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Duplex microstructures preparation by mechanical alloying and spark plasma sintering
Neboha, Oksana ; Štěpánek, Roman (referee) ; Moravčík, Igor (advisor)
This master´s thesis focuses on duplex microstructures preparation by powder metallurgy. A hybrid material can be created by combining two or more existing materials in different geometries, and thus the newly formed composite can provide a superposition of the properties of the starting materials (powders). This means that it will have an improved combination of the required properties. The theoretical part describes in detail the hybrid materials and the architectured materials that contain highly controlled structures. Structure control allows to change the variety of possible geometries and opens up a number of other useful properties. Therefore, this thesis also deals with the mechanical alloying and SPS. The experimental part describes procedures of preparation of four samples of composites with a duplex structure from a powder of a significantly tough alloy (austenitic steel 316L) in combination with a powder of a significantly strong alloy (titanium carbonitride). A crucial part of this thesis is characterization of these four samples by electron microscopy methods (SEM, TEM, EDS) and supported by hardness measuring.
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Hybrid materials with improved thermomechanical properties
Perchacz, Magdalena ; Beneš, Hynek (advisor) ; Vlček, Tomáš (referee) ; Brožek, Jiří (referee)
Epoxy resins have been broadly used in the industry for adhesives, laminates, coatings, composites, encapsulation of electronic devices, printed circuit boards, etc. Despite their excellent adhesion to different materials, heat and chemical resistance and good mechanical properties, they also exhibit few drawbacks like brittleness, high thermal expansion coefficient (CTE), poor resistance to crack initiation and growth. Therefore, the thesis is focused on the preparation of epoxy-silica hybrid materials exhibiting improved thermomechanical properties compared to the neat epoxides, without impairing their beneficial features. The main synthetic route of epoxy-silica hybrids' preparation has been the sol-gel process of alkoxysilanes, allowing either in-situ formation of high purity and homogeneity silica particles or creation of various siloxane structures in a form of liquid (sol) silica-based precursors. The sol-gel method, on one hand, helps to omit too high viscosity of nanofiller suspension and energy-intensive nanofiller dispergation problems, but on the other hand, is often associated with necessity to use solvents and to remove formed volatiles. Therefore, in the first part of the thesis, a simple solvent-free sol-gel procedure, enabling to minimize the side-effect of solvent evaporation and...
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Duplex microstructures preparation by mechanical alloying and spark plasma sintering
Neboha, Oksana ; Štěpánek, Roman (referee) ; Moravčík, Igor (advisor)
This master´s thesis focuses on duplex microstructures preparation by powder metallurgy. A hybrid material can be created by combining two or more existing materials in different geometries, and thus the newly formed composite can provide a superposition of the properties of the starting materials (powders). This means that it will have an improved combination of the required properties. The theoretical part describes in detail the hybrid materials and the architectured materials that contain highly controlled structures. Structure control allows to change the variety of possible geometries and opens up a number of other useful properties. Therefore, this thesis also deals with the mechanical alloying and SPS. The experimental part describes procedures of preparation of four samples of composites with a duplex structure from a powder of a significantly tough alloy (austenitic steel 316L) in combination with a powder of a significantly strong alloy (titanium carbonitride). A crucial part of this thesis is characterization of these four samples by electron microscopy methods (SEM, TEM, EDS) and supported by hardness measuring.
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Layered Transition Metal Hydroxides: Delamination and Properties
Hyklová, Barbora ; Lang, Kamil (advisor) ; Zima, Vítězslav (referee) ; Bujdák, Juraj (referee)
Charles University Faculty of Science Study programme: Inorganic Chemistry Mgr. Barbora Hyklová Layered Transition Metal Hydroxides: Delamination and Properties Extended abstract Supervisor: Ing. Kamil Lang CSc., DSc. Supervisor-Consultant: RNDr. Jan Demel PhD. Prague, 2017 Layered transition-metal hydroxides have attracted increasing attention as promising active electrode materials for electrochemical energy storage and conversion device due to facile preparation and modification, good tunability, high capacitance capability, fast reversible redox reactions, and cost effectiveness. Many reported hierarchical architectures based on nickel and cobalt hydroxides are composed of bulky nanoplatelet-like aggregates; however, the nanomorphology and behavior of the separated hydroxide nanosheets is much less known. Figure 1. Scheme of layered nickel or cobalt hydroxide delamination and subsequent restacking on conductive HOPG support. In this respect, the dissertation thesis reports characterization and electrochemical performance of nickel, nickel-cobalt, and cobalt hydroxide nanosheets, synthesized by an economical and environmentally friendly method based on delamination of corresponding layered hydroxides in water (Figure 1). For this purpose, lactate and nitrate layered hydroxides were prepared by two...
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Hybrid materials with improved thermomechanical properties
Perchacz, Magdalena ; Beneš, Hynek (advisor) ; Vlček, Tomáš (referee) ; Brožek, Jiří (referee)
Epoxy resins have been broadly used in the industry for adhesives, laminates, coatings, composites, encapsulation of electronic devices, printed circuit boards, etc. Despite their excellent adhesion to different materials, heat and chemical resistance and good mechanical properties, they also exhibit few drawbacks like brittleness, high thermal expansion coefficient (CTE), poor resistance to crack initiation and growth. Therefore, the thesis is focused on the preparation of epoxy-silica hybrid materials exhibiting improved thermomechanical properties compared to the neat epoxides, without impairing their beneficial features. The main synthetic route of epoxy-silica hybrids' preparation has been the sol-gel process of alkoxysilanes, allowing either in-situ formation of high purity and homogeneity silica particles or creation of various siloxane structures in a form of liquid (sol) silica-based precursors. The sol-gel method, on one hand, helps to omit too high viscosity of nanofiller suspension and energy-intensive nanofiller dispergation problems, but on the other hand, is often associated with necessity to use solvents and to remove formed volatiles. Therefore, in the first part of the thesis, a simple solvent-free sol-gel procedure, enabling to minimize the side-effect of solvent evaporation and...
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