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Physico-chemical properties of oxamic and glyoxylic acids and their affinity to lanthanides
Zakharanka, Anastasiya ; Tyrpekl, Václav (advisor) ; Šubrt, Jan (referee)
This bachelor work focuses on studies of chosen aspects of the basic physicochemical properties of oxamic and glyoxylic acids and their affinity to lanthanides, cerium, and gadolinium taken as the representatives. Room temperature solubilities, pKa values, thermal and photochemical stability of the acids have been evaluated. The acids' affinity to lanthanide (III) ions in an aqueous solution has been studied using various conventional laboratory techniques and instrumental methods. Lanthanide oxalate decahydrates have been synthesized using heterogeneous and homogeneous precipitation routes and characterized using classical solid-state analytical techniques. Keywords: oxalic acid precipitation, oxamic acid, oxamates, oxalates, glyoxylic acid, f-block metals chemistry
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Nonconventional synthesis of high entropy carbides
Šolcová, Pavlína ; Tyrpekl, Václav (advisor) ; Havlíček, David (referee)
This thesis aimed to streamline the method of the preparation of high entropy carbides. The simplification of synthesis and expends reduction were achieved using sol-gel method instead of using commercial starting powders. As precursors of transition metals, the chlorides (TiCl3, TaCl4, HfCl4 a NbCl5) and chlor-oxide (ZrOCl2) were used. The source of carbon was citric acid. All reactants were mixed in solution and dried to gel. The pyrolysis at 800 řC afterwards leads to creation of the amorphous carbon, which embedded the transition metal oxide nanoparticles. The carbothermal synthesis was completed in Spark plasma sintering device at 1400 řC, 1600 řřC and 1900 řC. Formation of high entropy carbide phase was achieved at 1600řC, which is almost 400 řC less than previously reported in literature. Intermediate and final products were characterized with powder X-Ray diffraction, scanning electron microscopy and products, in addition, were characterized with transmission electron microscopy and elements mapping. Key words: high entropy carbides, carbothermal reduction, high temperature ceramics, sol-gel method,
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Selected nanoparticles systems and their physical and chemical properties
Tyrpekl, Václav
of "rigorous" work Author: MSc. Václav Tyrpekl Supervisor: RNDr. Daniel Nižňanský, PhD. Katedra Anorganické Chemie Přírodovědecká Fakulta, Univerzita Karlova v Praze Name: Selected systems of nano-particles and their physico-chemical properties Presented work belongs to the topic of solid-state chemistry, which focuses mainly on the preparation and characterization of nano-particles and nano-composites. The introduction describes current knowledge of classical magnetism and magnetism of small particles. Next paragraphs describe the sol-gel technique, which uses alkoxides of transition elements for preparation of gels, xerogels and nano-composites. The introduction ends by the overview and explanation of experimental techniques that were employed for final sample characterization. The experimental work is divided in three thematic parts: i) Preparation and characterization of CoFe2O4/SiO2 composite in the form of spheres of few microns in diameter ; ii) Preparation and characterization of Fe3O4/SiO2 composite in the form of spheres with core- shell morphology with diameter of several tens of nanometers ; iii) Preparation and characterization of Fe2O3/TiO2 composite with photo-catalytic properties. In the first part, the SiO2 micro-spheres of average 11 micrometers in diameter, doped by...
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Preparation and characterisation of selected d and p elements carbides
Nižňanský, Matěj ; Tyrpekl, Václav (advisor) ; Vilémová, Monika (referee)
This thesis is focused on carbide ceramics synthesis, more specifically on the synthesis of a Ti2AlC MAX Phase carbide using solution chemistry rather than powder metallurgy. Chloride and nitrate precursors have been used as a source of metals and citric acid as a source of carbon for carbothermal reduction and as a complexing agent. A new route of precursor synthesis has been developed based on peroxo-titanic acid, which helps retain aluminium. The syntheses were performed using the SPS facility to ensure high heating rates. Al4C3 and TiC carbides and their mixtures were prepared successfully. However, the Ti2AlC phase was not synthesized under used conditions. The phase composition, structure and grain sizes of the samples were investigated by powder X-ray diffraction, X-ray fluorescence and electron microscopy. The contents of carbon in the precursors were determined by thermogravimetric analysis.
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Polymer nanoparticles generating singlet oxygen
Berzédiová, Veronika ; Mosinger, Jiří (advisor) ; Tyrpekl, Václav (referee)
This theses focuses on preparation and characterisation and comparison of two types of polymer nanoparticles using photophysical methods. The first type was polystyrene nanoparticles prepared by modified nanoprecipitation method from polymeric sulfonated nanofiber membranes with diffrent content of sulfonated groups. The second type was polymer nanoparticles with diferent lenght of hydrophobic polycaprolactone (PCL) and hydrophilic poly(ethyleneglycol) (PEG) blocks. Both types of nanoparticles conteined encapsulated photosensitizer 5,10,15,20-meso-tetraphenylporphyrin with a high quantum singlet oxygen yield. In the prepared nanoparticles with a photosensitizer, the kinetics of singlet oxygen generation was studied using time resolved spectroscopy. The relative efficiency of photooxidation was studied using external akceptor of singlet oxygen. The effect of temperature, size and matrix (type of polymer) of nanoparticles on photooxidation efficiency was also studied. In the next part of this these was studied the influence of time on the size and stability of nanoparticles and also the effect of solution pH and ionic strength on prepared nanoparticles.
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Synthesis of novel porous coordination polymers, their characterization and solvothermal stability
Ondrušová, Soňa ; Lang, Kamil (advisor) ; Tyrpekl, Václav (referee)
This diploma thesis builds on the already published work, in which phosphinate analogs of terephthalic acid were used to prepare new stable metal-organic frameworks (MOFs) Fe-ICR- 2 and Fe-ICR-4. With the use of analogous biphenylene linkers, two new Fe-MOFs were prepared - Fe-ICR-6 and Fe-ICR-7. Isoreticular MOFs were also prepared using Al3+ metal centers. These materials were characterized by X-ray powder diffraction and adsorption isotherm measurements. Their solvothermal stability was measured after shaking and refluxing in water, ethanol, and toluene and activation from water. Furthermore, their thermal stability and the disintegration mechanism in air were determined by thermal analysis. Keywords: coordination polymer, metal-organic framework, stability, phosphinate
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Preparation and characterization of bi-phasic magnetic nanoparticles
Alemayehu, Adam ; Tyrpekl, Václav (advisor) ; Brázda, Petr (referee)
Title: Preparation and characterization of bi-phasic magnetic nanoparticles Author: Bc. Adam Alemayehu Department: Department of Innorganic Chemistry Supervisors: doc. RNDr. Daniel Nižňanský, Ph.D. RNDr. Václav Tyrpekl, Ph.D. Consultant: M.Sc. Dominika Zákutná Abstract The work is focusing on the magnetic properties of ferrimagnetic spinel ferrites before and after the introduction of a shell on a core particle with different magnetic properties. The core nanoparticles were prepared by hydrothermal decomposition of oleate precursors. The introduction of shell was carried out by hydrothermal treatment of the already prepared core particles. The phase composition, spinel structure and the sizes of the prepared samples were investigated by powder X-ray diffraction and by transmission electron microscopy. Formation of the shell on top of the core particle was determined indirectly, using Mössbauer spectroscopy at room temperature. The interparticle interactions and the particle shape was studied by small angle X-ray scattering. The magnetic properties of the prepared samples were measured on a SQUID magnetometer. Key words: magnetic nanoparticles, core, shell, spinel structure, powder X-ray diffraction, Mössbauer spectroscopy, magnetic measurements, TEM
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Preparation and Characterization of Iron (III) Oxide Nanocomposites Substituted with Scandium
Kaščáková, Dorota ; Nižňanský, Daniel (advisor) ; Tyrpekl, Václav (referee)
In this work a preparation and characterization of nanoparticles of iron(III) oxide substituted with scandium in SiO2 matrix is described. The nanoparticles were prepared by the sol-gel method yielding mostly β-Fe2O3 substituted with various amount of scandium(III) ions. Mossbauer spectroscopy was carried out to determine purity of the samples and the content of other iron oxides phases. System was characterized by magnetic measurements. Powder X - ray diffraction was used to verify the composition and to determine the lattice parameter and particle size. β-Fe2O3 is formed at the temperatures of 1000 and 1100 ◦ C at composition Fe2−xScxO3 for x ≥ 0.2 and at temperature 1100 ◦ C for x = 0.1. Lattice parameter is linearly dependent on the scandium content and depends also on the annealing temperature. At temperatures higher than 1250 ◦ C, β-Fe2O3 is transformed into hematite. Key words: iron(III) oxide, scandium, sol-gel, Mossbauer spectroscopy, X-ray diffraction, magnetic measurements 1
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Material effect in nuclear Fuel - Coolant interaction: Structural characterization of the steam explosion debris and solidification mechanism
Tyrpekl, Václav ; Nižňanský, Daniel (advisor) ; Matějec, Vlastimil (referee) ; Cognet, Gérard (referee)
Thesis Abstract This thesis has been performed under co-tutelle supervision between Charles University in Prague (Czech Republic) and Strasbourg University (France). It also profited from the background and cooperation of Institute of Inorganic Chemistry Academy of Science of the Czech Republic and French Commission for Atomic and Alternative energies (CEA Cadarache, France). Results of the work contribute to the OECD/NEA project Serena 2 (Program on Steam Explosion Resolution for Nuclear Applications). Presented thesis can be classed in the scientific field of nuclear safety and material science. It is aimed on the so-called "molten nuclear Fuel - Coolant Interaction" (FCI) that belongs among the recent issues of the nuclear reactor severe accident R&D. During the nuclear reactor melt down accident the melted reactor load can interact with the coolant (light water). This interaction can be located inside the vessel or outside in the case of vessel break-up. These two scenarios are commonly called in- and ex-vessel FCI and they differ in the conditions such as initial pressure of the system, water sub-cooling etc. The Molten fuel - coolant interaction can progress into thermal detonation called also "steam explosion" that can challenge the reactor or containment integrity. Recent experiments have shown that...
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