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Ultrasound in material diagnostics
Kristek, Michal ; Frk, Martin (referee) ; Kazelle, Jiří (advisor)
Objectives of the semestral project are to study the physical basis of ultra acoustic and comprehend the basics of ultrasound usage in diagnostic of materials. I should also become familiar with functions and usage of ultrasound device EPOCH LT made by OLYMPUS and perform measurement of thickness and speed of ultrasound spreading in selected materials.
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Dielectric properties of epoxy resins
Matoušová, Klára ; Novák, Vítězslav (referee) ; Kazelle, Jiří (advisor)
This diploma thesis deals with the fundamental properties of epoxide mixtures, as determining of these fundamental properties of epoxide mixtures could in the case of favorable results lead to diminishing the amount of defects in epoxide-embedded instrument transformers. As the influence of effects in the manufacturing process of transformers causing poor quality is very extensit, the biggest emphasis is laid capitally on the influence of the epoxide casting mixture composition. The thesis describes the manufacture technology including used methodics and materials. The compositions of epoxide resins and the mechanisms of their curing. Also, the definitions of fundamental properties of dielectric materials and the description of diagnostic methods used to relative permitivity, dissipation factor and inner resistivity are included. suitable casts of acquired samples were set and dried out within the experimental part, followed by measurement of fundamental electrical properties in temperature and frequency relations. Hereafter a comparison of individual samples and the evaluation of their electrical properties will be carried out.
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High temperature conductivity measurements of ceramic materials
Grochal, Peter ; Kazelle, Jiří (referee) ; Novák, Vítězslav (advisor)
The aim of this work is to get acquainted with the detailed structure of yttrium-stabilized zirconia, focusing mainly on conductivity. Coating platinum electrodes by screen printing. Solution of complexity of conductivity segregation by electrode geometry. Measurement of the conductivity of macroscopic samples of ceramics by impedance spectroscopy to determine the electrical behavior of the system. Creating equivalent circuits to measured data. Detect system behavior when excited by different AC voltage and electrode geometry values.
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Degradation of epoxy resins vith various aditives by solar radiation
Škarabelová, Lenka ; Novák, Vítězslav (referee) ; Kazelle, Jiří (advisor)
This master’s thesis is focused on the study of chemical and physical properties of dielectric materials with main focus on epoxy resins. It includes possible processes that can influence the properties of epoxy resins, both processes that improve polymer properties and processes that cause material degradation. Next part of the thesis is a description of diagnostic methods suitable for measurement of basic electrical quantities of material and design of a suitable method for measuring properties of epoxy resins with different additives, influencing the samples by solar radiation. At the end, the work includes an experiment dedicated to the degradation of epoxy resins with various additives by solar radiation and the evaluation of the experiment.
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Comparation of the properties of the perovskit photovoltaic cells
Mudroch, Michal ; Kazelle, Jiří (referee) ; Novák, Vítězslav (advisor)
In this bachelor’s thesis it is introduced production technology and conversion of electromagnetic radiation into electric energy employing perovskites. In this paper are also described known types of perovskite photovoltaic cell structures and materials that are used to produce them. Furthermore, the theoretical part describes properties of perovskite photovoltaic cells, measured electric quantities and methods of measurement such as photospectroscopy photoimpedance spectroscopy and impedance spectroscopy that are also used to analyze cells functionality. In the following practical part is described fabrication of perovskite cells and evaluation of measured results of the perovskite cell.
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Cooling of Two-channel audio power-amplifier using FVM
Němec, Radek ; Kazelle, Jiří (referee) ; Vyroubal, Petr (advisor)
This bachelor´s thesis is dealing with the design and construction of two-channel audio Leach type power-amplifier, including the necessary additional components and subsequent design of the amplifier cooling using Flow Simulation tool included in the SolidWorks design system. The opening chapters is about theoretical analysis of audio amplifiers, heat transfer and description of SolidWorks design system. The main part of this thesis contains the design and construction of amplifier and design of each variants of amplifier cooling, including the best variation designed. The last part of the thesis is about assembling the amplifier and evaluation of economic aspects of its production.
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Drying and preheating in potting process of epoxides
Matoušová, Klára ; Novák, Vítězslav (referee) ; Kazelle, Jiří (advisor)
The bachelor's thesis is dealing with the defects in epoxy resin flooded transformer devices. Since these can be damaged severely in terms of quality by numerous forces, the main focus is dedicated to the impact of moisture. The thesis describes the manufacturing technology including the methods applied and materials used. It further encompasses the composition of epoxy resin and the mechanisms used for their hardening processes. Additionally, the description of the moisture, the impact of adverse forces and the method of their elimination using drying is presented. In the experimental part of the paper, a moisture of the banding materials was measured. On the basis of the results acquired, the paper reaches a conclusion on the ideal time frame of drying, the sufficiency of materials in terms of drying and in two cases two substitutes for contemporary uneasily dryable samples were considered.
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Piezoelectricity in technical practice
Škarabelová, Lenka ; Frk, Martin (referee) ; Kazelle, Jiří (advisor)
Bachelor's thesis is dedicated to the study of the principle and possibilities of use of the piezoelectric effect. Since the use of piezoelectric effect in electrical engineering is very extensive, the main focus is placed on the ability to exploit this effect in the field of ultrasonic and piezoelectric resonators. Next aim of this work is practically and theoretically to get acquainted with the measurement of small changes in weight, using electrochemical quartz crystal microbalance (EQCM), also with an ultrasonic equipment from company Olympus and ultrasonic defectoscopy for detection of possible imperfections in the material and their evaluation.
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