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Time-domain Dielectric Spectroscopy of Carboxymethylcellulose
Palai-Dany, Tomáš ; Lelák, Jaroslav (referee) ; Mentlík, Václav (referee) ; Liedermann, Karel (advisor)
The dissertation deals with the time-domain dielectric relaxation spectroscopy of carboxymethylcellulose. The main attention was paid to the experimental part of research, mainly to the design and subsequent development of an experimental setup for the measurement of discharge currents and for their processing and analysis. The subject of the measurement is carboxymethylcellulose (CMC), which is a simple polysaccharide used in wide range of applications, among else also in biomedical engineering. The study of CMC properties has required the development of a new experimental set-up of original design, which includes the equilibration (short-circuiting) of a sample before the measurement, charging and discharging at defined time intervals, switching between these two modes, recording of measurement, adjustments and processing of measured signals up to Fourier transformation into the frequency domain and, finally, calculation of complex permittivity of the sample. The frequency dependence of complex permittivity or its imaginary part, obtained by Fourier transformation of discharge current in time domain, is then referred to as the dielectric spectrum. In view of the fact that current measurements were done at very low levels of measured signal (below 10-12 A) the whole measurement was no easy matter. The framework of the work also necessitated studies and subsequent resolution of problems associated with shielding, grounding, presence of noise and sensitivity to various ambient influences. The research work focused on a reliable and trustworthy measurement of very low discharge currents and, subsequently, mathematical processing of noise present in them, i.e., operations with the original, experimentally established signal in time domain, leading in principle to a digital filtration of measured dielectric data. A further pursued objective is the explanation of dielectric parameters of tested carboxymethylcellulose sample in the widest possible frequency spectrum. The integral part of the research was the selection and application of the method for the transformation of the adjusted signal to the frequency domain. The experimental works, including data processing, were carried out in the Department of Physics, Brno FEEC BUT. Measurements were done with Keithley 617 Electrometer, HP4284A Frequency Analyzer and Janis CCS-400-204 cryogenic system. The results were completed with results obtained at the V Department of Experimental Physics, Centre for Electronic Correlations and Magnetism, University of Augsburg, Germany.
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Measurement of permitivity and dissipation factor of water
Zimáková, Jana ; Zatloukal, Miroslav (referee) ; Špinka, Jiří (advisor)
This master `s thesis deals about the dielectric properties of water. It describes the basic chemical and physical properties of water and its distribution in terms of structure. It also describes the basic parameters of distilled water, deionized and superclean. In the chapter number 5 described the behavior of dielectrics in an electric field, determining the dipole moment by Claus-Mossotti 'equation, measurement of permittivity and loss factor. Practical part is consists of the design of the electrode systém, of measuring the water quality and evaluation of measured data
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Measurement of dielectric properties of liquid fuels for automotive power units
Redr, Martin ; Čech, Ondřej (referee) ; Chladil, Ladislav (advisor)
This bachelor thesis dealt with measuring of dielectric properties of propellants. The aim of the thesis was to find out differences between dielectric quantities of propellants from various manufacturers and in different proportions of refined to so-called bio-components. The theoretical physical principles of dielectric substances – permittivity and dissipation factor were described. In the thesis the most famous electrical insulation fluids whose dielectric characteristics are similar as propellants were mentioned. Furthermore, the study about dielectric properties of propellants and chosen fuels on the Czech market were mentioned. In the experimental part of the thesis, selected fuel samples at varying frequency and temperature were measured. These results were then evaluated and compared.
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Preparation of Epoxy Based Insulating Materials Filled by Nanoparticles
Mockovčiak, Kristian ; Čech, Ondřej (referee) ; Chladil, Ladislav (advisor)
The present thesis deals with the preparation of epoxy insulating materials filled with nanoparticles and its electrical properties. Experimental samples are made of epoxy resin as a matrix and titanium dioxide nanoparticles (TiO2) as nanofillers in 0.5, 1 and 3 percent filling. Temperature dependencies of internal resistivity, relative permittivity and loss factor are measured on nanocomposite samples. The influence of the filler on the resulting electrical properties of the polymer used is discussed.
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Measurement of HV equipments by electronic bridge.
Kumičák, Ivan ; Pelikán, Luděk (referee) ; Krbal, Michal (advisor)
The main idea of this thesis is measurements of dielectric materials by using a device Tettex. The thesis is about basic physic properties of dielectric materials. The determination of a dielectric material is considered. The behavior of these materials in electrical fields and reasons, those can have an influence on it, are considered as well. In the text are described measuring methods of chosen parameters of dielectric materials by device Tettex and its functional principles. There are an evaluation of measurements, which were done, and a discussion about achieved results.
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Study of alternative electroinsulating liquids properties
Bannert, Tomáš ; Hylský, Josef (referee) ; Frk, Martin (advisor)
This bachelor´s thesis is dealing with the study of alternative electrical insulating properties of the materials used in the electronics industry, particularly liquids based on natural esters and especially their constituents in the form of higher fatty acids and esters. The work is divided into theoretical and practical part. The theoretical part deals with the characterization of vegetable oils, their constituents and mineral oils, their comparison in terms of electrical and non-electrical properties and current state of the use of vegetable oils and their constituents in the electronics industry. Further it’s dealing with analysis of diagnostic methods for these characteristics. In the experimental part were analyzed electrical and non-electrical properties of selected samples of vegetable oils, their constituents and mineral oils such as the density, the dynamic viscosity and the complex permittivity and its parts as relative permittivity and loss number. Evaluations of the results of each group are compared with each other.
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Degradation test of polymer material
Darebný, Tomáš ; Špinka, Jiří (referee) ; Vaněk, Jiří (advisor)
Basic knowledge of photovoltaic energy transformation, devices and materials, used in photovoltaics are summarized in this bachelor’s thesis. Sort of degradation factors of the photovoltaic panels and the norm ČSN EN 61215, are described there. The main purpose of this research is monitoring the change of volume and surface resistivity of selected covering materials. These covering materials were influenced of increased humidity.
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Wearable Antennas Operating in the ISM Band
Zapletal, Ondřej ; Hebelka,, Vladimír (referee) ; Vašina, Petr (advisor)
Presented thesis is oriented on wearable antennas. The main aim of this thesis is to introduce the basic properties, measurement of textile’s electric properties and several manufacturing methods. The antenna design for the ISM 5.8 GHz bandwidth is also included and further observed by numerical model in CST Microwave Studio. The impact of flexibility and the influence of human tissue are evaluated in the case of designed equipment. According to the optimized design was made several samples by various technologies and samples were measured. Achieved results are further compared to equivalent results listed in actual available references.
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Study of electric properties of composite
Bariš, Marián ; Havlíček, Svatopluk (referee) ; Polsterová, Helena (advisor)
The theme of this Bachelor's thesis is a problematics of composite materials. On a given samples of polyamide with a various weight filling of a milled mica were measured resistivity, permittivity and loss factor on a consequence of a temperature and filling. The chosen type was a filling with a milled mica in range from 0 to 40 of a weight percentage, temperatures were in range from 20 °C to 90 °C.
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Study of electric properties of nanocomposit material
Ovsík, Jiří ; Rozsívalová, Zdenka (referee) ; Polsterová, Helena (advisor)
This work deals with the electrical properties of nanocomposite materials. Samples for the experiment are made of epoxy resin as matrix and titanium dioxide TiO2 as nanofillers in varying percentage performance. Measurements are temperature dependent components of the permittivity, dissipation factor and resistivity. Furthermore, the internal resistivity is observed with regard to the percentage performance of a sample of nanoparticles.
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