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Analysis of one-dimensional structures using Kelvin Probe Force Microscopy
Kovařík, Martin ; Bartošík, Miroslav (referee) ; Kolíbal, Miroslav (advisor)
This bachelor's thesis deals with the use of Kelvin probe force microscopy (KPFM) for analysis of 1D nanostructures, namely germanium nanowires and tungsten disulfide (WS2) nanotubes. First part of this thesis is dedicated to the possibility of gold nanoparticles detection on germanium nanowires and also to the analysis of relevance of the KPFM method to measurements performed at various humidity. Second part deals with the measurement of surface potential changes on WS2 nanotubes induced by interaction with light. We have concluded, that relative surface potential changes can be measured at various humidity. This conclusion is also applied to study the interaction of WS2 nanotubes with monochromatic light. The experiment has revealed, that when exposed to light with defined wavelength, nanotubes coated with gold nanoparticles show opposite surface-potential changes as compared to pristine nanotubes, which indicates different physical processes under way.
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Oxidation barriers prepared by electrochemical procedures
Šťastná, Eva ; Pouchlý, Václav (referee) ; Jan, Vít (advisor)
A process with aim to prepare an oxidically and thermal resistant layer was performed on the samples from clear aluminium (99,99+ %, VÚK čisté kovy, s. r. o.) and on the samples from clear titanium (99,95 % Goodfellow) with a layer from sputtered aluminium (99,99 %, VÚK čisté kovy, s. r. o.), An oxidic layer was prepared on the samples by anodization in the oxalic acid. The layer had fine, hexagonally organized pores with the diameter of 30 nm. During the following processing was the structure prepared for the electrochemical deposition of copper to the pores. The aim of the electrodeposition was preparation of copper nanowires deposited into the pores of the oxidic layer. The process was performed in the solution of copper sulfate and sulfuric acid in water. The controlling parameter of the deposition was voltage which had a very asymmetric period. The period had to be optimized for a successful preparation of the wires. The result of the whole process was structure with oxidic matrix whose most of the pores were filled with copper.
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Investigation of nanomaterials for their nuclear power and research utilization
Jelínek, Martin ; ČEZ,, Jiří Skalička, (referee) ; Katovský, Karel (advisor)
This bachelor thesis provides a comprehensive overview of the properties of various nanomaterials and summarizes the latest findings and knowledge of advanced applications in all sectors of nuclear power engineering from construction materials through nuclear fuel, fuel cladding, neutron moderator and coolant to the advanced methods for detection of ionizing radiation ad its direct utilization for electricity production. A significant space is devoted to the applications in safety systems of nuclear power plants. The experimental part of the thesis deals with the possibility of using carbon nanofibers as an additive to the coolant in VVER reactor type in order to improve the thermal properties of the coolant. So far a very little examined issues of neutron balance changes due to interaction with nanoparticles was experimentally verified on the paraffin wax mixture of two different concentrations. The comparison with the reference sample of pure paraffin was also made.
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Semiconductor nanowire growth utilizing alloyed catalyst
Musálek, Tomáš ; Rezek, Bohuslav (referee) ; Kolíbal, Miroslav (advisor)
This master's thesis deals with growth of germanium nanowires using different catalyst particles. The emphasis is mainly layed on fabrication of specific alloyed catalyst consisting of (AgGa). In the first part of the thesis are mentioned two most common concepts of nanowire growth and the importance of phase diagrams for their interpretation. Method for production of alloyed catalyst is demonstrated and experiments focused on the growth of germanium nanowires using this catalyst were performed. Moreover, method for modification of germanium surface via anisotropic etching is demonstrated as well. Such etched structures are suitable for nanowire growth with the help of different kinds of catalyst particles or for the growth of nanowires made of various materials.
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Preparation Techniques and Characterization of Electrodes with Nanostructured Surface
Hrdý, Radim ; Trnková, Libuše (referee) ; Janderka,, Pavel (referee) ; Hubálek, Jaromír (advisor)
Nowadays, nanostructures fixed on solid substrates and colloidal nanoparticles permeate through all areas of human life, in area of sensors and detection as well. This dissertation thesis deals with the fabrication of nanostructures on the surface of planar electrodes via self-ordered nanoporous template of aluminum trioxide. The nanofabrication, as one of many possible techniques, is used to increase the active surface area of electrodes by creating unique surface types with specific properties. These electrodes are very perspective in the applications, such as biomolecules electrochemical detection and measurement. The transformation of aluminum layer into non-conductive nanoporous template in the process of anodic oxidation is a fundamental technique employed to obtain the array of nanostructures in this thesis. The fabrication of high quality nanoporous membranes with narrow pore size distribution on various types of metallic multilayers is one of the key experimental parts in this work. Several problems associated with the production of the thin-film systems, including the dissolving the barrier oxide layer, are discussed and solved. Another part of this work deals with the use of nanoporous membrane as a template for the production of metallic nanostructures via electrochemical metal ions deposition directly into the pores. The obtained nanostructures as nanowires, nanorods or nanodots are characterized by the scanning electron microscopy and energy-dispersive or wavelength X-ray spectroscopy. The electrode surface, modified by gold nanostructures suitable for the detection of biomolecules, has been chosen for the electrochemical measurements, due to the gold biocompatibility. The nanostructured electrodes were characterized by electrochemical impedance spectroscopy and cyclic voltammetry. The effect of nanostructured surface geometrical parameters, including the size of the electrochemically active area, on the results of electrochemical measurements has been observed and compared to flat gold electrodes. Two model biomolecules, namely guanine and glutathione, have been chosen for the study of potential application of these nanostructures in biosensors.
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Nanotechnology utilization in nuclear industry and research
Skalička, Jiří ; Štefánik, Milan (referee) ; Katovský, Karel (advisor)
This thesis introduces reader to current knowledge of nanomaterials and their usage. It summarises production methods and usage of different materials in nuclear power plants, nuclear research and nuclear medicine. Theoretical part of this thesis is dedicated to possible usage of carbon nanotubes for neutron beam collimation and guides. In experimental part different materials were tested in measuring box connected to horizontal radial channel of VR-1 nuclear reactor and their influence on neutron flux was measured. Tested samples were non-oriented carbon nanotubes, carbon nanofibers, alumina nanowires, oriented carbon nanotubes with several angles of rotation and these samples were compared with results of graphite.
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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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