samples and determination of vitamin E content by high performance liquid chromatography with fluorescence detection. The results are compared with the current literature. It was found that the treatment did not have a significant negative effect on vitamin E content.
|
|
|
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.
|
|
|
Generation of metallic nanoparticles by non-thermal plasma in liquids
Čechová, Ludmila ; Blahová, Lucie (referee) ; Kozáková, Zdenka (advisor)
This thesis focuses on the process of nanoparticle generation using new source of nonthermal plasma combining corona and pin-hole discharge in liquids. The theoretical part is focused on generation of metallic nanoparticles using various types of plasma discharge, the properties of metallic nanoparticles, their preparation by other methods and methods of characterization of nanoparticles. The experimental part deals with the preparation of copper, silver and gold nanoparticles from solutions of their precursors. The influence of experimental conditions, such as the influence of voltage polarity, effect of precursor concentration, effect of added electrolyte or reducing agent were investigated. All samples were analyzed by UV-VIS spectroscopy. Dynamic light scattering was used to determine the sice of nanoparticles. To confirm the presence of nanoparticles, samples were analyzed using scanning microscope with and energy dispersion spectrometer for elemental analysis.
|
|
|
Application of electric discharge in liquids for surface cleaning of non-metallic archaeological objects
Tihonová, Jitka ; Radko,, Tiňo (referee) ; Krčma, František (advisor)
This diploma thesis is focused on the plasma surface treatment of historical glass from the 18th and 19th centuries by low temperature electrical discharges in solutions of sodium chloride and potassium carbonate and finding the most suitable settings of conditions for the surface cleaning. Stainless steel electrode and a specially designed electrode system with wolfram wire in the quartz glass capillary were used for the generation of discharge using an audio frequency power supply. Each line of samples was made from one piece of historical glass that was cut to smaller pieces. All cleaned samples were photographed before and after the cleaning so the possible changes of the cleaned area could be visually compared. Then the samples were analysed by LA-ICP-MS (line scanning of surface), where was analysed the cleaned area of samples, and values were compared to the analysis of the reference sample that was not cleaned. Examined isotopes of elements were selected on the basis of the supposed composition of glass, corrosion products, and soil at the place of discovery. Analyses were standardized by NIST 610. Acquired values were transferred to oxides. The most important oxides (Na2O, MgO, SiO2, P2O5 a K2O) were chosen for deciding the most effective cleaning settings. It was decided that the most effective setting for cleaning was the one where the biggest difference of values between sample and reference occurred. Four series of these solutions were compiled and one parameter was changed for each of them. Solutions and their conductivity, frequency of the power supply, and time of cleaning were chosen as changing values. Three samples of different times of cleaning were cleaned without interruption. The time of cleaning was split into intervals of 30 seconds of cleaning and 1 minute of non-action for another two samples of this series. In this way we were trying to find out if the following surface analysis will be influenced by the diffusion of the particles into the sample, or not. The frequency of power supply was recorded and its dissipated power was calculated for each measurement. Emission spectra of a series of different solution conductivity were measured before cleaning of samples. Measurement of OES was made with the ignition of discharge so the active species of plasma were shown in spectra. These species are probably participating in the cleaning process of glass. Emission spectra were also measured after cleaning to find out if values of active species were changed or unknown spectral lines appeared. These lines should be from dirt and corrosion products that were cleaned from the surface of the glass. It was found out that the most effective cleaning of sample 1 (series where the conductivity of the NaCl solution was changed) was done in a solution of conductivity 900 S/cm. The most effective cleaning of sample 4 and sample 7 (series where the conductivity of the K2CO3 solution was changed) was done in a solution of conductivity 600 S/cm. The most effective cleaning of sample 6 (series where the frequency was changed) was done at frequency = (15200 ± 30) Hz. The most effective cleaning of sample 5 (series of different cleaning times) lasted seven minutes without time delay. The future research it should be appropriate to try a combination of these most effective cleaning settings on the surface of more samples, so the finding of this thesis will be confirmed.
|
guest ::
