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THE APPLICATION OF NANOMATERIALS FOR LEAD FREE SOLDERS DEVELOPMENT
Pešina, Zbyněk ; Pinkas, Jiří (referee) ; Spousta, Jiří (referee) ; Sopoušek, Jiří (advisor)
The present dissertation is motivated by the search for alternatives of lead-free soldering by nanoparticles of metals and their alloys. The research focuses on the possibility of replacing lead-free solders by nanoparticles. This issue is currently being addressed by the use of lead-free solders but their properties are not entirely equivalent to properties of lead-tin based alloys. The theoretical part of the dissertation first summarizes up-to date knowledge on the development of lead-free alloys currently used for soldering in the electronics. The work compares these lead-free solder candidates with previously used Pb-Sn alloys. The second section of the theoretical part is devoted to nanotechnology that offers possible solutions of problems associated with the use of lead-free solders. The text contains a description of the properties of nanocrystalline materials in comparison with those of compact alloys having the same chemical composition. The possibility of preparation of nanoparticles and potential problems associated with small particle sizes are also presented. Introduction of the experimental part focuses on the preparation of nanoparticles of pure metals and alloys by chemical and physical ways as well as on an instrumentation for characterisation and analysis. Attention is focused on the silver in nanoparticle form that exhibits the low temperature sintering effect, which is thermally activated by decomposition of oxide envelope covering the Ag nanoparticles. This factor is critical for low-temperature sintering and thus also for possible future applications. The thermal effects of the low sintering process were studied by methods of thermal analysis. The preparation of the Cu / Ag nano / Cu joints was carried out in-situ in inert atmosphere and under the action of atmospheric oxygen. In both cases varying conditions of thermal treatment were used. The cross sections of the prepared joints were then used for the metallographic analysis of the local mechanical properties of the resulting silver layer, for the chemical composition evaluation of the resulting layers of the joint, and for the microstructure study. Strength characteristics are represented by testing shear strength of individual joints.
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Systhesis and Characterisation of the Insulin-like Peptide 5 from Drosophila melanogaster
Halušková, Petra ; Žáková, Lenka (advisor) ; Poljaková, Jitka (referee)
Many evolutionary conserved proteins and mechanisms have been observed in nature, one of them is insulin and its signal pathway. Importantly, many parts of this pathway in humans are similar to those found in lower organisms, such as fruit fly (Drosophila melanogaster). Insulin is one of the most studied complex molecules; it acts primarily as a hormone but it can also act as a growth factor due to its evolutionary congeniality and similarity to the IGF. It has long been unclear how insulin binds to its receptor and how insulin or insulin-like proteins influence regulation of metabolism, cell proliferation, cell growth and also the size of organs and the whole body. Examining insulin-like peptide superfamily and its signal pathway in invertebrates may thus be used to better understand many metabolic processes in vertebrates thanks to high evolutionary conservation. In this thesis, we tried to prepare an analogue of insulin like peptide 5 (DILP5) of Drosophila melanogaster by a total chemical synthesis. This analogue is composed of A-chain of human insulin and B-chain of DILP5. In B-chain all methionins were replaced by amino acid norleucine using a chain combination method through S-sulfonate forms of each chain. The results show that this protein can be successfully prepared, however, the amount...
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THE APPLICATION OF NANOMATERIALS FOR LEAD FREE SOLDERS DEVELOPMENT
Pešina, Zbyněk ; Pinkas, Jiří (referee) ; Spousta, Jiří (referee) ; Sopoušek, Jiří (advisor)
The present dissertation is motivated by the search for alternatives of lead-free soldering by nanoparticles of metals and their alloys. The research focuses on the possibility of replacing lead-free solders by nanoparticles. This issue is currently being addressed by the use of lead-free solders but their properties are not entirely equivalent to properties of lead-tin based alloys. The theoretical part of the dissertation first summarizes up-to date knowledge on the development of lead-free alloys currently used for soldering in the electronics. The work compares these lead-free solder candidates with previously used Pb-Sn alloys. The second section of the theoretical part is devoted to nanotechnology that offers possible solutions of problems associated with the use of lead-free solders. The text contains a description of the properties of nanocrystalline materials in comparison with those of compact alloys having the same chemical composition. The possibility of preparation of nanoparticles and potential problems associated with small particle sizes are also presented. Introduction of the experimental part focuses on the preparation of nanoparticles of pure metals and alloys by chemical and physical ways as well as on an instrumentation for characterisation and analysis. Attention is focused on the silver in nanoparticle form that exhibits the low temperature sintering effect, which is thermally activated by decomposition of oxide envelope covering the Ag nanoparticles. This factor is critical for low-temperature sintering and thus also for possible future applications. The thermal effects of the low sintering process were studied by methods of thermal analysis. The preparation of the Cu / Ag nano / Cu joints was carried out in-situ in inert atmosphere and under the action of atmospheric oxygen. In both cases varying conditions of thermal treatment were used. The cross sections of the prepared joints were then used for the metallographic analysis of the local mechanical properties of the resulting silver layer, for the chemical composition evaluation of the resulting layers of the joint, and for the microstructure study. Strength characteristics are represented by testing shear strength of individual joints.
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Measures towards Increasing the Effectiveness of Research in the Field of Chemical Synthesis
Václavík, Jiří ; Hartman, Ladislav (advisor) ; Koubek, Josef (referee)
Research in the field of chemical synthesis is a very diverse and complex activity. Individual workplaces differ in many aspects and this essentially impacts the productivity. The aim of this Master's Thesis is to identify, name and analyse those aspects, and to suggest measures to be taken in order to help increase the performance, all that within defined assumptions. The first half of the Theoretical Part is devoted to academic studies on this topic, which are mainly focused on the HR part. Selected methods of lean manufacturing commonly used in industry are also described. The Experimental Part comprises an analysis of research facilities in which the author worked as a chemist, and a set of proposed measures that lead to an increased productivity. The Thesis is concluded by a demarcation of a series of factors that influence the performance of R&D workers, groups and institutions, and a vision of an ideal laboratory is presented.
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