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Pyrolytic graphite
Chýlková, Adéla ; Adam, Ondřej (referee) ; Němec, Karel (advisor)
The purpose of this bachelor thesis was to write a literature search summarizing knowledge about carbon-based materials and experimental determination of thermal expansion and thermal balance of samples of various types of graphite and evaluation of measured data. The research part of the work describes most of the currently known types of carbonaceous materials, with a more thorough study of pyrolytic graphite. The whole next chapter was devoted to a more thorough study of pyrolytic graphite. The second part of the thesis is focused on the experimental determination of thermal expansion and thermal balance on selected graphite samples (natural, expanded, pressed expanded and pyrolytic graphite). We used dilatometric analysis and thermogravimetry to solve this task. Finally, the measurement data were processed into graphs and relevant tables and conclusions were deduced.
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Fabrication and properties of doped piezoceramics based on BaTiO3
Mařák, Vojtěch ; Chlup, Zdeněk (referee) ; Drdlík, Daniel (advisor)
This diploma thesis deals with the preparation of doped piezoceramic materials based on BaTiO3 using electrophoretic deposition. Five rare earth oxides, i.e. Er2O3, Dy2O3, Eu2O3, Tb407 and CeO2, were used as dopants in amounts of 1, 3, and 5 wt. %. The prepared deposits were evaluated in terms of preparation methodology, high temperature dilatometry, X-ray diffraction analysis, relative density, mean grain size, hardness and fractographic analysis. The study of dilatometric curves described the sintering behavior and its changes at different material compositions. X-ray diffraction analysis revealed a tetragonal phase in all samples; the tetragonality of the BaTiO3 crystalline cell decreased with dopant content. By a suitable choice of dopant, it was possible to significantly increase the relative density of sintered samples, their hardness and at the same time prevent the samples from coarsening of the microstructure during heat treatment. A relative density up to 98 %, a mean grain size below 1 m and a hardness of over 10 GPa were achieved. Analysis of the fracture surfaces revealed that the fracture mode was transcrystalline for the most of studied materials; only the samples doped with cerium dioxide had fracture surfaces with both transcrystalline and intercrystalline fracture modes. Based on the obtained results, a suitable composition of the material for the intended use in a layered piezoceramic harvester was identified, which, in addition to the BaTiO3 layers, consists of functionally-protective Al2O3 and ZrO2 layers.
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3D printing methods for foundry applications
Rendek, Andrej ; Pernica, Vítězslav (referee) ; Krutiš, Vladimír (advisor)
The bachelor thesis is focused on the application of 3D printing methods for foundries, specifically for investment casting technology. The paper describes different printing methods and principles which they are based on with a more detailed description of materials containing their properties and in some cases recommended modifications of the casting process. The last part is devoted to price comparison of three selected methods of model printing for investment casting and dilatometry of six materials with evaluation of their coefficients of thermal expansion and glass transition temperatures.
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Sintering of advanced ceramic materials with the help of high-temperature dilatometry
Pouchlý, Václav ; Cihlář, Jaroslav (referee) ; Maca, Karel (advisor)
This diploma work is focused on exploitation of high-temperature dilatometry in sintering of advanced ceramic materials. Newly developed software is presented in this diploma work. This software is able to calculate activation energy of sintering process via concept of Master Sintering Curve. In the second part of diploma work the software was verified by evaluation of sintering of four different ceramics materials. The following activation energies of sintering were calculated: 990kJ/mol for tetragonal ZrO2 (3mol% Y2O3), 620kJ/mol for cubic ZrO2 (8mol% Y2O3) and 640kJ/mol resp. 720kJ for Al2O3 with two different particle size.
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Kinetics of the Coordination Polymerization of -olefins Catalyzed by Nickel Diimine Complexes
Peleška, Jan ; Kratochvíla, Jan (referee) ; Pinkas,, Jiří (referee) ; Petrůj, Jaroslav (referee) ; Cihlář, Jaroslav (advisor)
This Ph.D. thesis is focused on kinetic study of propene and hex-1-ene coordination polymerizations initiated by complex [(2-tBuC6H4)N=C(1,8-naphtalenediyl)C=N(2-tBuC6H4)]NiBr2 activated by simple organoaluminium compounds and on product properties. In first three parts proper activators are chosen in model polymerizations. The attention is paid to the reproducibility of polymerizations and analytical methods. The fourth part is focused on propene polymerization kinetics with the aim to define optimal reaction conditions, especially polymerization temperature and time. The four part concerns also properties of polymers. The fifth and sixth parts deal with hex-1-ene polymerization kinetics conducted at various activator/initiator molar ratios and various catalytic precursor concentrations, to find out kinetic orders with respect to catalyst and cocatalyst concentration. Last part is oriented on detail mechanistic investigation of nickel diimine complexes activation process. Results of measurements in presence or absence of monomer enabled to propose new interpretation of UV-vis spectra based on concrete structures of absorbing species.
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3D printing methods for foundry applications
Rendek, Andrej ; Pernica, Vítězslav (referee) ; Krutiš, Vladimír (advisor)
The bachelor thesis is focused on the application of 3D printing methods for foundries, specifically for investment casting technology. The paper describes different printing methods and principles which they are based on with a more detailed description of materials containing their properties and in some cases recommended modifications of the casting process. The last part is devoted to price comparison of three selected methods of model printing for investment casting and dilatometry of six materials with evaluation of their coefficients of thermal expansion and glass transition temperatures.
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Fabrication and properties of doped piezoceramics based on BaTiO3
Mařák, Vojtěch ; Chlup, Zdeněk (referee) ; Drdlík, Daniel (advisor)
This diploma thesis deals with the preparation of doped piezoceramic materials based on BaTiO3 using electrophoretic deposition. Five rare earth oxides, i.e. Er2O3, Dy2O3, Eu2O3, Tb407 and CeO2, were used as dopants in amounts of 1, 3, and 5 wt. %. The prepared deposits were evaluated in terms of preparation methodology, high temperature dilatometry, X-ray diffraction analysis, relative density, mean grain size, hardness and fractographic analysis. The study of dilatometric curves described the sintering behavior and its changes at different material compositions. X-ray diffraction analysis revealed a tetragonal phase in all samples; the tetragonality of the BaTiO3 crystalline cell decreased with dopant content. By a suitable choice of dopant, it was possible to significantly increase the relative density of sintered samples, their hardness and at the same time prevent the samples from coarsening of the microstructure during heat treatment. A relative density up to 98 %, a mean grain size below 1 m and a hardness of over 10 GPa were achieved. Analysis of the fracture surfaces revealed that the fracture mode was transcrystalline for the most of studied materials; only the samples doped with cerium dioxide had fracture surfaces with both transcrystalline and intercrystalline fracture modes. Based on the obtained results, a suitable composition of the material for the intended use in a layered piezoceramic harvester was identified, which, in addition to the BaTiO3 layers, consists of functionally-protective Al2O3 and ZrO2 layers.
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|
|
Pyrolytic graphite
Chýlková, Adéla ; Adam, Ondřej (referee) ; Němec, Karel (advisor)
The purpose of this bachelor thesis was to write a literature search summarizing knowledge about carbon-based materials and experimental determination of thermal expansion and thermal balance of samples of various types of graphite and evaluation of measured data. The research part of the work describes most of the currently known types of carbonaceous materials, with a more thorough study of pyrolytic graphite. The whole next chapter was devoted to a more thorough study of pyrolytic graphite. The second part of the thesis is focused on the experimental determination of thermal expansion and thermal balance on selected graphite samples (natural, expanded, pressed expanded and pyrolytic graphite). We used dilatometric analysis and thermogravimetry to solve this task. Finally, the measurement data were processed into graphs and relevant tables and conclusions were deduced.
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|
|
Kinetics of the Coordination Polymerization of -olefins Catalyzed by Nickel Diimine Complexes
Peleška, Jan ; Kratochvíla, Jan (referee) ; Pinkas,, Jiří (referee) ; Petrůj, Jaroslav (referee) ; Cihlář, Jaroslav (advisor)
This Ph.D. thesis is focused on kinetic study of propene and hex-1-ene coordination polymerizations initiated by complex [(2-tBuC6H4)N=C(1,8-naphtalenediyl)C=N(2-tBuC6H4)]NiBr2 activated by simple organoaluminium compounds and on product properties. In first three parts proper activators are chosen in model polymerizations. The attention is paid to the reproducibility of polymerizations and analytical methods. The fourth part is focused on propene polymerization kinetics with the aim to define optimal reaction conditions, especially polymerization temperature and time. The four part concerns also properties of polymers. The fifth and sixth parts deal with hex-1-ene polymerization kinetics conducted at various activator/initiator molar ratios and various catalytic precursor concentrations, to find out kinetic orders with respect to catalyst and cocatalyst concentration. Last part is oriented on detail mechanistic investigation of nickel diimine complexes activation process. Results of measurements in presence or absence of monomer enabled to propose new interpretation of UV-vis spectra based on concrete structures of absorbing species.
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|
|
Sintering of advanced ceramic materials with the help of high-temperature dilatometry
Pouchlý, Václav ; Cihlář, Jaroslav (referee) ; Maca, Karel (advisor)
This diploma work is focused on exploitation of high-temperature dilatometry in sintering of advanced ceramic materials. Newly developed software is presented in this diploma work. This software is able to calculate activation energy of sintering process via concept of Master Sintering Curve. In the second part of diploma work the software was verified by evaluation of sintering of four different ceramics materials. The following activation energies of sintering were calculated: 990kJ/mol for tetragonal ZrO2 (3mol% Y2O3), 620kJ/mol for cubic ZrO2 (8mol% Y2O3) and 640kJ/mol resp. 720kJ for Al2O3 with two different particle size.
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