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Structural study of nanocrystalline titanium oxide films and their temperature stability
Chlanová, Lea ; Kužel, Radomír (advisor) ; Čapková, Pavla (referee) ; Ganev, Nikolaj (referee)
Title: Structural study of nanocrystalline titanium oxide films and their temperature stability Author: Lea Chlanová Department: Department of Condensed Matter Physics Supervisor: Prof. RNDr. Radomír Kužel, CSc., Department of Condensed Matter Physics Abstract: TiO2 thin films can exhibit photocatalytic activity and photoinduced su- perhydrophilicity depending on crystallinity, phase composition and mi- crostructure. These parameters were studied by X-ray diffraction (XRD) and reflectivity (XRR) for magnetron deposited films - nanocrystalline and amorphous, namely their temperature and time evolution. For nanocrystalline films, it was found that higher partial oxygen pressure during the deposition is beneficial. Small anatase crystallites were stable up to about 450 ◦ C. Depth-profiling XRD of some samples revealed that rutile phase was only present close to the substrate. For amorphous films it was found that the crystallization depends strongly on the film thickness and it is slower for very thin films. Evolution of the intensities of anatase diffraction peaks with annealing time could be described by a modified Avrami equation. XRD profile was relatively narrow from the very be- ginning of crystallization (at about 220 ◦ C), which indicated relatively larger crystallites (> 100 nm), and hence, nanocrystalline films...
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Iron Functionalized Nanoparticles of Titanium Dioxide
Volfová, Lenka ; Nižňanský, Daniel (advisor) ; Tabor, Edyta (referee)
Diploma thesis Iron Functionalized Nanoparticles of Titanium Dioxide Lenka Volfová 2017, ABSTRACT Iron-functionalized TiO2 were obtained by hydrolysis of aqueous solutions of titanyl sulfate with addition of ferric nitrate with ammonium hydroxide and the reaction filtered and washed with hydrogen peroxide. The colloid solutions thus prepared were lyophilized and the products were subsequently annealed at three different temperatures of 650 řC, 800 řC and 950 řC. The prepared doped materials were characterized by powder X-ray diffractometry, electron microscopy, infrared spectroscopy, Mössbauer spectroscopy, UV/VIS spectroscopy, thermogravimetric analysis and differential thermal analysis, and measurement of the specific surface area. Photocatalytic activity was determined by measuring of the decomposition of kinetics of 4-chlorophenol in an aqueous solution in the ultraviolet and visible area. For comparison of activity in the UV area and in the visible area were used a previously prepared highly photoactive specimen and standard TiO2 from Kronos, respectively. Keywords: Doped titanium dioxide, nanostructure, X-ray diffraction, electron microscopy, Mössbauer spectroscopy, suppression of photoactivity
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Investigation of defects in thin metallic films
Hruška, Petr ; Čížek, Jakub (advisor)
In the present work Mg films prepared by RF magnetron sputtering were studied. Variable energy positron annihilation spectroscopy (VEPAS) was employed for investigation of defects in the Mg films. VEPAS characterization was combined with scanning electron microscopy and X-ray diffraction in order to determine grain size, phase composition and texture. The effect of different deposition rate and deposition temperature, annealing, various substrates and film thickness on the structure and amount of defects present in the Mg films was examined. Defect studies by VEPAS showed that positrons in studied Mg films are trapped at misfit dislocations and at vacancy-like defects in grain boundaries and their density can be reduced by the deposition at elevated temperature. 1
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Studium defektů v tenkých kovových vrstvách
Hruška, Petr ; Čížek, Jakub (advisor) ; Bulíř, Jiří (referee)
In the present work Mg films prepared by RF magnetron sputtering were studied. Variable energy positron annihilation spectroscopy (VEPAS) was employed for investigation of defects in the Mg films. VEPAS characterization was combined with scanning electron microscopy and X-ray diffraction in order to determine grain size, phase composition and texture. The effect of different deposition rate and deposition temperature, annealing, various substrates and film thickness on the structure and amount of defects present in the Mg films was examined. Defect studies by VEPAS showed that positrons in studied Mg films are trapped at misfit dislocations and at vacancy-like defects in grain boundaries and their density can be reduced by the deposition at elevated temperature. 1
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Growth of single crystals and their basic characterization.
Hanzlíková, Kateřina ; Pospíšil, Jiří (advisor) ; Matěj, Zdeněk (referee)
Basic methods of single crystals growth have been studied in this bachelor thesis. The preparation of anatase and ruby single crystals has been realized by floating zone method in different compositions of the surrounding atmosphere. Crystallinity of prepared materials has been verified by Laue method. The same method has been used for orientation of the prepared single crystals along the principal crystallographic axes. The tetragonal structure of TiO2 has been proved by powder X-ray diffraction. The floating zone method has been found as a very suitable and effective method to grow anatase single crystals.
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Mineralogical analysis of historical paintings
Čermáková, Zdeňka ; Hradil, David (advisor) ; Kanický, Viktor (referee) ; Artioli, Gilberto (referee)
Historical painted works of art have a very complex inner structure. The period painting technique led to the execution of a ground layer followed by several layers of underpainting and a top paint layer, over which a layer of glaze has been applied to increase the resistance to external wear. Each of these colour layers is composed of a dye or a pigment (or their mixture) bound by organic binder. Throughout the history, pigments were commonly prepared from minerals, either extracted from natural deposits or created artificially. In these heterogeneous layers containing both inorganic and organic components, undesirable degradation changes either driven by processes taking place directly in the colour layer or influenced by external agents may occur. Mineralogical approach, which focuses primarily on the structure of studied pigments, helps in the clarification of the occurring processes, in the determination of conditions leading to degradation as well as in the identification of original/degradation phases. Furthermore, it can be profitably applied in the micro- analysis of mineral pigments present in tiny micro-samples obtained from works of art, contributes to the artwork's provenance/authorship studies and the determination of regional provenance of the employed mineral pigments. This Ph.D....
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Structure of submicrocrystalline materials studied by X-ray diffraction
Matěj, Zdeněk ; Kužel, Radomír (advisor) ; Lukáš, Petr (referee) ; Čerňanský, Marian (referee)
Structure of submicrocrystalline materials was investigated by X-ray powder diffraction, mainly by modelling of widths and shapes of diffraction profiles. The diffraction method was applied to colloid gold nanoparticles, copper samples deformed by equal channel angular pressing and titanium dioxide nanoparticles prepared by various chemical routes. Dislocations and twin faults were identified in the metallic samples from characteristic broadening of diffraction lines. Densities of lattice defects were estimated from the diffraction data. Possibilities and limits of the diffraction method for characterisation of a crystallite size distribution were tested on the titanium dioxide samples. Crystallites of size in the range 3-25 nm could be well characterised. The problems were encountered only for samples with extremely broad size dispersion. Diffraction methods and a computer program were developed and tested, which can be applied also for the analysis of thin films.
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Organic materials for molecular quantum bits
Tuček, Marek ; Bábor, Petr (referee) ; Čechal, Jan (advisor)
In this thesis we briefly outline the properties and utilization of metal phthalocyanines, the procedure of iron phthalocyanine thin film deposition on Si(100), the supplementary post-deposition analysis by XPS and the equipment used to measure X-ray reflectivity. Further we describe the theoretical description of physical background of X-ray diffraction on a crystal, the measurement of X-ray reflectivity and evaluation of acquired data, focusing on determination of the thin film thickness, identification of its crystal structure and lattice parameters. It has been found out that iron phthalocyanine thin films deposited on a substrate at room temperature grow as an alpha-phase in the shape of needles perpendicular to substrate surface, so the film thickness, due to high rougness of the film, can be only estimated with the help of Scherrer equation for long depositions. In the case of shorter depositions (and thus lower roughness) the Kiessig fringes method can be used. By the post-deposition annealing we were not able to induce a phase transition; at required temperatures all the material on the substrate evaporated. By a deposition on a substrate heated to 160°C we acquired considerably rough film with unclear crystalline phase.
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Investigation of Functional Properties of Thin NiTi Filaments for Applications in Smart Structures and Hybrid Textiles
Pilch, Jan ; Pokluda, Jaroslav (advisor)
PhD thesis focuses the field of textile application of modern functional materials, namely metallic shape memory alloys with unique thermomechanical properties deriving from martensitic transformation in solid state. Particularly, it deals with the development of a nonconventional thermomechanical treatment of thin NiTi filaments via Joule heating by electric current and related basic research involving thermomechanical testing and modeling of functional properties of the filaments, investigation of martensitic transformations and deformation processes in NiTi and investigation of the fast recovery and recrystallization processes in metals heated by short pulses of controlled electric power. The method was developed and called FTMT-EC. In contrast to conventional heat treatment of metallic filaments in environmental furnaces, this method allows for precise control of the raise of the filament temperature and filament stress during the fast heating (rate ~50 000 °C/s). As a consequence, it is possible to precisely control the progress of the fast recovery and recrystallization processes in heat treated filaments. In this way it is possible to prepare filaments with desired nanostructured microstructure and related functional properties. A prototype equipment for application of the method for heat treatment of continuous SMA filaments during respooling in textile processing was designed and built. Comparing to the conventional heat treatment of SMA filaments in tubular environmental furnaces, this approach is faster, saves energy and allows for preparation of filaments with special functional properties. International patent application was filed on the method. It is currently utilized in the research and development of smart textiles for medical applications.
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Investigation of Functional Properties of Thin NiTi Filaments for Applications in Smart Structures and Hybrid Textiles
Pilch, Jan ; Dlouhý, Antonín (referee) ; Heczko,, Oleg (referee) ; Pokluda, Jaroslav (advisor)
PhD thesis focuses the field of textile application of modern functional materials, namely metallic shape memory alloys with unique thermomechanical properties deriving from martensitic transformation in solid state. Particularly, it deals with the development of a nonconventional thermomechanical treatment of thin NiTi filaments via Joule heating by electric current and related basic research involving thermomechanical testing and modeling of functional properties of the filaments, investigation of martensitic transformations and deformation processes in NiTi and investigation of the fast recovery and recrystallization processes in metals heated by short pulses of controlled electric power. The method was developed and called FTMT-EC. In contrast to conventional heat treatment of metallic filaments in environmental furnaces, this method allows for precise control of the raise of the filament temperature and filament stress during the fast heating (rate ~50 000 °C/s). As a consequence, it is possible to precisely control the progress of the fast recovery and recrystallization processes in heat treated filaments. In this way it is possible to prepare filaments with desired nanostructured microstructure and related functional properties. A prototype equipment for application of the method for heat treatment of continuous SMA filaments during respooling in textile processing was designed and built. Comparing to the conventional heat treatment of SMA filaments in tubular environmental furnaces, this approach is faster, saves energy and allows for preparation of filaments with special functional properties. International patent application was filed on the method. It is currently utilized in the research and development of smart textiles for medical applications.
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