National Repository of Grey Literature 94 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
In-situ Synthesised Intermetallic Compounds in Powder Materials
Hanusová, Petra ; Novák, Pavel (referee) ; Skotnicová, Kateřina (referee) ; Dlouhý, Ivo (advisor)
The mechanical treatment of solids is one of the most common and widely used operations. The volume of solids subjected to chemical treatment is very large too. Therefore, combining these two ways into one seems to be a logical solution. This method is called the mechanochemical processing of materials. Processing materials in this way has many advantages. On the one hand, this processing is economically as well as technologically feasible. Even the materials that not react together in conventional way can be prepare in this way. The mechanochemistry/mechanochemical synthesis utilizes the mechanical energy to activate chemical reactions and structural changes. The aluminothermic reduction reactions induced by the high – energy ball milling are gaining importance because of the potential applications like the synthesis of microcrystalline and nanocrystalline in – situ metal matrix composites. The mechanical activation of the chemical reactions by high energy ball milling often changes the reaction mechanism and produces metastable materials. Changes of reaction mechanisms during mechanical alloying on four different systems were studied. The system was based on this composition: Al - B2O3 - X (X = C, Ti, Nb, Cr). The possibility of another in – situ reactions during spark plasma sintering process (SPS) was also investigated. All systems were mechanically alloyed under the same conditions. After alloying, on each system scanning electron microscopy was performed and qualitative and quantitative analysis was performed using X-ray diffraction. The indentation hardness and the indentation modulus of elasticity were evaluated using nanoindentation. All analyzes were performed after mechanical alloying as well as SPS and the results were compared to each other. Based on the results, a change of reaction mechanisms was proposed for all systems. It has been found that metal matrix composites are formed and, when chromium is used, hybrid composite material reinforced with intermetallic phase and aluminum borate has been developed.
Czech-British cultural standards: comparison of work and business relations
Bajerová, Kamila ; Křečková Kroupová, Zuzana (advisor) ; Novák, Pavel (referee)
The aim of this thesis is to identify and evaluate cultural standards at workplace and business environment from perspective of Czechs who live or lived in Great Britain or are in long-term work or business relationship with British. The theoretical part deals with culture theory, cultural dimensions and fields of intercultural cooperation. The practical part gives basic socio-economical and historical analysis of Great Britain. The research is conducted according to cultural standards identification method, specifically by in-depth interviews. Cultural standard findings are analyzed on theoretical basis and on socio-economic and historical context of Great Britain. Last, the author gives recommendation to Czechs who plan to work or trade with British.
Microstructure and mechanical properties of lightweight structural AZ31 alloy prepared by twin-roll casting method.
Zimina, Mariia ; Cieslar, Miroslav (advisor) ; Málek, Jaroslav (referee) ; Novák, Pavel (referee)
Title: Microstructure and mechanical properties of lightweight structural AZ31 alloy prepared by twin-roll casting method Author: Mariia Zimina Abstract: Microstructure of AZ31 twin-roll cast magnesium alloy was studied using light optical, electron and atomic force microscopy. The effect of annealing temperature on the microstructure was tested. Mechanical properties of a thin magnesium strip were investigated by means of microhardness tests and tensile tests at a relatively low strain rate 10-3 s-1 . Results show that the ductility of the twin roll cast strip increases with increasing deformation temperature, however, a remarkable decrease was observed at about 200 řC. This effect appears also in a conventionally cast ingot of a master alloy and is caused by a change of a deformation mode occurring at this temperature. Moreover, the effect of severe plastic deformation on the microstructure and mechanical properties was studied. Equal channel angular pressing was applied on magnesium strip samples and lead to a significant grain refinement accompanied by an unfavorable strengthening of the initial basal texture, which is effectively suppressed by a subsequent annealing. A constrained groove pressing was for the first time successfully applied on AZ31 twin-roll cast strip leading to an increase of...
Fabrication, heat treatment and characterization of thin layer NiTi alloys
Svatuška, Michal ; Vokoun, David (advisor) ; Dlouhý, Antonín (referee) ; Novák, Pavel (referee)
NiTi alloys with nearly equiatomic chemical composition are the most studied and the most practically utilized materials from the group of the shape memory alloys (SMA). The NiTi alloy has a thermoelastic martensitic transfor- mation (MT), which its two most important properties are based on: the shape memory and the superelasticity. Thin films of NiTi alloys with thicknesses from hundreds of nm to units of µm have a wide use mainly in microelectromechanical systems (MEMS). The doctoral thesis deals with a fabrication of thin NiTi films using a deposition on silicon substrates with two techniques - the magnetron sputtering and the pulsed-laser deposition (PLD), an investigation of their mi- crostructure using x-ray diffraction, a heat treatment of amorphous NiTi films and with a verification of MT using resistometry. Furthermore, thermomechan- ical properties of a system NiTi-polyimide (NiTi-PI), namely a dependence of a curvature radius of a NiTi-PI bilayer on temperature, are studied. 1
Nanoscale AFM and TEM observations of elementary dislocation mechanisms
Veselý, Jozef ; Cieslar, Miroslav (advisor) ; Dlouhý, Antonín (referee) ; Novák, Pavel (referee)
Single crystals of iron with 20, 28 and 40 at. % aluminium were deformed in compression at room temperature. The later two alloys were deformed also at temperatures in the range of yield stress anomaly. Room temperature deformation was carried under the atomic force microscope (AFM) and the evolution of surface was recorded in-situ. Samples deformed at elevated temperatures were investigated by AFM after the deformation. Dislocation structures in deformed samples were then investigated in transmission electron microscope (TEM). Observations of surface (AFM) and bulk (TEM) are compared. Results of both techniques mutually agree and support the interpretation of observed phenomena. Several original analysis methods were developed. Most notably the stereographic reconstruction, which was applied to dislocation structures and carbide particles present in investigated alloys. Model explaining the distribution of carbide particle axes is presented. Powered by TCPDF (www.tcpdf.org)
Forward and Inverse Modeling of Planetary Gravity and Topography
Pauer, Martin ; Čadek, Ondřej (advisor) ; Martinec, Zdeněk (referee) ; Novák, Pavel (referee)
Title: Forward and Inverse Modeling of Planetary Gravity and Topography Author: Martin Pauer Department/Institute: Department of Geophysics MFF UK Supervisor of the doctoral thesis: Doc. RNDr. Ondřej Čadek, CSc., Department of Geophysics MFF UK Abstract: The aim of this work was to investigate various mechanisms compensating the observed planetary topography - crustal isostasy, elastic support and dynamic support caused by mantle flow. The investigated models were applied to three different planetary problems. Firstly we applied dynamic compensation model to explain today large-scale gravity and topography fields of Venus and investigate its mantle viscosity structure. The results seem to support not only models with constant viscosity structure but also a model with a stiff lithosphere and a gradual increase of viscosity toward a core. In the second paper several crust compensation models were employed to estimate the density of the Martian southern highlands crust. Since the used methods depends differently on crustal density changes, we were able to provide some constraints on the maximum density of the studied region. In the third application, the strength of a possible ocean floor gravity signal of Jupiter's moon Europa was studied. It turned out that if the long wavelength topography reaches height at...
Low-field excitations in magnetite
Švindrych, Zdeněk ; Janů, Zdeněk (advisor) ; Novák, Pavel (referee) ; Svoboda, Pavel (referee)
We have performed detailed measurements of magnetic and dielectric properties of high quality magnetite (Fe3O4) single crystals in weak magnetic and electric fields. These measurements can reveal details of phase transitions and other features that are not yet fully understood. We focused not only at the Verwey transition - a well known phase transition taking place at about 120 K in stoichiometric samples - but we also explored and described new relaxation effects in magnetite at low temperatures. The low-temperature properties were also found to be exceptionally sensitive to sample quality, stoichiometry and homogeneity. The results presented in this thesis were acquired on sensitive non-commercial SQUID magnetometer complemented by four-probe dielectric spectroscopy and dc conductivity measurements.

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