National Repository of Grey Literature 10 records found  Search took 0.01 seconds. 
Preparation of nanocrystalline ceramic materials made from zirconia oxide
Vlček, Ondřej ; Prajzler, Vladimír (referee) ; Šťastný, Přemysl (advisor)
Bachelor thesis is focused on preparation of nanocrystalline stabilized zirconia ceramics. The theoretical part is dedicated to zirconia ceramics. Theoretical part describes and unveil the transformation-induced toughening mechanism in partially stabilized zirconia ceramics, the processing routes of these ceramic materials and their utilization. The research part describes preparation of yttria partially stabilized nanocrystalline zirconia ceramics by slip casting method.
The intrinsic submicron ZnO thin films prepared by reactive magnetron sputtering
Remeš, Zdeněk ; Stuchlík, Jiří ; Purkrt, Adam ; Chang, Yu-Ying ; Jirásek, Vít ; Štenclová, Pavla ; Prajzler, V. ; Nekvindová, P.
The DC reactive magnetron sputtering of metallic target in oxide atmosphere is a simple method of depositing the intrinsic (undoped) nanocrystalline layers of metal oxides. We have optimized the deposition of the intrinsic ZnO thin films with submicron thickness 50-500 nm on fused silica glass substrates and investigated the localized defect states below the optical absorption edge down to 0.01 % using photothermal deflection spectroscopy from UV to IR. We have shown that the defect density, the optical absorptance and the related optical attenuation in planar waveguides can be significantly reduced by annealing in air at 400 °C.
The microstructure evaluation of advanced oxide ceramics during fast sintering
Prajzler, Vladimír ; Chlup, Zdeněk (referee) ; Maca, Karel (advisor)
The diploma thesis deals with influence of fast pressure-less sintering on the microstructure of advanced ceramic materials, namely -Al2O3 and tetragonal ZrO2 (doped by 3 mol% Y2O3) with particle sizes ranging from 60 nm to 270 nm. Fast and controlled heating rate was enabled by utilization of the special superkanthal furnace with moving sample holder. Defect-free bulk and dense samples were prepared using heating rates in order of 100-200 °C/min. Higher densities reached the samples pressed by higher pressures; the specimens with densities higher than 99 % t.d. were prepared within tens of minutes for alumina as well as for zirconia with very low thermal conductivity. Different behavior was observed only for material TZ-3Y, which exhibited core-shell structure with dense surface and porous centre after sintering at heating rates higher than 10 °C/min. It was shown in this work that such behavior was not primarily caused by the high thermal gradient resulting from high heating rates. Its creation was probably caused by chlorine impurities. The mechanism of desintering of these samples was described and eliminated by calcination of the samples at 1000 °C for 10 hours prior to fast sintering at 1500 °C, so even this material could be fast sintered up to 99.9 % theoretical density.
Calculations of nanocrystalline diamond-covered waveguides based on amorphous silicon
Jirásek, Vít ; Prajzler, Václav ; Remeš, Zdeněk
Nanocrystalline diamond (NCD) coatings on planar waveguides (WG) in the IR region allow to design optical sensors sensitive to absorbers like proteins or other biomolecules. In this contribution, we present a 2D model of a multi-layer WG developed under FEM (finite element method) simulation software Comsol Multiphysics. The model is based on the modified wave equation solved in the frequency domain and includes optical absorption. It was found that for the single-mode WG working in the narrow region of 1550-2000 nm the silicon thickness must be 150-320 nm. It was found that in order to keep a reasonable signal attenuation, the NCD film must be prepared with the optical absorption coefficient lower than 10 cm-1, being a rather challenging task. Dependencies of the signal attenuation on the NCD film thickness, absorbing layer height, its absorption coefficient and exciting wavelengths are presented.\n
Fast sintering of advanced ceramic materials
Prajzler, Vladimír ; Salamon, David (referee) ; Maca, Karel (advisor)
The bachelor thesis is dealing with fast sintering of advanced ceramic materials, such as tetragonal zirconia and alumina in conventional resistance furnace. This approach is made possible by special superkanthal furnace, which is capable to reach a heating rate of 200 °C/min. Samples obtained through fast sintering reached relative density higher than 93% for zirkonia and 97% for alumina, without forming any cracks in samples. Achieved relative density in the case of tetragonal zirconia was higher for samples with larger pores in the green body. This behavior is different of conventional sintering and leads to considerations of heat transfer mainly by radiation.
Výzkum postupu pro přípravu aktivních a pasivních vlnovodů v polovodičích
Prajzler, V. ; Špirková, J. ; Oswald, J. ; Peřina, Vratislav ; Hüttel, I. ; Hamáček, J. ; Machovič, V. ; Burian, Z.
The magnetron sputtering was used to fabricate RE doped GaN layers fabricated by magnetron sputtering on various substrate using a gaseous mixture of nitrogen and argon as precursors. The doping of the GaN films with RE occurred simultaneously with the sputtering process when placing the metal RE pellets or RE powder onto the Ga2O3 target. The amount of the incorporated erbium increased with increasing weight of the RE pellets or RE powder. We observed photoluminescence emission at 1 550 nm due to the 4I13/2 → 4I15/2 transition under excitation at 488 nm and 980 nm.
Magnetron Sputtering in Microwave and Optical Technology
Prajzler, V. ; Schröfel, J. ; Hüttel, I. ; Špirková, J. ; Machovič, V. ; Oswald, J. ; Studnička, V. ; Novotná, M. ; Peřina, Vratislav
The paper describes the preparation and properties of gallium nitride layers with erbium content.
Uhlíkové planární vlnovody pro integrovanou optiku
Prajzler, V. ; Hüttel, I. ; Špirková, J. ; Schröfel, J. ; Machovič, V. ; Gurovič, J. ; Peřina, Vratislav
The paper describes the fabrication of carbon layers and their potential usage for integrated optics.
Galium-nitridové vrstvy dopované erbiem
Prajzler, V. ; Hüttel, I. ; Špirková, J. ; Schröfel, J. ; Machovič, V. ; Peřina, Vratislav
The paper describes the preparation and properties of gallium nitride layers with erbiu content.

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2 Prajzler, Vladimír
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