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Study of microstructure and real structure of nanoparticles prepared by gas aggregation cluster source
Košutová, Tereza ; Dopita, Milan (advisor) ; Rohlíček, Jan (referee) ; Zákutná, Dominika (referee)
The scope of this work is the characterization of nanoparticles prepared by aggregation from the gas phase. The main focus is on their microstructure and real structure investigated by x-ray scattering methods, although combined with complementary methods such as electron microscopies and optical measurement. The microstructural characteristics, i.e. nanoparticle morphology and crystal and inner structure, were found to be tightly connected with the deposition parameters. For chosen systems, we also analysed the nanoparticle thermal or temporal stability and evolution. Multiple gas aggregation deposition systems were used for the preparation of nanoparticles consisting of different materials. In detail, we studied single-metal nanoparticles - gold, silver and copper. For these, the behaviour with increasing temperature changes with the type of material and also its amount on the substrate. However, in general, the annealing of nanoparticles reduces the amount of structural defects in the crystal structure and causes the coalescence of nanoparticles. In the case of the copper nanoparticles, the coalescence is limited due to the nanoparticle oxidation in the air atmosphere. Similarly, in another system composed of niobium nanoparticles, we observed and described the gradual oxidation during annealing. On the...
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Microstructure and properties of multiferroic complex oxide thin films prepared by pulsed laser deposition method
Machovec, Petr ; Dopita, Milan (advisor)
Title: Microstructure and properties of multiferroic complex oxide thin films prepared by pulsed laser deposition method Author: Petr Machovec Department: Department of Condensed Matter Physics Supervisor: RNDr. Milan Dopita, Ph.D., Department of Condensed Matter Physics Abstract: In the frame of this thesis, structure, microstructure, and real structure of multiferroic epitaxial layers of LuFeO3 were studied by means of X-ray reflectivity and X-ray diffraction. In theoretical part the theory of X-ray scattering on crystalline layers is described. Standard description of X-ray reflectivity on series of rough layers is presented. Moreover, a model of X-ray scattering on mosaic layer is described. For experimental part of the work three samples were prepared by pulsed laser deposition method. First sample on sapphire substrate (Al2O3), second on platinum layer deposited on sapphire substrate and third on yttrium stabilized zirconia substrate. From the X-ray reflectivity curves the parameters such as layer thickness, interface roughness, surface roughness and material density, were determined. By analysing measured reciprocal space maps, lattice parameters and mosaic model parameters, such as mean mosaic block size, mosaic block size distribution, mosaic block misorientation and residual microstrain, were...
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V-pit Defects in InGaN/GaN Studied by X-ray Diffraction
Stránská Matějová, Jana ; Holý, Václav (advisor) ; Dopita, Milan (referee) ; Rafaja, David (referee)
V-pit defects in InGaN/GaN heterostructures were studied by high-resolution x-ray diffraction accompanied by numerical simulations. The work is focused on the role of the V-pits in strain relaxation, on their impact on the appearance of the x-ray reciprocal- space maps and on their relation to the threading dislocations. Analysis of the diffuse part of the diffracted intensity by kinematical scattering theory, together with principal strains and their directions in the vicinity of the V-pit, explains why the lateral position of the InGaN peak is not affected by the V-pits presence. The strain relaxation by V-pit formation was confirmed, while plastic relaxation by misfit dislocations was not observed. The density of the V-pits in the epilayer turned out to be given by the content of threading dislocation with a screw component in the substrate. Pure edge threading dislocations do not affect the V-pit density. The In concentration has an influence on the size of the V-pits, but not their density. 1
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Study of indium doped shape-memory alloy Ni2MnGa
Cejpek, Petr ; Dopita, Milan (advisor) ; Dobročka, Edmund (referee) ; Mikulík, Petr (referee)
Title: Study of indium doped shape-memory alloy Ni2MnGa Author: Petr Cejpek Department: Department of Condensed Matter Physics Supervisor: RNDr. Milan Dopita, PhD., Department of Condensed Matter Physics Abstract: The alloys related to Ni-Mn-Ga system exhibit effects connected to the magnetic shape-memory and martensitic transformation and therefore attract attention of researchers for their application potential. Properties and especially transformation temperatures are strongly dependent on composition, doping and also on external conditions as a magnetic field or pressure. The main aim of the work was to prepare own single crystals of Ni2MnGa1−xInx and to study their properties with respect to the temperature and applied fields in dependence on a various indium doping. The transformation temperatures obtained from the measurement of electrical resistivity and magnetisation re- vealed the systematic decrease of martensitic transformation temperature TM , pre-martensitic transformation temperature TP and Curie temperature TC. The martensitic transformation should vanish at indium concentration of x ≈ 0.10. The decrease with indium content is much faster than in the study published previously on the polycrystalline samples (vanishing at x ≈ 0.20). This dis- crepancy is probably caused by the residual stress...
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Microstructure and properties of multiferroic complex oxide thin films prepared by pulsed laser deposition method
Machovec, Petr ; Dopita, Milan (advisor) ; Kužel, Radomír (referee)
Title: Microstructure and properties of multiferroic complex oxide thin films prepared by pulsed laser deposition method Author: Petr Machovec Department: Department of Condensed Matter Physics Supervisor: RNDr. Milan Dopita, Ph.D., Department of Condensed Matter Physics Abstract: In the frame of this thesis, structure, microstructure, and real structure of multiferroic epitaxial layers of LuFeO3 were studied by means of X-ray reflectivity and X-ray diffraction. In theoretical part the theory of X-ray scattering on crystalline layers is described. Standard description of X-ray reflectivity on series of rough layers is presented. Moreover, a model of X-ray scattering on mosaic layer is described. For experimental part of the work three samples were prepared by pulsed laser deposition method. First sample on sapphire substrate (Al2O3), second on platinum layer deposited on sapphire substrate and third on yttrium stabilized zirconia substrate. From the X-ray reflectivity curves the parameters such as layer thickness, interface roughness, surface roughness and material density, were determined. By analysing measured reciprocal space maps, lattice parameters and mosaic model parameters, such as mean mosaic block size, mosaic block size distribution, mosaic block misorientation and residual microstrain, were...
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Microstructure and Properties of Nanocrystalline Hard Coatings and Thin Film Nanocomposites
Dopita, Milan
In this work, microstructure and properties of M-Al-(Si-)N nanocrystalline hard coatings and thin film nanocomposites deposited by cathodic arc evaporation (CAE) process at different positions of substrates in the deposition apparatus were investigated using the combination of electron probe microanalysis, X-ray diffraction, transmission electron microscopy with high resolution and hardness measurement. Six series of specimens that differed in the transition metal type (Cr, Ti and Zr) and in the amount of Si and Al were deposited using the CAE process in the deposition apparatus π-80 produced by Platit AG. The essential microstructural parameters; the chemical and phase composition, the residual stress, preferred orientation of crystallites, crystallite size and mutual disorientation of crystallites were determined in all coatings under study. The derived microstructural parameters were correlated with the hardness of coatings. Finally, the microstructural model of the nanocrystalline hard coatings and thin film nanocomposites formation was developed. Depending on the sample chemical composition, three regions with different phase compositions exist in the coatings. In the transition metal richest samples, a single fcc M1-x- yAlxSiyN phase exists in the coating. With increasing Al content,...
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Microstructure of carbon black nanomaterials studied by X-ray scattering
Machovec, Petr ; Dopita, Milan (advisor) ; Horák, Lukáš (referee)
Název práce: Studium mikrostruktury uhlíkových nanomateriálů pomocí rentgenové difrakce Autor: Petr Machovec Katedra: Katedra fyziky kondenzovaných látek Vedoucí bakalářské práce: RNDr. Milan Dopita, Ph.D., Katedra fyziky kondenzovaných látek Abstrakt: Předkládaná práce se zabývá studiem mikrostruktury, struktury a reálné struktury turbostratického uhlíku a uhlíkových nanotrubic pomocí metod rozptylu rentgenového záření. Klastry turbostratického uhlíku jsou popsány pomocí sady fyzikálních parametrů. Pomocí počítačových simulací je popsán vliv těchto parametrů na výslednou rozptylovou křivku. Dále je předkládán popis dvou typů uhlíkových nanotrubic a je popsán vliv typu a rozměrů uhlíkových nanotrubic na výslednou rozptylovou křivku. Pro experimentální část práce byla připravena série vzorků turbostratického uhlíku žíhaného při teplotách 300℃, 600℃, 800℃, 1000℃, 1200℃, 1400℃ a 1800℃. Pomocí maloúhlového rozptylu rentgenového záření byla určena velikost nanočástic a jejich rozdělení, velikost mikropórů, specifický povrch a dimenze povrchového fraktálu. Další fyzikální parametry jako velikosti a rozdělení velikostí klastrů La a Lc turbostratické uhlíku, mřížové parametry a a c a střední kvadratické výchylky atomů ve směru grafenových vrstev a ve směru kolmém byly určeny z širokoúhlových rentgenografických...
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Microstructure and Properties of Nanocrystalline Hard Coatings and Thin Film Nanocomposites
Dopita, Milan
In this work, microstructure and properties of M-Al-(Si-)N nanocrystalline hard coatings and thin film nanocomposites deposited by cathodic arc evaporation (CAE) process at different positions of substrates in the deposition apparatus were investigated using the combination of electron probe microanalysis, X-ray diffraction, transmission electron microscopy with high resolution and hardness measurement. Six series of specimens that differed in the transition metal type (Cr, Ti and Zr) and in the amount of Si and Al were deposited using the CAE process in the deposition apparatus π-80 produced by Platit AG. The essential microstructural parameters; the chemical and phase composition, the residual stress, preferred orientation of crystallites, crystallite size and mutual disorientation of crystallites were determined in all coatings under study. The derived microstructural parameters were correlated with the hardness of coatings. Finally, the microstructural model of the nanocrystalline hard coatings and thin film nanocomposites formation was developed. Depending on the sample chemical composition, three regions with different phase compositions exist in the coatings. In the transition metal richest samples, a single fcc M1-x- yAlxSiyN phase exists in the coating. With increasing Al content,...
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Microstructure and Properties of Nanocrystalline Hard Coatings and Thin Film Nanocomposites
Dopita, Milan ; Rafaja, David (advisor) ; Richter, Frank (referee) ; Šutta, Pavol (referee)
In this work, microstructure and properties of M-Al-(Si-)N nanocrystalline hard coatings and thin film nanocomposites deposited by cathodic arc evaporation (CAE) process at different positions of substrates in the deposition apparatus were investigated using the combination of electron probe microanalysis, X-ray diffraction, transmission electron microscopy with high resolution and hardness measurement. Six series of specimens that differed in the transition metal type (Cr, Ti and Zr) and in the amount of Si and Al were deposited using the CAE process in the deposition apparatus π-80 produced by Platit AG. The essential microstructural parameters; the chemical and phase composition, the residual stress, preferred orientation of crystallites, crystallite size and mutual disorientation of crystallites were determined in all coatings under study. The derived microstructural parameters were correlated with the hardness of coatings. Finally, the microstructural model of the nanocrystalline hard coatings and thin film nanocomposites formation was developed. Depending on the sample chemical composition, three regions with different phase compositions exist in the coatings. In the transition metal richest samples, a single fcc M1-x- yAlxSiyN phase exists in the coating. With increasing Al content,...
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