National Repository of Grey Literature 16 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
3D tomography of thin film catalysts by means of FIB/SEM techniques
Dinhová, Thu Ngan ; Matolínová, Iva (advisor) ; Khalakhan, Ivan (referee)
One of the actual problems of today society are decreasing sources of fossil fuels. They are raw minerals and by their burning is energy produced. Regarding to the importance of energy in todays world, it's necessary to find an alternative way how to generate energy. A possible solution to this problem are fuel cells, which work on the principle of converting chemical energy into electric energy. At this moment, the development of fuel cells is in progress. In this bachelor thesis, we are concerned with morphology of catalytic layers Pt/CeO2 deposed on a polymer membrane for hydrogen fuel cells. By using of tomography method with focused ion beam system (FIB) we are creating three-dimensional models of their surface structures. 1
Tip modification for high-resolution AFM imaging of nanostructures
Faitová, Hana ; Matolínová, Iva (advisor) ; Vorokhta, Mykhailo (referee)
Atomic force microscopy (AFM) is a young and widely used method of ima- ging surface, nanostructures, biological and other sensitive objects using sharp tip on a flexible cantilever scanning the sample surface. When operating in air it reaches resolution of about several nanometers. The resolution is mainly depen- dent on the used tip. The thesis deals with modification of old tips by carbon nanotubes (CNT) in scanning electron microscope (SEM) using techniques inclu- ding focused ion beam (FIB) and gas injection system (GIS). Several procedures of CNT sample preparation and attaching the CNT on tip are presented. The functionality of modified tips was checked in AFM using the calibration sample consisting of well-defined nanostructures. 1
Study of 3-phase catalytic layers for polymer electrolyte fuel cells and electrolysers
Fuka, Šimon ; Matolínová, Iva (advisor) ; Khalakhan, Ivan (referee)
Title: Study of 3-phase catalytic layers for polymer electrolyte fuel cells and electrolysers Author: Šimon Fuka Department: Department of Surface and Plasma Science Supervisor: doc. Mgr. Iva Matolínová, Dr., Department of Surface and Plasma Science Abstract: The diploma thesis focuses on the study of catalytic layers for Proton Exchange Membrane Fuel Cells (PEMFC) or electrolyzers based on the mixture of platinum and cerium oxide. These layers are prepared by using magnetron sputtering, their properties are studied depending on the deposition parameters or the choice of the substrate by using SEM, AFM, XPS and then tested as an anode in the fuel cell. In addition to the morphology of the catalytic layers, it has been shown that the dispersion of very small nanoparticles of the catalyst with a size of 1-2 nm has a great effect on PEMFC performance. Most of the prepared samples gave maximal and maximal specific performance much higher than the state of art values published for Pt-CeOx system. By studying properties of the layers used as the anode catalysts, this work contributes to the understanding of PEMFC fuel cell behavior and, consequently, to its potential commercialization. Keywords: Fuel cell, cerium oxide, platinum, catalyst, magnetron sputtering
Electron microscopy study of nanostructured thin film catalysts for micro-fuel cell application
Lavková, Jaroslava ; Matolínová, Iva (advisor) ; Ruterana, Pierre (referee) ; Šubrt, Jan (referee)
Present doctoral thesis is focused on electron microscopy and spectroscopy investigation of novel metal-oxide anode catalyst for fuel cell application. Catalyst based on Pt- doped cerium oxide in form of thin layers prepared by simultaneous magnetron sputtering deposition on intermediate carbonaceous films grown on silicon substrate has been studied. The influence of catalyst support composition (a-C and CNx films), deposition time of CeOx layer and other deposition parameters, as deposition rate, composition of working atmosphere and Pt concentration on the morphology of Pt-CeOx layers has been investigated mainly by Transmission Electron Microscopy (TEM). The obtained results have shown that by suitable preparation conditions combination we are able to tune final morphology and composition of catalyst. Composition of carbonaceous films and Pt-CeOx layers was examined by complementary spectroscopy techniques - Energy Dispersive X-ray Spectroscopy (EDX), Electron Energy Loss Spectroscopy (EELS) and X-ray Photoelectron Spectroscopy (XPS). Such prepared porous structures of Pt-CeOx are of promising as anode catalytic material for real fuel cell application. Keywords: cerium oxide, platinum, fuel cell, magnetron sputtering, Transmission Electron Microscopy
Preparation and Characterization of Porous Cerium Oxide/Carbon Bilayers on Silion Substrates
Dubau, Martin ; Matolínová, Iva (advisor) ; Jiříček, Petr (referee) ; Píš, Igor (referee)
This doctoral thesis concerns the preparation of porous cerium oxide/carbon bilayers on silicon substrates. In this regard, carbonaceous films in the form of amorphous carbon (a-C) and nitrogenated amorphous carbon (CNx) are considered. The influence of various process parameters of the cerium oxide deposition on the morphology of the final cerium oxide/carbon bilayer is investigated. A correlation could be found between the morphol- ogy of the bilayer and the stoichiometry of the cerium oxide film determined by means of XPS. Furthermore, a study regarding the chemical composition of the used carbonaceous films by means of various spectroscopic techniques is presented. It was found that the chemical composition of the carbonaceous films strongly depends on the deposition con- ditions of these films and influences the behaviour of these films during oxygen plasma treatment and cerium oxide deposition, respectively. 1
Study of deposition of catalytic materials into fuel channels of micro-fuel cells on a chip
Chlupová, Šárka ; Matolínová, Iva (advisor) ; Grym, Jan (referee)
This diploma thesis is interested in usage of Electron Beam lithography process as an instrument of transport of contacts and catalytic layers to micro-channels of the micro monolithic planar fuel cell. Experimental part includes optimization of the PMMA resist deposition method on the 3D topography - spray coating - is performed with alternative spray coating system. The optimal spin speed resist, molecular weight and concentration is chosen during the optimization. Parameters of the exposition, developing and lift-off are also modified and three EBL processes are performed. The first ensures deposition of Au contacts to the channels; the second is for application of Pt layer to the cathode channel and the last aimed to cover the anode channel with CeO/CNx layer. All layers are deposited by magnetron sputtering.
Investigation of membrane electrode assembly (MEA) for fuel cells
Fuka, Šimon ; Matolínová, Iva (advisor) ; Vorokhta, Mykhailo (referee)
Title: Investigation of membrane electrode assembly (MEA) for fuel cells Author: Šimon Fuka Department: Department of surface and plasma science Supervisor: doc. Mgr. Iva Matolínová, Dr., Department of surface and plasma science Abstract: This bachelor thesis is focused on the study of degradation of the fuel cell, specifically on the study of the catalyst diffusion into the membrane and of the chemical and morphological changes at the interface. The catalyst is prepared by magnetron sputtering directly on the membrane. Morphological changes at the interface will be monitored either by scanning electron microscope (SEM) or by using the focused ion beam (FIB). Diffusion of the catalyst will be observed using energy-dispersive X-ray spectroscopy (EDX). The bachelor thesis will contribute to the lifetime of the fuel cell type PEMFC (proton exchange membrane fuel cell). Keywords: Catalyst, Diffusion, Membrane, Fuel cell, SEM
Novel nanocatalysts for fuel cells II: micro-fuel cells on chip
Onderková, Kristýna ; Matolínová, Iva (advisor) ; Johánek, Viktor (referee)
Title: Novel nanocatalysts for fuel cells II: micro-fuel cells on chip Author: Kristýna Onderková Department: Department of Surface and Plasma Science Supervisor: Doc. RNDr. Iva Matolínová, Dr., Department of Surface and Plasma Science Abstract: The thesis examines layers of cerium oxide doped with platinum, prepared by magnetron sputtering on various types of planar substrates. The work focuses primarily on how the layers are affected by doping different amounts of platinum. The samples were studied mainly using Scanning Electron Microscopy (SEM). Using the combination of SEM and Focused Ion Beam (FIB), we have prepared thin samples (lamellae), which allow the passage of electrons. The lamellae were observed using SEM with a detector of transmitted electrons. The lamellae were prepared with the focus on parameters of the protective layer. The chemical composition of Pt-CeOx samples was studied by Energy- Dispersive X-ray spectroscopy (EDX) and X-ray Photoelectron Spectroscopy (XPS). Keywords: Pt-CeOx, lamella, SEM-FIB, EDX, XPS 1
Modifying the AFM tip using FIB/GIS in scanning electron microscope
Faitová, Hana ; Matolínová, Iva (advisor) ; Dvořák, Filip (referee)
Atom force microscopy (AFM) is a widely used imaging method of solids' surface structure. Collecting the information about relief is realized by a very sharp tip fixed on a flexible cantilever. The surface is scanned by this tip and the flexion of the cantilever is recorded using the reflection of a laser ray. The tip gradually becomes blunt, dirty or destroyed by this process. The work deals with a possibility of reparation of such tips, which still have usable cantilevers. We used focused ion beam (FIB) and gas injection system (GIS) which are built in the scanning electron microscope (SEM). We tried various techniques and parameters of ion etching and deposition. The modified tips were tested using the AFM on KFPP workplace. Powered by TCPDF (www.tcpdf.org)
Contacting nanostructures for sensor measurements
Chlupová, Šárka ; Matolínová, Iva (advisor) ; Dvořák, Filip (referee)
Title: Contacting nanostructures for sensor measurements Author: Šárka Chlupová Department: Department of Surface and Plasma Science Supervisor: Doc. Mgr. Iva Matolínová, Dr., Department of Surface and Plasma Science Abstract: The bachelor thesis is dealing with contacting nanostructures using electron beam lithography (EBL). Work was carried out in a scanning electron microscope on a mica dielectric substrate with WOx nanorods on the surface in order to prepare a sensor for the detection of H2. In this experiment, parameters for individual sub- processes of EBL were modified. Optimal thicknesses of the PMMA resist 120K (5% anisole) and PMMA 996K (1% anisole) were selected to prepare multilayer resist for an EBL mask. On the resulting bilayer resist electron beam exposure doses were optimized. The appropriate dose was selected and used for creating a matrix designed to contact the WOx nanorods supported on mica. To contact the nanostructures, macrocontacts were deposited on the surface of mica at first, and then the EBL process ran. The result was a conductive connection of the tungsten oxide nanorods by created nanocontacts with macrocontacts. Sensoric properties of the sensor in this way contacted were subsequently successfully tested with H2. Keywords: Sensor, WOx nanorods, Electron beam lithografhy

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