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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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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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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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Sol-gel synthesis of ternary ZnxTiyOz nanostructures for applications in solar cell technologies and photonics
Mrázek, Jan ; Nižňanský, Daniel (advisor) ; Pinkas, Jiří (referee) ; Pollert, Emil (referee)
The presented study deals with the sol-gel synthesis of nanocrystalline ternary phases of the general formula ZnxTiyOz, their characterization and potential application in photonics. Achieved results brings new fundamental knowledge about the processes leading to the formation of ZnxTiyOz nanocrystals from amorphous xerogels and gives novel information about structural and opto-electrical properties of prepared materials. Based on the presented results, most of all up-to-date reported ZnxTiyOz compounds with tailored nanocrystalline size and structure can be prepared as powders or thin films. Two sol-gel approaches based on the cluster process and direct heteronucleation were employed to prepare initial sol. Sols were optionally doped by Eu3+ ions to evaluate the effects of rare earth element to crystallization properties of formed compounds. In the first part of our study crystallization properties and structural evolution of thermally treated xerogels were analyzed. As a result a versatile method allowing the preparation of inverse spinel Zn2TiO4, cubic defect spinel ZnTiO3 and rhombohedral ZnTiO3 with tailored nanocrystal sizes was established. Initial composition and thermal annealing allow us to prepare selected ternary phase with tailored nanocrystal size ranging from tens of nanometers up to...
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Porphyrin-layered double hydroxide hybrids as novel photofunctional materials
Káfuňková, Eva ; Lang, Kamil (advisor) ; Pinkas, Jiří (referee) ; Bujdák, Juraj (referee)
This Ph.D. Thesis is based on publications to which the author contributed considerably. The list of the publications is attached at the end of this text. This work describes preparation and photophysical properties of hybrid materials derived from layered double hydroxides (LDH) containing Zn2+ /Al3+ or Mg2+ /Al3+ cations. The materials were prepared in the form of powders or thin films. In the first part of my work, photosensitizing porphyrins have been intercalated into ZnRAl and MgRAl LDH (R = 2, 3, 4) using anion-exchange, rehydration, and coprecipitation procedures. According to the obtained results of X-ray analysis, the orientation of the equatorial plain of the porphyrin molecules is nearly perpendicular to LDH layers and fosters the photosensitizing properties of the hybrid materials. Furthermore, the porphyrin-LDH hybrids were used as nanofillers and nanocontainers in eco-friendly polymers, polyurethane (PU) and poly(butylene succinate) (PBS). The porphyrin-LDH material is well dispersed in PU polymer (nanofiller function) to form transparent colored films while porphyrins remain intercalated between LDH layers (nanocontainer function). The polymers allow oxygen diffusion. The second part has been dedicated to investigation of photophysical properties of the porphyrin-LDH powders and the...
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Homogeneous and heterogeneous titanium complexes and their use for selective ethylene trimerization to 1-hexene
Hodík, Tomáš ; Pinkas, Jiří (advisor) ; Merna, Jan (referee)
This diploma thesis is focused on the design and synthesis of new half-sandwich titanium complexes for anchoring to selected supports (SiO2, SBA-15) and the study of their catalytic activity and selectivity in ethylene trimerization to 1-hexene. The synthetic strategy of half-sandwich titanium complexes with a suitable leaving group for direct anchoring through Ti−O bond was carried out (Cl, Oi-Pr). In addition, the titanium complexes with pendant alkenyl group were prepared and utilised for anchoring to a SiMe2H modified support by Pt-catalysed hydrosilylation reaction. Prepared compounds were characterised by standard spectroscopic methods (IR, NMR, MS). The heterogeneous systems were characterised by MAS NMR and IR spectroscopy, powder XRD, ICP-OES, TGA and the textural parameters were determined from nitrogen adsorption/desorption isotherms. For all prepared materials was studied the catalytic activity for ethylene trimerization and the selectivity to 1-hexene.
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Magnetic insulators with hexagonal and cubic structure
Soroka, Miroslav ; Tyrpekl, Václav (advisor) ; Pinkas, Jiří (referee) ; Sedmidubský, David (referee)
Title: Magnetic insulators with hexagonal and cubic structure Author: Mgr. Miroslav Soroka Department: Department of Inorganic Chemistry, Faculty of Science, Charles University of Prague Supervisor: RNDr. Václav Tyrpekl, Ph.D. Consultants: Ing. Josef Buršík, CSc., RNDr. Karel Knížek, Dr. Abstract The presented work deals with the preparation of thin films of transition metal oxides by chemical solution deposition method and the study of their physical properties. Thin films of Z-type (Sr3-xBaxCo2Fe24O41) and W-type (SrCo2-xZnxFe16O27) hexaferrites were prepared with the intention of studying magnetic properties, magneto-electric effect (ME) and spin Seebeck effect (SSE). The study of SSE in hexaferrites as a spin-caloritronic phenomenon was extended by the study of SSE in ε-Fe2-xAlxO3 films and the anomalous Nernst effect (ANE) in La0.7Sr0.3CoO3. Several types of deposition precursors were used for the preparation of thin films: metal alkoxides, 2-ethylhexanoic acid salts and metal citrate complexes. Synthetized materials were structurally characterized by powder X-ray diffraction (pXRD). The texture and orientation relation of the prepared films with substrate were characterized by ω-curves and φ-scan measurements. Scanning transmission electron microscopy (STEM) and atomic force microscopy were used to...
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