The presented work focuses on study of electron - positive ion recombination in low temperature plasma. The principal method used were Flowing afterglow with Langmuir probe and Stationary afterglow with Cavity Ring-Down Spectrometer. For the first time electron and neutral assisted collisional radiative recombination of Ar+ ions was studied in temperature range of 50 - 200 K. Resulting ternary recombination rate coefficients are in good agreement with theoretical predictions. Recombination of H3 + and D3 + ions with electrons was studied in the temperature range of 50 - 300 K and binary and ternary recombination rate coefficients were obtained. The effect of nuclear spin on recombination of H3 + ions with electrons was studied in the temperature range of 80 - 200 K and state selective recombination rate coefficients were obtained for ortho- and para-H3 + . Results show that at 80 K para-H3 + recombines with electrons substantially faster than ortho-H3 + .

The thesis deals with methods for viability evaluation of the phytopathogenic bacterium Xanthomonas euvesicatoria after low-temperature plasma treatment. Low-temperature plasma produced by Gliding Arc experimental device was used for treatment of X. euvesicatoria. The viability of the bacterial cells was assessed using a scanning electron microscope (SEM) and by measuring of the fluorescence in the Smart-DART device using PrestoBlue chemical reagent. Methodology has been optimised for the sample preparation for the treatment by low temperature plasma and used for evaluation of applied methods. Lethal effect of gliding arc plasma to this gram-negative bacteria was verified by SEM which showed. There is significant structural changes on the cell surface. Viability assessment of X. euvesicatoria using Smart-DART device is a fast, time-saving and inexpensive evaluation of cell viability. The great advantage of this device is its ability to measure the fluorescence in real time. The disadvantage of this method is lower reliability in current stage of research.

This thesis has studied the low-temperature atmospheric pressure plasma as a potential technological application for the degradation of waste oils. The study has been approached initially by investigating the degradation of oil in gas phase only, in order to understand the gas chemistry and elucidate the plasma-chemical degradation mechanism. Gaseous odourless kerosene and dodecane have been used as simulants to waste oil and their plasma-chemical degradation has been studied using a BaTiO3 packed bed plasma reactor and a gliding arc discharge reactor. Kerosene showed similar degradation behaviour to dodecane and the latter one was chosen as a surrogate to allow quantitative analysis. The dodecane plasma degradation efficiency and the distribution of end-gaseous products have been studied under these two reactors in different gas compositions. Optical emission spectroscopy was used to identify intermediate excited species and calculate the rotational and vibrational temperature profiles. Differences in the dodecane degradation gas chemistry between the packed bed and the gliding arc plasma are discussed and postulated mechanisms are presented for each condition. Gliding arc discharge demonstrates higher degradation efficiency and it will be used mainly for the plasma-liquid treatment. The plasma-liquid dodecane treatment is firstly studied using argon dielectric barrier discharge. The effect of different reactor configuration, humidity and temperature to the discharge characteristics and degradation efficiency will be discussed. The study of the liquid dodecane degradation is extended by using the gliding arc discharge. Using N2 and Ar in both dry and humid conditions for the batch treatment of dodecane, the degradation efficiency, gas chemistry and liquid chemistry are discussed and correlated to the gas chemistry observed during the plasma treatment of gaseous dodecane under the same conditions, in order to gain an overall understanding of the plasma-liquid clean-up process. Finally, the gliding arc plasma treatment of liquid dodecane is studied using the recycling method and shows a significant improvement to the degradation efficiency.

No description available.

Since being discovered, combustion of fuels, especially fossil fuels in the last centuries, has been the dominant source of energy for human life. However, over the years, the adverse effects and shortcomings caused by the vast utilization of these energy sources have been observed; the three most important of which are unreliable resources, unfavorable natural outcomes, and limited performance. Using biofuels is one of the well-established proposed solutions to the scarcity and environmental issues of fossils as they are sustainable sources of energy with acceptable and even superior combustion characteristics. As a second-generation biofuel, anisole has shown promising results with high flame speed and high knock resistance. Therefore, the first chapter of this thesis is focused on experimental investigation of anisole laminar burning speed and stability properties so that it can be used as a benchmark for future kinetic mechanism validations. Stability is another important parameter in combustion systems, especially in diffusion jet flame combustion as used in many applications like thrusters or burners. Different methods are applied to improve the stability of such diffusion flames in propulsion systems, e.g., changing geometrical or flow characteristics of the burner. Most of these efforts have not been practically successful, due to the cost and compatibility issues. Another technique which minimizes such problems is to use electron impact excitation, dissociation and ionization and generate highly concentrated charged/excited species and active radicals. These methods include microwave, dielectric barrier, and repetitive nanosecond pulsed (RNP) discharge and the latter has shown promising results as one of the most effective low-temperature plasma (LTP) methods. In chapters 3 to 5, the benefits and issues associated with using RNP discharge in a single-element concentric methane-air inverse diffusion jet flame are discussed. It has been shown that RNP discharge with adequate discharge properties (voltage and repetition) can increase the stability of the flame and expand the flammability of the jet toward leaner compositions. However, the effectiveness is significant in a certain voltage-frequency ranges which results a non-thermal spark discharge mode. Hence, different modes of discharge were investigated and a parametric study on the transition between these modes were done.

No description available.

South Africa has natural resources in mineral feedstock containing gold, manganese, chromium, vanadium, copper, antimony, phosphate rock, uranium, fluorspar and titanium. A high percentage of these ores are exported in unbeneficiated form. There are beneficiation opportunities to transform the raw materials to value-added products, thus increasing employment and stimulating the South African economy. Fluorocarbon (CxFy) gases can be produced via high-temperature plasma processes, where fluorspar and carbon (CaF2 + C) react at -6000K. These gases are traditionally separated by means of costly and unsafe cryogenic distillation. The focus of this project is to propose a feasible separation process and to interlink it to a plasma system in order to develop a conceptual plant that can produce 2500 t/a C2F4 and 625 t/a C3F6 safely and cost-effectively, both with 96% purity. To execute the above a literature survey was done giving vital information on absorption and distillation systems as well as membranes that can be used to separate CF4 from CxFy gas streams at acceptable pressures and temperatures. / Thesis (M.Sc. Engineering Sciences (Chemical Engineering))--North-West University, Potchefstroom Campus,

South Africa has natural resources in mineral feedstock containing gold, manganese, chromium, vanadium, copper, antimony, phosphate rock, uranium, fluorspar and titanium. A high percentage of these ores are exported in unbeneficiated form. There are beneficiation opportunities to transform the raw materials to value-added products, thus increasing employment and stimulating the South African economy. Fluorocarbon (CxFy) gases can be produced via high-temperature plasma processes, where fluorspar and carbon (CaF2 + C) react at -6000K. These gases are traditionally separated by means of costly and unsafe cryogenic distillation. The focus of this project is to propose a feasible separation process and to interlink it to a plasma system in order to develop a conceptual plant that can produce 2500 t/a C2F4 and 625 t/a C3F6 safely and cost-effectively, both with 96% purity. To execute the above a literature survey was done giving vital information on absorption and distillation systems as well as membranes that can be used to separate CF4 from CxFy gas streams at acceptable pressures and temperatures. / Thesis (M.Sc. Engineering Sciences (Chemical Engineering))--North-West University, Potchefstroom Campus,

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.

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.