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Dielectric properties of liquid insulators
Jahn, Michal ; Starý, Jiří (referee) ; Špinka, Jiří (advisor)
This master‘s thesis deals with measurement of liquid dielectric materials (insulators). Above all, it is the different kinds of clean and drinking water, but also transformer oils. There was done theoretical information retrieval about the given topic in this project and on the basis of theory there were realized the relevant measurements of selected properties of liquid dielectric, such as permittivity, capacitance, loss number, conductivity, but also temperature dependence of these parameters. The measurements were realized with the help of product manufactured at the faculty FEKT VUT and with the help of measuring system AGILENT 16452A. The measured results were evaluated, graphically processed and compared.
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Insulation and dielectric properties of water
Grill, Jiří ; Frk, Martin (referee) ; Špinka, Jiří (advisor)
This master´s thesis deals about insulation and dielectric properties of water. It describes the structure of water, covalent and hydrogen bonds. It outlines primary chemical and physical properties of water and then it describes parameters of water - dynamic viscosity, conductivity, surface tension, pH and also describes dielectric properties - dielectric loss, loss factor, permittivity, polarization. Part of the work is practical section, which includes measurements of deionized water, destilled water, tap water and shows primary dependence such as dependence loss factor on frequency or relative permittivity on frequency.
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Measurement of conductivity of liquids
Mašláň, Stanislav ; Havránek, Zdeněk (referee) ; Beneš, Petr (advisor)
The first part of thesis is theoretical and it is the introduction into conductometry. It defines the essential terms of this field as well as contact and contactless methods of measurement of fluid conductivity and also the influential parasitic phenomena and possibilities of their elimination. The second part is dealing with design of the contactless transformer conductivity probe. The characteristics of designed probe are verified in the practical part of the thesis. The final part of the thesis is dealing with measurement according to the defined points in the assignment. The characteristics of several contact probes are verified and also the characteristic of the contactless transformer probe, which was implemented according to the design from the second part. Outcomes of these measurements establish the suitable power supply frequencies and currents for all these probes.
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Liquid electrolytes for lithium-ion accumulators
Štichová, Zuzana ; Vondrák, Jiří (referee) ; Sedlaříková, Marie (advisor)
The aim of this master´s thesis was the measurement of electrical conductivity and dynamic viscosity of the electrolytes. Based on these measurements to verify Walden theorem between measured variables. Electrolytes were used on sulfolane base in combination with propylene carbonate and salt. The thesis also deals with the measuring method of dielectric properties of electrical and optical method with a refractometer. The freezing point of combination of sulfolan and propylene carbonate were determined by cryoscopy.
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Study of organic based structures for solar cells
Kostovčík, Tomas ; Hégr, Ondřej (referee) ; Boušek, Jaroslav (advisor)
Práce se zabývá problematikou využití organických materiálů v solárních článcích. V úvodu práce jsou rozebrány a vysvětleny jednotlivé fyzikální a chemické jevy, které ovlivňují vlastnosti organických materiálů. Práce pokračuje rozborem působení rozličných struktur organických solárních článků na jejich vlastnosti. Dále je popsána technologie výroby vzorku a jsou v ní uvedeny výsledky měření fotovodivosti.
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Plasma diagnostics of electric discharges generated in selected configurations in liquids
Vašíček, Michal ; Bartlová, Milada (referee) ; Kozáková, Zdenka (advisor)
My diploma thesis is focused on a comparison of direct-current and high frequency (15-80 kHz) electric discharge, which generates non-thermal plasma in water solution of sodium chloride. Mainly current-voltage and Lissajous charts are discussed in the first part of this thesis. These charts describe different discharge phases: electrolysis, bubble formation, discharge breakdown and discharge regular operation in a pin-hole of a dielectric barrier. Influence of frequency, electrolyte conductivity, thickness of the diaphragm (or length of the capillary) and pin-hole diameter on discharge breakdown and bubble generation was studied, too. Measurements were realized in a polycarbonate reactor with total volume of 110 ml, which was divided by a changeable polyacetal insulating wall. This wall divided the reactor into two approximately equal spaces with one stainless steel planar electrode in each part. The Shapal-MTM ceramic discs (thickness of 0.3–1.5 mm and diameter of the central pin-hole of 0.3-0.9 mm) were mounted in the centre of the insulating wall. Initial conductivity of sodium chloride solution was chosen within the interval of 100900 S/cm. The second part of my thesis compares an influence of the direct-current (DC) and high frequency (HF) power sources on physical solution properties (conductivity, pH and temperature) and generation of hydrogen peroxide. A plasma reactor with total volume of 4 l and with mixing set up was divided into two equal spaces with one planar platinum electrode in each part. Diaphragm with thickness of 0.6 mm and pin-hole diameter of 0.6 mm was installed in the middle of the separating wall. Experiment was held at discharge operation of 45 W for 40 minutes with both power sources. Detection of hydrogen peroxide was realised by using a titanium reagent forming a yellow complex, which was analysed by absorption spectroscopy. If HF discharge power is plotted as a function of applied frequency, exponential decrease of frequency with increasing power can be observed. Higher breakdown voltage is necessary for thicker dielectric barriers, on the other hand for bigger diameter of the pin-hole lower breakdown voltage and higher power is needed in DC as well as in HF regime. Breakdown voltage is decreased by the increasing conductivity in both regimes; due to more charge carriers in the higher conductivity lower breakdown voltage is needed. However frequency in HF regime and DC discharge power increases. HF discharge power is decreased by the increasing conductivity. Solution conductivity and temperature are increased by initial conductivity value in both discharge regimes. Solution pH drops to acidic conditions when HF or DC positive regime is applied due to the generation of reactive species and electrolysis (in DC regime). However solution becomes alkaline when DC negative regime is applied. Concentration of hydrogen peroxide is produced linearly when HF or DC negative regime is applied and it depends on initial solution conductivity.
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Sensoric properties of organic N-type semiconductors and their air stability
Saska, Pavel ; Vala, Martin (referee) ; Salyk, Ota (advisor)
Hydrogen has been for some time discussed as a successor to fossil fuels whose stocks are constantly running low. One of the crucial requirements for the possible usage of hydrogen as an energy carrier is our ability of reliable detection. In context with development of organic electronics there occurred a possibility to use derivatives of diketopyrrolopyrroles as sensing materials of hydrogen sensors. Derivatives of diketopyrrolopyrrole are organic pigments that behave as semiconductors. Their analogues with pyridyl side group are due to free electron pairs of nitrogen atoms sensitive to hydrogen. The problem of organic N-type semiconductors is in general their instability on the air. This thesis is focused on testing of hydrogen sensors with active layer made from derivatives of diketopyrrolopyrrole and judging their stability on the air.
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Study of electrolyte influence on diaphragm discharge stability and efficiency
Němcová, Lucie ; Krčma, František (referee) ; Kozáková, Zdenka (advisor)
This thesis is focused on so-called diaphragm discharge, which is one kind of electric discharges in liquid, which belongs among so-called AOP´s techniques, still more used for water cleaning in the present. One of effectiveness and stability indicators of diaphragm discharge is generation of hydrogen peroxide. In theoretical part, detail principle description of electric discharge in liquid is situated. Further, properties of electrolyte are introduced and general spectrophotometric method of obtained sample determination is described. In experimental part, a full procedure of experiment is introduced. Next part containing results and discussions introduces particular results of individual measurements and their reasons. Final chapter is the end, which forms total summary and evaluation of all results. By the application of all chosen electrolytes in solution at diaphragm discharge formation of hydrogen peroxide has appeared. Inorganic and organic electrolytes were used. As inorganic electrolytes following salts were selected – solutions of halogenides, next sodium nitrate as a representative of nitrates, potassium dihydrogenphosphate as a representative of phosphates, etc. Representative of organic electrolytes was citric acid. The value of initial conductivity of electrolytes had the main influence on hydrogen peroxide formation. Electrolytes potassium dihydrogenphosphate and sodium sulphate the great influence on effectiveness and stability of the diaphragm discharge. Their rate constants reached maximum value by the application of solution with initial conductivity of approximately 400 mikrosiemens, particularly 0.0492 mmol/l.min and 0.048 mmol/l.min. On the contrary, low values of rate constant were achieved in electrolyte ammonium chloride at around the same initial conductivity – 0.0269 mmol/l.min. During experiments stainless steel and platinum electrodes were used. It was found that kind of electrode material hadn’t influence on generation of hydrogen peroxide. Hydrogen peroxide was formed only in the cathode space.
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Study on interactions of protonated aminoacids with low-molecular weight hyaluronan
Chlumská, Jana ; Kalina, Michal (referee) ; Chytil, Martin (advisor)
This bachelor thesis deals with interactions between hyaluronic acid (HA) of low molecular weight (110-130 kDa) and protonated aminoacids lysine and 6-aminocaproic acid. For investigation of these interactions, methods such as pH-metry, conductance measurement, viscometry and dynamic light scattering were used. The electrostacic interactions between carboxylic group of HA and the aminogroup of the aminoacids are presumed. Proving these interactions would allow us to physically modify HA and further more, using such a system as a carrier of pharmaceuticals. The interactions of protonated lysine with HA were studied in pure water or in the solution of NaCl (c = 15 mmol•dm-3). Interactions of 6-aminocaproic acid were studied only in pure water. Both aminoacids were in the concentration range 0.9-20 mmol•dm-3. The decrease in the viscosity of the solutions indicates the interactions for lysine; for 6-aminocaproic acid the interactions also occured, but not as signifciantly as for the system containing lysine.
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