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Electrical characteristics of gliding discharge for VOC decomposition
Jeřábek, Martin ; Sysel, Petr (referee) ; Bartlová, Milada (advisor)
The subject of this bachelor's thesis was to get familiar with the characteristics of plasma, its divisinon and diagnostics. In physics and chemismy plasma is considered to be, an ionized gas composed of ions, electrons (and possibly neutral atoms and molecules), which is produced by detachement of electrons from the atomic shell, or by dissociation and ionization of molecules. The plasma is often referred as the fourth state of matter. Attention was given to the description of various types of electric discharge, its characteristics and occurrence. One of the most idey known electrical discharges occurring in nature is lightning, a spark discharge, which occurs in the storm. Lightning is an electric discharge between centres of positive and negative charge of one or more clouds, between cloud and earth, or rarely between the cloud and the stratosphere. The greatest attention is paid mainly to gliding electric arc discharge, called Glide-Arc; it is a representative of on-thermal plasma formed by weakly ionized gas. It has many industrial applications, especially for its high energy efficiency, specific productivity and high selectivity of chemical reactions. Under low and atmospheric pressure, Glide-Arc represents a simple and non-expensive way of non-thermal plasma generation. The discharge is excited between two electrodes of different materials in the pressure range from very low pressures up to the pressures of the order of units of MPa. The gliding arc system consist of horn-gaps electrodes diverging in the direction of the working gas flow. After the application of DC or AC voltage, a breakdown occurs at the smallest distance between the electrodes, and a spark plasma channel drifts (“glides“) in the direction of the flowing gas. The final experimental part deals with the measurement of VA characteristics and oscillation characteristics of the current, and with the determinativ of gliding arc ignitron for selected of nitrogen and methane gases at various flow rates. The values of ignition voltage for variol mixtures of gases have been compared. Furthermore, the properties various combinations of gases at different gas flow rates have been evaluated. Measurements were carried out in the plasma laboratory of the Faculty of Chemistry BUT in the plasma reactor at the atmospheric pressure.
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Microplasma Noise as a Diagnostic Tool for PN Junctions of High-Voltage Rectifier Diodes
Raška, Michal ; Chobola, Zdeněk (referee) ; Hájek, Karel (referee) ; Koktavý, Pavel (advisor)
The doctoral thesis deals with diagnostics of local defects in PN junctions and brings new information about microplasma noise behaviour and its usage for the temperature changes detection inside PN junctions. Defects in PN junctions are the source of microplasma noise. There were deviations observed in microplasma noise from the common known rectangle shape pulses during the measurements. These deviations were correlated with the temperature change directly in the defect area and in the defect area surroundings. Generation and recombination coefficients are commonly thought to be constant. However, these coefficients were observed to be not stable with time and this effect is explained in this work. The doctoral thesis then focuses on the PN junction parameters determination in the case when it is not possible to define unambiguously whether it is abrupt or linearly graded PN junction. The most significant parameters which are to be determined are barrier capacity, diffusion voltage and depleted area width in dependence on the voltage. The correlation between local avalanche discharge in PN junction and negative differential resistance appearance on VA characteristics of reverse-biased diode was qualitatively verified. The last important point in the work is computer modelling of temperature behaviour in the defect area and its surroundings during local avalanche breakdown. Thus the method of real diodes heating area parameters determination was introduced.
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Design of VA-characteristic meter
Štěpnička, Martin ; Szabó, Zoltán (referee) ; Steinbauer, Miloslav (advisor)
The thesis describes the design of a measuring device volt-ampere characteristics of PN junction suitable for measuring characteristics of stabilizing diodes. Describes the basic principle of PN junction and related events. Part of the text discusses how to minimize the adverse parasitic effects. Furthermore, the proposal deals with an AC adapter suitable for this device. With that analyzes marginally rectifiers, stabilizers and filters. The following is a description of the device for measurement, principle of communication with the computer and the method of data processing. The annex contains schematic design, printed circuit boards and part list.
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V-I characteristic of solar cells
Kaderka, Tomasz ; Křivík, Petr (referee) ; Vaněk, Jiří (advisor)
The theoretical part is to outline the possibilities of solar energy conversion, learn about the issues solar cells and describe the history of photovoltaics and photovoltaic energy conversion. Then describe principle of the measurement VA characteristics of photovoltaic cells. This issue is not as easy as it seems at first sight, because the solar cell isn’t a linear component, which is very easy to measure. Analysis of VA characteristic of photovoltaic cells affects parameters such as: light intensity, temperature, serial and parallel resistance, the slope of the light source, and more. The practical part deals with creating a workplace for automatic measurement of VA characteristics of photovoltaic cells in the LabVIEW. Challenge is to create a functional program, which automatically measures the VA characteristics not only in the lighted cells, but also in the shaded cell (diode mode). The program calculates the power and important parameters, such as short-circuit current, open circuit voltage, maximum power, current and voltage at maximum power article. The program allows you to export the measured values to a text file. In the last chapter of this work is made control measurements of three samples of monocrystal photovoltaic cell by the measuring workplace. The measurement is compared with the reference device Solar Cell Tester.
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Electrical features of surface discharge for organic material decomposition
Budík, Martin ; Zdražil, Vladimír (referee) ; Bartlová, Milada (advisor)
The aim of this semestral work is to describe importance of electric surface discharges for decomposition of organic substances. This will serve to practical measurement of VA characteristic of surface discharge ignition, flow effect and type of portative gas for VA characteristic and moment of ignition of surface discharge. Then measurement of dynamic characteristic of surface discharge in assorted portative gases with diverse kind of flowage and setting of energetic ratios in discharge by means of dynamic characteristics. The main part of this work is dedicated to conditions of discharge ignition, its characteristics in different conditions and another types of discharges.
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Photovoltaic system with sun-tracker
Riabov, Mikhail ; Křivík, Petr (referee) ; Vaněk, Jiří (advisor)
The aim of the bachelor thesis " Model of photovoltaic system with solar tracker“ is to apprise with principles of operation of solar systems. We will focus on the tracking system, which is turning itself depending on the position of the sun. In the theoretical part we will describe the principle of operation of photovoltaic cells and solar systems. In the practical part of the work we will compare the parameters of the static and dynamic solar system and make decision, which of these systems is more profitable for use.
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Study of the crystallization process kinetics of perovskites and their precursors
Sršeň, Bohdan ; Gavranović, Stevan (referee) ; Zmeškal, Oldřich (advisor)
This thesis focuses on the properties of perovskite materials and examines the methods for preparing layers and potentially monocrystals of these materials. Emphasis is placed on analyzing the electrical and optical properties of perovskites. The experimental part of the thesis is dedicated to the preparation of perovskite material layers and subsequent measurement of their electrical properties during the crystallization process and after its completion. The prepared samples exhibit a macroscopic size due to the interdigitated electrode structure, ensuring a large active surface area. Special attention is given to the influence of nano-particles on the crystallization process and the resulting current-voltage (I-V) characteristics of the prepared samples. Understanding how the presence of nano-particles affects the crystallization and electrical properties of perovskite layers is crucial. These insights are necessary for further optimization of the preparation processes and enhancing the performance of perovskite materials in their final applications. The thesis provides an overview of the properties of perovskites and their preparation. The experimental results yield important insights into the relationship between nano-particles, crystallization, and electrical characteristics of perovskite layers.
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