|
|
Processing and properties of transparent polycrystalline ceramic materials
Tásler, Jan ; Pouchlý, Václav (referee) ; Maca, Karel (advisor)
The presented diploma thesis is focused on the preparation and properties of transparent polycrystalline ceramic materials based on Al2O3. Theoretically, the most important technological aspects of the processing of these materials are presented. Detailed attention is given to transparent Al2O3 polycrystalline ceramics doped with rare earth elements. The influence of microstructural parameters on the optical properties (represented by RIT) is investigated on Al2O3 samples doped and codoped with dysprosium, terbium and chromium. A significant effect of the average grain size on the light transmittance of all samples is observed. The highest RIT = 55 % (measured by a laser beam with a wavelength of 632,8 nm) was achieved by an optimized preparation process for a sample doped with 0,05 at. % of dysprosium. For all samples photoluminescent properties are also analysed. The photoluminescent emission spectra correspond to the activation of doping elements. In case of the terbium and chromium codoped samples, the differences in the activation of individual dopants depending on different excitation wavelengths were demonstrated, resulting in different colour emissions for different excitation wavelengths.
|
|
|
Transparent polycrystalline ceramic materials with cubic lattice structure
Kučera, Jan ; Pouchlý, Václav (referee) ; Maca, Karel (advisor)
The presented work is focused on the study of the influence of preparation parameters on the optical properties of polycrystalline cubic ZrO2 (stabilized with 8 mol.% Y2O3). Furthermore, the work deals with the doping of c-ZrO2 with TiO2 and its effect on the luminescence properties of ZrO2. The examined samples were prepared by uniaxial pressing (10 MPa), followed by a cold isostatic pressing (300 and 700 MPa), pressureless sintering (1340–1380 °C, 10 min), and hot isostatic pressing (1200–1400 °C, 4 h, 200 MPa). In this work, it is shown that the optical properties are significantly affected by the temperature of the hot isostatic pressing, the thickness of the sample, and also by the wavelength of the incident light. A maximum real in-line transmission of 68.8 % was achieved, which is 90.5 % of the theoretical limit for c-ZrO2 at an incident radiation wavelength of 632.8 nm. A low-pressure infiltration method and a powder mixing method were used to prepare the doped ZrO2 ceramic sample. With doping, the maximum of the excitation spectrum shifted from 295 nm (4.20 eV) for the undoped ZrO2 to 320 nm (3.87 eV) for the doped samples. Doping led to an increase in emission intensity compared to a pure ZrO2 by up to 23 times. The maximum emission intensity at 545 nm wavelength was achieved for samples doped by infiltration method with a nominal 0.1 mol.% TiO2 content.
|
|
|
Preparation of large and complex-shaped ceramics parts
Prehradná, Jana ; Pouchlý, Václav (referee) ; Trunec, Martin (advisor)
This bachelor’s thesis deals with research of ceramic materials in field of material engineering. The first part deals with biomaterials, especially bioceramics, its types, properties and its usage. The second part of this thesis deals with transparent ceramics and the third part includes the procedure and method of gel casting. The experimental part is dedicated to production of large and complex shaped components - knee joint, spherical cover and discs with transparent properties. The method of gelcasting was used for samples preparation of this type. The task was not only to produce these samples, but also to find suitable surrounding conditions for the proper course of the entire production process.
|
|
|
Transparent polycrystalline ceramics for ballistic and high-temperature applications
Malík, Petr ; Pouchlý, Václav (referee) ; Trunec, Martin (advisor)
Alumina based transparent ceramic bodies were prepared within this diploma thesis by the gel casting process followed by presintering to closed porosity stage with subsequent hot isostatic pressing. The problematic drying of large bodies was solved by means of careful temperature and relative humidity control and by osmotic drying. Almost perfectly dense ceramics were achieved thanks to colloidal processing of TM-DAR and TM-UF ceramic powders providing a final structure with grain size of 381 nm, resp. 302 nm. High real in-line transmission of 72,3 % was achieved at wavelength of 632,8 nm and thickness of 0,8 mm. Among mechanical properties high values of hardness HV10 = 22,5 GPa, fracture toughness KIC = 3,99 MPam0,5, Young’s modulus E = 400 GPa a bending strength o = 494 MPa were achieved.
|
|
|
Ceramic materials based on spinel MgAl2O4 for optical applications
Rychnovský, Daniel ; Maca, Karel (referee) ; Drdlík, Daniel (advisor)
This diploma thesis deals with preparation of transparent ceramics based on spinel MgAl2O4 and effect of Cr3+, Tb3+ doping on optical properties. Preparation of samples was optimized using several ways to prepare non-defect ceramic samples with the highest relative density of green body. The final step of the processing included hot isostatic pressing resulting in transparent undoped and doped spinel ceramics. The highest values of RIT (real in- line transmittance) of undoped and doped samples were measured between 77–79 %. It was found by measuring photoluminescence properties of prepared samples that increasing concentration of Cr3+ resulted to higher peak intensities. The most intense emission peak was measured in red spectral area at wavelength of 685 nm. In the case of Tb3+-doped spinel, the maximum peak intensities were measured at concentration of 0.075 at. % and the most intense emission peak was measured in green spectral area at wavelength of 545 nm.
|
|
|
Transparent polycrystalline ceramic materials with cubic lattice structure
Kučera, Jan ; Pouchlý, Václav (referee) ; Maca, Karel (advisor)
The presented work is focused on the study of the influence of preparation parameters on the optical properties of polycrystalline cubic ZrO2 (stabilized with 8 mol.% Y2O3). Furthermore, the work deals with the doping of c-ZrO2 with TiO2 and its effect on the luminescence properties of ZrO2. The examined samples were prepared by uniaxial pressing (10 MPa), followed by a cold isostatic pressing (300 and 700 MPa), pressureless sintering (1340–1380 °C, 10 min), and hot isostatic pressing (1200–1400 °C, 4 h, 200 MPa). In this work, it is shown that the optical properties are significantly affected by the temperature of the hot isostatic pressing, the thickness of the sample, and also by the wavelength of the incident light. A maximum real in-line transmission of 68.8 % was achieved, which is 90.5 % of the theoretical limit for c-ZrO2 at an incident radiation wavelength of 632.8 nm. A low-pressure infiltration method and a powder mixing method were used to prepare the doped ZrO2 ceramic sample. With doping, the maximum of the excitation spectrum shifted from 295 nm (4.20 eV) for the undoped ZrO2 to 320 nm (3.87 eV) for the doped samples. Doping led to an increase in emission intensity compared to a pure ZrO2 by up to 23 times. The maximum emission intensity at 545 nm wavelength was achieved for samples doped by infiltration method with a nominal 0.1 mol.% TiO2 content.
|
|
|
Processing and properties of transparent polycrystalline ceramic materials
Tásler, Jan ; Pouchlý, Václav (referee) ; Maca, Karel (advisor)
The presented diploma thesis is focused on the preparation and properties of transparent polycrystalline ceramic materials based on Al2O3. Theoretically, the most important technological aspects of the processing of these materials are presented. Detailed attention is given to transparent Al2O3 polycrystalline ceramics doped with rare earth elements. The influence of microstructural parameters on the optical properties (represented by RIT) is investigated on Al2O3 samples doped and codoped with dysprosium, terbium and chromium. A significant effect of the average grain size on the light transmittance of all samples is observed. The highest RIT = 55 % (measured by a laser beam with a wavelength of 632,8 nm) was achieved by an optimized preparation process for a sample doped with 0,05 at. % of dysprosium. For all samples photoluminescent properties are also analysed. The photoluminescent emission spectra correspond to the activation of doping elements. In case of the terbium and chromium codoped samples, the differences in the activation of individual dopants depending on different excitation wavelengths were demonstrated, resulting in different colour emissions for different excitation wavelengths.
|
|
|
Transparent polycrystalline ceramics for ballistic and high-temperature applications
Malík, Petr ; Pouchlý, Václav (referee) ; Trunec, Martin (advisor)
Alumina based transparent ceramic bodies were prepared within this diploma thesis by the gel casting process followed by presintering to closed porosity stage with subsequent hot isostatic pressing. The problematic drying of large bodies was solved by means of careful temperature and relative humidity control and by osmotic drying. Almost perfectly dense ceramics were achieved thanks to colloidal processing of TM-DAR and TM-UF ceramic powders providing a final structure with grain size of 381 nm, resp. 302 nm. High real in-line transmission of 72,3 % was achieved at wavelength of 632,8 nm and thickness of 0,8 mm. Among mechanical properties high values of hardness HV10 = 22,5 GPa, fracture toughness KIC = 3,99 MPam0,5, Young’s modulus E = 400 GPa a bending strength o = 494 MPa were achieved.
|
|
|
Preparation of large and complex-shaped ceramics parts
Prehradná, Jana ; Pouchlý, Václav (referee) ; Trunec, Martin (advisor)
This bachelor’s thesis deals with research of ceramic materials in field of material engineering. The first part deals with biomaterials, especially bioceramics, its types, properties and its usage. The second part of this thesis deals with transparent ceramics and the third part includes the procedure and method of gel casting. The experimental part is dedicated to production of large and complex shaped components - knee joint, spherical cover and discs with transparent properties. The method of gelcasting was used for samples preparation of this type. The task was not only to produce these samples, but also to find suitable surrounding conditions for the proper course of the entire production process.
|
guest ::
