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Advanced high-temperature resistant metal-ceramic composites based on TiB2 for cutting tools
Halmazňa, Jiří ; Drdlík, Daniel (referee) ; Chlup, Zdeněk (advisor)
This diploma thesis deals with the preparation of new high-temperature resistant cermets based on TiB2. The hard ceramic phase is bonded by NiW metallic alloy, which was prepared by mechanical alloying using a planetary ball mill. The first part of the thesis is targeted to the optimization of mixing of both powders in the planetary ball mill. The procedure of preparation of powders mixture with homogenous particles distribution of the NiW alloy was designed and verified with simultaneous particle size refinement. The second part is focused on the microstructure characterisation and mechanical properties evaluation of sintered materials. In this case both powders, TiB2 and NiW, were mixed in a tubular mill and consequently compacted by a rapid hot pressing method at four different sintering temperatures. The influence of the sintering temperature on the microstructure development characterized by the density, porosity and grain size was monitored. The elastic modulus, fracture toughness, flexural strength and hardness were measured on prepared test specimens. The results of conducted experiments show a significant dependence of the microstructure and mechanical properties on applied sintering temperatures. The higher sintering temperatures are used the better mechanical properties are observed. However, the sintering temperature of 1375°C seems to be an optimal one. The sintering temperature of 1400°C leads to the significant losses of the metal phase due to sublimation of nickel resulting in increased porosity in the metal phase regions.
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Low temperature tests and fracture toughness of selected ceramic materials
Beck, Branislav ; Drdlík, Daniel (referee) ; Chlup, Zdeněk (advisor)
Diploma thesis deals with the determination of fracture toughness values of sintered silicon carbide and casted basalt using both the Single Edge V-Notch Beam (SEVNB) and the Chevron Notched Beam (CNB) methods at room and cryogenic temperatures. The first part of this thesis offers general overview and categorization of ceramic materials. Fracture mechanics of the ceramic materials and available fracture toughness testing methods are discussed in following chapters. The last section in the theoretical part is aimed to the microstructure and properties of the silicon carbide. Experimental part of the work summarizes methods used for characterization of selected materials from the microstructural and fracture point of view. Preparation of samples for microstructural observation and samples for fracture toughness determination are described in details. The results of the fracture toughness data for sintered silicon carbide and cast-basalt obtained at room temperature and at -100 °C are displayed. Consideration of possible measurements errors and application of various fracture toughness testing methods are discussed in the next chapter of this work. The difference in the fracture toughness values with the decrease of testing temperature was found. The difference depends on both, the used method of fracture toughness determination and the material used for the tests. The most important results gained during the experimental work are summarized in the chapter “Conclusions”.
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Mechanical properties of doped piezoceramics based on BaTiO3
Zeman, Dominik ; Chlup, Zdeněk (referee) ; Drdlík, Daniel (advisor)
This master‘s thesis deals with study of basic physical, microstructural and mechanical properties of doped piezoceramic materials based on BaTiO3 prepared by electrophoretic deposition. The dopants used were rare earth oxides, i.e. Eu2O3, Er2O3, CeO2, Dy2O3 and Tb4O7 in amounts 1, 3 and 5 wt. %. The influence of dopants and their amount on density, phase composition, mean grain size, hardness, elastic modulus, fracture toughness, and flexural strength was examined. Suitable dopant choice enabled decrease in mean grain size and increase in relative density, hardness, elastic modulus, fracture toughness and flexural strength of sintered specimens. Relative densities up to 99 %, mean grain size below 1 m, hardness up to 13,1 GPa, elastic modulus up to 199 GPa, fracture toughness above 1 MPa·m1/2 and flexural strength above 115 MPa were achieved.
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Study of manganese segregation in Mn-doped transparent alumina ceramics
Pišťák, Jan ; Maca, Karel (referee) ; Drdlík, Daniel (advisor)
This work deals with the preparation of Al2O3 ceramics doped with manganese, the study of basic physical and microstructural properties and the description of the dissolution kinetics of manganese in the Al2O3 matrix. Al2O3 ceramics and Al2O3 ceramics doped with 1 and 5 at.% Mn3O4 with different dopant particle sizes were successfully prepared by the slip casting method. The prepared ceramic materials were sintered at temperatures of 1100 and 1150 °C with different dwell times. The density in sintered samples was monitored depending on the preparation parameters and thermal treatment conditions. It was found during the microstructure observation that even at a relatively low temperature, the rapid dissolution of the dopant in the Al2O3 matrix occurred, while in the samples containing 1 at.% Mn3O4, this dopant was already completely dissolved. In the case of samples with a concentration of 5 at.% Mn3O4, a spinel phase was identified in the matrix. In addition, some samples were found to have unreacted dopant particles excreted from the matrix during ceramographic processing. Therefore, the goal of the bachelor thesis could not be completely fulfilled, i.e. the kinetics of dopant dissolution could not be studied for objective reasons.
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Fabrication and properties of doped piezoceramics based on BaTiO3
Mařák, Vojtěch ; Chlup, Zdeněk (referee) ; Drdlík, Daniel (advisor)
This diploma thesis deals with the preparation of doped piezoceramic materials based on BaTiO3 using electrophoretic deposition. Five rare earth oxides, i.e. Er2O3, Dy2O3, Eu2O3, Tb407 and CeO2, were used as dopants in amounts of 1, 3, and 5 wt. %. The prepared deposits were evaluated in terms of preparation methodology, high temperature dilatometry, X-ray diffraction analysis, relative density, mean grain size, hardness and fractographic analysis. The study of dilatometric curves described the sintering behavior and its changes at different material compositions. X-ray diffraction analysis revealed a tetragonal phase in all samples; the tetragonality of the BaTiO3 crystalline cell decreased with dopant content. By a suitable choice of dopant, it was possible to significantly increase the relative density of sintered samples, their hardness and at the same time prevent the samples from coarsening of the microstructure during heat treatment. A relative density up to 98 %, a mean grain size below 1 m and a hardness of over 10 GPa were achieved. Analysis of the fracture surfaces revealed that the fracture mode was transcrystalline for the most of studied materials; only the samples doped with cerium dioxide had fracture surfaces with both transcrystalline and intercrystalline fracture modes. Based on the obtained results, a suitable composition of the material for the intended use in a layered piezoceramic harvester was identified, which, in addition to the BaTiO3 layers, consists of functionally-protective Al2O3 and ZrO2 layers.
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Laminated Ceramic Composites - Deposition, Structure and Properties
Drdlík, Daniel ; Maca, Karel (referee) ; Cihlář, Jaroslav (advisor)
The work was focused on the preparation of layered ceramic materials and their characterizations. The direct measurment of weight deposite for enhanced description of one component system was studied within this work. The kinetics of electrophoretic deposition obtained from theoretical calculation and from experimental values were confronted. It was prepared a lot of depositions for described kinetic of electrophoretic deposition with applied constant currents. The relative density and porosity were determined on the annealled and sintered bodies. The hardness measurments were performed on sintered bodies and then resulted values were confronted with the used currents. A ceramic composite based on Al2O3 and ZrO2 was prepared by using of precision describtion of electrophoretic deposition kinetic.
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Glass-ceramic composite biomaterials
Žaludek, Jakub ; Hadraba, Hynek (referee) ; Drdlík, Daniel (advisor)
The bachelor thesis is focused on the preparation of bioglass 45S5 and composites containing bioglass 45S5 and alumina or zirconia fibres in amount of 1, 3 and 5 wt% by slip-casting method from aqueous and 2-propanolic suspensions. The materials prepared were characterised in term their porosity, relative density, high temperature dilatometry, X-ray diffraction analysis, microstructure and hardness. The slip-casting method produced porous samples which is promising result for a possible biomedical application. The high temperature dilatometry identified three stages of the sintering process and a shrinkage of ~40% of the bioglass-based materials was measured. The crystalline phase of Na2Ca2Si3O9 was created at the sintering temperature of 1050°C but the dissolution of Al2O3 or ZrO2 fibres into the bioglass matrix was not confirmed using the X-ray diffraction analysis. It was found that the hardness of the samples decreased with the amount of the fibres in the materials which was caused by their increasing porosity and large clusters of fibres.
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Study of preparation and properties of Ca-phosphates/ZrO2 biocomposites
Sláma, Martin ; Drdlík, Daniel (referee) ; Cihlář, Jaroslav (advisor)
The thesis was focused on preparation of bioceramic composite materials containing Ca-phosphates and zirconia fibers using electrophoretic deposition. A series of experiments were aimed at determining the appropriate composition of the suspensions. High-energy milling was used for preparing deposits with good physical and mechanical properties using EPD. The influence of milling time, the amount of monochloroacetic acid in isopropanol slurry indifferent electrolyte LiCl and ZrO2 were evaluated on the course deposition and the resulting properties of the deposits. Influence of sintering temperature, the milling time and the fiber content of ZrO2 on the chemical and structural composition was determined by X-ray analysis, measurement of density and structural analysis using a scanning electron microscope. Mechanical and bioactive properties of sintered deposits were determined depending on the milling time and content of ZrO2 fibers.
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Transparent ceramic materials
Krupa, Filip ; Drdlík, Daniel (referee) ; Maca, Karel (advisor)
This Bachelor thesis deals with processing of transparent cubic ZrO2 ceramic doped by 8 mol% Y2O3. Technology used in this Bachelor thesis are uniaxial pressing, cold isosatic pressing, SPS and hot isostatic pressing. Microstructure, real in-line transparency and hardness were evaluated for sintered transparent materials.
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Transparent fibre reinforced ceramics
Lövy, Vít ; Drdlík, Daniel (referee) ; Chlup, Zdeněk (advisor)
This bachelor thesis summarizes possibilities of toughening of ceramic materials with various types of fibres and describes the basic principles for preparation of transparent fibre-reinforced composite materials. The role of fibre-matrix interface and the measurement methods enabling estimation of the interfacial strength and other characteristics are explained. The single fibre push-out test using a standard indentation technique was chosen for interfacial parameters determination of the composite consisting from a borosilicate matrix reinforced by SiC fibres in the practical part of this work.
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