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Cold sintering of dielectric materials
Kocman, Lukáš ; Prajzler, Vladimír (referee) ; Salamon, David (advisor)
CSP (Cold Sintering Process) is an innovative production route due to the dramatic reduction in sintering temperature and processing time, which leads to a reduction in energy and production costs. During this low temperature process, the ceramic powder is compacted using a liquid phase under intense uniaxial external pressure and limited heating conditions (typically below 400 °C). Barium titanate BaTiO3 has gained worldwide interest from the scientific community due to its excellent dielectric, ferroelectric and piezoelectric properties. In particular, it is a suitable candidate for dielectric ceramic materials for energy storage. Barium titanate can be prepared by various methods, where the synthesis depends on the desired properties for the final application. The method used has a significant effect on the structure and properties of the materials. In the experimental part of the work, BaTiO3 samples were prepared by the cold sintering method and the possibility of doping ceramic materials during the cold sintering process was investigated. Furthermore, various factors and influences such as heating rate, temperature, dwell time, maximal pressure or sintering flux on the compaction and dielectric properties of the material were discussed.
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Evaluation of Different Dielectrics For Mid-Infrared Waveguides
Konečný, Aleš ; Arregi Uribeetxebarria, Jon Ander (referee) ; Detz, Hermann (advisor)
Využití plasmonovo polaritonových vlnovodů se ukázalo vhodné pro senzorové aplikace ve středně infračervené oblasti spektra. Vlnovod je v kontaktu s médiem v plynném či kapalném stavu, který obsahuje měřenou koncentraci hledané látky. Při šíření elektromagnetického vzruchu jsou na něj kladeny podmínky nízkých ztrát a dostatečné interakce s médiem. Tyto podmínky jsou splněny, je-li na kov nanesena tenká dielektrická vrstva. Tato práce je zaměřena na dielektrika na bázi křemíku. Součástí práce byla výroba vícevrstevnatých vlnovodů technikou plazmaticky vylepšené chemické depozice, magnetronového naprašování a metodou fotolitografie. Nanášení vrstev probíhalo na obvykle užívané Si substráty. Hodnocení dielektrických vrstev a výrobních metod probíhá na základě elipsometrických měření indexu lomu a absorbce v infračervené oblasti spektra.
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Computer modelling of mixture formulas of composite materials
Matoušek, Jiří ; Frk, Martin (referee) ; Rozsívalová, Zdenka (advisor)
Submitted work engage in modelling of progressions of dielectric variables and aplication of mixture formulas for solution of composite materials in dependency on frequency. Theoretical part engage in theory of dielectric materials and composite materials and contains summary of basic mixture formulas. A part of work is programm which can be used in education. It allows modelling of permitivity, loss factor and loss number in dependency on frequency and Cole-Cole circle diagram in materials. In mixtures modelling of Maxwell´s, Bőttcher´s and Lichtenecker´s mixture formulas.
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Dielectric Relaxation Spectroscopy of Glycerol
Stráník, Rostislav ; Liedermann, Karel (advisor)
This doctoral thesis deals with the analysis of dielectric spectra of glycerol with dielectric relaxation spectroscopy (DRS). Dielectric spectra of glycerol have been measured in the frequency range 20 Hz to 10 MHz and in the temperature range 10 K to 300 K. The observed dielectric spectra featured a typical relaxation maximum, which could be in the first approximation described by the Arrhenius equation. The activation energy of the relaxation process observed was 90 MJ/kmol. The relaxation strength as well as the shape of the relaxation peak remained in the temperature interval 180 K - 230 K (visibility of peak) almost the same, thus indicating that no change of the relaxation mechanism comes about. Much attention was in the thesis paid to the analysis of the excess component of the relaxation alfa process, in the literature commonly denoted as "excess wing". The thesis puts forward a procedure for the quantification of the magnitude of the excess wing. The excess wing magnitude thus determined turns out to increase monotonously with increasing temperature. The excess wing is here interpreted as a manifestation of a weakly-pronounced beta relaxation.
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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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Modelling and behaviour of composite systems in AC electric field
Matoušek, Jiří ; Frk, Martin (referee) ; Rozsívalová, Zdenka (advisor)
This work deals with modeling of progression of dielectric variables and mixture formulas for solution of properties of composite materials in dependency on frequency. Theoretical part of the work explains physical principles of polarisation mechanisms and influence on dielectric constant with changing temperature and frequency. In theoretical part processes inside the composite material, which is in electrical field are described. The work contains summary of mixture formulas and methods of their derivation. Program for use in education is a part of the work. It allows modelling of progression of dielectric variables in dependency on frequency and Cole-Cole circle diagram. In mixtures it allows modelling of frequency dependencies of dielectric constant in accordance to Maxwell's, Bőttcher's and Lichtenecker's mixture formulas.
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Automated workplace for the direct current measurements
Plocr, Radek ; Frk, Martin (referee) ; Rozsívalová, Zdenka (advisor)
The present thesis attempts at an overview of DC methods used for diagnosing electrical isolation systems. It investigates the problem of small currents and how to measure them. Part of the thesis deals with building a workstation designed for long-term monitoring of absorbing characteristics of dielectric materials and it also presents a layout of a workstation used for measuring recovery voltage. Both workplaces are computer-automated using the VEE Pro application provided by Hewlett-Packard. Tests were performed on both workstations and the obtained results were processed in a test report as specified under ČSN IEC 93. During the experiment, every effort was made to ensure and monitor the atmospheric conditions of the measuring process.
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Characterization of lead-free piezoelectric ceramics
Šťastná, Magdaléna ; Holcman, Vladimír (referee) ; Tofel, Pavel (advisor)
This project is focused on lead-free piezoelectric ceramics which are meda in CEITEC. Behaviour of these ceramics is quite different from the lead one. The first part is dedicated to dielectrics and its polarisation techniques. These techniques also include the piezoelectric effect which occurs only in crystals without central symmetry. The following part is focused on piezoelectric materials, piezoelectric polymers and piezoelectric ceramics respectively. The next section of the project is dedicated to the design of an experimental workplace for direct measurement of the piezoelectric charge coefficient đť‘‘33. The experimental part of the work is focused on electric characterisation of lead-free piezoceramics.
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Additives effect on electrical properties of the epoxy resins
Šebesta, Petr ; Kazelle, Jiří (referee) ; Frk, Martin (advisor)
Work was carried out in collaboration with SYNPO, Inc. Pardubice, which provided samples resins with various additives for measurement. The work is divided into three theoretical and one practical chapters. The first chapter focuses on dielectrics in general. It deals with their properties and storyline running in them. The second chapter discusses epoxy resins, their formulation, production and application in manufacturing. The third chapter offers a view of the measurement methods used for diagnosing electrical dielectrics. The practical part describes the preparation of samples and their composition, and consequently their measurement with the evaluation of measurement data.
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Ferroelectrics in an electric field
Pavelka, Petr ; Rozsívalová, Zdenka (referee) ; Frk, Martin (advisor)
The submitted thesis describes characteristics and use of ferroelectric materials which find their utilization in electrotechnical and electronics industry. The thesis is mainly aimed at their behaviour in the electrical field at various intensity. The method using an osciloscope is selected for measuring. For the main measuring in part of this thesis was produced experimental wafer with five samples which were subsequently mesuared. The VEE PRO program was used for creating of collecting datas for histeresis loop and it’s functionality was checked on wafer with five examples in measuring. During this measuring was also measured electric tension dependence of components of complex permittivity.
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