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Nanocomposites with a metal matrix
Chlupová, Monika ; Kohout, Jan (referee) ; Zapletal, Josef (advisor)
This baechelor thesis is focused on metal matrix nanocomposites (MMNCs), whose research has started recently. In the first part of this thesis are generally defined composite materials, the larger part is dedicated to metal matrix composites (MMCs), on which are described the strengthening mechanisms that are also applied to MMNCs. The second part of the thesis is focused specifically on MMNCs. The concept of MMNCs and their distribution is defined first, followed by a definition of the reinforcement that can be used for the production of MMNCs. There are also described the posibilities for the production of these reinforcing phases, and their influence on the structural and mechanical properties of the final MMNCs. This section is followed by a description of possible processes of MMNCs production with their advantages and limitations. The last part outlines how research and development of these materials should be carried out in order to be commercially produced and used in the future.
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Advanced ceramic layered materials with heterogeneous microstructure for ballistic applications
Mařák, Vojtěch ; Kachlík, Martin (referee) ; Drdlík, Daniel (advisor)
This bachelor thesis deals with a preparation technology of layered ceramic materials (laminates) with heterogeneous microstructure containing Al2O3 as a matrix with addition of SiC. For the preparation of these materials, dry and wet shaping of ceramic powder with subsequent SPS (Spark Plasma Sintering) was chosen. Due to the goals of the bachelor thesis, the dry shaping proved to be less suitable due to the difficult preparation of the layered structure and the significant wear of the graphitic dies used in the SPS technology. However, the information obtained about mechanical and physical properties has led to the design of the ceramic suspension used in wet shaping (slip-casting). As optimal design 5 vol % of SiC in Al2O3 was chosen. Via this way, ceramic laminates with a sharp layer interface were prepared and the graphitic die wear was minimized. Prepared ceramic samples reached relative density up to 99 % and hardness up to 20.7 GPa. The obtained knowledge has shown the need to optimize the technology of suspension preparation to create ceramic material suitable for ballistic applications.
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Testing of Surge Arresters
Jeřábek, Lukáš ; Paar, Martin (referee) ; Krbal, Michal (advisor)
This bachelor's thesis is devoted to metal oxide surge arresters. After historical and theoretical introduction, which explains their principles and describes their characteristical properties, analysis of the standard IEC 60099-4 and testing according to the standard with focus on the type tests follows. This chapter is also amended with review of the standard's imperfections and with its most probable future development. The work concludes with a market survey, a review of the largest manufacturers and a comparison of their products.
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Negative electrode materials for lithium-ion batteries
Šikuda, Milan ; Vondrák, Jiří (referee) ; Libich, Jiří (advisor)
This theses deal with a study of basic functional principles of cells. It is focused on carbon materials, which are the basic for negative electrode masses of lithium-ion accumulators. The aim of this work is understanding principle lithium-ion accumulator, get an overview about the most widespread materials currently using for negative electrode materials with measuring their characteristics. Then compare characteristics of carbon materials with alternatives materials for negative electrode on the base of silicon. First part of the work is devoted of principle functionality lithium-ion accumulators together with description of galvanostatics and potentiostatics measuring methods. Practical part deals with preparation and measuring negative electrode masses characteristics.
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Non-Destructive Local Diagnostics of Optoelectronic Devices
Sobola, Dinara ; Pína,, Ladislav (referee) ; Pinčík,, Emil (referee) ; Tománek, Pavel (advisor)
Chceme-li využít nové materiály pro nová optoelektronická zařízení, potřebujeme hlouběji nahlédnout do jejich struktury. K tomu, abychom toho dosáhli, je však nutný vývoj a aplikace přesnějších diagnostických metod. Předložená disertační práce, jako můj příspěvek k částečnému dosažení tohoto cíle, se zabývá metodami lokální diagnostiky povrchu optoelektronických zařízení a jejich materiálů, většinou za využití nedestruktivních mechanických, elektrických a optických technik. Tyto techniky umožňují jednak pochopit podstatu a jednak zlepšit celkovou účinnost a spolehlivost optoelektronických struktur, které jsou obecně degradovány přítomností malých defektů, na nichž dochází k absorpci světla, vnitřnímu odrazu a dalším ztrátovým mechanismům. Hlavní úsilí disertační práce je zaměřeno na studium degradačních jevů, které jsou nejčastěji způsobeny celkovým i lokálním ohřevem, což vede ke zvýšené difúze iontů a vakancí v daných materiálech. Z množství optoelektronických zařízení, jsem zvolila dva reprezentaty: a) křemíkové solární články – součástky s velkým pn přechodem a b) tenké vrstvy – substráty pro mikro optoelektronická zařízení. V obou případech jsem provedla jejich detailní povrchovou charakterizaci. U solárních článků jsem použila sondovou mikroskopii jako hlavní nástroj pro nedestruktivní charakterizaci povrchových vlastností. Tyto metody jsou v práci popsány, a jejich pozitivní i negativní aspekty jsou vysvětleny na základě rešerše literatury a našich vlastních experimentů. Je také uvedeno stanovisko k použití sondy mikroskopických aplikací pro studium solárních článků. V případě tenkých vrstev jsem zvolila dva, z hlediska stability, zajímavé materiály, které jsou vhodnými kandidáty pro přípravu heterostruktury: safír a karbid křemíku. Ze získaných dat a analýzy obrazu jsem našla korelaci mezi povrchovými parametry a podmínkami růstu heterostruktur studovaných pro optoelektronické aplikace. Práce zdůvodňuje používání těchto perspektivních materiálů pro zlepšení účinnosti, stability a spolehlivosti optoelektronických zařízení.
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Characterization of Nanostructures Deposited by High-Frequency Magnetron sputtering
Hégr, Ondřej ; Boušek, Jaroslav (advisor)
This thesis deals with the analysis of nano-structured layers deposited by high-frequency magnetron sputtering on the monocrystalline silicon surface. The content of the work focuses on the magnetron sputtering application as an alternative method for passivation and antireflection layers deposition of silicon solar cells. The procedure of pre-deposite silicon surface cleaning by plasma etching in the Ar/H2 gas mixture atmosphere is suggested. In the next step the silicon nitride and aluminum nitride layers with hydrogen content in Ar/N2/H2 gas mixture by magnetron sputtering are deposited. One part of the thesis describes an experimental pseudo-carbide films deposition from a silicon target in the atmosphere of acetylene (C2H2). An emphasis is placed on the research of sputtered layers properties and on the conditions on the silicon-layer interface with the help of the standard as well as special measurement methods. Sputtered layers structure is analyzed by modern X-ray spectroscopy (XPS) and by Fourier infrared spectroscopy (FTIR). Optical ellipsometry and spectrophotometry is used for the diagnostic of the layers optical properties depending upon the wavelength of incident light. A special method of determining the surface lay-out of the charge´s carrier life in the volume and on the surface of silicon is employed to investigate the passivating effects of the sputtered layers.
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Experimental flyback switching supply 1200 W/150 kHz with SiC switches
Grom, Martin ; Huták, Petr (referee) ; Vorel, Pavel (advisor)
This master’s thesis deals with design and construction of experimental flyback converter with utilization of novel lossless clamp circuit for switching transistor and with utilization of silicon carbide devices. The issue of flyback converter for higher power and possible control strategies are discussed. The thesis also describes power and control circuits design, design of PCB, construction of the converter and measured waveforms. End of the thesis contains technical documentation of designed board. Designed converter was successfully built and tested.
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Development of negative electrodes for lithium-ions batteries
Drahokoupil, Petr ; Libich, Jiří (referee) ; Sedlaříková, Marie (advisor)
This thesis deals with lithiation of negative electrode li-ion batteries. In this thesis is used several electrode materials: carbon, FeCl3, lithiated carbon electrodes and silicon carbide. Reduction of irreversible capacity lithium-ion batteries leads to increased capacity and also we can use new materials as a positive electrode. Thesis deals with the differences in the properties of materials using lithiation and their use in practice
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Switching supply source 5,5kV/4,3kW with silicon-carbide semiconductors
Gabriel, Petr ; Patočka, Miroslav (referee) ; Vorel, Pavel (advisor)
This thesis is about to introduce the development of switched power supply with output voltage of 5,5 kV and power of 4,3 kW. This thesis directly follows the outputs of two previous semester projects. Main task is about to finish the development of remaining printed circuit boards and perform launching of all parts of developed power supply. Next necessary task is about to assemble a functional prototype of the supply using the developed parts, performing a series of measurement supply’s parameters and creating of technical documentation of mechanical part. There are all stages of supply’s development included in this thesis. From the first part, that describes various types of converters, through the design of all the supply’s parts, to final implementation of functional prototype. There are the results of measurement supply’s parameters at the end of this thesis.
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