Topics of PhD.

Proposed topics for 2018/2019

Oxynitride-based transparent luminescent materials
Supervisor: doc. Ing. Zoltán Lenčéš, PhD. (Department of ceramics)

  • The work will be focused on the cost effective preparation of oxynitride (MgAlON and SiAlON)-based phosphors from a mixture of oxides and nitrides and/or from siloxane- and polysilazane-based polymer precursors. The composition of the starting powder mixtures, the nitridation conditions, and the high-temperature annealing of the phosphors will be optimized. The main goal of the work will be the preparation of high-intensity green and red phosphors, which can be used for the construction of warm white-light-emitting diodes (LEDs). The prepared materials will also be tested for applications in photovoltaics, especially for solar spectral conversion, i.e. for the conversion of UV, NUV and violet light to a wavelength which can be absorbed by a silicon-based photovoltaic device.

Effect of Si3N4 microspheres addition on mechanical and biological properties of bone cements based on brushite
Supervisor: doc. Ing. Miroslav Hnatko, PhD. (Department of ceramics)

  • Proposed work will be focused on the preparation and characterization of composite cements based on calcium phosphate with the addition of strengthening phase in the form of silicon nitride based microspheres. Porous Si3N4 microspheres with various content of Ca3(PO4)2 will be prepared by flame synthesis. The effect of Si3N4 microspheres as fillers will be studied, except the possible strengthening of calcium phosphate cement (quantity effect, size effect, structure etc.) the change of the biological properties (biotoxicity and antibacterial effect of Si3N4, resorption rate, etc.) are also expected.

Assessment of secondary raw materials for the preparation of materials used in extreme conditions.
Supervisor: Ing. Jaroslav Sedláček, PhD. (Department of ceramics)

  • The subject of proposed theme will be focused to up to date waste recovering issue with their potential use as a secondary raw material sources for the preparation of ceramic materials for extreme conditions (high temperatures, mechanical stress, corrosive environments, etc.). The main objective is development of ceramic materials and/or composites based on nitrides, oxynitrides, carbides as well as oxide materials from the system SiO2-Al2O3-CaO-MgO-MexOy from existing streams of secondary raw materials which come from the production of ferroalloys, nickel, magnesite, combustion of solid fuels or municipal waste, mining processes, etc. The results will extend the knowledge on the application potential of secondary raw materials for production of advanced materials with higher added value. The planned development plan will involve the characterization of raw materials, their treatment, thermodynamic analysis, optimization of the treatment process (carbothermal reduction, nitridation, etc.) and sintering, and the evaluation of the properties of the materials. In cooperation with the Slovak industrial partners will be discussed the potential possibilities for extension of existing technologies in terms of the direct processing or recovery of waste streams to advanced ceramics and thus significantly reduce the environmental and energy demands.

Influence of grain boundary chemical composition of nitride ceramics on the mechanical properties

Supervisor: prof. RNDr. Pavol Šajgalík, DrSc. (Department of ceramics)

  • Experimental verification of the assumption that different content of rare earth oxides results in different mechanical behaviour of nitride ceramics will be aim of the thesis. The simulation experiments show that the different concentration of the same rare earth oxide in different concentration result in a different grain boundary strength of nitride ceramics.  Part of the work will be focused on the processing of the silicon nitride based ceramics with the addition of the lanthanum and lutetium oxide. Main portion of the work will be concentrated on the processing of silicon nitride ceramics with these (possibly also other) additives and on the study of the grain boundary strength with respect to the different concentrations of particular additive. Grain boundary strength will be studied in cooperation with the Institute of Materials Research in Košice.

New joining methods for advanced ceramic materials.
Supervisor: Ing. Peter Tatarko, PhD. (Department of ceramics)

  • Silicon carbide (SiC) based ceramics and composites are primary used as materials for nuclear and aerospace applications due to their excellent combination of properties. However, their application in such extreme conditions will depend on the ability to join them, because the manufacture of these materials as large components with complicated shapes is extremely difficult and expensive. The development of reliable, inexpensive and user-friendly joining methods is, therefore, a critical issue of the development of next generation of nuclear reactors and aerospace vehicles. The main aim of the work will be to develop new diffusion bonding methods of these materials to their counterparts, or the materials with different chemical compositions (e.g. metals). The investigation of bonding mechanism, physical and chemical processes, as well as mechanical and functional properties of the joints will be an important task. The dissertation thesis will bring new knowledge in the fundamental research on the joining of ceramics; and help to broaden the application potential of such an important material for nuclear and aerospace applications as SiC.

Synthesis and characterisation of refractory transition metal borides and their composites.
SupervisorIng. Peter Tatarko, PhD. (Department of ceramics)

  • Transition metal borides (mainly Zr and Hf) belong to the so-called group of “ultra-high temperature ceramics” owing to their extremely high melting temperatures, over 3000°C. Due to their excellent combination of properties, ceramic materials containing these compounds are being used in the applications performing in extreme environments, such as nuclear and aerospace applications. The materials are formed by densification and sintering of high purity chemical powders, while their sinterability and properties are strongly affected by the initial raw materials. This dissertation thesis is therefore focused on the synthesis of refractory borides of zirconium and hafnium from various precursors with the aim to develop an appropriate technique to manufacture ultra high purity ZrB2 and HfB2 powders with nanometric or submicron particle size. During the synthesis, these compounds will be chemically modified/doped by various additives in order to further improve high temperature properties of the materials. An important task will be to perform a detail characterisation of the as-synthesized powders with the aim to understand the effect of precursors and dopants on the synthesis, sinterability and the final properties of these materials and their composites. This PhD work will contribute to the understanding and clarification of the processes taking place during the development of transition metal diborides. The work will propose the most appropriate manufacturing technique of these materials with regard their microstructure, phase composition, and required properties for nuclear and aerospace industry. This will significantly improve the applicability of the materials for commercial use.

Fluorescence nanofilms with cyanine dyes and clay minerals
Supervisor: Mgr. Adriana Czímerová, PhD. (Department of hydrosilicates)

  • Cyanine dyes represent a group of dyes that have been extensively studied for decades. Due to their structural and chemical variability, ability to form fluorescence aggregates, and different possibilities for interaction with other molecules, these dyes offer a wide range of practical applications. The topic of this study is the preparation of thin layers using various preparation technics. The hybrid nanosystems in this study consist of an inert inorganic matrix – mainly of clay minerals – and adsorbed cyanine dyes. Nanofilms will be prepared and studied using absorption spectroscopy in the UV/VIS and near-infrared regions. In this context, particular attention will be paid to the orientation of cyanine dyes inside the structure of the clay minerals and calculation of the thickness of the prepared films. However, the main focus of the study will be the characterization of the prepared thin layers by means of fluorescence spectroscopy.

Quantum dots as a light harvesting antennas
Supervisor: Mgr. Adriana Czímerová, PhD. (Department of hydrosilicates)

  • The integration of inorganic and organic molecules on the nanoscale range opens the door to the study of novel and promising nanomaterials. This work will be focused on the preparation of various types of quantum dots, followed by study of energy transfer between the prepared quantum dots and dye molecules. In such systems, quantum dots can play the role of light-harvesting antennas. The most important part of the work will be the preparation of quantum dots and optimization of the conditions for an efficient energy transfer process. The prepared systems will then be investigated using absorption spectroscopy in the UV/VIS and near-infrared region. The optical and photophysical properties will be studied in detail by means of fluorescence spectroscopy.

Development and efficient implementation new relativistic methods for interpretation NMR and EPR spectra of heavy elements compounds.
Supervisor: Dr. Oľga Malkina, DrSc. (Department of theoretical chemistry)

Development of new advanced quantum chemical approaches.
SupervisorDr. Vladimir Malkin (Department of theoretical chemistry)

Development and efficient implementation of fully relativistic methods for calculation of response properties of heavy elements containing paramagnetic systems.
SupervisorMgr. Stanislav Komorovský, PhD. (Department of theoretical chemistry)

  • Nowadays, the study of heavy-element containing paramagnetic systems is becoming more important in various scientific areas. For instance: a) in the development of advanced magnetic materials for data storage, b) in decreasing the radio toxicity and heat load of nuclear spent fuel, c) in the development of new organic light-emitting diodes (OLEDs). The main goal of the thesis is the development of new relativistic methods for calculation of spectroscopic parameters (such as nuclear magnetic resonance) of paramagnetic systems, followed by their efficient implementation into program package ReSpect (www.respectprogram.org). This requires skills from both relativistic quantum physics and computational science. An optional goal is to apply the newly implemented methods to relevant systems in close collaborations with our foreign partners from Germany, Norway, Austria or Czech Republic.

Development of methods for synthesis of ternary fluorides for modern applications.
Supervisor: doc. Ing. Miroslav Boča, DrSc. (Department of molten systems)

  • The analysis of fluorides melts requires knowledge of the phases present. Analysed mixtures often consist of more than one phase that cannot be separated. Thus it is necessary to prepare these phases in pure form. The application of common methods, however, often fails. The object of the work will be the development of new methods for the synthesis of inorganic fluorides, or suitable modification of existing methods.

Molten systems in solar applications
Supervisors: doc. Ing. Miroslav Boča, DrSc., Ing. Viliam Pavlík, PhD. (Department of molten systems)

  • The student will be dealing with simplified input/output thermodynamic calculations used for thermal storage proposal, including suggestions of salts and materials of storage.

Corrosion of superalloys for energy applications
Supervisor: doc. Ing. Miroslav Boča, DrSc., Ing. Viliam Pavlík, PhD. (Department of molten systems)

  • The focus of the work will be on corrosion resistance of a high-temperature alloy, including measurements of the surface, microgeometry, thickness of the corrosion layer, aggressiveness of the environment and gravimetry of the samples.

The solid electrolytes on the basis of fluoride complexes
Supervisor: Ing. František Šimko, PhD. (Department of molten systems)

  • The topic deals with the preparation of inorganic fluoride complexes with alkaline cations which can be used as solid electrolytes with high conductivity. Thermodynamic, thermochemical, spectral and structural characterisation of the complexes will be performed, as well as how its properties change with temperature. Synergy between data from classical and modern techniques is expected.

Energy future in inorganic melts. Macro and micro characteristics of selected fluoride systems
Supervisor: Ing. Blanka Kubíková, PhD. (Department of molten systems)

  • Molten salts have a wide range of industrial uses in such different areas as applications connected with fuel and cooling systems and heat exchange circuits of nuclear reactors, pyrochemical separation of spent nuclear fuel, and electrochemical deposition of metals. However, any application of a molten salt requires its basic physico-chemical properties to be known over a wide concentration and temperature range. Therefore the object of this work will be the analysis of selected fluoride molten salt systems based on transition d- or f- elements regarding phase equilibrium, volume, surface and transport properties.

Phase equlibrium, electrochemical and physico-chemical characteristics of fluoride melts for electrodeposition of rare earth metals and other metals declared by European Commission as critical materials
Supervisor: Ing. Michal Korenko, PhD. (Department of molten systems)

  • The Rare Earth Metals (along with certain other materials, like Mg, Ti, etc.) have been declared to be critical for EU economies by the European Commission.  The reason for the selection of these materials is Chinese dominance, and in some cases, even a global monopoly in their production.  For the EU, these materials have both a high supply risk and high demand for recycling. One way to develop a recycling pathway is to commercialize high-temperature electrowinning of these metals from molten fluorides.  The main focus of the project will thus be on the identification of suitable systems, their electrochemical analysis (kinetic and diffusion parameters), and also the investigation of their physico-chemical properties (phase equilibria, transport properties, volume properties and surface properties).