National Repository of Grey Literature 138 records found  1 - 10nextend  jump to record: Search took 0.02 seconds. 
3D microstructure evaluation of developed Si3N4 material for alloyed wire rolling applications
Lövy, Vít ; Salamon, David (referee) ; Chlup, Zdeněk (advisor)
This diploma thesis is devoted to the use of 3D reconstruction using EBSD method for microstructural analysis of silicon nitride ceramic material predetermined for the rolling-mill used in the wire production. Application of this method can be used for the grain structure reconstruction and basic microstructural parameters can be than extracted. The development of a suitable method for 3D reconstruction of the structure of the materials the main aim of this work. There are described the different steps begun by sample preparation from the investigated material trough the optimisation of analysis parameters up to the visualization of the grain structure. New type of sample geometry has been designed which leads to the better and faster observation of the microstructure of ceramic materials. This thesis also describes optimal reconstruction parameters such as the geometry of the assembly used in the microscope without mechanical movement of the sample or the influence of conductive coating prepared via in-situ sputtering of suitable metal, or adjustment of the electron and ion beams. Further are described two options of software which can be used for the final generation of 3D structure information and are assessed their advantages and disadvantages. The effect of the filter setting and other parameters and their influence on the resulting structural parameters are also evaluated.
Design of Car Initiator
Suchý, Jan ; Píštěk, Václav (referee) ; Novotný, Pavel (advisor)
The bachelor thesis is focused on proposal solution of automotive initiator construction and design. The proposal is being carried out with regard to the need to ensure the maximum functionality of the whole element. As for the choice of materials and used technology the costs and procedures commonly used today are not being taken into account. The main objective is to eliminate the shortcomings of current automotive initiators and the proposal of technological procedures in the production of a new component.
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”.
Synthesis and sintering of zirconia based ceramics for biomedical applications
Jahodová, Daniela ; Novotná, Lenka (referee) ; Částková, Klára (advisor)
The present thesis focuses on the preparation of tetragonal zirconia doped with yttria oxide, ceric dioxide, and magnesium oxide. In its theoretical part the thesis covers the characteristics of doped ceramics, the possible methods of powders preparation and of their further processing. The experimental part describes the precipitation synthesis of zirconia in base environment and further processing for ceramics. Also studied were the influences of dopant and of the processing technique used on the phase composition and microstructure of the resulting ceramics. To describe the powder structure, the thermal, dilatometric, surface area, and x-ray analyses were performed; as well as both the scanning and transmission electron microscopy employed. Dry processed ceramics showed the average grain size of 87–94 nm and the relative density in the range of 84,0–99,3 %. In comparison, the ceramics produced of hydrothermally synthesised powders proved the average grain size of 75–85 nm and the relative density between 92,7-99,9 %. As the next step, samples were subjected to low-temperature degradation for the time of 5 and 15 hours. Samples consisting of pure tetragonal ZrO2 were resistant to 5 and 15 hours of low-temperature degradation at 180 °C.
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.
The thermal properties of glasses for preparation of composites ceramic - glass
Halasová, Martina ; Šiler, Pavel (referee) ; Havlica, Jaromír (advisor)
Results of DTA and TG methods and next thermal methods will be explored for evaluation of processes in temperature range up to temperature of softening for assessing of possibilities of application of glasses in composites ceramic-glass
The influence of simulated body fluids on the apatite production
Horváthová, Lenka ; Beranová, Denisa (referee) ; Bartoníčková, Eva (advisor)
This bachelor thesis deals with the interaction of various simulated body fluids with ceramic biomaterials. It includes fluid preparation, sample preparation and subsequent analysis of their interaction. Individual samples of biomaterials were exposed to a simulated body fluid for a certain amount of time. After this time, a change in the calcium and phosphorus content of the solutions was determined. At the same time, an electron microscope analysis of sample surface was performed where the dependence of calcium and phosphorus changes was demonstrated. Electron microscopy analysis revealed the formation of new phases on the surface of the studied materials.
Modern Assembly for Microelectronic and Electronic Modules
Janík, Pavel ; Švecová, Olga (referee) ; Šandera, Josef (advisor)
Project is focused on describe modern assembly of microelectronic and electronic modules in electronic devices. Sense of the project is analyse reliability and inadequacies electronic devices assembled by modern technogies. Inadequacies modern technologies are impulse for design, implementation and testing new our way of assembly microelectronic modules. Main kind of materials which are used in this project are ceramics Al2O3 and printed circuit board FR4.
Failure probability of the ceramics part using Weibull weakest link theory
Kovář, Jaroslav ; Návrat, Tomáš (referee) ; Fuis, Vladimír (advisor)
This thesis compares Weibull weakest link theory with inclusion of one and all three principal stresses. Principal stresses needed for this theory were calculated with finite element method. The informational research is in the introduction of this thesis. It includes ceramic materials, Weibull weakest link theory, Gaussian quadrature over spherical surface and ceramic head of hip joint endoprothesis. Theoretical part is used for next calculations of probability of failure. The probability of failure of ceramic rod loaded by four-point bending is calculated in first calculations. This task is solved as contact in the next step. Next part of this thesis is about selection of suitable method of numerical integration. This method will be used in the calculation with all three principal stresses. The results of calculation with all three principal stresses are compared with the results of the calculation which includes only first principal stress. Firstly, this is done for cylindrical body and then used on head of hip joint endoprothesis. In the last part of this thesis, probability of fracture of head hip joint endoprothesis with shape deviation of nominal conicity is calculated.
Synthesis of ferroelectric and dielectric ceramic composite materials
Čípová, Eva ; Salamon, David (referee) ; Částková, Klára (advisor)
The topic of the thesis is preparation of ferroelectric and dielectric composite materials, particularly the work deals with the preparation of barium strontium titanate. In the theoretical part the possibilities of BST synthesis and its processing are described. The experimental part deals with precipitation synthesis of barium strontium titanate. Prepared powders were characterized in terms of morphology and phase composition. Further, pressureless sintering and hot isostatic pressing (HIP) were used for preparation of dense ceramics. Pure BST powders, that were formed and sintered, were prepared by sol-gel precipitation synthesis. The highest density was reached by slow sintering cycle (slow increase of temperature and delay during sintering) and sintering by HIP.

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