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Study of electric properties of nanocomposites
Libra, Miroslav ; Rozsívalová, Zdenka (referee) ; Polsterová, Helena (advisor)
The present master´s thesis deals with the electrical properties of nanocomposite materials. Samples for the experiment are made epoxi resin and oxides TiO2 and Al2O3 as nanofillers in different percent performace. The samples nanocomposites are measured temperature dependence of the resistivity inside, dissipation factor and relative permittivity. It discusses the effect of the filler on the resulting electrical properties of the polymer.
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Study of the influence of fillers and external conditions on the resistivity of cement composites
Kejda, Dalibor ; Melichar, Jindřich (referee) ; Černý, Vít (advisor)
The progress of new materials is important for the construction industry. Modern materials include cement composites with reduced resistivity. This is achieved by adding suitable electrically conductive fillers. If there is enough of these fillers, the so-called percolation threshold occurs. Suitable fillers (Condufit C4 and Supragraphite C300) have been proposed. Recipes have been designed to be before and after the percolation threshold. The tests were performed on beams measuring 40x40x160 mm with built-in electrodes for measuring their resistivity. The aim of the work was the research of influencing external conditions on cement composites. The effect of temperature was verified. The lowest values of resistivity were evaluated at temperatures of 50 ° C and the resistivity increased with decreasing temperature. The effect of humidity on the resistivity was then verified. Reference samples and samples with a smaller proportion of graphite powder showed larger differences in resistivities with increasing humidity. The samples above the percolation threshold were not much affected by increasing humidity. Finally, the effect of loading on the resistivity of the samples was verified. Almost all samples with increasing compressive stress showed an increasing value of resistivity.
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Simulation of earthing system resistance measurement
Pirochta, Josef ; Topolánek, David (referee) ; Vyčítal, Václav (advisor)
In this bachelor thesis, the effect of different soil models and random wire placed underground on the results of earth resistance measurements using the 4-pole method was investigated. To determine this influence, simulations were performed in Ansys Electronics software, in which different soil models (with local inhomogeneity, horizontally divided soil and soil divided at an angle) were created. In these models, the measured earth was placed together with the measured random wire and its resistance was determined by simulating the measurements and with respect to the distant ground. The effect of the different soil models on the accuracy of the measurements was determined from the differences in the resistance of the earth random wire obtained by measurement and with respect to the distant ground. It was found by simulations that, of all the variants investigated, performing measurements in the presence of different soil models and a random wire can lead to a measurement error of up to 7,2 %.
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Non-metallic resistive low temperature thermometers
Duda, Daniel ; Rotter, Miloš (advisor) ; Janů, Zdeněk (referee)
temperature calibration has been carried out on series of resistors made of RuO2 of SMD type in the bath of normal and superfluid helium in temperatures at 1.4 - 4.2 K with reference thermometer of saturated vapor pressure. Measured temperature dependence of electrical resistance of resistors was analyzed using the exponential function and Chebychev's polynomials. It was established an optimum calibration for the use of resistors as thermometers.
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Fabrication of conducting patterns by material electroless plating of printed precursor
Kováčová, Silvia ; Gemeiner,, Pavol (referee) ; Dzik, Petr (advisor)
The subject of this diploma thesis is the preparation of conductive structures by electroless plating of an extruded precursor. The experimental part deals with the preparation of standard patterns based on the length of immersion time in a coppering bath. The precursor layers were applied with Fujifilm Dimatix to various receiver substrates. The individual substrates with the precursor layer were immersed in the copper solution within different time intervals. The structure of the layers of grown copper and their thickness was characterized by a profilometer.
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Dielectric Absorption of Electroinsulating Materials
Pavlinský, Branislav ; Krbal, Michal (referee) ; Pelikán, Luděk (advisor)
This bachelor thesis deals with the basic physical principles of dielectrics as well as the description of the phenomenon of dielectric absorption. The work presents diagnostic methods that use this phenomenon, based on the events taking place in the dielectric after the connection of DC voltage. Furthermore, the work deals with diagnostic methods for determining the state of insulation of various high-voltage electrical equipment. The work also deals with the properties and parameters of electrical insulating materials - specifically polymers. We obtain these parameters using the mentioned diagnostic methods. By knowing these parameters, we achieve enough information about the insulation to determine its condition and prevent possible damage.
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Measurement of tissue impedance during electroporation
Uher, Jakub ; Novotná, Veronika (referee) ; Červinka, Dalibor (advisor)
The Bachelor's thesis is devoted to the impedance of tissue in relation to the modern medical method electroporation. The Bachelor's thesis is divided into five chapters. The first three chapters describe the behaviour of the tissue and its impedance, whether during the passage of an electrical current or a phenomenon before and after the electroporation procedure. The fourth and fifth chapters examine those phenomena in the previous chapters on measurements made on animal and plant tissue.
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Fabrication of conductive paths by electroless plating of printed precursors
Kováčová, Silvia ; Zita, Jiří (referee) ; Dzik, Petr (advisor)
The subject of this bachelor thesis is the preparation of conductive tracks by electroless plating of printed precursors. The experimental part deals with the preparation of standard samples based on the length of immersion time in the coppering bath. The precursor layers were applied with a technical pen to ceramic corundum substrates. The individual precursor layer substrates were immersed in the coppering bath in various time intervals. The structure of the grown copper layers was observed by an optical microscope and their thickness was determined by a profilometer.
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