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Ab initio study of phase stability of multicomponent alloys
Fikar, Ondřej ; Brož, Pavel (referee) ; Černý, Miroslav (referee) ; Zelený, Martin (advisor)
Ab initio methods are based on purely theoretical findings of quantum physics that can be used to predict among others physical, chemical and mechanical properties of materials. Due to rapid increase in accessibility of computational resources in the recent decades the theoretical prediction of material properties became an integral part of materials design. This work is focused on theoretical prediction of phase stability and solubility of solid solutions. Ab initio calculations based on Density Functional Theory were performed using Projector-Augmented Waves method and thermal dependencies of thermodynamic quantities were obtained using phonon calculations and Monte Carlo simulations. Attention is paid to alloys mainly based on aluminium, silver and magnesium, which were investigated in order to assess the reliability and precision of theoretical predictions of solubility in the solid state. Phase stability of solid solutions was evaluated multiple times including different energy contributions and using various methods in order to determine the influence of each contribution and method on the prediction accuracy. Calculated solubilities are compared with experimental data provided using the CALPHAD method.
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Materials of Tank Armour
Fikar, Ondřej ; Němec, Karel (referee) ; Molliková, Eva (advisor)
This bachelor’s thesis named „Materials of Tank Armour“ deals at first with anti-tank ammunition and its distribution, followed by a brief description of some tanks constructed in Great Britain, Germany and Russia and their impact on development of tank technology. In the next part the thesis describes armour, basic principles of its function and division of armours according to its purpose and chemical composition. In conclusion, particular examples of chemical composition of some armour materials are introduced.
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Computational prediction of solubility limits in solid solutions
Fikar, Ondřej ; Friák, Martin (referee) ; Zelený, Martin (advisor)
This diploma thesis is focused on a theoretical study of the phase stability of solid solutions in selected aluminium and silver alloys. The ab initio calculations were performed using projected augmented waves method and the thermal dependencies of thermodynamic quantities were acquired using phonon calculations. The main focus of this work is the of aluminium-germanium alloy, while the other examined alloys (Al-Pb, Ag-Ge and Ag-Pb) serve the purpose of comparison of the solid solubility prediction and its reliability in systems with different composition. The temperatures, at which the solid solutions become stable, were evaluated using the energy difference between possible states and this evaluation was carried out for different contributions to the total energy. Also the electronic and phonon densities of states were calculated for all pure elements and solid solutions. The temperatures of solubility were compared to the experimental ones provided by the CALPHAD method and the individual contributions to the total energy were determined and depicted. The results obtained in this work tend to underestimate temperatures of solubility of individual solid solutions by hundreds of Kelvin.
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Computational prediction of solubility limits in solid solutions
Fikar, Ondřej ; Friák, Martin (referee) ; Zelený, Martin (advisor)
This diploma thesis is focused on a theoretical study of the phase stability of solid solutions in selected aluminium and silver alloys. The ab initio calculations were performed using projected augmented waves method and the thermal dependencies of thermodynamic quantities were acquired using phonon calculations. The main focus of this work is the of aluminium-germanium alloy, while the other examined alloys (Al-Pb, Ag-Ge and Ag-Pb) serve the purpose of comparison of the solid solubility prediction and its reliability in systems with different composition. The temperatures, at which the solid solutions become stable, were evaluated using the energy difference between possible states and this evaluation was carried out for different contributions to the total energy. Also the electronic and phonon densities of states were calculated for all pure elements and solid solutions. The temperatures of solubility were compared to the experimental ones provided by the CALPHAD method and the individual contributions to the total energy were determined and depicted. The results obtained in this work tend to underestimate temperatures of solubility of individual solid solutions by hundreds of Kelvin.
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Materials of Tank Armour
Fikar, Ondřej ; Němec, Karel (referee) ; Molliková, Eva (advisor)
This bachelor’s thesis named „Materials of Tank Armour“ deals at first with anti-tank ammunition and its distribution, followed by a brief description of some tanks constructed in Great Britain, Germany and Russia and their impact on development of tank technology. In the next part the thesis describes armour, basic principles of its function and division of armours according to its purpose and chemical composition. In conclusion, particular examples of chemical composition of some armour materials are introduced.
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