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The optimization of phosphate binders compozition used for refractories
Kalousová, Hana ; Ptáček, Petr (referee) ; Opravil, Tomáš (advisor)
This thesis deals with optimization of the composition phosphate binders. These binders are used in production of refractories. In this branch, the bauxite is very often used as an aggregate, but it contains tiny particles of iron which arise in milling process. These particles of iron react with the phosphate binder to form hydrogen – it is consequence of the reaction between phosphoric acid and iron. The formed gas causes the formation of bubbles and the deformation of refractories. The goal of this thesis is to find suitable additives which can be used to stop or to limit the production of hydrogen. Usually used binders were replaced by a model binder to simplify the system and for better understanding. The model binder was prepared in laboratory by dissolving aluminium hydroxide in phosphoric acid. They used pure powdered pentacarbonyl iron instead of tiny iron particles from the milling process. The model binder was modified with using a few inhibitors. The calcimetr was used to measure their influence on the production of hydrogen, as well as measuring concentrated rows of selected inhibitors. These rows are necessary to optimize the inhibitors quantity added in the binder.
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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.
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Core-Shell Ceramic Structures Prepared by Thermoplastic Co-Extrusion Method
Kaštyl, Jaroslav ; Pabst, Willi (referee) ; Hadraba, Hynek (referee) ; Trunec, Martin (advisor)
In the doctoral thesis, the bi-layer ceramic bodies with core-shell geometry were prepared by thermoplastic co-extrusion method and for these composite bodies the mechanical properties were studied. For study of co-extrusion and mechanical properties were designed two composite systems. First system ZTA-A combined the dense core ZTA (zirconia-toughened alumina) and the dense shell Al2O3. Second system ZST-Z consisted of porous core and dense shell made from ZrO2 for both cases. In the thesis, the rheology of ceramic thermoplastic suspensions and their mutual influence during co-extrusion was studied. Subsequently, the debinding process and sintering were studied, and based on the optimization of all process steps were obtained defect-free bodies with core-shell geometry. The mechanical properties (elastic modulus, hardness and bending strength) were determined for sintered bodies. To estimate the stress path in the core shell bodies loaded in bending, the relationship considering different elastic moduli of the core and the shell was used. For bodies of ZTA-A system was increased the strength in comparison with monolithic bodies of the individual components. Thus, bodies with high surface hardness of shell from Al2O3 and moreover having high fracture strength in bending were obtained. The effective elastic modulus was decreased for bodies of ZST-Z system up to 25 % in comparison with the elastic modulus of dense monolithic samples. The same effective modulus of elasticity was possible to achieve with core-shell bodies while maintaining significantly higher fracture strength than monolithic porous bodies or pipes.
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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.
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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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Behaviour of the Interface of Low Toughness Materials
Halasová, Martina ; Pabst, Willi (referee) ; Tatarko, Peter (referee) ; Fintová, Stanislava (referee) ; Chlup, Zdeněk (advisor)
The work is focused on evaluation of factors influencing behaviour of interface in low toughness ceramic materials reinforced with fibres. The main aim was to characterise processing effects influencing the quality of fibre-matrix interface, with respect to final behaviour of composites at various loading type. The partial goal was to map the possibility of influencing the composite material by choice of matrix material, eventually by change of its processing, leading to change of interfacial properties without need of modification of reinforcement surface. The materials used in studied composites as a matrix were based on thermal transformation of polymer precursors, thus, the resulting materials were characterised in partially as well as in fully pyrolyzed state. Behaviour of interface in cpomposite materials was first evaluated from the global behaviour (i.e., change of mechanical properties) and in chosen representative composites also from the point of local changes in close surrounding of the interface (i.e., microstructure, chemical processes, fracture-mechanic processes, etc.) due to thermal exposition. In experiment were used particularly composite materials prepared by pyrolysis of polysiloxane resins reinforced by basalt fibres or Nextel™720 fibres. With respect to thermal resistance of the reinforcement, the basalt reinforced composites contained only partially pyrolyzed matrix (i.e., to temperature of 800°C), and in composites with Nextel™720 reinforcement was the matrix in form of fully pyrolyzed polymer into ceramic (SiOC). At partial pyrolysis of polysiloxane resin occurs rapid change of behaviour at temperature of 600°C. It was demonstrated, that around this temperature the formed interface with basalt fibre exhibits optimum adhesion/strength, allowing to reach sufficient level of composite strength at acceptable fracture toughness. Above temperature of 750°C occur significant difusion processes in the area of the interface and formation of new crystalline phases in the fibre, what deteriorates the fibre strength, and on the contrary, strengthen the interface cohesion, what leads to degradation of properties of the whole composite. At composite materials determined for high temperatures, reinforced by Nextel™720 fibres, was detected significant resistivity against oxidation caused especially by fully pyrolyzed matrix. As similarly important factor was observed the formation of mullite interphase in surface area of the fibre. Volume changes caused by formation of the interphase, difusional transport of the matter and thermal exposition led to formation of thermally and stress-induced micro-cracks, weakening interfacial surrounding in matrix as well as in fibre. This mechanism in contrast to amplifying chemical bond between fibre and matrix led to preserving of the composite properties also at high temperatures up to 1500°C. The work also dealed with effects of loading rate, where in contrast to static loading were observed different failure mechanisms. Realized research led to description and explanation of the influence of the fibre-matrix interface by change of matrix material processing parameters, which allow processing of economically advantageous and thermally stable composite.
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Coextrusion of laminated ceramic bodies
Kaštyl, Jaroslav ; Cihlář, Jaroslav (referee) ; Trunec, Martin (advisor)
In the diploma thesis, an overview of the existing literature focused on the thermoplastic co-extrusion method was worked out and based on the findings, extrusion of the monolayer and homogenous bodies from ZrO2, Al2O3, ZTA a ATZ was studied. For thermoplastic extrusion the capillary rheometer was modified and the nozzle was designed and fabricated. Applying the co-extrusion method, homogenous ceramic rods and monolayer rods in structure core/layer: ZrO2/Al2O3, ZrO2/ATZ and ZTA/Al2O3 were fabricated. In monolayer rods, the interface quality and defects that originate during preparation were evaluated. Technological parameters and properties of homogenous rods were used to rate the structure and defects in monolayer rods. Monolayer rods ZrO2/ATZ and ZTA/Al2O3 with 2.5 mm diameter and 45 mm length (containing small defects) were prepared by thermoplastic co-extrusion.
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Frost resistance of clay roofing tiles - methodology of laboratory testing
Khongová, Ingrid ; Stančík,, Hynek (referee) ; Sokolář, Radomír (advisor)
This bachelor´s work is focusing on a frost resistance of clay roofing tiles. Frost resistance is among the most important parameters, which is derive from its resistance and lifespan. Direct laboratory methods are very time-consuming so there is a great effort to improve indirect methods, which could most likely determine if tested clay roofing tile is frost resistance or not. Main targer of this bachelor´s work is to summary present knowledge about a issue of frost resistance, description of making frost resistance brick body and description of used methods establishing frost resistance. Practical part is focused on a different tests, which give us informations about microstructure and characteristic of a ceramic body.
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Ceramic materials applied in medicine - challenges and opportunities
Vitásek, Ladislav ; Sláma, Martin (referee) ; Novotná, Lenka (advisor)
This thesis deals with ceramic materials applied in medicine, mainly in orthopaedics and dentistry. The first part is focused on requirements and current state of biomaterials in bone tissue engineering and their advantages and disadvantages. Composite materials, where ceramic material is one component at least, are mentioned in the next part. Dense ceramics based on alumina and toughened zirconia is described in the separate part. The main part of this thesis deals with porous ceramic materials based on calcium phosphates. There are also defined scaffolds requirements such as porosity, mechanical and biological properties and moreover processing methods. The experimental part of this thesis has been devoted to the preparation of bioactive porous ceramic material based on hydroxyapatite and silica with improved properties. Samples with different amount of silica in structure (6-21 wt%) were fabricated by polymer replica technique. Prepared scaffolds with structure similar to cancellous bone can be promising candidates for using in bone tissue engineering applications.
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DPF for SI Engines
Pohludková, Lenka ; Prokop, Aleš (referee) ; Dundálek, Radim (advisor)
This bachelor thesis deals with gasoline particulate filters. Emissions of internal combustion engines and their impact on air pollution and human health, especially the impact of particulate matter, are discussed. It also describes what these filters are made of, where they are located in the car, and explains the principle of their function and regeneration.
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