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Vakuová metalurgie intermetalik TiAl
Zemčík, L. ; Dlouhý, Antonín ; Król, S. ; Pražmowski, M.
To be able to melt successfully type gamma TiAl alloys it is absolutely necessary to solve the fundamental metallurgical problems associated with the reactions between the melt and the refractories of crucibles and ceramic moulds, with the reactions between the melt and residual gases in the furnace chamber, and with the evaporation of aluminium from the melt. The paper deals with the physico - chemical analyses of the above processes and gives their evaluation based on the results of experimental melts of the type of Ti48Al2Cr2Nb1B (at.%) obtained in vacuum induction furnace. The work also gives the results of oxidation tests for the Ti48Al2Cr2Nb1B(at.%) alloy.
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Propagation of inclined cracks to the interface of ceramic laminates
Novotná, Lenka ; Trunec, Martin (referee) ; Chlup, Zdeněk (advisor)
Composite materials with laminated structure provide advantages which are utilised during component design. Low density, temperature and chemical stability are the profitable properties predetermining application of ceramic laminates. The main obstacle for wide spread of ceramic materials is their inherent brittleness. Therefore, in this thesis, the crack propagation in ceramics laminates has been extensively studied. Laminated structures with various volume fractions of components (alumina and zirconia) were prepared by electrophoretic deposition. Evaluation of crack propagation through the interface and determination of basic mechanical properties was conducted on the basis of extensive literature search. Crack deflection originated in both presence of internal stresses and differences in elastic modulus during the crack interface passing was monitored. A special type of specimen geometry was employed with the aim to set arbitrary angle between crack and interface. It was experimentally found that the degree of crack deflection is dependent on entering angle and volume fraction of components. Higher crack deflection was already found in the bulk of the test piece comparing to the test piece surface. The 3D fracture surface reconstruction generated using laser confocal microscopy was used in this detailed crack propagation study. Further basic elastic and strength characteristics of laminates were determined and compared to those obtained from monolithic materials. The validity of the mix rule for elastic characteristics was confirmed by comparing of elastics modulus. The most reliable method for elastic modulus determination was marked the dynamic resonance method due to low scatter and consistency in measurement. The flexural strength of all laminates tends to be close to the flexural strength of the weakest component. Therefore the mix rule is not applicable for flexural strength estimation on the contrary of elastic characteristics. The change of component volume fraction leads only to change of flexural strength scatter. Thanks to gained knowledge about crack propagation and basic characteristic determination will be possible to design ceramic laminates more efficiently for given needs of application.
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Multiscale design of advanced materials
Král, L. ; Million, Bořivoj
In this paper, the results of measurements of chemical diffusion of Mn in steel weldments are reported. Chemical concetnration of Mn an interval 0-15 wt.% Mn was varied. Alloys were casted in induction furnace under protective Ar atmosphere. Diffusion couples were annealed at 800-1100°C for 96-1.5 hours respectively. Measurement of Mn redistribution was done in a normal direction to welding interface using scanning electron microscope Philips SEM-505WDS equipped with Microspec WDX-2A. Diffusion coefficients of Mn were obtained by fitting experimental curves to the known analytical solution.
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NOx reduction in flue gas
Rumánek, Tomáš ; Jedlička, Filip (referee) ; Dvořák, Radek (advisor)
My master´s thesis deals with the problems of NOx abatement that are included in flue gas. The accent is put on flue gases treatment throug cloth filter or ceramic candles, where the deposited catalyst enables NOx reduction throug the method of selective cytalytic reduction. In thesis is also describe experimental unit which current remove gaseous pollutants (dioxin, VOC and NOX) and ash on catalytic cloth filter or catalytic ceramic candles. For experimental unit has been calculated pressure drop. Pressure drop has been calculated for nominal and maximal conditions for cloth filter and ceramic candle. Last part of thesis deals with compile a experimental schemes for different concentration of NO, flow and temperature of combustion.
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CNC turning of shaped stainless steel parts.
Vostřel, Jan ; Polzer, Aleš (referee) ; Píška, Miroslav (advisor)
This diploma thesis is focused on a CNC turning operation of form parts made of stainless steels. The first part of the diploma thesis is focused on a theoretical analysis of stainless steels material characteristics. The second part is focused on a concept of experiment of complex form experimental stainless steel components. In this thesis the new CNC technology is defined in a new operation system Sinumerik 840D/ShopTurn V06.04 with an application for a new multi-purpose turning centre SP280SY. The final part comprehends technical documentation, CNC programs of shaped components, their verification and overall photographic documentation.
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Study of phenolic compounds in some biologic materials using method LC/MS
Měřínská, Radana ; Zemanová, Jana (referee) ; Kočí, Radka (advisor)
Presented bachelor thesis was focused on suitable methods for analysis of phenolics, especially modern instrumental methods were studied. In experimental part some standard phenolic compounds were analysed using combined technique HPLC/ESI-MS with off-line and/or on-line detection. Mass spectra of individual stadards and/or mixtures were determined in MS full scan and/or MS/MS full scan mode. Ionisation of chosen standard compounds was done in pozitive and/or negative mode. Parent ions of followed compounds were identified: reserpine (PI 609.9, NI 607.7), acid chlorogenic (NI 353), quercetin (PI 303.5, NI 301.5), rutin (PI 611, NI 609), morin (PI 303.1, NI 301.1). Typical fragments of studied standards were produced using MS/MS full scan mode. By fragmentation characteristic product ions were identified: acid chlorogenic (NI 191), quercetin (PI: 229.1 and 257.1; NI: 179.0 and 151.0), rutin (in MS/MS NI: 301; in MS3 NI: 179, 151.1), morin (PI: 285.1 a 257.1; NI: 283.2, 273.2, 257.1, 229.1). Optimal conditions of phenolic HPLC separation were determined including gradient elution and Restek column use. In conclusion on-line HPLC/MS detection using negative ionization was observed as the best configuration for phenolic analysis.
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Optimisation of experimental parameters for double-pulse LIBS
Roščák, Michal ; Novotný, Karel (referee) ; Kaiser, Jozef (advisor)
Diploma thesis presents the description of laser induced breakdown spectroscopy (LIBS) analytical method. The possibility to decrease LIBS detection limits using double pulse LIBS (DP-LIBS) is also detailed. Properties of laser induced plasma (LIP) are discussed. Thesis describes the optimisation process of DP-LIBS setup at laser spectroscopy laboratory of Faculty of Mechanical Engineering, Brno University of Technology. Optimisation was carried out for detection of chrome in steel with respect to detection limits and ablation crater size. Optimised DP-LIBS setup is appropriate for mapping chrome distribution in steel samples.
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