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.

Title: Spectroscopic investigations of lattice dynamics in multidomain ferroelectrics Author: Elizabeth Vakkechalil John Department: Department of Condensed Matter Physics Institution: Department of Dielectrics, Institute of Physics, AVČR, Na Slovance 2, Praha 8, 182 21, Czech Republic. Supervisor: Ing. Jiří Hlinka, PhD., Department of Dielectrics, Institute of Physics, AVČR., Na Slovance 2, Praha 8, 182 21, Czech Republic. Consultants: RNDr. Stanislav Kamba CSc., Ing. Ivan Gregora CSc. Fyzikální ústav AVČR, Na Slovance 2, Praha 8, 182 21, Czech Republic. Abstract: Lead based ferroelectric perovskites exhibit attractive physical and structural properties. Ferroelectric domains are known to have a very essential impact on dielectric and piezoelectric properties of ferroelectrics. Tailoring of domain structures allows to change the macroscopic symmetry of the material and to purposely modify its average tensor properties. Ferroelastic domains play also a key role in physics of epitaxial ferroelectric films. Here we studied signature of domain structure in PbTiO3 thin film grown by metalorganic chemical vapor deposition technique on different substrates, namely LaAlO3, MgO, NdGaO3, SrTiO3 (100), SrTiO3 (110), SrTiO3 (111) doped with 0.5% Nb and LSAT. Certain aspects of domain structure can be...

The aim of the work was a processing of ceramic material based on BST for ferroelectric application. Wet chemical techniques based on precipitations and sol-gel methods with ultrasound, hydrothermal or mechanochemical treatment supporting deaglomeration and reducing particle growth were used for BST ceramic powder synthesis. Suitable powders were selected by the evaluation of particle morphology, size and agglomeration, from these powders BST bulk ceramic with defined phase composition and morphology applicable for ferroelectric applications was prepared. It was found, that the most suitable method for preparation of phase pure and nanosized BST powder was sol-gel synthesis with solvothermal treatment (200 °C/48 h). Ceramic with relative density of 85 % TD and with the average grain size of about 1, 22 µm was prepared by pressing and sintering of the powder synthesized by the sol-gel method.

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This thesis deals with Bell Beaker Culture at the end of the Eneolithic in two areas of its extension, in the Czech Republic and the Iberian Peninsula. We consider it as a one culture; however we can observe some differences mostly based on different domestic cultural background. Differences and similarities in manifestation of culture derived from an analysis of its various aspects in both areas such as settlement structure, funeral rite and material culture, of which the most characteristic are decorated Bell Beakers and archery equipment coming from the graves. This work is devoted to the characterization of Bell Beaker society and evolution of opinions on this phenomenon too.

The present work was written following a master thesis on the settlement and the shape of the early mediaeval agglomeration of Žatec in the 9th century. Subject of this dissertation is the processing of pottery from settlement features and from the 10th -century fortification. This enabled to study the development of the fortification system and changes of the settlement structure within individual settlement components. On the basis of excavations a relative chronology of the pottery and in accordance with the dendrochronological data a hypothesis on absolute dating has been presented. In view of this new chronology a new quantitative and qualitative analysis of information on the early mediaeval strongholds and hill-top settlements of the 9th and 10th century in the central and lower Ohře Region and in the Ore Mountain foothills was undertaken. A processing of the research on Drahúš stronghold has contributed substantially to this new perspective. The 1960s opinion on the affiliation of early mediaeval strongholds on the territory in question to the tribal territory of the Lučans, which should have been opposed to the Central Bohemian Přemyslid patrimony, based on the gathered information and its analysis could have been rejected. It was possible to comprise the evaluation of the excavation at...

This work deals with the study of diagnostic methods suitable for monitoring of the drying process of brick raw materials. Based on the extensive literature search, several parameters are selected, which are appropriate to monitoring during drying. In addition, a methodology for measuring these selected parameters is proposed. In the experimental part, the use of all described methods is gradually verified on the brick raw material with and without shortening additive (also known as grog). Was carried out: measurement of the surface temperature in the climatic chamber, determination of humidity distribution in the sample, determination of moisture diffusivity, determination of tensile strength, determination of ultrasonic wave velocity and determination of dynamic E-modulus of elasticity. Results of experiments and the gained experiences show, that at least two of the above-mentioned monitoring methods are very appropriate and beneficial – determination of moisture diffusivity and determination of tensile strength. In the work was described in detail the procedure of determination of moisture diffusivity of material. The dependence of moisture diffusivity on the moisture content of the dried material, has been described. Also, differences between raw material with grog and without grog has been described. As part of the practical verification of the experiment designed to determine the tensile strength at different humidity levels of test samples. A new shape of the test specimens and a new device were designed to allow them to be attached to a hydraulic press. The results of this work show that the tensile strength of the ceramic green bodies is primarily dependent on the moisture content of the material. The type of raw material almost does not affect the tensile strength.

Polymer and composite polymer-ceramic nanofibers were prepared by electrospinning process. Solution of 20 wt.% polyvinylidene fluoride (PVDF) in a mixture of dimethyl sulfoxide (DMSO) and acetone in the ratio of 7:3 was chosen as the most suitable precursor. When preparing composite nanofibers, 20 wt.% of barium calcium zirconate titanate (BCZT) or barium titanate (BT) nanoparticles was added to this PVDF solution. Given parameters were defined as the most suitable for the process of electrospinning: voltage of 50 kV, feeding rate of 30 l/min, distance between emitter and collector of 20 cm and needle diameter of 17 G. The effect of polymer molecular weight and the rotation speed of collector was also studied. Various properties of prepared samples were studied: morphology and fiber diameter, phase composition with the use of x-ray diffraction and Fourier transform infrared spectroscopy and also chosen electrical properties. Lower fiber diameters appeared with lower polymer molecular weight and higher rotation speed of the collector. These parameters resulted in higher percentage of the piezoelectric phase as well. The smallest achieved fiber diameter was around 300 nm, the highest percentage of phase was 92 % and the highest piezoelectric constant had a value of 16 pC/N. Composite fibers filled with BT particles showed better properties that the ones filled with BCZT particles.

The master thesis focuses on the preparation of nickel coating on ceramic (Al2O3) substrate. The deposition of nickel was carried out by the electroless plating method in bath at various kinetic conditions. An impact of varied size, shape and roughness on the quality of the coated surface was investigated. The main goal was to find optimized conditions of the plating process of the thin metal coatings. Prepared nickel coatings were analysed by SEM, EDX analysis, mechanical profilometry and the plating bath was analysed by UV-VIS spectrophotometry. The continuous nickel coatings were achieved by modifying the deposition process, and the kinetic mechanism of experimental conditions was described.

The content of this thesis is about preparation and processing of lead-free piezoceramic materials with perovskite structure. Potassium sodium niobate (KNN) powder was prepared by solid state reaction (SSR) and liquid phase reaction (sol-gel reaction). The powders were formed by uniaxial and isostatic pressing and further sintered. The density, grain size and morphology were determined on the sintered samples. The powder, synthesised by SSR and sintered in a conventional furnace, was chosen as a standard. The maximum density achieved on samples after optimization of sintering cycle was 93 %TD. The sintering optimization involved a homogenization step at 950 °C, which promotes the correct development of the phase composition and microstructure, followed by sintering at 1120 °C. The same approach and sintering cycle were used for sintering the samples, prepared by sol-gel synthesis. The maximum density of the samples prepared by sol-gel reaction and sintered in a conventional way, was 92 %TD. For further comparison, both of the synthesised powders were sintered using SPS (spark plasma sintering), which increased their final density up to 97 %TD. The approximate value of the piezoelectric coefficient d33 (pC/N) has been measured on selected SSR samples with pure phase composition ((K0,5Na0,5)NbO3). The best measured value of d33 was around 100 pC/N.