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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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Draft modified winding technology of composite pipes
Bednár, Peter ; Pinkas, Jan (referee) ; Kandus, Bohumil (advisor)
This diploma thesis focuses on composite pipes production by winding of composite fibres soaked in resin binder and feeding with additional third type material simultaneously. It also describes the production machine FWMS180 and all of its additional devices necessary for the composites production by filament winding. The production process of composite pipes on the production machine FWMS180 is described in this paper as well as detailed description of the winding method. Furthermore, the technological bend and vibration tests procedures conducted on pipes of different material composition are discussed with related results and comparison. The thesis proves that presence of the third type material in composite pipes structure has different influence depending on observed and evaluated property.
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Processing of aerogel coatings on bulk materials substrates
Torres Rodríguez, Jorge Alberto ; Torre, Sebastián Díaz de la (referee) ; Pinkas, Jiří (referee) ; Kaiser, Jozef (advisor)
Tato práce se zabývá systematickou studií syntézy a zpracováním pokročilých tepelně stabilních aerogelů pro potenciální vysokoteplotní aplikace. V první části dizertační práce jsou podrobně popsány syntetické implikace pro přípravu aerogelů a jejich aplikace spolu s popisem depozičních metod povlaků vytvořených pomocí sol-gel procesu. Experimentální postup je rozdělen do tří částí. První z nich představuje syntetické protokoly k přípravě ZrO2, YSZ, Ln2Zr2O7 (Ln = La3+, Nd3+, Gd3+, and Dy3+) aerogelů, Ln2Zr2O7 prášků a xerogelů. Dále je popsána depoziční metoda, která byla použita pro přípravu povlaků z aerogelů na kovových substrátech. Poté jsou následně specifikovány techniky, jež byly použity pro charakterizaci. Bylo zjištěno, že množství vody a kyseliny dusičné hraje rozhodující roli v přípravě gelů vhodných pro transformaci na aerogely. Po kalcinaci při 500 °C mají ZrO2 a YSZ aerogely velký povrch, a to až do 114 m2 g-1, avšak při 1000 °C dochází k úplnému zhuštění a ztrácí se tak veškerá jejich porézní struktura. Naopak ve srovnání s ZrO2 and YSZ jsou aerogely Ln2Zr2O7 tepelně stabilnější, protože si zachovávají svou porozitu při vyšší kalcinační teplotě (1000 °C), při které dosahují hodnot > 160 m2 g-1. Experimentálně bylo dále zjištěno, že ve studovaném teplotním rozsahu ZrO2 aerogel tvoří tetragonální komplex monoklinický fázový přechod řízený velikostí krystalitů, zatímco YSZ je tvořena jedinou tetragonální fází. Fázové složení zirkoničitanů vzácných zemin je vysoce závislé na způsobu syntézy; všechny Ln2Zr2O7 materiály jsou pyrochlorické nebo fluoritové krystalické fáze. Přímým odléváním aerogelu na kovový substrát dochází k úplnému rozpraskání povlaku z důvodu smršťování, zatímco máčením kovového substrátu v suspenzi je možné vyrobit homogenní, silné a hrubé povlaky z aerogelu. Tyto povlaky neobsahují fázové změny a zůstávají vysoce porézní i po různých tepelných úpravách.
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Heating the house by heat pump
Pinkas, Jan ; Kudela, Libor (referee) ; Pospíšil, Jiří (advisor)
The point of this bachelor thesis is a family house heating with a use of a heat pump. In the first part of the thesis the principle and working of a heat pump are explained. Also the basic sources of energy for the heat pump including their pros and negatives are talked over. Secondly in the practical part thermal losses and energy consumption of the chosen house are calculated. Based on those calculations the heat pump and the heating system are chosen. In the end the investment is evaluated.
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Condensing heat exchager for solid fuel boiler 200 kW
Pinkas, Jan ; Lisý, Martin (referee) ; Baláš, Marek (advisor)
The point of this thesis is a waste gas condensator for 200kW woodchips burning boiler. In the first part of the thesis types of heat exchangers are introduced. Condensation is introduced. Further all necessary equations and relations for vertical shall and tube heat exchanger are specified. Following those relations waste gas condensator is designed. Situation under different input conditions is talked over in the end.
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Teaching History in Times of Climate Crisis What Implications Should Have Contemporary Environmental Crisis on Teaching History at Czech Secondary/Middle Schools?
Černínová, Anna ; Pinkas, Jaroslav (advisor) ; Najbert, Jaroslav (referee)
This thesis responds to the need to update education due to the urgency of current environmental problems and it tries to relate it to the school subject of history. The goal of this thesis is to answer at least partially how history could or should adapt to the ongoing climate crisis so that students have a better chance to successfully face its challenges. For such a task, it was first necessary to map out what concepts and approaches are used in Czechia and abroad to approach climate change in the context of education. I analyzed the environmental education in the RVP ZV (the curriculum for primary schools) and the publication Klima se mění - a co my? (Climate is changing - and what about us?) by Petr Daniš et al. Other possible approaches also resulted from the analysis of some foreign curricula - namely from Finland and New Jersey. Finally, I expanded the possible implications for history lessons thanks to the analysis of some other professional publications of foreign provenance. These were, for example, works related to transformative education or environmental history. Following on from these analyses, I tried to question in more detail some figures of modern discourse, which seem somehow dysfunctional due to the environmental crisis. In this way, I approached the problematic perception of...
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Utilization of modified polyethylenes as macroscopic ligands
Ráliš, Václav ; Pinkas, Jiří (advisor) ; Vojtíšek, Pavel (referee)
Charles University in Prague Faculty of Science Department of Inorganic Chemistry Author: Václav Ráliš Supervisor: Mgr. Jiří Pinkas, Ph.D.prof. Consultant: RNDr. Petr Štěpnička, Ph.D., DrSc. Title: Utilization of modified polyethylenes as macroscopic ligands Termination of growing polyethylene (PE) chain by silane HSiR1 R2 R3 leads to polymers bearing chain-end silyl group (SiPE). These materials can be further modified to form polymers terminated by silanol group (PE-SiOH). Using suitable default conditions, a modified PE with relatively low molecular weight (Mn ~1000 Da) and useful solubility profile can be obtained. Due to the presence of reactive silanol or hydrosilane groups, such materials can serve as a support for grafting a wide range of metals. The aim of the thesis is to verify the possibility of grafting metals by chemical bonding on a modified PE (which in this particular case can be seen as a "slightly larger" ligand. Prepared materials will be tested with regard on their possible use in catalysis. This research is interdisciplinary at the border between inorganic (coordination chemistry) and physical chemistry (polymers, catalysis). Keywords: supported complexes, modified polyethylene, catalysis
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MRI contrast agents for modern applications
Kotková, Zuzana ; Hermann, Petr (advisor) ; Pinkas, Jiří (referee) ; Drahoš, Bohuslav (referee)
Zuzana Kotková - Ph.D. Thesis: MRI Contrast Agents for Modern Applications 1 Abstract Over the last few decades, Magnetic Resonance Imaging (MRI) has become one of the most powerful medicinal methods for the diagnosis of various diseases (Fig. A1a ). In several types of examinations, contrast agents (CAs) are used to increase the quality of images (Fig. A1b ). These contrast agents are usually based on paramagnetic metal complexes of macrocyclic ligands. In dependence on the measured nuclei, two basic groups of CAs are considered - 1 H MRI CAs and, recently, also 19 F "hot-spot" CAs. The 1 H MRI CAs are based on Gd3+ complexes of macrocyclic ligands with one water molecule coordinated to the central metal ion (Fig. A1c ) and the effect of the CAs is to shorten the relaxation times of water protons. (a) (b) (c) Fig. A1: Illustrative pictures for Magnetic Resonance Imaging (MRI) method; (a) whole body MRI tomograph,* (b) an example of MR head scans with the use of MRI CA** and (c) schematic general structure of a contrast agent based on Gd3+ complex of macrocyclic ligands (for more details see the Thesis, section 1.3.3, Fig. 18). * https://www.ottawaheart.ca/test-procedure/cardiac-mri (Accessed 25 Febr. 2023) ** https://affordablemri.com/mri-explained (Accessed 25 Febr. 2023) The shortening of relaxation...
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Study of active centers in zeolite catalysts for cascade Prins-Friedel-Crafts reaction
Golis, Petr ; Shamzhy, Mariya (advisor) ; Pinkas, Jiří (referee)
Conventional zeolites are important shape-selective heterogeneous acid catalysts due to the presence of acid sites accessible through uniform micropores. Recently designed hierarchical zeolites with combined micro-mesoporosity also contain acid sites on the external surface or in mesopores. These highly accessible acid sites are promising active centres for the transformation of bulky molecules, which cannot pass through the micropore openings of conventional zeolites. An example of a reaction that can benefit from the use of zeolites is the one-pot cascade Prins-Friedel-Crafts (PFC) reaction of an aldehyde, homoallylic alcohol, and aromatic compound, which yields valuable heterocyclic compounds containing 4- aryltetrahydropyran moieties. In this work, the acidic characteristics of a series of hierarchical aluminium- and gallium- containing MFI and MWW zeolites were evaluated by FTIR-monitored thermodesorption of probe molecules and further related to the catalytic properties of zeolites in the PFC reaction of butyraldehyde, 3-buten-1-ol, and anisole. The nature, strength, and total concentration of acid sites in the catalysts were evaluated using thermodesorption of pyridine (kinetic diameter 0.54 nm), while the characteristics of the external surface Brønsted acid sites were probed using...
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Synthesis of phosphine derivatives of ferrocifen
Křelinová, Magda ; Schulz, Jiří (advisor) ; Pinkas, Jiří (referee)
Title: Synthesis of phosphine derivates of ferrocifen Author: Magda Křelinová Department: Department of Inorganic Chemistry Supervisor: RNDr. Jiří Schulz, PhD. Abstract: The goal of this bachelor thesis was to synthesize and characterize 1-{1-[bis(4-hydroxyphenyl)methylene]propyl}-1'-(diphenylphosphino)ferrocene (compound 7). As a ferrociphenol derivative, this compound should possess significant biological activity against breast cancer cells of both types (hormone-dependent and hormone-independent). Such treatment is currently not available and it is urgently needed. The diphenylphosphine moiety could serve as a linker to form conjugates with other organometallic pharmacophores. This could result in a better targetting or may otherwise enrich the effect of the compound 7. Thioketone 2 was prepared from 1,1'-dibromoferrocene by lithiation and reaction with Weinreb amide which afforded ketone 1 that was treated with Lawesson's reagent. Thiirane 3 was then synthesized by reaction of 2 with 1,1'-(diazomethylene)bis[4-methoxybenzene]. Its desulfurization afforded bromoderivative of methoxyferrociphene 4. Phosphinylation of compound 4 gave phosphinomethoxyferrociphene 5. Reaction with boronium tribromide formed aduct 6, which was deprotected by DABCO to give compound 7. All new compounds were characterized by...
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