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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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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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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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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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