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The effect of modification of cermic surface on the sintering of advanced ceramic materials
Vykydal, Adam ; Spusta, Tomáš (referee) ; Pouchlý, Václav (advisor)
This thesis is focused on the effect of modification of ceramic surface on the sintering of the advanced ceramic materials. To modify the surface of ceramic materiál was used method atomic layer deposition. For the research we used materiál TiO2 and materiál TiO2, which was modified using gas in an ALD chamber. To determine the appropriate sintering temperature we used high-temperature dilatometry, where we found that the sintering temperature is about 800 °C. Moreover, the coefficient of thermal expansion (CTE) was determined using subsequent calculation with the data of shrinkage from sintering densification curve. The samples were placed in a kiln where they were sintered on the mentioned temperature on four different dwell times to find effective dwell time for the best value of density of material. Using a scanning electron microscope, the surface-modified material was found to have a uniform structure when sintered to 800 ° C. At a sintering temperature of 1500 ° C, it can be observed that the ZrO2 did not remain only at the grain boundaries, but is more or less evenly distributed. The core-shell structure was not preserved in the structure, however ZrO2 was agglomerated into particles and in the vicinity of these particles titanium dioxide and zirconia react according to the phase diagram. Based on the diagram, it can be stated that this is the ZrTiO4 phase. The occurrence and size of this pase can be verified by RTG analysis.
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Sintering of Advanced Ceramic Materials
Pouchlý, Václav ; Svoboda, Jiří (referee) ; Ptáček, Petr (referee) ; Maca, Karel (advisor)
Sintering is a one of the key step in a processing of bulk ceramic materials. New sintering methods were invented in the last years. These new sintering methods, according to their authors, can be used for obtaining finer final microstructure of ceramics only by modifying the heating schedule. This work is focused on an influence of the Two Step Sintering method on the final microstructure for oxide ceramics. Obtained experimental results have shown that the effectivity of the Two Step Sintering method is rising with crystallographic symmetry of used material. Thesis is also focused on a high-temperature dilatometry and concept of the Master Sintering Curve. This concept was used for calculation of the activation energy of sintering and finding different sintering mechanisms acting in the intermediate and final stage of sintering. Activation energy of sintering was compared with activation energy of grain growth with target to find the kinetic window. Kinetic window can allow a sintering without a grain growth. Master Sintering Curve method was also used in a pressure assisted unconventional sintering technique Spark Plasma Sintering. Master Sintering Curve applied to a Spark Plasma Sintering technique reveals and quantified different sintering mechanisms acting in Spark Plasma Sintering. These findings led to preparation of transparent tetragonal ZrO2.
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The effect of modification of cermic surface on the sintering of advanced ceramic materials
Vykydal, Adam ; Spusta, Tomáš (referee) ; Pouchlý, Václav (advisor)
This thesis is focused on the effect of modification of ceramic surface on the sintering of the advanced ceramic materials. To modify the surface of ceramic materiál was used method atomic layer deposition. For the research we used materiál TiO2 and materiál TiO2, which was modified using gas in an ALD chamber. To determine the appropriate sintering temperature we used high-temperature dilatometry, where we found that the sintering temperature is about 800 °C. Moreover, the coefficient of thermal expansion (CTE) was determined using subsequent calculation with the data of shrinkage from sintering densification curve. The samples were placed in a kiln where they were sintered on the mentioned temperature on four different dwell times to find effective dwell time for the best value of density of material. Using a scanning electron microscope, the surface-modified material was found to have a uniform structure when sintered to 800 ° C. At a sintering temperature of 1500 ° C, it can be observed that the ZrO2 did not remain only at the grain boundaries, but is more or less evenly distributed. The core-shell structure was not preserved in the structure, however ZrO2 was agglomerated into particles and in the vicinity of these particles titanium dioxide and zirconia react according to the phase diagram. Based on the diagram, it can be stated that this is the ZrTiO4 phase. The occurrence and size of this pase can be verified by RTG analysis.
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Sintering of Advanced Ceramic Materials
Pouchlý, Václav ; Svoboda, Jiří (referee) ; Ptáček, Petr (referee) ; Maca, Karel (advisor)
Sintering is a one of the key step in a processing of bulk ceramic materials. New sintering methods were invented in the last years. These new sintering methods, according to their authors, can be used for obtaining finer final microstructure of ceramics only by modifying the heating schedule. This work is focused on an influence of the Two Step Sintering method on the final microstructure for oxide ceramics. Obtained experimental results have shown that the effectivity of the Two Step Sintering method is rising with crystallographic symmetry of used material. Thesis is also focused on a high-temperature dilatometry and concept of the Master Sintering Curve. This concept was used for calculation of the activation energy of sintering and finding different sintering mechanisms acting in the intermediate and final stage of sintering. Activation energy of sintering was compared with activation energy of grain growth with target to find the kinetic window. Kinetic window can allow a sintering without a grain growth. Master Sintering Curve method was also used in a pressure assisted unconventional sintering technique Spark Plasma Sintering. Master Sintering Curve applied to a Spark Plasma Sintering technique reveals and quantified different sintering mechanisms acting in Spark Plasma Sintering. These findings led to preparation of transparent tetragonal ZrO2.
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