Dissertations / Theses on the topic 'Corona discharge'

The goal of this work was to assess the feasibility of using corona discharge quenching by anesthetic gases as a technique for anesthetic gas concentration measurement. Two experiments were conducted to investigate corona discharge and measure changes due to anesthetic gases. Experiment One used a chamber in which a high voltage was imposed across two parallel plane electrodes, between which gases under test could flow. Halothane, ethrane, and nitrous oxide were shown to have corona discharge quenching effects proportional to their relative potency. In an attempt to improve accuracy and decrease baseline drift a second system was fabricated. This system used an improved voltage source, temperature and humidity control and a chamber in which gases flowed between two concentric cylindrical electrodes. Results from the second experiment showed that the complex physics of corona discharge quenching by anesthetic gases could not be easily used for reliable measurement of anesthetic gas concentrations.

Carbon dioxide mitigation technologies have garnered increasing attention over the past decade to prevent further detrimental effect to the environment and increased global warming. Non-thermal plasma technology, specifically corona discharge, is a technology that is capable of reducing CO2 to CO which can then be utilised as a feedstock for various chemical feedstocks. As there is no existing work on this specific discharge type, a new reactor and experimental method was developed in order to assess its viability as a CO2 splitting technology. Additionally, a numerical model was built to validate the experimental results. This thesis investigates pulsed power corona discharges for the splitting of CO2 and its ad-mixtures with argon and nitrogen. Special attention is paid to the conversion percentage and the energy efficiency of this process. Few previous works have examined the use of pulsed power in plasma applications and thus there is little understanding of the mechanisms and kinetically pathway of CO2 reduction in this type of system. this thesis aims to propose what they may be and how it differs from other plasma technology. The results indicate that pulsed power corona discharges offer superior energy efficiency compared to other technologies however, the conversion is somewhat lower than other reported works. It is theorised that the input voltage waveform plays a significant role in determining the kinetical pathway of CO2 reduction and future work should revolve around optimising the voltage waveform to maximise both the conversion and energy efficiency. Argon and nitrogen both have a positive effect on CO2 conversion and efficiency, up to a point, yet further addition sees more energy directed towards reactions and energy transfer to these species instead of the desired reaction of CO2 to CO.

Corona on electrified conductors (power lines, transmission lines, and antennas) is a significant source of electromagnetic interference to aircraft. When corona occurs in radio frequency equipment, it usually signals the failure of the system to operate as designed. The Townsend integral, which describes breakdown in low-frequency non-uniform fields, was derived from the electron continuity equation. Predictions of corona onset were developed using new formulas for net ionization. Measurements of 60 Hz corona onset for an isolated cylindrical monopole were compared with these predictions. A corona onset criterion, which describes breakdown in non-uniform radio frequency (RF) fields, was also derived from the electron continuity equation. Measurements of corona onset at 300 MHz for the same isolated cylindrical monopole were compared with predictions. The results confirm that the derived breakdown criteria are good predictors of corona onset at both 60 Hz and 300 MHz for cylindrical geometries in the range 0:1 rp 10:0 cm torr. A discussion of the transition frequency between power frequency and high frequency corona onset is included. The argument is made that corona onset criteria developed for cylindrical geometries are useful for any geometry where the local electric field strength can be characterized.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
Full Text

To enhance the bondability of polyetheretherketone (PEEK), surface treatment techniques of plasma and corona discharge have been evaluated. The results have shown that these two methods are effective and practical. The treated materials not only reach their highest possible joint strength, but also show very promising joint durability. In addition, the various environments, e. g. atmosphere, heat, water, and solvent, have little effects on the enhanced bondability of the treated materials. By using Contact Angle Measurement, Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS) and Time of Flight Secondaty Ion Mass Spectrometry (TOF-SIMS) to characterise the PEEK surfaces before and after treatment, it was established that the lack of active chemical groups, which if present can form strong interatomic and intermolecular forces across the adhesive/PEEK interface, is the main cause for the poor bondability of the untreated PEEK. Both plasma and corona discharge treatment introduce such active functional groups, for instance, hydroxyl, carboxylic acid, amine and etc., onto the surface of PEEK film and so greatly enhance the intrinsic adhesion at the interface between treated PEEK surfaces and epoxy adhesive, as confirmed by the TOF-SIMS interfacial analysis. It is deduced that low molecular weight molecules (LMWM) are formed on treated surfaces, which contain high concentration of oxygen and/or nitrogen, and can be removed by solvent washing. The removal of LMWM will drastically reduce the wettability of the treated surfaces, but does not impair the enhanced bondability. It has been found that both plasma and corona discharge treated surfaces are in a thermodynamically unstable state. When exposed to the atmosphere, the treated surfaces tend to lose their improved wettability and decrease their surface polarity. Increasing temperature can not only accelerate these processes but also change the surface chemical structures of the treated materials back to that of the untreated films to some extent, as revealed by the TOF-SIMS analysis. Water immersion, on the contrary, tend to reverse the above processes.

Electrohydrodynamics (EHD) is a promising research field with several trending applications. Even though the phenomenon was first observed centuries ago, there is very little research until the middle 20th century, as the mechanisms behind it were very poorly understood. To this date, the majority of research is based on the development of empirical models and the presentation of laboratory experiments. This work begins with an extensive literature review on the phenomenon, clarifying conflicts between researchers throughout the history and listing the findings of the latest research. The literature review reveals that there are very few mathematical models describing even the most important parameters of the EHD fluid flow and most are either empirical or greatly simplified. As such, practical mathematical models for the assessment of all primary performance characteristics describing EHD fluid accelerators (Voltage Potential, Electric Field Intensity, Corona Discharge Current and Fluid Velocity) were developed and are begin presented in this work. These cover all configurations where the emitter faces a plane or another identical electrode and has a cylindrical surface. For configurations where the emitter faces a plane or another identical electrode and has a spherical surface, Corona Discharge Current and Fluid Velocity models have been presented as well. Laboratory experiments and computer simulations were performed and are being thoroughly presented in Chapter 4, verifying the accuracy and usability of the developed mathematical models. The laboratory experiments were performed using two of the most popular EHD electrode configurations - wire-plane and needle-grid. Finally, the findings of this research are being summarized in the conclusion, alongside with suggestions for future research. The step-by-step development of the equipotential lines mathematical model is presented in Appendix A. Appendix B covers the mathematical proof that the proposed field lines model is accurate and that the arcs are perpendicular to the surface of the electrodes and to all of the equipotential lines.

Corona discharge is one of the crucial problems related with high-voltage equipment. This paper focuses on the physical and numerical modelling of corona discharge in an Electrostatic precipitator (ESP). The model is based on Maxwells equations and the Finite element method (FEM) and is implemented with the COMSOL Multiphysics software.The simulation allows studying the electric charge distribution and the behaviour of the electric field inside the ESP. The work is focused primarily on time-dependent studies of the corona discharge.

Due to the universal considerable population and economic growth rate, demands for energy have risen significantly over the past decade. This means that the integration of renewable energies in the power grid has escalated as well as requests for reactive power compensation, voltage stability, and mitigation of harmonic filters. Capacitor banks are widely used in the modern electrical transmission system in order to improve power quality and efficiency. In other words, this device aims to be involved in harmonic disturbance elimination, improve the power factor (PF), provide voltage control and stability which leads into more sustainable energy systems. Utilizing high voltage components, such as shunt capacitors in the power grid can introduce new challenges. One of these challenges is known as corona discharge. The aim of the presented master thesis is to study and develop corona discharge suppression models on high voltage capacitor banks which is implemented in collaboration with ABB power grids, Sweden. The main concerns are, effective factors on corona emergence, corona inception voltage levels, and corona suppression methods. Also, this study evaluates the verification of existing suppression. Two various approaches were applied and compared. The aim of the first approach is to evaluate corona discharge by electric field calculations on three various capacitor banks with different voltage levels. The simulation was implemented based on Maxwell’s equations and finite element method (FEM) by utilizing COMSOL Multiphysics software. The second approach is based on streamer inception and propagation. The calculation on this method is fulfilled with the help of MATLAB software. The results of both approaches were found reasonably compatible. It is discovered that corona discharge can appear in different voltage levels on capacitor banks based on various factors, such as the geometry of the bank. Consequently, the suppression method may vary case by case and different proposals were suggested in order to optimize the corona suppression rings.
På grund av den allmänna betydande befolknings- och ekonomiska tillväxttakten har kraven på energi ökat markant under det senaste decenniet. Detta innebär att integrationen av förnybara energier i elnätet har eskalerat samt begäran om reaktiv effektkompensering, spänningsstabilitet och mildring av harmoniska filter. kondensatorbatterier används ofta i det moderna elektriska transmissionssystemet för att förbättra strömkvaliteten och effektiviteten. Med andra ord syftar denna enhet till att vara involverad i eliminering av harmonisk störning, förbättra effektfaktorn (PF), tillhandahålla spänningskontroll och stabilitet som leder till mer hållbara energisystem. Att använda högspänningskomponenter, som shuntkondensatorer i elnätet, kan skapa nya utmaningar. En av dessa utmaningar kallas korona-urladdning. Syftet med den presenterade masteruppsatsen är att studera och utveckla korona-urladdningsmodeller på högspännings-kondensatorbatterier som implementeras i samarbete med ABB Power Grids, Sverige. De viktigaste problemen är effektiva faktorer för korona uppkomst, spänningsnivåer korona och metoder för att underlätta korona. Dessutom utvärderar denna studie verifieringen av befintliga undertryckningsmetoder. Två olika tillvägagångssätt tillämpades och jämfördes. Syftet med det första tillvägagångssättet är att utvärdera korona-urladdning genom elektriska fältberäkningar på tre olika kondensatorbatterier med olika spänningsnivåer. Simuleringen implementerades baserat på Maxwells ekvationer och finita elementmetoden (FEM) genom att använda COMSOL Multiphysics programvara. Det andra tillvägagångssättet är baserat på strömningslinjernas början och utbredning. Beräkningen av denna metod genomförs med hjälp av MATLAB-programvaran. Resultaten från båda metoderna tycktes vara rimligt kompatibla. Det upptäcks att korona-urladdning kan förekomma i olika spänningsnivåer på kondensatorbatterier baserat på olika faktorer, till exempel batteriets geometri. Följaktligen kan undertryckningsmetoden variera från fall till fall och olika förslag föreslogs för att optimera koronaundertryckningsringarna.

The degradation of high voltage electrical insulation is a prime factor that can significantly influence the reliability performance and the costs of maintaining high voltage electricity networks. Little information is known about the system of localized degradation from corona discharges on the relatively new silicone rubber sheathed composite insulators that are now being widely used in high voltage applications. This current work focuses on the fundamental principles of electrical corona discharge phenomena to provide further insights to where damaging surface discharges may localize and examines how these discharges may degrade the silicone rubber material. Although water drop corona has been identified by many authors as a major cause of deterioration of silicone rubber high voltage insulation until now no thorough studies have been made of this phenomenon. Results from systematic measurements taken using modern digital instrumentation to simultaneously record the discharge current pulses and visible images associated with corona discharges from between metal electrodes, metal electrodes and water drops, and between waters drops on the surface of silicone rubber insulation, using a range of 50 Hz voltages are inter compared. Visual images of wet electrodes show how water drops can play a part in encouraging flashover, and the first reproducible visual images of water drop corona at the triple junction of water air and silicone rubber insulation are presented. A study of the atomic emission spectra of the corona produced by the discharge from its onset up to and including spark-over, using a high resolution digital spectrometer with a fiber optic probe, provides further understanding of the roles of the active species of atoms and molecules produced by the discharge that may be responsible for not only for chemical changes of insulator surfaces, but may also contribute to the degradation of the metal fittings that support the high voltage insulators. Examples of real insulators and further work specific to the electrical power industry are discussed. A new design concept to prevent/reduce the damaging effects of water drop corona is also presented.

The degradation of high voltage electrical insulation is a prime factor that can significantly influence the reliability performance and the costs of maintaining high voltage electricity networks. Little information is known about the system of localized degradation from corona discharges on the relatively new silicone rubber sheathed composite insulators that are now being widely used in high voltage applications. This current work focuses on the fundamental principles of electrical corona discharge phenomena to provide further insights to where damaging surface discharges may localize and examines how these discharges may degrade the silicone rubber material. Although water drop corona has been identified by many authors as a major cause of deterioration of silicone rubber high voltage insulation until now no thorough studies have been made of this phenomenon. Results from systematic measurements taken using modern digital instrumentation to simultaneously record the discharge current pulses and visible images associated with corona discharges from between metal electrodes, metal electrodes and water drops, and between waters drops on the surface of silicone rubber insulation, using a range of 50 Hz voltages are inter compared. Visual images of wet electrodes show how water drops can play a part in encouraging flashover, and the first reproducible visual images of water drop corona at the triple junction of water air and silicone rubber insulation are presented. A study of the atomic emission spectra of the corona produced by the discharge from its onset up to and including spark-over, using a high resolution digital spectrometer with a fiber optic probe, provides further understanding of the roles of the active species of atoms and molecules produced by the discharge that may be responsible for not only for chemical changes of insulator surfaces, but may also contribute to the degradation of the metal fittings that support the high voltage insulators. Examples of real insulators and further work specific to the electrical power industry are discussed. A new design concept to prevent/reduce the damaging effects of water drop corona is also presented.

Usando geometrias do tipo ponta e plano estudou-se as características elétricas da descarga corona positiva e negativa. Mediram-se as distribuições da densidade de corrente elétrica e do campo elétrico sobre o plano coletor dos íons. São discutidos os resultados obtidos para o sistema ponta planos e para o sistema em que o campo elétrico externo é aplicado através de uma placa adicional colocada perto da ponta. Neste último caso os resultados são interpretados com um modelo teórico que supõe que os íons se movem direção perpendicular entre as placas, sob a ação de um campo constante e lateralmente sob o campo de repulsão da carga espacial.
Electric characteristics of a positive and negative corona discharge were studied for geometries of the type point and plane. The electric current density and the electric field distributions on the collector plane were measured. We discuss the results obtained with the point and plane geometry and with the geometry were a external electric field is applied by means of an additional metallic plate fixed near the point. For the latter geometry the results were interpreted by using a theoretical model in which it is assumed that the ions drift in the direction perpendicular to the plates under a constant electric field and laterally under the field of the ionic space charge.

In this thesis possibilities of generating corona discharges in supercritical carbon dioxide inside a micro fabricated glass chip are investigated. Managing to do so would enable high throughput research of new chemical reaction fields and analytical spectrometry in the supercritical phase with low equipment costs compared to available technology used today. The aims of the thesis were to design, manufacture and test a chip of this kind that can withstand pressures of 125 bar and be used to study corona discharges by investigating how pressure, electrode geometry and interelectrode distance can affect operating voltages and if light emission from corona discharges could be captured from outside the chip. Chips were successfully manufactured using standard cleanroom techniques like lithography, wet etching, sputter deposition and fusion bonding. Testing showed that one electrode design was superior to the others in terms of operation stability, corona current and light emission and that interelectrode distance of 2 um and 3 um seem preferable compared to larger distances. Electrode erosion during operation proved to be a big problem for electrode lifetime and measurement repeatability and must therefore be improved for further development.

An Electromagnetic Pulse (EMP) resulting from, for example, the detonation of a nuclear weapon is characterised by a wave of electromagnetic activity able to couple with power lines and electro-sensitive equipment with the potential of rendering an establishment or on a greater scale, a whole city impotent. Protection against such occurrences is of paramount importance. It is now accepted that an important consideration when devising protective schemes against such phenomena is an accurate understanding of the effects on propagating waveforms such as those coupled to wires, when electrical breakdown of the dielectric material surrounding such wires occurs, otherwise known as electrical discharge. Such issues can occur around the affected wires if the electric fields generated exceed the dielectric strength of the surrounding medium, typically air or soil. Under these circumstances, the signature of the coupled waveform is known to change in characteristic ways. The form and degree of distortion needs to be understood if the harmful effects are to be prevented by protection systems put in place. The purpose of this thesis is to first describe the mechanisms that lead to the development of the Nuclear–Electromagnetic Pulse (NEMP) and the mechanisms of the discharge that can result once such pulses have coupled to a wire. Next, some of the previous corona-modelling approaches are discussed. Many of the modelling approaches have been applied to 1-D transmission-line simulations. When 3-D simulations have been performed, the Finite-Difference (Time Domain) or FD-TD approach seems to be the preferred method. At the time of writing, no 3-D Transmission Line simulations of discharge phenomena around wires were available. Hence, here, the 3-D Transmission Line Modelling Method (TLM) is described with a view to modelling such behaviour. In particular, the Embedded-Wire-Node (EWN) is used to model the discharge development around the wire. This is a fine-wire technique used to reduce computational fatigue. The node can be adapted to accept changes related to electrical discharge allowing for a real-time, self-consistent recreation of such effects. The 3-D TLM approach proves to be a decent candidate to the modelling of such behaviour. Both advantages and disadvantages of this method are discussed.

Orientador: João Sinezio de Carvalho Campos
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: Os polímeros, em especial as poliolefinas, apresentam baixa energia livre de superfície, caracterizada pela adesão relativamente fraca a outros materiais. Para resolver este problema, suas superfícies são tratadas por diversas técnicas, destacando-se a descarga corona, amplamente utilizada na indústria. Muitos problemas pós-tratamento surgem por falta de entendimento das propriedades de superfície e sua relação com a adesão. Neste trabalho, estudam-se as modificações causadas na superfície de filmes de polipropileno (PP) isotático tratados por descarga corona. Para isto, os filmes são tratados sob condições ambientes controladas e após o tratamento, parte das amostras é armazenada a diferentes temperaturas, sendo que as armazenadas em temperatura ambiente são retratadas; outra parte é lavada com solventes e também armazenada (temperatura ambiente). As superfícies destes filmes são caracterizadas através de espectroscopia FTIR/ATR, microscopia de força atômica (AFM), ângulo de contato (8), DSC e teste de descolagem Peel. O tratamento por descarga corona induz a formação de grupos polares contendo oxigênio na superfície dos filmes e mudanças na topografia, tais como, o aparecimento de novas estruturas, aumento da rugosidade e dimensão fractal, resultando no aumento da energia livre superficial, molhabilidade e melhoria na adesão. Tratamento estendido promove a formação de material oxidado de baixa massa molar, o qual é facilmente removido pela lavagem com solvente. O envelhecimento ambiente dos filmes tratados e dos tratados/lavados diminui ligeiramente a força de adesão dos filmes em conseqüência da reorientação (lenta) dos grupos formados na superfície e diminuição da energia livre superficial e da molhabilidade. Envelhecimento acima de 60°C acelera os efeitos observados no envelhecimento ambiente. O retratamento dos filmes tratados recupera as propriedades superficiais perdidas após o envelhecimento
Abstract: Many polymer films (polyolefins) present low energy surfaces, characterised by their relatively weak adhesion to other materiais. Numerous methods have been developed to modify polymer surfaces. Among these methods, corona discharge treatment, is widely used in industry. In this work, the surface modification of corona treated polypropylene films (PP) is studied. The films are treated by corona discharge in controlled ambient conditions and after treatment, some samples are aged under different temperatures; other samples are washed by immersion in solvent (acetone and water) and also aged. Their surfaces are characterised by FTIRlATR spectroscopy, atomic force microscopy (AFM), contact angle (8), differential scanning calorimeter (DSC) and peel tests. Discharge treatment introduces oxygen polar groups into the films surface and dramatic change in the topography (new structures, increase in the roughness and fractal dimension), resulting in increased wettability and much enhanced adhesion. Extended oxidation results in the formation of low molecular weight oxidised material (LMWOM), which is easily removed by washing with solvent. For corona treated PP films ageing at ambient temperature, only a slight decrease in adhesion is observed. This decrease is attributed to the reorientation of oxidised functionalities within the surface region and to slight decrease in the surface free energy and wettability. At elevated storage temperatures, migration of oxidised species out of the surface region occurs leading to significant decreases in the wettability and a loss of surface oxidation. The treated films surface properties lost after ageing are restored by re-treatment
Doutorado
Ciencia e Tecnologia de Materiais
Doutor em Engenharia Química

Neste trabalho foi investigado o comportamento elétrico dos sistemas poliméricos preparados com o poliestireno, PS, e poli(metacri1ato de metila), PMMA, dopados com o corante vermelho disperso 1, DR1. O processo de polarização dos filmes poliméricos foi realizado usando o triodo de corona operando em duas configurações: i) carregamento com corrente de carga constante, ii) com tensão de grade constante. O processo de polarização por corona foi investigado variando-se os parâmetros do processo, tais como: corrente de carga, tempo, temperatura, campo elétrico de saturação e porcentagem de corante das amostras. As medidas da corrente elétrica no estado estacionário em função campo elétrico permitiram mostrar que o processo de condução elétrica nos dois sistemas obedecem o modelo de Poole-Frenkel. O valor da polarização elétrica induzida foi avaliada através de medidas do coeficiente piroelétrico, o qual é diretamente proporcional a polarização na amostra. No caso do PS(DR1) deu-se ênfase a investigação de medidas de corrente termo estimulada para avaliar a polarização elétrica induzida nas amostras por aplicação de uma ddp. Medidas da constante dielétrica complexa para os dois sistemas poliméricos foram realizadas em função da freqüência para diferentes temperaturas. Os resultados obtidos mostraram que a orientação e relaxação dos corantes nas amostras são associados ao movimento das cadeias poliméricas, i.e., relaxação do tipo α.
Some electrical properties of guest-host polymeric systems made with polystyrene, PS, and poly(methyl methacrylate), PMMA, and the disperse red 1 dye, DR1 were investigated. The poling process of films were performed with the corona triode set up operating in two modes: i) charging with constant current, ii) with a constant grid voltage. The influence of parameters such as the charging current, electric field at the s, time, temperature and the percentage of DR1 was investigated. Measurements of the steady state current versus the electric field allowed us to show that the electric conduction process in both polymeric systems follow the Poole-Frenkel model. The electric polarization induced in samples was evaluated measuring the piroelectric coefficient, which is directly proportional to the polarization value. For PS(DR1) samples thermally stimulated current measurements were performed to investigate the electric polarization obtained by application of a dc voltage. Measurements of the complex dielectric constant with the two polymeric systems as function of the frequency for different temperatures were performed. Results showed that orientation and relaxation of DR1 dye in samples are related to the chain movement, i.e., α relaxation process.

The high altitude balloon operations at Esrange Space Center have been goingon since 1972, and about 550 launches have been performed. Their present service system for the high altitude balloons is about 18 years old. To be able to meet the requests from their customers, SSC have started the development of a new service system. A service system contains all features and technology required to perform a high altitude balloon mission. This system is separated from the payload. Important design aspects for the new service system have been investigated to be able to leave recommendations to SSC. These are frequency for the radio communication, modulation scheme for the communication link, prevention of corona discharge, and available computer systems to be used as on-board computers. These design aspects have been evaluated according to the requirements for the development project. Theory, articles, available standards and analyzes have been read and evaluated to reach a conclusion about these subjects. It was found that the best frequency bands are the 400MHz-band, downlink, and the 450MHz-band, uplink. The operation in these bands will be unmodified for many years, and the link suffers little loss. The 2.3GHz-band is interesting from an international perspective, and it is suggested that SSC work to get a band dedicated to aeronautical services in this band. The best modulation scheme for the service system is GMSK, as it has very good spectral eficiency. The corona discharge can only be prevented indirect by SSC, as the phenomena occurs within or between components, aspects which SSC can't control. Standardized methods for tests and specications lists was suggested to minimize the risk of a discharge. The best computer system is an in-house designed service system that have been used on sounding rockets. It fits the present requirements the best. It suggested that the Beaglebone Black should be implemented in basic systems, providing processing and storage via simple serial communication, as it is a very cost eficient solution.

Orientador: João Sinezio de Carvalho Campos
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: Estudos das modificações superficiais de polímeros, causadas por descarga corona, são desenvolvidos com o objetivo de mudar as propriedades hidrofóbicas apresentadas por esses materiais, melhorando suas propriedades superficiais sem alterar suas propriedades mecânicas. No presente estudo, realizou-se, alterações na superfície da borracha natural, por tratamento corona de configuração ponta/plano com potência de 5 kV, visando, num segundo momento, a facilitação da incorporação de cargas com caráter hidrofílico à borracha natural. Um planejamento fatorial 22 foi utilizado para a análise dos resultados obtidos por medidas de ângulo de contato, tendo como objetivo a determinação do tempo e altura ótimos para a diminuição do ângulo de contato medido na superfície do polímero em relação à água destilada. Utilizaram-se técnicas complementares como FTIR/ATR, para a determinação das alterações físico-químicas ocorridas na superfície da borracha, bem como, análises térmicas da borracha natural visando à sustentação da não ocorrência de modificações na estrutura polimérica da borracha natural, tais como, reticulações. Através da técnica de microscopia ótica, foi possível verificar que para alturas menores que 2 mm, a superfície da borracha sofre degradação causada pela intensidade das descargas
Abstract: Studies of the superficial modifications of polymers, caused by corona discharges, are developed with the objective to change the hydrophobic properties presented by these materials, improving their superficial properties without changing their mechanical properties. In the present study, superficial modifications were carried out in the natural rubber, for corona treatment from needles-plane electrode system configuration with power of 5 kV, aiming, on a second moment, the facilitation of the incorporation of fillers with hydrophilic characteristic into the natural rubber. A factorial planning 22 was used on the analysis of the results obtained by contact angle measures, taking as an objective the determination of the best time and height for the reduction of the contact angle measured in the polymer surface regarding the distilled water. Complementary techniques were used, like the FTIR/ATR, to determine the chemical-physic alterations taken place in the rubber surface, as well, thermal studies of the natural rubber aiming for sustenance of not-incident modifications in the internal polymeric structure of the natural rubber, such as, reticulations. Through the optical microscopy technique, it was possible to confirm that, for heights less than 2 mm, the rubber surface suffers degradation caused by the intensity of the applied electric charges.
Mestrado
Ciencia e Tecnologia de Materiais
Mestre em Engenharia Química

Within this master thesis work, a novel application of a corona discharge is presented. The phenomenon of an electro-hydro-dynamic (EHD) flow is used for the precipitation of airborne particles onto a restricted surface of a non-coronizing electrode. The non-coronizing electrode surface can be replaced by a liquid interface, by which aerosol particles can be transferred from the airflow into a liquid solution, allowing for further analysis. Due to a small volume of the liquid container, the increased concentration of trapped particles will potentially enhance the resolution of the detection system. Aerosol droplets can originate from a human breath, which opens the possibility to utilize the system for narcotics or viruses detection. In this work, effort was laid on adapting a simulation model and an experimental set-up to the concept of the airborne particle trapping. Electrical measurements were conducted to characterize the set-up, through which the main limitations of the input parameters of the system could be extracted. Moreover, an approach for the determination of the upper limit of the applicable voltage was introduced. The data collected was used to build general conclusions and recommendations, relevant to the further research on this topic.

This thesis has proposed a simplified model of corona discharge from an overhead wire struck by lightning for surge computations using the FDTD method. In the corona model, the progression of corona streamers from the wire is represented as the radial expansion of cylindrical conducting region around the wire. The validity of this corona model has been tested against experimental data. Then, its applications to lightning electromagnetic pulse computations have been reviewed.
博士(工学)
Doctor of Philosophy in Engineering
同志社大学
Doshisha University

A obtenção de compósitos poliméricos condutores de eletricidade tem sido alvo de pesquisa com o objetivo de combinar as propriedades de diferentes materiais poliméricos. Neste trabalho foram preparados compósitos de filmes de poli(tereftalato de etileno) (PET) com camadas superficiais do polímero condutor polianilina (PANI). Para obter a camada condutora o filme de PET foi imerso no meio reacional da síntese da PANI, realizada em solução método este freqüentemente empregado para a produção de PANI. Foram otimizados os parâmetros da síntese (temperatura, concentração dos reagentes, tempo de polimerização, etc..) com o objetivo de se obter uma camada de PANI com espessura adequada, condutividade superficial elevada e com boa adesão no substrato de PET. O processo da reação de polimerização foi monitorada pela medida do potencial de circuito aberto e também diretamente pela camada de PANI depositada no PET, através de medidas de espectrocospia UV-Vis-NIR, condutividade elétrica e adesão da camada de PANI. Em condições otimizadas da síntese, realizada a temperatura ambiente durante o tempo de 20 minutos, pode-se obter camadas de PANI com condutividade da ordem de 10 S/em, boa adesão ao substrato de PET e com razoável transparência óptica. Os compósitos obtidos nas condições otimizadas foram caracterizados usando-se microscopia por SEM, microscopia óptica, microscopia AFM, difratogramas de raios-X, DSC, análise DMTA, análise TGA, correntes termo estimuladas, medidas de ruptura elétrica, medidas de adesão e solubilidade da camada de PANI. Verificou-se também que o tratamento térmico dos compósitos melhora a adesão da camada de PANI ao substrato de PET. Foi descoberto um novo método para dopar as camadas condutoras de PANI no qual o compósito desdopado é tratado por descarga corona. O processo é realizado totalmente a seco e pode-se obter uma condutividade da camada de PANI da ordem de 0,3 S/em com boa adesão. Observou-se que a eficiência do processo é dependente da umidade relativa do ar na câmara de tratamento e que a estabilidade da condutividade elétrica é melhor que nas amostras dopadas em solução
Composites with conductive properties have been proposed as materiais in which different physical properties of polymers are combined. In this work a composite consisting of surface layers of polyaniline, PANI, deposited on films of poly(ethylene terephtalate), PET, were prepared. In order to deposit the PANI the PET film were immersed in the solution in which the synthesis reaction is carried out. The parameters of the synthesis usually optimized in order to obtain a layer of PANI with enough thickness, high electric conductivity and good adhesion to the PET substrate. The synthesis was monitored by means of open circuit potential and also using UV-Vis-NIR spectroscopy and the electric conductivity of the PANI layer on PET. Using the optimized conditions, at room temperature and polymerization time of 20 minutes, a composite with a surface conductivity of the order of 10 S/em, good adhesion and a reasonable optical transparence can be obtained. Such composite were characterized employing electron scanning microscope, atomic force microscope, optic microscope, X-rays diffractometry, differential scanning calorimeter, thermal dynamic analysis, thermogravimetric analysis, thermally stimulated depolarization current, electric thermal stability of the conductivity, electric breakdown measurements, adhesion measurements and solubility of the PANI layer. It was also found that the thermal treatment leads to an improvement of the adhesion properties of the PANllayer. It was found that a corona discharge could be used to dope the PANI layer of a dedoped composite, leading to a new method for doping polymeric materiais. Such process is performed under dry conditions and gave a conductivity of the order 0.3 S/em. The process efficiency is dependent of the relative air humidity of the corona chamber and the thermal stability of the electric conductivity is betler when compared with the composites obtained by doping in solution.

Fluorescence spectroscopy is a powerful tool for obtaining information on microscopic processes in discharge (corona) plasmas in dense media, such as high pressure supercritical gases and even liquids. Spectroscopic observations of the light emitted from an ionization zone near a tip electrode can be used to determine structural information of the local environment of the emitting atoms or molecules. The spectra observable are sensitive to the immediate surroundings of the emitting species, making them useful for the study of cold non-equilibrium plasmas at varying pressures and temperatures. The aim of this project is to further our understanding of helium (4He) in different phases, providing information to help understand the nature of the interaction between the helium atoms within this environment. In this work, spectra have been recorded for a corona discharge in gaseous and liquid helium. The experimental conditions covered a wide region of thermodynamic states in two different designs. The first experiment was carried out at cryogenic temperatures at 3.8, 4.0, 4.5 and 5.0 K under a range of pressure (0.1-5.0 bar). The second set of experiments were carried out at room temperature with range of pressures 0.1-30 bar. Several thousand spectra were recorded in the visible and near-infrared regions. Analyses were conducted on spectra including the atomic 3s 1S→2p 1P and 3s 3S→2p 3P transitions. These transitions showed line shifts, spectral broadening and intensity changes that were dependent on the magnitude of the pressure and temperature, and therefore on the thermodynamic phase. In addition to atomic lines, rotationally-resolved molecular emission bands arising from the δ3Σu+→b3Πg and D1Σu+→BΠg transitions of the electrically excited helium dimer (excimer), He2∗, were recorded. Remarkably, and similarly to the analysis of atomic lines, the molecular (excimer) emission showed sharp and distinct lines at low temperature in the region below the saturated vapor pressure (SVP) of helium. However, lineshifts, linewidths and line intensities of the excimers increased strongly upon an increase in pressure, indicating that solvated He2∗ in the liquid phase exhibits hindered rotation. The rotation of excimers within the liquid phase was attributed to the location of the excimer within a large bubble. A further interesting observation was the abrupt changes of lineshift and linewidths with pressures that occurred by crossing the SVP curve for both atomic and molecular transitions. A model was developed to explain this in which clusters form around excimers and excited helium atoms before the helium liquefies. In a separate application of the corona discharge, it was employed to make plasmas from a mixture of pure air and perfume. The idea here was collecting spectra of this mixture with and without helium to explore and understand some of the emitted species generated in this mixture of plasmas at atmospheric pressure and to the first time.

Les matériaux textiles occupent une place importante dans notre quotidien. Les recherches actuelles s'orientent vers l'élaboration de matériaux à nouvelles propriétés techniques. Parmi les voies d'obtention, on peut citer le greffage de microcapsules ou de molécules cages rechargeables contenant un principe actif qui va être libéré au cours du temps donnant aux textiles de nouvelles fonctionnalités. Dans cette thèse, nous avons synthétisé des cyclodextrines originales dotées de groupements permettant leur greffage sur des fibres de coton après activation du substrat et qui conservent en partie leur capacité à inclure des principes actifs. Dans le souci d'utiliser des technologies propres et d'éviter l'utilisation de produits chimiques, notre choix s'est porté sur une activation par traitement Corona. Nous avons mis en évidence que ce traitement entraîne la formation de radicaux libres, une oxydation et un accroissement de la rugosité en surface des fibres cellulosiques. La conduite en parallèle d'expériences basées sur une activation chimique a confirmé que les radicaux libres formés au cours du traitement Corona sont impliqués dans le mécanisme de greffage de molécules allylées et notamment de la tétradécakis-(2,6-di-O-allyl)-β-cyclodextrine. Des analyses par gravimétrie, spectroscopie de photoélectrons X, thermogravimétrie et microscopie électronique à balayage ont démontré que le greffage avait bien lieu. Après greffage, la cyclodextrine conserve sa capacité à former des complexes d'inclusion notamment lorsque l'on utilise la phénolphtaléine comme molécule invitée ce qui ouvre des perspectives intéressantes pour ce travail
Textiles are omnipresent in our everyday life. Research in this area tends to elaborate more sophisticated or "clever" materials i.e. confer new properties by means of innovative protocols. Among the available protocols, we can propose the grafting of microcapsules or host molecules able to guest an active substance which can be evolved. In our study, we synthesized original cyclodextrins bearing functional groups that allow their grafting on activated cotton fabrics. These entities maintain their inclusion ability. For activation purpose, we chose an "ecofriend" technology which does not require solvents, the corona discharge treatment (CDT). We evidenced that formation of free radicals, oxidation, and increase of roughness occur at the surface of cellulose during treatment. By carrying out experiments based on chemical activation, we concluded that free radicals are implied in grafting mechanism of allyl molecules and especially tetradecakis-(2,6-di-O-allyl)-β-cyclodextrin. Analysis by gravimetry, X ray photoelectron spectroscopy, thermogravimetry and scanning electon microscopy give the proof that grafting was effective. The inclusion ability of the modified β-cyclodextrins after grafting was studied with the dye extinction method determined by inclusion of phenolphthalein

Electrical discharges with a variety of different forms (streamers, glow corona, leaders, etc.) broadly exist in nature and in industrial applications. Under certain conditions, one electrical discharge can be transformed into another form. This thesis is aimed to develop and use numerical simulation models in order to provide a better physical understanding of two of such transitions, namely the glow-to-streamer and the streamer-to-leader transitions in air. In the first part, the thesis includes the two-dimensional simulation of the glow-to-streamer transition under a fast changing background electric field. The simulation is performed with a fluid model taking into account electrons. An efficient semi-Lagrangian algorithm is proposed to solve the convection-dominated continuity equations present in the model. The condition required for the glow-to-streamer transition is evaluated and discussed. In order to enable such simulations for configurations with large interelectrode gaps and long simulation times, an efficient simplified model for glow corona discharges and their transition into streamers is also proposed. The second part of the thesis is dedicated to investigate the dynamics of the streamer-to-leader transition in long air gaps at atmospheric pressure. The transition is studied with a one-dimensional thermo-hydrodynamic model and a detailed kinetic scheme for N2/O2/H2O mixtures. In order to evaluate the effect of humidity, the kinetic scheme includes the most important reactions with the H2O molecule and its derivatives. The analysis includes the simulation of the corresponding streamer bursts, dark periods and aborted leaders that may occur prior to the inception of a stable leader. The comparison between the proposed model and the widely-used model of Gallimberti is also presented.
Elektriska urladdningar av olika former (streamers (från engelska), glöd-korona, ledare, etc.) förekommer i stor utsträckning i naturen och i industriella applikationer. Under vissa förhållanden kan en elektrisk urladdning omvandlas till en annan form av elektrisk urladdning. Denna avhandling syftar till att utveckla och använda numeriska simuleringsmodeller för att ge en bättre fysikalisk förståelse av två sådana övergångar, nämligen glöd-till-streamer- och streamer-till-ledar-övergångar, i luft. I den första delen, avhandlas en tvådimensionell simulering av glöd-till-streamer-övergången med ett hastigt föränderligt elektriskt fält i bakgrunden. Simuleringen utförs med en flödesmodell som tar hänsyn till elektronerna. En effektiv semi-Lagrangesk algoritm föreslås för att lösa de konvektionsdominerade kontinuitetsekvationerna i modellen. Vidare utvärderas och diskuteras förutsättningarna för glöd-till-streamer-övergången. För att möjliggöra sådana simuleringar i konfigurationer med stora elektrodavstånd och långa simuleringstider, föreslås också en effektiv och förenklad modell för glöd-korona-urladdningar samt deras övergång till streamers. Den andra delen av avhandlingen är tillägnad att undersöka dynamiken i streamer-till-ledar-övergångar över långa avstånd i luft, under atmosfäriskt tryck. Övergången studeras med en endimensionell termohydrodynamisk modell och en detaljerad kinetisk modell för blandningar av N2/O2/H2O. För att utvärdera effekten av luftfuktighet, innefattar den kinetiska modellen de viktigaste reaktionerna med H2O-molekylen och dess derivat. Analysen innefattar simuleringen av motsvarande streamer-kedjor, mörka perioder och avbrutna ledare som kan förekomma före starten av en stabil ledare. En jämförelse mellan den föreslagna modellen och den allmänt använda modellen av Gallimberti presenteras också.

QC 20170418

Thesis (MEng) -- Stellenbosch University, 2014
ENGLISH ABSTRACT: The electrodynamics of arbitrary, point-to-plane electrospraying geometries, were investigated in this research both analytically and numerically. Electrospraying is the process during which particles of sizes in the nanometre range are simultaneously generated and charged by means of an applied electrostatic field. A high electrostatic potential is applied to a conductive capillary needle, which overcomes the force exerted by the liquid surface tension. One of the primary limitations of this process are corona discharges. The effect of corona discharges have not been studied quantitatively, even though it is frequently reported in the electrospraying literature. The main objective of this research was to understand the corona discharge thresholds associated with electrospraying. Previously, only one theoretical, and two empirical investigations studied this phenomenon, over a time period of approximately forty years. It was clear that by better understanding these thresholds, electrospraying could be applied much more effectively. A corona discharge threshold model is proposed, using either a numerical or analytical model for the calculation of polarization fields. When compared with the experimental results of other researchers, both these two models have average relative percentage errors of approximately 15%. These are the first models proposed in the literature for the calculation of electrospraying corona thresholds. A new method to determine surface tension using electrospraying is described theoretically. In addition to this method, the calculation of corona discharge thresholds have various applications. For example, the dynamics of electrostatic ion thrusters are much better described, powder production by means of electrospraying can be optimised, and pattern generation using pulsed electrospraying cone-jets can be optimised as well.
AFRIKAANSE OPSOMMING: Die elektrodinamika van arbitrêre, punt-tot-vlak elektrosproei geometrieë was beide analities en numeries ondersoek in hierdie tesis. Dit is die proses waartydens nanodeeltjies gelyktydig gegenereer en elektrostaties gelaai word. Deur 'n hoë elektriese potensiaal aan te lê tot 'n geleidende kapillêr, is dit moontlik om die krag van die oppervlakte spanning te oorkom. Een van die primêre beperkings van elektrosproei is corona ontladings. Die effek van corona ontladings was nog nie kwantitatief bestudeer nie, selfs al word dit dikwels rapporteer in die elektrosproei literatuur. Die primêre doel van hierdie navorsing was om die corona ontlading drempels te verstaan wat geassosieer word met elektrosproei. In die verlede was daar nog net een teoretiese, en twee empiriese ondersoeke gewees wat hierdie verskynsel bestuur het, oor 'n tydperk van ongeveer veertig jaar. Dit was duidelik dat deur 'n beter begrip te hê van hierdie elektrosproei drempels, kan hierdie proses baie meer doeltreffend toegepas word. In hierdie tesis word 'n corona ontlading drempel model voorgestel, wat gebruik maak van 'n analitiese of numeriese model om die polarisasie velde te bereken. Wanneer vergelyk met die resultate van ander navorsers, het beide die modelle 'n gemiddelde relatiewe persentasie fout van ongeveer 15%. Hierdie is die eerste modelle wat voorgestel word vir die berekening van corona ontlading drempels. Deur gebruik te maak van elektrosproei, word 'n nuwe metode ook voorgestel om die oppervlakte spanning te bereken. In byvoeging tot hierdie, het die berekening van corona ontlading drempels vele ander toepassings. As 'n voorbeeld, die dinamika van elektrostatiese ioon stuwers word beter beskryf, en poeier produksie deur middel van elektrosproei kan optimeer word.

The thesis is focused on electrical discharge in liquid solutions, in particular in ethanol solutions. In the theoretical section, the plasma is defined along with its important parameters, types of plasma generation and usage of plasma technologies. Main part is focused on the discharges in water solutions. Electric discharges in liquid solutions enable physical processes (shock waves, UV radiaton, electric current) as well as chemical ones (generation of radicals and ions). Both types of the processes are used in many fields – medicine (tool sterilization, destruction of pathogens), consumer technologies (surface adjustemen, processing of the textiles, surface clearing) of environmental protection (clearing water, decomposition of organic compounds). Goal of the thesis was to analyze discharge products on ethanol solution. Multiple samples were measured and concentration od selected products was monitored during the measurement – ethanol, acetone and acetaldehyde. PTR-TOF-MS method was used to collect and analyze the data. This method is well used thanks to quick response and immediate measurement. It produce the reset accurate enough for our purpose. It would be more efficient to use this method in combination with another analytical metohod in the future research, e.g. gas chromatography.

Este trabalho traz como contribuição o início sistemático de estudos para o projeto e execução de ozonizadores dedicados a estações de tratamento de água e esgotos domésticos com tecnologia totalmente nacional. O objetivo é desenvolver um sistema que apresente custo reduzido de fabricação, implantação, manutenção e também boa eficiência na produção de ozônio. Equipamentos auxiliares para bombeamento e tratamento do ar não são necessários, além de ser possível a ampliação do sistema. Devido ao caráter multidisciplinar, este trabalho aborda a problemática da geração de subprodutos danosos ao homem e ao meio ambiente pelo uso de desinfetantes tradicionais, bem como um processo alternativo de tratamento pelo emprego do ozônio. Após descrever os fenômenos físicos envolvidos no método das descargas corona, um tratamento matemático apresenta elementos para o projeto ótimo deste sistema. Contudo, para viabilizar o uso de materiais disponíveis no mercado, os valores adotados nos arranjos iniciais seguiram aproximadamente estas indicações. Os ensaios foram realizados e a produção de ozônio foi obtida por titulação iodométrica. Os primeiros resultados foram tabulados e comparados com valores informados pelos equipamentos de mercado. Sugestões de implantação em campo para trabalhos futuros são apresentadas.
Studies for the project and execution of ozonizers dedicated to the wastewater and water treatment with total national technology were presented. The aim of this work consists of developing a system which minimize the manufacturing process, implementation and maintenance costs and also improves the ozone production efficiency. Accessory pumping equipments has been eliminated with the use of Venture\'s system to inject the ozone in liquid and air treatment has not been used to reduce costs. While this system loses efficiency with air no treatable, it allows a parallel and serial set-up to improve its performance. To support this work, an extended bibliographical analyzes has been carried out, which due to its multidiscipline characteristic was separated into studies of the traditional disinfectant procedures, alternative ozone treatment and, the physical corona discharges phenomena. The two prototypes were developed and, their obtained with the iodometric titration method, was also compared with those of market equipments. These preliminary comparisons have shown that these prototypes have a good performance inclusive with one of them having an ozone production superior than one of market equipments. Suggestions of implantation in field and other improvements for future work are also presented.

Plasma chemistry is a rapidly growing field to develop and exploit the great potential of plasma to perform chemical reactions. This thesis deals with the oxidation of organic pollutants in air and water promoted by the action of air non-thermal plasma (NTP). Such plasmas, which are conveniently produced by electric non-thermalizing discharges like corona and dielectric barrier discharges in air at atmospheric pressure and ambient temperature, provide highly reactive oxidizing environments comprising electrons, excited molecules, atomic and radical species (O, OH), ions (O2+, N2+, NO+, O–, O2–, O3–), O3 and NO. Despite the numerous successful applications of NTP in processes of environmental and commercial relevance, the chemistry of organic compounds within air non-thermal plasmas is still not well characterized, both as far as products and mechanisms are concerned. This thesis developed as a contribution to this field of research along three lines dealing, respectively, with plasma processing of: volatile organic compounds (VOCs) in air with plasma alone; VOCs in air with plasma plus an heterogeneous catalyst; organic pollutants in aqueous solutions above which an air plasma is generated. All three projects had a common focus in the mechanistic characterization of the oxidation processes within these very complex and highly reactive systems. The study of VOC oxidation in air NTP was carried out with a large prototype corona reactor developed at the Department of Chemical Sciences in Padova, which can be energized with DC or pulsed high voltage of either polarity. Comparative studies were carried out to evaluate the response of selected model VOCs to different corona regimes (+DC, −DC and +pulsed). The VOCs considered include two alkanes (n-hexane and i-octane), toluene and two halogenated methanes, dibromomethane (CH2Br2) and dibromodifluoromethane (CF2Br2, halon 1202). Remarkably, all these different VOCs, including the highly inert halon, can be oxidized to CO2 at room temperature with efficiencies which depend on VOC type (despite their high reactivity NTPs display some selectivity), on VOC concentration (the efficiency increases linearly with the reciprocal of VOC concentration) but also on the way energy is given to the plasma. Thus, for all VOCs examined the efficiency decreases in the order: +pulsed > -DC > +DC corona. This means that any given amount of energy produces an extent of VOC conversion ([VOC]/[VOC]0) which depends on the corona regime and decreases in the order +pulsed > –DC > +DC. The greater efficiency of +pulsed corona is due to the higher mean electron energy achieved, for any given input of energy, with this type of power supply with respect to DC high voltage. The mean electron energy of the plasma under the different corona regimes was experimentally determined in our reactor by emission spectroscopy measurements following a published procedure. Another important variable tested was the humidity in the air, which is known to produce the strongly oxidizing OH radicals via electron induced dissociation or via reaction with O2+ and N2+ ions. Thus, the greater efficiency in humid with respect to dry air observed for the oxidation of hydrocarbons and of CH2Br2 with –DC and +pulsed corona was attributed to reaction with OH radicals. Surprisingly, in experiments with + DC the same VOCs undergo less efficient oxidation in humid air than in dry air, despite the presence of OH radicals. Analysis of the plasma ionized species, performed by APCI-MS (Atmospheric Pressure Chemical Ionization – Mass Spectrometry), coupled to the determination of current/voltage characteristics of DC coronas, led to the proposal that in the case of +DC corona the oxidation of hydrocarbons and of CH2Br2 is initiated by reactions with ions (O2+, H3O+ and their hydrates, NO+) both in dry as well as in humid air. In contrast, with –DC and +pulsed corona in humid air, OH radicals are involved in the initial stage of hydrocarbons and of CH2Br2 oxidation. Consistent with its very low reactivity with the OH radical, the oxidation of CF2Br2 in humid air proceeds less efficiently with both +DC and –DC corona. It was thus proposed that the oxidation of CF2Br2 occurs via a common mechanism under all corona regimes tested, the initial step being electron induced C-Br dissociation. The process efficiency is lower in humid air because the mean electron energy is lowered due to reaction of the electrons with water molecules. The two halomethanes also form different products: FTIR analysis of post-discharge gas has shown that CH2Br2 produces both CO2 and CO, whereas CF2Br2 forms CO2 and F2C=O. The latter product is a longlived oxidation intermediate due to its low reactivity with atmospheric radicals. It is however very rapidly hydrolized to CO2 and HF as shown by combined ion chromatography and FT-IR analysis of the solution and of the exhaust gas obtained after a water scrubbing step. Other non-carbon containing products of the discharge were analyzed by FT-IR analysis, including ozone, HNO3 and N2O. In experiments with both halomethanes evidence was found for brominesustained catalytic ozone destruction cycles, responsible also for increased conversion of NOx into HNO3. Efficiency and, especially, product selectivity can be improved by the combined action of plasma and heterogeneous catalysts which usually result in synergic effects. The nature and origin of this synergy was the focus of the research I carried out in my second year in graduate school during a stage at the Advanced Industrial Science and Technology Institute (AIST) in Tsukuba (Japan), in the group of dr. Hyun-Ha Kim. As molecular probe to compare the effects of plasma alone and plasma plus catalyst we selected the O-scrambling reaction to form 16O18O starting from a mixture of 16O2 and 18O2. Four different reactors were used and various catalysts, including TiO2, MS-13X and gAl2O3 also containing a few % of Ag. It was possible to conclude that, in the absence of a catalyst the O-exchange reaction occurs in the gas phase and not on the electrodes surface. It was also possible to use the results of these experiments to estimate, for any given energy input the average concentration of O atoms within the plasma. This is a most interesting outcome of these studies since the traditional method for obtaining O atom density involves sophisticated laser spectroscopy instrumentation and procedures. As for the catalyst/plasma interaction, using again a labelled molecular probe, 18O2, it was possible to conclude that the plasma induces oxygen fission on the catalyst surface and that this oxygen is then used in the oxidation of VOCs. The third project dealt with the plasma induced oxidation of phenol in aqueous solution. For these studies two prototype reactors were developed and tested, both characterized by application of electric discharges in the air above the solution. The first is a dielectric barrier discharge reactor which afforded the efficient removal of phenol from the aqueous solution according to an exponential decay as a function of treatment time at constant power. A qualitative analysis of the intermediate and final products of phenol oxidation was performed and the major reactive species formed upon the application of the discharge in air were identified and determined. It is concluded that the decomposition of phenol is initiated by reactions with ozone, taking place on the surface of the solution, and with hydroxyl radicals, both at the surface and within the bulk of the solution. An interesting and most convenient result is the better efficiency of phenol removal in tap water than in milliQ water. After ruling out possible effects due to conductivity, to Fenton’s reaction due to Fe2+ and to active chlorine, it was concluded that the efficiency increase is due to the higher pH of the solution mantained by the presence of bicarbonate salts. The second developed reactor allowed us to perform some interesting comparisons since it can be powered by different types of high voltage for the generation of plasma. The possibility to apply this technology to the treatment of waste water depends on many factors: the process efficiency, the final composition of the treated solution, the general applicability of the system to the organic pollutants. The data obtained so far are very promising due to the efficient oxidation all the way to CO2 and to the absence of any hazardous organic byproduct after a proper treatment time. The results of this thesis confirm that plasma processing is a promising highly efficient means for the advanced oxidation of organic pollutants both in air and in aqueous solution.
Lo studio di processi chimici indotti da plasmi sta suscitando un notevole interesse per il grande potenziale che questi sistemi possono sviluppare. Questa tesi riguarda l’ossidazione di inquinanti organici in aria e in soluzione acquosa promossa dall’interazione con plasma non-termico (NTP). Questi plasmi, che sono convenientemente generati da scariche elettriche non termalizzanti, principalmente scariche corona e a barriera di dielettrico, in aria a temperatura e pressione ambiente, costituiscono ambienti di reazione molto reattivi e fortemente ossidanti per la presenza di elettroni, molecole eccitate, specie atomiche e radicali (O, OH), ioni (O2+, N2+, NO+, O–, O2–, O3–), O3 e NO. Nonostante siano numerose le applicazioni tecnologiche di questi plasmi in processi di rilevanza ambientale e commerciale, la chimica dei composti organici in questi sistemi è tuttora non ben nota sia per quanto riguarda i prodotti che i meccanismi di reazione. Questa tesi è uno studio meccanicistico che si è sviluppato lungo tre linee di ricerca riguardanti l’ossidazione di: i) composti organici volatili (VOC) in aria con solo plasma; ii) VOC in aria con plasma e un catalizzatore eterogeno; inquinanti organici in soluzioni acquose poste a contatto con plasma non termico in aria. I tre progetti hanno un obiettivo comune che riguarda la caratterizzazione dei meccanismi di ossidazione che operano in questi sistemi di enorme complessità chimica. Lo studio dell’ossidazione di VOC in plasmi non termici in aria è stato condotto utilizzando un reattore prototipo a scarica corona sviluppato presso il Dipartimento di Scienze Chimiche a Padova, che può essere alimentato da alta tensione DC o ad impulsi di polarità sia positiva che negativa. Sono stati svolti studi comparativi per valutare la risposta di alcuni modelli di VOC a diversi regimi di scarica corona, precisamente +DC, -DC e +pulsed. I composti studiati sono due alcani (esano ed iso-ottano), il toluene e gli alometani dibromometano (CH2Br2) e dibromodifluorometane (CF2Br2, halon 1202). E’ notevole il fatto che tutti questi VOC, compreso l’halon notoriamente molto inerte, possono essere ossidati a CO2 in questi plasmi a temperatura ambiente con un’efficienza che dipende dal tipo di VOC (nonostante la loro elevata reattività questi plasmi presentano comunque un certo grado di selettività), dalla concentrazione del VOC (l’efficienza aumenta linearmente col reciproco della concentrazione iniziale del VOC) e dal modo in cui l’energia viene fornita al reattore. Infatti, per tutti i VOC considerati, l’efficienza del trattamento aumenta nell’ordine: +DC < -DC < +pulsed. Questo significa che il grado di conversione ([VOC]/[VOC]0) prodotto da una certa quantità di energia fornita al sistema dipende dal tipo di scarica utilizzato, che a sua volta determina la composizione e natura del plasma e quindi la sua reattività. La maggiore efficienza del corona ad impulsi rispetto al corona DC è attribuibile alla maggiore energia media degli elettroni in questo regime di scarica. L’energia media degli elettroni è stata determinata sperimentalmente nel nostro reattore nelle diverse condizioni di scarica mediante esperimenti di spettroscopia di emissione utilizzando un metodo pubblicato in letteratura. Un’altra importante variabile di questi processi è il grado di umidità dell’aria, che determina la formazione di maggiori o minori concentrazioni del radicale OH. Questo radicale si forma dall’acqua attraverso reazione con elettroni ad alta energia o reazione con gli ioni O2+ and N2+. La maggior efficienza dell’ossidazione di idrocarburi e del CH2Br2 osservata con -DC in aria umida rispetto all’aria secca è stata quindi attribuita alla reazione con radicali OH. Sorprendentemente, con +DC l’umidità produce un effetto opposto per gli stessi VOC, nonostante la presenza in aria umida di radicali OH. L’analisi degli ioni del plasma, effettuata mediante spettrometria di massa APCI-MS (Atmospheric Pressure Chemical Ionization – Mass Spectrometry), accoppiata allo studio della caratteristica corrente/tensione del corona DC, ha portato a concludere che nel caso del corona +DC l’ossidazione degli idrocarburi e del dibromometano è iniziata da reazione con ioni (O2+, H3O+ e i loro idrati, NO+) sia in aria secca che in aria umida. Al contrario, nel caso del corona –DC e del corona +pulsed la principale reazione di attacco a questi VOC risulta essere quella del radicale OH. Per quanto riguarda invece l’halon CF2Br2, sia con +DC che con –DC l’ossidazione in aria umida risulta meno efficiente che in aria secca, un risultato coerente con la nota scarsa reattività di questo VOC con il radicale OH. E’ stata quindi avanzata l’ipotesi che l’ossidazione di questo halon proceda attraverso un meccanismo comune, indipendentemente dal regime di scarica applicato, che comporta la dissociazione iniziale del legame C-Br indotta da interazione con elettroni del plasma. Il processo è meno efficiente in aria umida probabilmente perché la reazione di dissociazione dell’acqua provoca una riduzione dell’energia media degli elettroni rispetto a quella in aria secca. L’ossidazione dei due alometani in aria secca dà prodotti diversi: l’analisi FT-IR del gas in uscita dal reattore ha individuato sia CO2 che CO fra i prodotti di CH2Br2 mentre nel caso di CF2Br2 i prodotti sono CO2 e F2C=O. Quest’ultimo è un intermedio di ossidazione con tempo di vita sufficientemente lungo da poter essere rivelato in quanto notoriamente poco reattivo nelle reazioni con radicali. E’ tuttavia idrolizzato molto velocemente a CO2 e HF come dimostrato da analisi integrate di cromatografia ionica e FT-IR della soluzione e del gas ottenuti dopo gorgogliamento del gas trattato in acqua. Altri prodotti di questi trattamenti rivelati e quantificati mediante spettroscopia FT-IR sono l’ozono, l’acido nitrico e l’ossido N2O. Con entrambi gli alometani si è osservato l’intervento di cicli catalitici di distruzione dell’ozono in cui il bromo atomico è la specie propagatrice. Gli stessi cicli sono inoltre responsabili della conversione degli NOx in HNO3. L’efficienza e la selettività dei processi di ossidazione al plasma possono essere migliorati attraverso l’azione combinata del plasma e di catalizzatori eterogenei. Ne deriva un effetto sinergico, la cui origine e natura sono tuttora in fase di studio. Di questo problema mi sono occupato durante un soggiorno presso l’Advanced Industrial Science and Technology Institute (AIST) a Tsukuba (Giappone), presso il gruppo del Prof. Hyun-Ha Kim. Per confrontare gli effetti di solo plasma e plasma più catalizzatore abbiamo utilizzato come sonda molecolare la reazione di scambio di ossigeno che produce 16O18O partendo da miscele di 16O2 e 18O2. Sono stati utilizzati diversi reattori al plasma con diverse alimentazioni elettriche e parecchi catalizzatori fra cui TiO2, MS-13X e gAl2O3 contentente varie modeste percentuali di Ag. Questi studi hanno permesso di concludere che, in assenza di catalizzatore, la reazione di scambio di ossigeno avviene in fase gas e non sulle superfici degli elettrodi. I risultati di questi esperimenti sono stati utilizzati per sviluppare un metodo basato sulla reazione di scambio isotopico al fine di determinare la concentrazione di ossigeno atomico in questi plasmi. Questo è un risultante importante che si propone come alternativa al metodo tradizionale per la determinazione della concentrazione di ossigeno atomico con strumentazioni ottiche laser e procedure piuttosto sofisticate. Per quanto riguarda l’interazione catalizzatore/plasma, è stato possibile concludere, sempre utilizzando la sonda molecolare 18O2, marcata isotopicamente, che il plasma determina la fissazione dell’ossigeno sulla superficie del catalizzatore e che questo ossigeno è quindi trasferito al VOC nel processo di ossidazione. Infine, il terzo progetto ha riguardato l’ossidazione del fenolo in soluzioni acquose esposte all’azione di plasma non-termico in aria. Per questi studi sono stati sviluppati due prototipi di reattore caratterizzati entrambi dall’applicazione di scariche elettriche nell’aria sovrastante la soluzione da trattare. L’ossidazione del fenolo nel primo reattore, che utilizza scariche a barriera di dielettrico, procede efficacemente fino a CO2 seguendo un decadimento esponenziale in funzione del tempo di trattamento a potenza applicata costante. Dall’analisi dei prodotti ed intermedi di ossidazione nonché dalla determinazione delle principali specie reattive è emerso che la decomposizione del fenolo avviene per reazione con l’ozono sulla superficie della soluzione a contatto con il plasma, e con il radicale OH, sia sulla superficie che all’interno della soluzione. Un risultato molto interessante e utile in vista di applicazioni pratiche di questi processi riguarda la maggiore efficienza dell’ossidazione del fenolo in acqua di rubinetto rispetto all’acqua milliQ. Dopo aver escluso che all’origine di questo fenomeno potessero esserci effetti dovuti alla conduttività maggiore, alla presenza di ioni Fe2+ capaci di indurre la reazione di Fenton, e alla presenza di cloro attivo nell’acqua potabile, è stato verificato che l’effetto tampone esercitato dallo ione bicarbonato mantiene un pH elevato e consente al processo di procedere velocemente.

An investigation of ion flow control was performed to determine the effect of a positive, DC corona discharge on the boundary layer profile along a flat plate and to examine its ability to prevent separated flow in a low-speed compressor cascade. Flat plate tests were performed for two electrode configurations at free-stream velocity magnitudes of 2.5, 5, 7.5, and 10 m/s. Boundary layer velocity profile data was taken to measure the performance of the electrode pairs. Ion flow control was also tested in the compressor cascade for a stagger angle of 25° at angles of attack equal to 6° and 12°. The cascade tests were performed at free-stream velocities of 5 and 10 m/s. Static tap data was used to characterize separated flow behavior and the effect of ion flow control on flow reattachment. A computational model was developed using the commercial CFD software Fluent. This model simulates ion flow control as a body force applied to the flow through user-defined functions. The study showed that the corona discharge has the ability to increase near-wall velocities and reduce the thickness of the boundary layer for flow over a flat plate. Ion flow control successfully prevented trailing edge separation in a compressor cascade for angles of attack of 6° and 12°; however, the flow control scheme was not able to prevent leading edge separation for angle of attack equal to 12°. The ion flow control CFD model accurately predicted flow behavior for both the flat plate and cascade experiments. The numerical model was able to simulate the boundary layer velocity profiles for flat plate tests with good accuracy, and was also able to predict the flow behavior over a compressor blade. The model was able to show the trends of separated and reattached flow over the blade surface.
Master of Science

The presented diploma thesis deals with the design of an electrostatic precipitator for a domestic automatic wood fuel boiler. The individual chapters describe the products of the combustion process, the principles of charging dust particles, describe existing patents related to electrostatic precipitators, commercial electrostatic precipitators and the last part of the work calculates a mathematical model, according to which previously designed and evaluated separator variants were designed and evaluated. Based on the results, the optimal variant of the electrostatic precipitator designed for a domestic boiler is then selected.

Les recherches actuelles dans le domaine des composites montrent l'utilisation croissante de matrices biodégradables et/ou de renforts fibreux naturels issus de ressources renouvelables. Néanmoins, une étape de compatibilisation fibres/matrice est très souvent nécessaire. Dans cette thèse, nous avons exploré une méthode physique : le traitement corona. Son impact sur les propriétés physicochimiques de différentes fibres a été étudié par XPS, mesure d'angle de contact et MEB. Il ressort qu'il entraîne principalement une oxydation de surface et une augmentation de sa rugosité. Nous avons évalué le comportement mécanique de composites, préparés par extrusion à partir de fibres de chanvre ou miscanthus et de matrices polypropylène (PP) ou acide polylactique (PLA). L'incorporation de renforts accroît la rigidité des matériaux et le transfert de contrainte et leur traitement permet d'obtenir des caractéristiques encore supérieures en raison d'un ancrage mécanique accru. Les valeurs optimales sont obtenues pour un taux massique de fibres de l'ordre de 20%. Les propriétés thermiques et thermomécaniques des composites ont été caractérisées par ATG, DMA et DSC. La stabilité thermique des matériaux est abaissée après incorporation de renforts bruts mais très largement améliorée (+ 15-20°C) après traitement des fibres. Dans certaines conditions, les fibres agissent comme des agents nucléants qui influent sur le processus de cristallisation et le taux de cristallinité. Le traitement des fibres par corona ne permet pas de retarder la dégradation des matériaux au cours d'un vieillissement accéléré en milieu humide et l'évolution des propriétés thermomécaniques est plus prononcée pour les matériaux à base de PLA plus hydrophile
The field of composites materials shows increasing use of biodegradable matrices and / or natural reinforcements from renewable resources. Nevertheless, a compatibilization step between fiber and matrix is necessary. In this PhD study, we have explored a physical method: corona treatment. Its impact on the physicochemical properties of different fibres has been studied by XPS, contact angle measurement and SEM. It appears that it mainly involves surface oxidation and roughness increase. We have also evaluated the mechanical behaviour of composites, prepared by extrusion from hemp or miscanthus fibres and polypropylene (PP) or polylactic acid (PLA) matrices. The incorporation of raw reinforcements increases the stiffness and the stress transfer. Composites based on treated fibres show better mechanical performances, resulting from an enhanced mechanical anchorage. The optimum values are obtained for 20% (wt) fibres content. The thermal and thermomechanical properties of composites have been characterized by TGA, DMA and DSC. The thermal stability of materials is reduced after incorporation of raw reinforcements but very much improved (+ 15 - 20 ° C) after treatment of fibres. Under certain conditions, the fibres act as nucleating agents that affect the crystallization process and crystallinity rate. The corona treatment of fibres does not delay the degradation of materials during an accelerated aging in humid environment and the evolution of the thermomechanical properties is more pronounced for PLA based materials because of its hydrophilic character

Il lavoro presentato verte sullo sviluppo, la caratterizzazione e l’ottimizzazione di sistemi plasma per verificare la possibilità dell’impiego della tecnologia dei plasmi freddi a pressione atmosferica nei trattamenti d’inattivazione microbica di packaging alimentare. Le sorgenti plasma investigate sono state due: sorgente corona multipin per il trattamento di capsule in polipropilene (PP), sorgente DBD (Dielectric Barrier Discharge) per il trattamento di film di alluminio. I test di decontaminazione sono stati svolti con le seguenti specie microbiche target: E. coli, S. aureus, C. albicans. Si sono ottenuti riscontri positivi (livelli di abbattimento prossimi o superiori a LogR=2) per entrambe le sorgenti con tempi compatibili a quelli della produzione industriale. A valle di questi risultati si è proceduto alla caratterizzazione superficiale dei substrati trattati per verificare possibili alterazioni degli stessi a seguito dei trattamenti. Le prove condotte in questa fase hanno riguardato la misura dell’angolo di contatto (WCA) al fine di investigare possibili modifiche della bagnabilità del materiale indotte dal plasma ed analisi ATR-FTIR per indagare possibili variazioni della composizione chimica delle superfici trattate. Inoltre si è investigato come il trattamento plasma su PP e su alluminio possa inficiare sul processo di saldatura previsto durante la sigillatura delle capsule. Infine per ogni tipologia di sorgente ed alle varie condizioni operative si è svolta una caratterizzazione elettrica allo scopo di acquisire le forme d’onda specifiche di ogni trattamento con cui calcolare l’energia e la potenza medie trasferite dalle sorgenti ai substrati oltre che verificare la ripetibilità e affidabilità della generazione di plasma. Il lavoro si è concluso con lo scale up della sorgente multipin ovvero la progettazione e la realizzazione di una sorgente in grado di essere inserita all’interno di macchine automatiche per la produzione di capsule.

Ever since the discovery of DNA, there has been many pathologies identified effecting mankind. With the development in technology, there are many methods to alleviate these pathologies. One such is gene therapy or gene delivery. It is a process of introducing some foreign material into the body to correct the effected cells. In principle, it is a modern method to cure cells or a method to transfer nucleic acid into a cell to treat specific cells in the body. The process of delivering a genetic material is carried out using vectors, namely, viral vectors and non-viral vectors. In viral vectors, viruses are modified to make it efficient for delivery into the host cells. This method has high transduction rate as compared to non-viral method. Non-viral methods include chemical and physical transfection methods, which are used to deliver the gene of interest into the host cell unlike viral methods. In this study, a physical method using high voltage is used to deliver a genetic material into cells. High voltages are used to permeabilize the cell to allow the foreign material into it and to express it in the host cell. This process is termed as Electroporation. In specific, in this research, studying a process of charging a region that mimics skin and trying to localize the presence of electric fields on the surface where the strongest uptake of genetic material is found. In other words, region where the gene expression is strongest at a specific region if performed on skin is studied by localizing electric fields on the surfaces. My work is to characterize and develop where this effect takes place on the surface based on both positive and negative electric fields. A physical method is useful as it is a non-toxic way to get a DNA/protein into someone’s body without making them sick, unless if not using a virus to deliver. This is all done using high voltages up to 8kV and the electric fields produced due to high voltages are localized, visualized and characterized with both positive and negative polarities of voltages. In this study, experiments with high voltages are performed and the spread of charges at specific regions are collected using a needle. This needle goes into corona, which may be called as a secondary corona. It might be called a secondary corona because the flat conductor is being charged by a metal finger but not directly by the power supply. Here, the conductor is charged by a metal finger of high input voltage, which ionizes the air molecules above the flat conductor to form a conductive region. As the input voltage is increased further, electrons escape from the needle to air or from molecules to needle forming negative or positive ions respectively. The outputs at needle were measured on the oscilloscope. In this study, repeated sets of experiments are carried out to collect consistent and reliable data. Visualizing/characterizing these fields are important as maximum delivery takes place at high voltage regions, with a condition that permeability of the cells should be known for proper transfection to occur, otherwise cells would die due to high voltages or no transfection takes place due to poor permeability of cell membrane.

Issus de l'industrie de la microélectronique, les MEMS (Micro Electro Mechanical Systems) envahissent progressivement le marché avec des applications dans de nombreux domaines tels que l'aérospatiale, la médecine, l'industrie ou encore le grand public. Une des vocations de ces microstructures est de permettre le déploiement de réseaux de capteurs autonomes, c'est-à-dire d'un ensemble de systèmes capables de collecter des informations de leur environnement, de les traiter, de les transmettre et d'interagir entre eux, et ceci, sans intervention humaine. Comment rendre ces microsystèmes énergétiquement autonomes ? Utiliser des piles... Malheureusement, le défaut majeur des piles est leur durée de vie, puisqu'il faudra à un moment ou à un autre les recharger ou les remplacer. En fait, avec la miniaturisation, les systèmes deviennent de moins en moins consommateurs d'énergie et ceci permet de concevoir de nouvelles sources d'énergie basées sur la récupération de l'énergie ambiante (soleil, gradients de température,...). Il est par exemple possible de récupérer l'énergie des vibrations ambiantes à l'aide de systèmes piézoélectriques, électromagnétiques ou encore électrostatiques. Dans ce travail de thèse, nous nous concentrons sur l'étude de structures électrostatiques utilisant les électrets (diélectriques chargés électriquement). De l'étude des électrets à la réalisation et à l'optimisation de structures de récupération d'énergie, nous exposons dans ce mémoire, les résultats obtenus au cours de ce travail de thèse.

La lutte contre la pollution atmosphérique est un enjeu majeur de ce XXIème siècle. Le centre deMarcoule du CEA développe différents procédés de traitement de déchets issus du nucléaire parincinération/vitrification qui génèrent des gaz de combustion nécessitant un traitement. Pour cefaire, le CEA utilise la précipitation électrostatique, technique de traitement d’effluents gazeuxemployée pour la filtration des particules fines.Cette thèse est consacrée à l’optimisation des performances d’un électrofiltre alimenté parhautes puissances pulsées. L’un des objectifs est de dimensionner et réaliser une nouvelle électrodeémissive adaptée au développement d’un nouveau procédé d’incinération. Cette nouvelle électrodecouplée à son alimentation HT, dont les paramètres électriques ont été optimisés, ont permisd’obtenir des rendements de filtration maximum durant des temps de fonctionnement enadéquation avec des applications industrielles. L’impact des caractéristiques physico-chimiques despoussières sur l’efficacité de filtration a été analysé.Une étude spécifique a également porté sur l’évolution des différents régimes de décharge quise développent dans l’électrofiltre de manière à identifier les phénomènes responsables de la chuted’efficacité du procédé. Les bénéfices de l’électrode émissive et d’un générateur hybride, combinantdes impulsions de tension superposées à un fond continu, ont clairement été mis en évidence parleurs effets sur l’initiation des "back corona" et par conséquent sur la durée de fonctionnement àrendement optimal
The fight against air pollution is a major issue in the twenty-first century. The center of Marcouleof CEA develops different waste treatment processes by incineration / vitrification that generatecombustion gases requiring treatment. To do this, the CEA uses the electrostatic precipitation, atechnical waste gas treatment employed for thin particles filtration.This thesis is dedicated to optimizing the performance of an electrofilter supplied by high pulsedpowered. One of the goals is to size and achieve a new emissive electrode adapted to thedevelopment of a new incineration process. This new electrode coupled to its High Voltage (HV)power supply, which electrical parameters were optimized, allowed to obtain maximum filtrationefficiency during operating times in line with industrial applications. The impact of thephysicochemical characteristics of dusts on the filtration efficiency was analyzed.A specific study also focused on the evolution of different discharge conditions that develop inthe electrofilter to identify the phenomena responsible for the process efficiency fall. The intake ofthe emissive electrode and a hybrid generator, combining a continuous background voltagesuperimposed with impulses, has clearly been demonstrated by their effects on back coronainitiation and therefore on the optimal efficiency operation duration

This diploma thesis is aimed to the corona-like discharge in solutions of alcohols, specifically in ethanol, methanol, glycerol, butanol and isopropyl alcohol. The electric discharge was diagnosed by two methods. The first method was the measuring of electrical characteristics. Current-voltage characteristics were constructed from the measured average values of voltage and current. The breakdown voltages were determined from the current-voltage characteristics. The breakdown voltages of the individual alcohol solutions were dependent on the alcohol concentration, polarity of the electrodes in the reactor and solution conductivity. The breakdown voltage was determined for solutions of butanol, glycerol and isopropyl alcohol with a concentration of 20 vol. % and conductivity of 200 µS. The highest value of the breakdown voltage was determined for solution of glycerol at 580 V. The lowest voltage at which the discharge was observed was estimated for butanol (320 V), but due to the limited miscibility with water this value is inaccurate, and therefore in the second part of experiment butanol was not used. Alcohol series was supplemented with methanol. The second diagnostic method was the proton ionization mass spectrometry with the time of flight analyzer. The products formed in the reactor due to the plasma discharge were identified from the mass spectrum. Mostly, aliphatic hydrocarbons and their radicals were detected. The amount of products was observed in the dependence on the changing experimental conditions: alcohol concentration in the solution, the polarity of the electrodes in the reactor and the duration of the discharge. Only a small amount of compounds were detected in methanol. However, more molecules were formed with the increasing carbon chain in the alcohol molecule. More compounds were also detected with the increasing alcohol concentration and in case of the negative polarity of the main electrode. The formation of acetaldehyde as a typical discharge product was studied in details. Its production in time was observed and the reaction pathways of its formation in the ethanol solution were suggested.

This diploma thesis focuses on quinine solutions and quality of these solutions after applying plasma discharge. These electric discharges can be used to destroy some substances from the water. The theoretical part is focused on description of electric discharges in liquids and on the properties of quinine. In the experimental part, the properties of quinine solutions containing different electrolytes were analysed by UV-VIS spectrophotometer and fluorescence spectroscopy. Two different types of configurations of plasma discharges in liquids were used. Solutions were compared on the base of different concentration of quinine, different electrolytes, different configurations of plasma discharges and pH values of the solutions. Furthermore, the experimental work focuses on quinine solutions with the sodium nitrate. The time instability of the solutions was analysed. Also, the influence of the solution age and different types of the plasma discharge on the excitation and emission spectra of quinine were investigated.

Ce travail porte sur l'étude de la propagation de décharges couronnes impulsionnelles à pression atmosphérique dans les milieux poreux et/ou alvéolaires. Face à la complexité des phénomènes mis en jeu, liés aux interactions entre la décharge et les surfaces du matériau qui la confine, nous proposons l'étude de décharges confinées par des structures élémentaires. L'étude du confinement radial des décharges, assuré par un large panel de capillaires, a été réalisée. Des diagnostics électriques et optiques de pointe permettent d'étudier la propagation de la décharge au sein des différents capillaires. La corrélation entre ces diagnostics a même permis des mesures de vitesse de propagation au sein de capillaires opaques. Les résultats montrent que la propagation de la décharge dépend grandement de la géométrie des capillaires et des paramètres électriques de génération de la décharge. Dans le cas de sections carrées ou rectangulaires, les arêtes induisent un renforcement local du champ qui attire la décharge. Dans le cas de capillaires cylindriques, le diamètre interne est le paramètre crucial qui détermine aussi bien la structure de la décharge que sa vitesse de propagation. Quelle que soit la nature du capillaire, la propagation présente alors une vitesse optimale à tout autre paramètre constant pour une valeur donnée du diamètre interne. Dans le cas du verre, la vitesse est maximale pour un diamètre interne de 200 µm. L'épaisseur et la permittivité diélectrique du capillaire possèdent également une influence sur la propagation de la décharge radialement confinée. Ainsi, diminuer l'épaisseur ou la permittivité diélectrique engendre une accélération de la décharge. Si l'épaisseur est très faible, la décharge peut même se déconfiner pour se propager à l'extérieur du capillaire. Une étude spectroscopique complémentaire montre que la réduction du diamètre de confinement implique une augmentation de la température du plasma, ce qui pourrait contribuer à l'obtention de ce profil de vitesse en fonction du diamètre de confinement. L'étude du confinement axial des décharges a ensuite été réalisée en insérant des membranes de différentes natures et caractéristiques, perpendiculairement à l'axe pointe plan. Les résultats montrent que la décharge présente une propagation en trois étapes : pointe/membrane, radialement au voisinage de la membrane, puis membrane/plan. Dans cette étude, nous avons mis en évidence l'importance du critère poreux ou non de la membrane. Dans le cas poreux, la propagation de la décharge dans l'ensemble du gap est continue, même pour des pores de l'ordre de la dizaine de µm. Dans le cas non poreux, la propagation est discontinue, et il est nécessaire pour assurer la propagation dans l'ensemble du gap qu'un ré-allumage ait lieu de l'autre côté de la membrane. Après l'instant de l'impact sur la membrane, la décharge marque un arrêt qui correspond à la réorganisation des charges et à la restructuration du champ électrique dans le gap. Elle se propage ensuite radialement au voisinage de la membrane en plusieurs fronts d'ionisation. Si les conditions de claquage sont réunies dans le volume membrane/plan, alors un ré-allumage apparaît à partir de la membrane pour atteindre le plan. L'étude de ces ré-allumages semble montrer l'importance de la position de la membrane au sein de l'espace inter-électrodes et de la dynamique des charges aux surfaces de la membrane. Plus on diminue la distance membrane/plan, plus il est facile d'en observer. Nous montrons également que la diminution de la permittivité diélectrique de la membrane ou l'augmentation de son épaisseur, semble augmenter la probabilité de ces ré-allumages. Dans le cas poreux, nous avons également mis en évidence l'influence de la taille des pores de la membrane sur l'ensemble des étapes de propagation. Lorsque la porosité est inférieure à 100 µm la propagation de la décharge est ralentie du fait de la difficulté de la décharge à traverser directement le matériau.

Tyrimų tikslas – laboratorinėmis sąlygomis eksperimentiškai nustatyti džiovinimo vainikinio išlydžio elektriniame lauke efektyvumą ir palyginti jį su džiovinimu elektromechaniniu ventiliatoriumi. Darbe aptariami kviečių ir gražgarstės lapų džiovinimo vainikinio išlydžio lauku eksperimentinio tyrimo rezultatai naudojant elektrodų sistemą „lygiagrečių laidų tinklelis virš įžemintos plokštumos“. Darbe apžvelgtos technologijos pagrįstos vainikinio išlydžio lauko naudojimu Tyrimai atlikti Kauno technologijos universitete elektromagnetinių laukų įtaisų mokslinėje laboratorijoje, su įtaisu kurį sudaro aukštos įtampos šaltinis ir elektrodų sistema „lygiagrečių laidų tinklelis virš įžemintos plokštumos“. Atliktas joninio ir elektromechaninio ventiliatoriaus oro srautų palyginimas.
The aim of the research is to establish experimentally the effectiveness of drying affected by the corona field in comparison with the effectiveness of drying affected by the external airflow driven by electromechanical ventilator. Review of various techniques applying of corona field is given. Results of wheat drying by using the corona field of electrode system „ a set of parallel wires under the grounded plate“ are presented and discussed. Experimental study of drying is performed in Research laboratory of electromagnetic field devices of Kaunas university of technology. Test drying device consists of the high voltage source and the electrode system „a set of parallel wires under the grounded plate“. Comparison of corona field airflow and electromechanical ventilator airflow is given.