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Grain growth kinetics study of advanced oxide ceramic materials
Kazda, Adam ; Kachlík, Martin (referee) ; Pouchlý, Václav (advisor)
The goal of this work was to study the grain growth kinetics of five different materials: tetragonal ZrO2 (doped 3mol.% Y2O3 and particle size 80 nm), two cubic ZrO2 (doped 8 mol.% Y2O3 and particle sizes 80 and 140 nm) and two hexagonal Al2O3 (with particle sizes 100 and 240 nm). These ceramic powders were isostatically pressed and then they were isothermally sintered at 3 different temperatures for 1-60 hours. The biggest coarsening was discovered during temperature increase to sintering temperature. The dwelt at sintering temperature was not so important for coarsening. The activation energy of grain growth QG, growth exponent n and kinetic constant k0 were discovered for four materials. The activation energy of grain growth was 511±49 kJ/mol for tetragonal ZrO2, 645±84 kJ/mol for cubic ZrO2 a 428±75 kJ/mol a 606±24 kJ/mol for Al2O3. Possibility of kinetic window of sintering process for cubic ZrO2, tetragonal ZrO2, and Al2O3 with particle size 240 nm (doped MgO) were discovered by comparison of established activation energy of grain growth QG with activation energy of sintering QS from literature. Kinetic window of sintering process wasn’t found for high purity alumina with particle size 100 nm.
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Manufacturing inaccuracies influence on an appearence of the additional moment on a sailboat rudder
Kazda, Adam ; Fic, Miloslav (referee) ; Štigler, Jaroslav (advisor)
This Master’s thesis is dedicated to a generation of an additional torque, which can occur due to the inaccuracy of the manufacturing. This issue is inspired by a real case from 2013. In this work CFD modeling is used to investigate three different sources of the additional torque: misalignment of the rudder, deviation of the propeller shaft and asymmetry of the rudder. A simplified 2D simulation is done for all three cases. This simulation is more suitable for a jet powered boat. Therefore the asymmetry of the rudder is investigated also in a 3D case, where the rotational component of the flow behind the propeller is included.
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Manufacturing inaccuracies influence on an appearence of the additional moment on a sailboat rudder
Kazda, Adam ; Fic, Miloslav (referee) ; Štigler, Jaroslav (advisor)
This Master’s thesis is dedicated to a generation of an additional torque, which can occur due to the inaccuracy of the manufacturing. This issue is inspired by a real case from 2013. In this work CFD modeling is used to investigate three different sources of the additional torque: misalignment of the rudder, deviation of the propeller shaft and asymmetry of the rudder. A simplified 2D simulation is done for all three cases. This simulation is more suitable for a jet powered boat. Therefore the asymmetry of the rudder is investigated also in a 3D case, where the rotational component of the flow behind the propeller is included.
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Grain growth kinetics study of advanced oxide ceramic materials
Kazda, Adam ; Kachlík, Martin (referee) ; Pouchlý, Václav (advisor)
The goal of this work was to study the grain growth kinetics of five different materials: tetragonal ZrO2 (doped 3mol.% Y2O3 and particle size 80 nm), two cubic ZrO2 (doped 8 mol.% Y2O3 and particle sizes 80 and 140 nm) and two hexagonal Al2O3 (with particle sizes 100 and 240 nm). These ceramic powders were isostatically pressed and then they were isothermally sintered at 3 different temperatures for 1-60 hours. The biggest coarsening was discovered during temperature increase to sintering temperature. The dwelt at sintering temperature was not so important for coarsening. The activation energy of grain growth QG, growth exponent n and kinetic constant k0 were discovered for four materials. The activation energy of grain growth was 511±49 kJ/mol for tetragonal ZrO2, 645±84 kJ/mol for cubic ZrO2 a 428±75 kJ/mol a 606±24 kJ/mol for Al2O3. Possibility of kinetic window of sintering process for cubic ZrO2, tetragonal ZrO2, and Al2O3 with particle size 240 nm (doped MgO) were discovered by comparison of established activation energy of grain growth QG with activation energy of sintering QS from literature. Kinetic window of sintering process wasn’t found for high purity alumina with particle size 100 nm.
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