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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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Preparation and characterization of crystalline materials - salts of N-guanylglycinium and guanidinium
Skopalík, Jiří ; Matulková, Irena (advisor) ; Zákutná, Dominika (referee)
The scope of this bachelor thesis is the preparation and study of new salts, which can be obtained from systems N-guanylglycine - inorganic acid and guanidine - amidosulfuric acid, as new materials with potential for applications in nonlinear optics. Prepared crystalline salts of N-guanylglycinium - i.e. chloride, two hydrogenphosphites and sulfate dihydrate along with guanidinium amidosulfate were characterized by methods of vibrational spectroscopy (infrared and Raman) and X-ray diffraction (single crystal and powder methods). To estimate the nonlinear optical properties and for the interpretation of the vibrational manifestations of N-guanylglycinium cation, quantum-chemical calculations were performed. Finally, for two non-centrosymmetric N-guanylglycinium hydrogenphosphites, the efficiency of second harmonic generation was determined for powder samples.
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Synthesis and properties of transition metal carbides
Nedvědová Šolcová, Pavlína ; Tyrpekl, Václav (advisor) ; Zákutná, Dominika (referee)
This master thesis is a follow-up of my bachelor's project, where the goal was to prepare high entropy carbide (HEC), namely (Ti, Zr, Hf, Nb, Ta)C, by the sol-gel method followed by carbothermal reduction using spark plasma sintering facility (SPS). In this work, the first aim is to substitute SPS with ultra-fast high-temperature sintering (UHS) for the same HEC, (Ti, Zr, Hf, Nb, Ta)C. The advantages of UHS compared to SPS are a thousand times lower consumption of electricity and simpler set-up. The second aim is the adaptation of the synthesis for the preparation of HEC of different compositions, (Cr, Mn, Fe, Co, Ni)C. The third aim is the testing of the presented sol-gel technique on the production of borides, while the initial experiments were focused on boro- carbothermal reduction. Keywords: high entropy carbides, high entropy borides, transition metals, carbothermal reduction, high-temperature ceramics, sol-gel method
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Synthesis and Characterization of Perovskite Nanostructures
Hricov, Štefan ; Zákutná, Dominika (advisor) ; Kalbáčová Vejpravová, Jana (referee)
The present Bachelor's thesis is focused on the improvement of the hydrothermal condi- tions for BaTiO3 nanoparticles synthesis to obtain better morphology, narrow size distri- bution, and high purity of the prepared product. Particular emphasis is on the influence of different parameters in reaction, such as co-solvent, co-surfactant, the ratio between oleic acid to oleylamine, and ex-situ sodium oleate, on the resulting structure and morphology of BaTiO3 nanoparticles. The structural purity was examined with powder X-ray diffraction with Rietveld refinement to obtain and follow changes in lattice parameters and coherent domain sizes. Moreover, from the refinement of PXRD patterns, the rough estimate of a synthesis by-product (BaCO3) abundance was extracted. Furthermore, implementing the spherical harmonics function within the Rietveld refinement allowed us to access the average nanocrystallite shapes with direction-dependent crystallite sizes. The crystallite shapes and sizes were compared with the physical nanoparticle size obtained from trans- mission electron microscopy experiments. The thesis is completed with attenuated total reflectance Fourier-transform infrared spectroscopy spectra, which gave us insight into the attachment of the oleic acid at the nanoparticle surface. Keywords: BaTiO3,...
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Preparation of magnetic nanostructures of chromites and their characterization
Zákutná, Dominika ; Nižňanský, Daniel (advisor) ; Honecker, Dirk Olaf (referee)
The present Diploma thesis provides an original synthesis for the preparation magnetic cobalt chromite nanoparticles (CoCr2O4 NPs) well dispersed in non-polar solvents and extensive structural, morphological, phonon and magnetic characterization. Particular emphasis is on determination of the spiral magnetic structure in CoCr2O4 NPs prepared by various procedures such as hydrothermal synthesis and sol-gel method. CoCr2O4 NPs with diameters in the range of 3.0 - 4.1 nm are prepared by high temperature hydrothermal method. For the first time, the CoCr2O4 NPs are stable in non-polar solvents and they are prepared by one-step synthesis without post treatment. The structure of prepared NPs is refined by Rietveld analysis. Size of prepared NPs is determined and compared using various techniques as powder X-ray diffraction (PXRD), transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). Magnetic measurements reveal the transition from superparamagnetic (SPM) state to super spin glass - like (SSG) state. From a.c. susceptibility measurements, the spin dynamics studies and strength of inter-particles interaction are investigated. CoCr2O4 NPs with mean diameter of 26.9(1) nm are prepared by sol-gel method. The magnetization measurements reveal the transition from superparamagnetic to...
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Příprava a vlastnosti nanočástic chromitů
Zákutná, Dominika ; Nižňanský, Daniel (advisor) ; Němec, Ivan (referee)
Title: Preparation and Characterization of Chromites nanoparticles Author: Dominika Zákutná Department: Department of Inorganic Chemistry, Faculty of Science, Charles University of Prague Supervisor: RNDr. Daniel Nižňanský, Ph.D. Consultant: RNDr. Jana Vejpravová, Ph.D. Supervisor`s e-mail address: niznansk@natur.cuni.cz Abstract: This work concerns the hydrothermal preparation of cobalt chromite nanoparticles (CoCr2O4), their characterization and the study of their magnetic properties. The preparation is based on the chlorides in the water-ethanol-oleic acid system. The samples were characterized by Powder X-ray Diffraction (PXRD), Transmission and High Resolution Electron Microscopy (TEM, HRTEM), Scanning Electron Microscopy (SEM), Raman and Infrared Spectroscopy and magnetic measurements of magnetization as a function of temperature and field. It was found, that furcation temperature, Tf depends on particle size. Keywords: CoCr2O4, superspin-glass like system, hydrothermal method, magnetic properties, oleates
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