National Repository of Grey Literature 13 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Influence of Water-Ethanol-Modified Supercritical Carbon Dioxide at the Preparation of Crystalline Monolithic TiO2 Aerogels.
Cerhová, Marie ; Sajfrtová, Marie ; Matějová, L. ; Dřínek, Vladislav ; Daniš, S. ; Jandová, Věra
This work is focused on a study of TiO2 aerogel SFC with scCO2 modified by mixture of ethanol and water in a ratio 1:1. The effect of temperature (40-100 °C), pressure (10-30 MPa) and modifie concentration in scCO2 (5-15 wt.%) and the additional drying with pure CO2 on microstructure, purity and textural properties of TiO2 aerogel was investigated. Processed monoliths were characterized by XRD analysis, Raman spectroscopy and N2 physisorption.
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Non-Thermal Crystallization of TiO2 Thin Films using Supercritical Carbon Dioxide Modified by Ethanol-Water Mixture.
Sajfrtová, Marie ; Cerhová, Marie ; Jandová, Věra ; Dřínek, Vladislav ; Matějová, L. ; Daniš, S.
In this work, the scCO2 modified by mixture of water and ethanol was used for a preparation of crystalline and pure nanostructured TiO2 thin films in one step processing. All the experiments were performed over precursor titania thin films prepared by reverse micelles assisted sol-gel method, using hardly removable nonionic surfactant Triton X-114, however, forming uniform nano-domains. The effect of temperature (40-150 °C), pressure (10-30 MPa), modifier composition \n(20, 50 and 80 % w/w of water in ethanol) and concentration inscCO2 (5-15 wt. %) and consumed amount of solvent (50-200 g) on microstructure and purity\nof TiO2 thin films was thoroughly studied by means of Raman spectroscopy, X-ray diffraction, and contact angle measurements.
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Determination of the amount of the amorphous phase using x-ray diffraction
Málek, Tomáš ; Daniš, Stanislav (advisor) ; Kužel, Radomír (referee)
Using quantitative analysis based on x-ray diffraction entails complication in the amorphous phase contribution to signal background which may affect results. Often it is impossible to ignore this contribution and thus is appropriately to use some method for separation of the amorphous phase contribution from signal eventually also determine amount of amorphous phase in the sample. Although x-ray diffraction is used for crystalline samples is almost inevitable keep sample clear from amorphous phase which is in all polycrystalline sample in some amount. In this thesis we will effort to determine method or combination of methods which is possible to use for determination of the amount of the amorphous phase that we can use for cleaning results of quantitative analysis from the amorphous phase contribution.
Structural changes in intermetallic compounds
Doležal, Petr ; Prchal, Jiří (advisor) ; Daniš, Stanislav (referee)
This diploma thesis is focused on the study of the structural phase transitions in intermetallic compounds LaPd2(Al,Ga)2 by low-temperature x-ray powder diffraction and macroscopic measurements on single crystals. The results obtained from powder diffraction at room temperature confirm that the compounds crystallize in tetragonal CaBe2Ge2 structure type (space group P4/nmm). At low temperature all the compounds undergo the same structural phase transition by lowering the symmetry to the orthorhombic space group Cmma. Although the structural transformation is of first order, the transition is not-manifested in step-like change of the phase at a certain temperature, but occurs in a broader temperature interval. In this interval the different phases coexist and transform gradually from high- to low- temperature phase. After application of hydrostatic pressure the structural transition is shifted to higher temperatures. Despite that the low temperature structures are of the same type, there is a difference between compounds containing Ga and Al in the discontinuity of the lattice parameters resulting in a distinct anomaly in electrical resistivity. In pressures >0.6 GPa this characteristic anomaly on single crystalline CePd2Al2 is changed, indicating a pressure- induced change of the low-temperature...
Diffusion x-ray reflection from rough multilayers
Cejpek, Petr ; Holý, Václav (advisor) ; Daniš, Stanislav (referee)
This bachelor work follows with the theory of diffusion x-ray scattering from rough multilayers. In the first chapter we will recap some basic principles - statitistic properties of interfaces, Fresnell coefficients, scattering theory, etc. - this stuff we will use to derive the expressions for specular reflection and diffusion scattering from rough interfaces, which we will consider as the random fractals. We will demonstrate the use of these derived expressions at a measurement on the multilayers coumpounded from and layers and substrate of mineral glass. Fitting of the measured data on the derived expressions will be done with Matlab software. Moreover, we will measure the roughness of interfaces with AFM microscope and we will compare these two measuring metodes. 2SiO 2ZrO
X-ray investigation of defects in graded SiGe/Si thin layers
Endres, Jan ; Daniš, Stanislav (advisor) ; Holý, Václav (referee)
The goal of presented work is a study of defects in graded Si1xGex/Si thin layers. Misfit dislocations are dominant type of defects in this kind of layers. Diffuse scattering of radiation, which is caused by the presence of defects, was measured with high-resolution diffractometer. Misfit dislocations arrangement in the layers was determined from measured reciprocal space maps. Misfit dislocations distribution is discussed within the scope of two models. Equilibrium one, which is based on energy minimization, and kinetic one, which considers thermally activated movement of dislocations. Measured reciprocal space maps were compared with simulations, which were realized via kinematic theory of X-ray radiation scattering.

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