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Electrochemical preparation of fluorescence sensor with highly ordered nanostructured surface
Bedlek, Marek ; Kolíbal, Miroslav (referee) ; Drbohlavová, Jana (advisor)
This work deals with fabrication and examination of optical properties of self-ordered TiO2 and Au quantum dots array and its potential usage in medicine as optical sensor for biomolecules detection. Controlled anodization of Ti through Al2O3 template was chosen as a fabrication method for TiO2 QDs, in case of Au galvanic deposition through Al2O3 template onto beforehand prepared TiO2 QDs or substrate with dimple structure. The influence of anodization and deposition conditions on the final structure of QDs and their emission spectrum is also examined.
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Technology of Galvanic Anodization of Non-ferrous Materials and Its Alloys
Remešová, Michaela ; Hadraba,, Hynek (referee) ; Čelko, Ladislav (advisor)
The thesis is focused on the theoretical description of the technology of anodizing of aluminium, magnesium, zinc and their alloys. In this work, methods for formation of oxide layers and the used chemical processes are described in detail. The experimental part of this work deals with formation of oxide layers on aluminium, magnesium and zinc of high purity under different conditions. Oxide layers of different thicknesses were created on all three experimental materials. Aluminium was anodized in a bath of 10% H2SO4, magnesium in the bath of 1 mol/dm3 NaOH, and zinc in the bath of 0.5 mol/dm3 NaOH. Processes were carried out at laboratory temperature. On the aluminium, continuous oxide layer was formed. Furthermore rule "312" was verified, that can indicatively be used for calculating the thickness of the resulting oxide layer on the aluminium. When using lower current of 0.08 and 0.2 A for magnesium anodizing, dark colored layer was created comparing to higher current of 0.5 A. More rough appearance of the oxide layer was produced with increasing voltage. Further, it was observed for magnesium that the resulting layer comprises of two sublayers. For zinc, black colored layer was created when the voltage 20 V and current from 0.4 to 0.5 A were used. In the layer, two sublayers were also observed. For lower voltage and current (0.05 A, 0.17 V), formation of the oxide layer on the zinc does not occur, but the crystallographic etching was observed.
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Fabrication and Characterization of Templates for Fabrication of Nanowires
Lednický, Tomáš ; Čechal, Jan (referee) ; Škoda, David (advisor)
The bachelor thesis is focused on fabrication of alumina templates by anodization of pure aluminium. The theoretical part discusses the growing process of anodized oxide layers and its dependency on the crucial parameters (solutions, anodization voltage, time). The theoretical part is particularly based on literature retrieval. The experimental part is aimed to the fabrication of alumina membranes: the apparatus design, aluminium foils preparation, aluminium anodization, membrane modifications for next applications (nanowires deposition) and membrane characterization.
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Fabrication of aluminium nano-templates by controlled dip anodizing
Stehlíček, Kamil ; Dvořák, Petr (referee) ; Lednický, Tomáš (advisor)
In this thesis we focus on the optimization of the technological process of making porous aluminium oxide (porous alumina), with emphasis on the level of orderliness of the final structure. Theoretical part is aimed primarily at the research part with overlap to defining the initial parameters values for experimental part. Experimental part is then focused on finding the optimal values of experimental parameters. Parallel task to the experimental part is the assembly of the laboratory setup used for anodization process.
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Self-organized nanostructured oxide layers
Šťastná, Eva ; Pouchlý, Václav (referee) ; Jan, Vít (advisor)
Series of anodization experiments was conducted on pure aluminium (99,95 Goodfellow) substrates with the aim to map the possibilities and evaluate available techniques. Oxalic acid electrolyte was used for anodization at different voltage levels ranging from 20 to 60V, while current was always measured continuously during the experiment. The influence of substrate surface treatment, time and grain size of the substrate was documented for as anodized oxide structures using FEG-SEM. Well aligned and evenly distributed pores of the diameters ranging 20- 35 nm were achieved. Extremely fine pores down to 10 nm were achieved using the step-down technique governed by current limitation. Further post-anodizing treatment was evaluated – pore widening by chemical and electrochemical etching, which resulted in pores 80nm wide. The feasibility of electrodeposition of metallic wires directly into the AAO structure without substrate removal was evaluated. DC, AC symmetric and non-symmetric voltage setups were used. The deposition experiments results varied strongly depending on the post anodization treatment. For combination of pore-widening after anodizing with step-down stage, the deposition of copper nanowires was achieved. For simple step-down procedure, creation of very fine copper particles was realized using non-symmetric AC deposition. Further experiments and feasibility of metals electrodeposition in the AAO pores without substrate removal is discussed.
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Nanostructured sensors for detection of organic compounds
Šťávová, Karolína ; Fohlerová, Zdenka (referee) ; Hrdý, Radim (advisor)
This bachelor's thesis is focused on the fabrication of sensitive layers composed of an array of gold nanorods and their modifications. Firstly, a nanoporous mask is made from a layer of aluminum using a method called anodic oxidation. Afterwards electrochemical deposition of gold and polypyrrole or gold and mercury is carried out into the mask. The sensitive layer is characterized by the scanning electron microscopy and other methods for elemental analysis. A sensor with this type of sensitive layer can be used for the detection of various organic compounds.
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Functional Tungsten-based thin films and their characterization
Košelová, Zuzana ; Horáková, L. ; Sobola, Dinara ; Burda, Daniel ; Knápek, Alexandr ; Fohlerová, Z.
Anodizing is a technique by which thin oxide layers can be formed on a surface. Thin oxide layers have been found to be useful in a variety of applications, including emitters of electrons. Tungsten is still a common choice for cold field emitters in commercial microscopy applications. Its suitable quality can be further improved by thin film deposition. Not only the emission characteristic can be improved, but also the emitter operating time can be extended. Tungsten oxide is known for its excellent resistance to corrosion and chemical attack due to its stable crystal structure and strong chemical bonds between tungsten and oxygen atoms. Many techniques with different advantages and disadvantages have been used for this purpose. Anodization was chosen for this work because of the controllable uniform coverage of the material and its easy availability without the need for expensive complex equipment. The anodizing process involves applying an electrical potential to tungsten while it is immersed in an electrolyte solution. This creates a thin layer of tungsten oxide on the surface of the metal. The thickness and properties of the resulting oxide layer can be controlled by adjusting the anodization conditions, such as the electrolyte solution, voltage, and the duration of the process. In this work, H3PO4 was used as the electrolyte to test whether these tungsten oxide layers would be useful for electron emitters, for use in electron guns and other devices that require high-quality electron emitters. The properties were evaluated using appropriate techniques. In general, anodization of tungsten to form thin layers of tungsten oxide layers is a promising technique for producing high quality electron emitters.
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Electrochemical synthesis, characterization and applications of new types of 1D valve metal oxide nanostructures
Alijani, Mahnaz ; Prof. Lluis F. Marsal (referee) ; Tsuchiya, Hiroaki (referee) ; Macák, Jan (advisor)
Tato disertační práce představuje komplexní výzkum růstu TiO2 nanotrubicových (TNT) vrstev s vysokým poměrem délka/šířka (HAR) a jejich využití v pokročilých světelně-sensorických aplikacích. Výzkumné výstupy dosažené během tohoto doktorského studia zahrnují sérii článků, které se zabývají výzkumem syntézy a charakterizace vrstev HAR TNT na jedné straně a hodnocení výkonu těchto vrstev v různých senzorických modalitách na straně druhé. Počáteční studie se zaměřuje na anodizaci Ti fólií za účelem získání vrstev HAR TNT pomocí speciálně formulované elektrolytu obsahujícího NH4F/H2O/ethylene glycol s přídavkem mléčné kyseliny (LA). Výsledky ukazují, že regulací stáří a složení elektrolytu a použitím dostatečně vysokých potenciálů lze dosáhnout vrstev HAR TNT s vysokým poměrem délka/šířka (přibližně 450) v pozoruhodně krátkých časech anodizace ( 15 minut) ve srovnání s literaturou dostupnou před zahájením této disertační práce. Tento přístup nabízí slibnou cestu k získání robustních vrstev TNT bez dielektrického průrazu, eliminující potřebu řízení dalších procesních parametrů, jako je ohřev nebo ochlazování elektrolytu. Na základě úspěšných výsledků byla v následující práci zkoumána galvanostatická anodizace pro získání vrstev HAR TNT v elektrolytu obsahujícím LA. Bylo zjištěno, že mléčná kyselina účinně předchází dielektrickému průrazu při použití vysokých proudových hustot. Tento nález poukazuje na potenciál galvanostatické anodizace pro výrobu vrstev HAR TNT v podstatně zkrácených časech anodizace při pokojové teplotě. Navazující výzkum v disertační práci se zabývá mikrovlnnou fotoelektrickou vodivostí TNT vrstev s různou tloušťkou (15, 50, 80 a 110 m) při frekvencích X-pásma (~8 GHz) pro aplikace v senzorice a bezdrátové vesmírné komunikaci. Integrace anatasových TNT vrstev s rovinným rezonátorem se rozděleným kroužkem (SRR) umožňuje hodnocení jejich mikrovlnné fotoelektrické vodivosti. Experimentální výsledky odhalily významné variace v rezonanční amplitudě a frekvenčních odezvách TNT vrstev, přičemž TNT vrstvy o tloušťce 80 m vykazovaly nejvyšší citlivost. Byly stanoveny korelace mezi účinností fotoelektrické vodivosti, velikostí krystalitů a tloušťkou vrstev TNT, což podporuje využití optimalizovaných vrstev TNT pro co nejlepší mikrovlnného snímání. Kromě toho práce zkoumá vrstvy TNT na SRR pro detekci viditelného světla. Depozicí CdS tenkých vrstev na TNT vrstvy pomocí technologie depozice atomárních vrstev (ALD) se TNT vrstvy stávají velmi citlivé ve viditelné oblasti spektra, což umožňuje efektivní detekci UV a viditelného světla a detekci světlem indukovaných změn dielektrických vlastností TNT vrstev. Experimentální výsledky souhlasí s teoretickými modely a zdůrazňují výjimečný potenciál senzorů založených na TNT při detekci nebezpečí, monitorování znečištění, analýze materiálů a světelné komunikaci mezi satelity. Celkově tato práce poskytuje komplexní porozumění o růstu HAR TNT vrstev a jejich schopnostem pro pokročilé senzorické aplikace. Získané poznatky z tohoto výzkumu přispějí k rozvoji senzorů založených na nanomateriálech a otevírají nové možnosti jejich využití v různých odvětvích a nových technologiích.
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Corrosion of Aircraft Structures
Poláček, Juraj ; Juračka, Jaroslav (referee) ; Katrňák, Tomáš (advisor)
Presented bachelor's thesis deals with the corrosion attack of aircraft structures and their influence on the mechanical properties of individual parts of aircraft structures. The research part of the thesis describes the principles of corrosion attack formation and the influence of aggressive envi- ronments on their formation and development. The influence of aggressive environments is demonstrated through corrosion tests. The thesis maps the most commonly used materials in the aerospace industry. At the same time, it assigns specific materials to typical locations of aircraft structures. Through information and assistance with LOM Prague company, the thesis identifies and displays the most common corrosion-prone areas. Additionally, possible hazards arising from corrosion in specific locations of aircraft structures are described. The output of the thesis presents options for corrosion protection. This is especially the process of anodization, surface treatments, maintenance and appropriate material design in the development of aircraft structures. Due to the extensive use of the anodization process and surface treatments, an analysis was conducted to assess their impact on the mechanical properties of aluminium alloy 6061.
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