National Repository of Grey Literature 26 records found  previous11 - 20next  jump to record: Search took 0.01 seconds. 
Silicification of diatoms from a cellular, evolutional and ecological point of view
Šmída, Adam ; Kulichová, Jana (advisor) ; Němcová, Yvonne (referee)
Diatoms are a significant protist group. They've been getting a lot of attention because of their various silica cell walls since their discovery at the end of the 18th century. Even though the mechanism of the morphologically variable cell wall synthesis is well known in terms of shape and ornamentation, only recently it has been enabled to investigate the diatom silicification on the molecular basis. The knowledge of the silica cell wall synthesis can then be used to understand general acpects of biosilica handling and to enlighten the possible evolutionary substance and the progress of this phenomenon. Key words: biomineralisation, diatoms, long chain polyamins, nanostructure, silaffins, silica transporters, silica deposit vesicle, silicification
Neutron investigation of Nitinol stents and massive samples before and after PIRAC coating
Rogante, M. ; Buhagiar, J. ; Cassar, G. ; Debono, M. ; Lebedev, V. ; Mikula, Pavol ; Ryukhtin, Vasil
Nitinol, a thermoelastic Ni-Ti Shape Memory Alloy (SMA) with approximately 50 at. % Ti, is adopted in a wide range of medical equipment and devices used in interventional radiology, orthopaedics, neurology and cardiology, in particular as a smart material for stents. In this work, NiTi real stents and massive samples before and after different Powder Immersion Reaction Assisted Coating (PIRAC) treatments have been investigated by using two neutron techniques: (1) Small and Ultra-Small Angle Neutron Scattering (SANS, USANS) for nano- and micro-scale characterization, obtaining information on structure and the effects due to the coating treatment, and (2) High-Resolution Neutron Diffraction (HRND), evaluating the macrostrain components resulting from angular shifts of diffraction peaks and the micro-strains in the plastically deformation region by means of profile-broadening analysis. The obtained results contribute: improving knowledge of defects and other key features of the materials complementary to those achieved by using traditional examination techniques. helping to better understand the functional characteristics of Nitinol parts and predict the material's mechanical behaviour.
Structuring of plasma polymers: new methods for fabrication of nano-architectured thin films
Nikitin, Daniil ; Shukurov, Andrey (advisor) ; Novák, Stanislav (referee) ; Straňák, Vítězslav (referee)
Title: Structuring of plasma polymers: new methods for fabrication of nano-architectured thin films Author: Daniil Nikitin Department / Institute: Department of Macromolecular Physics/Charles University Supervisor of the doctoral thesis: Doc. Ing. Andrey Shukurov, PhD, Department of Macromolecular Physics/Charles University Abstract: The PhD thesis aims at the investigation of nanostructures based on plasma polymers. The main attention is paid to the combination of a gas aggregation cluster source with plasma-assisted vapor phase deposition for the fabrication of metal-polymer nanocomposites with bactericidal potential. Copper nanoparticles were incorporated into a biocompatible matrix of plasma polymerized poly(ethylene oxide) (ppPEO). The efficiency of such nanocomposite against multi-drug resistant bacteria was demonstrated. It was found that the segmental dynamics of the plasma polymer significantly changed in the presence of nanoparticles as revealed by the measurements of the dynamic glass transition temperature. The nanoscale confinement crucially influences the non-fouling properties of poly(ethylene oxide). A separate chapter is dedicated to the examination of the nanoparticle formation, growth and transport inside the source. Copper and silver nanoparticles were detected in situ in the gas phase...
Temperature drift compensation for nanostructure analysis
Hakira, Stanli ; Páleníček, Michal (referee) ; Bábor, Petr (advisor)
An ultra high vacuum apparatus for nanostructure experiments is being developed by the Tescan company in cooperation with the Institute of Physical Engineering of the Faculty of Mechanical Engineering. The apparatus is designed for preparation, modification, and analysis of nano-scale structures. A sample holder which allows heating and cooling has been developed for the apparatus. A scanning electron microscope is attached to the chamber to provide analytical and manufacturing capabilities. During experiments with heating enabled, the sample moves relative to the SEM column, causing drift of the image. This bachelor thesis proposes a solution to the problem of temperature drift by the means of motion tracking based on image registration using Fourier transform. An application complementary to the SEM control software which implements the algorithm was designed and tested at the instrument.
Characterisation of dielectric films on a silicon wafer
Fillner, Patrik ; Boušek, Jaroslav (referee) ; Hubálek, Jaromír (advisor)
This bachelor thesis focuses on thin oxide based dielectric layers on silicon wafer. Main effort is for characterization of properties of samples. This technology can be used for manufacturing capacitors on silicon chips. Samples are based on planar oxide layers made with thin film technology on single silicon wafers coated with electrodes deposited by evaporation or by sputtering.
W-B-C Nanostructured Layers - Microstructure and Mechanical Properties
Buršík, Jiří ; Kuběna, Ivo ; Buršíková, V. ; Souček, P. ; Zábranský, L. ; Mirzaei, S. ; Vašina, P.
Several W-B-C layers were prepared by magnetron sputtering. The microstructure of thin layers was observed by means of scanning and transmission electron microscopy on cross sections prepared using a focused ion beam. Both undisturbed layers and the volume under indentation prints were inspected.
Characterization of Ta-B-C nanostructured hard coatings
Buršík, Jiří ; Buršíková, V. ; Souček, P. ; Zábranský, L. ; Vašina, P.
Microstructure and mechanical properties of Ta-B-C nanocrystalline layers prepared by magnetron sputtering were studied. DC magnetron sputtering was used to prepare thin layers on rotated substrates. Various deposition parameters were tested. Microstructure of layers was studied by means of scanning and transmission electron microscopy on thin lamellar cross sections prepared using a focussed ion beam. Both undisturbed layers and the volume under relatively large indentation prints (load of 1 N) were observed. The microstructure observations were correlated with mechanical properties characterized by means of nanoindentation experiments in both the static and the dynamic loading regime. Elastic modulus, indentation hardness and fracture resistance of prepared nanostructured coatings were evaluated and discussed.
Characterization of Mo-B-C nanostructured coating microstructure by means of AEM and GDOES
Buršík, Jiří ; Svoboda, Milan ; Švábenská, Eva ; Buršíková, V. ; Souček, P. ; Zábranský, L. ; Vašina, P.
A Mo-B-C nanostructured coating was prepared on WC-Co hard-metal substrate by magnetron sputtering. The details of microstructure of deposited thin layer as well as elements redistribution caused by subsequent annealing at 1000°C were studied by several experimental techniquec.
Iron Functionalized Nanoparticles of Titanium Dioxide
Volfová, Lenka ; Nižňanský, Daniel (advisor) ; Tabor, Edyta (referee)
Diploma thesis Iron Functionalized Nanoparticles of Titanium Dioxide Lenka Volfová 2017, ABSTRACT Iron-functionalized TiO2 were obtained by hydrolysis of aqueous solutions of titanyl sulfate with addition of ferric nitrate with ammonium hydroxide and the reaction filtered and washed with hydrogen peroxide. The colloid solutions thus prepared were lyophilized and the products were subsequently annealed at three different temperatures of 650 řC, 800 řC and 950 řC. The prepared doped materials were characterized by powder X-ray diffractometry, electron microscopy, infrared spectroscopy, Mössbauer spectroscopy, UV/VIS spectroscopy, thermogravimetric analysis and differential thermal analysis, and measurement of the specific surface area. Photocatalytic activity was determined by measuring of the decomposition of kinetics of 4-chlorophenol in an aqueous solution in the ultraviolet and visible area. For comparison of activity in the UV area and in the visible area were used a previously prepared highly photoactive specimen and standard TiO2 from Kronos, respectively. Keywords: Doped titanium dioxide, nanostructure, X-ray diffraction, electron microscopy, Mössbauer spectroscopy, suppression of photoactivity
Nanoscale phases on surface Fe-6Si magnetic sheets
Švábenská, Eva ; Roupcová, Pavla ; Král, Lubomír ; Bulín, Tomáš ; Vondráček, Martin ; Foldyna, Josef ; Čechal, J. ; Schneeweiss, Oldřich
Analysis of the nanoscale phases which appear on the surface Fe-6Si samples were carried out after the various treatments – grinding and etching, annealing, and water jet abrasion. The basic information on structure, chemical and phase composition was obtained by X-Ray Powder Diffraction (XRD), Scanning Electron Microscopy with EDX, Glow Discharge Optical Emission Spectrometry (GDOES), Mössbauer Spectroscopy and X-ray Photoelectron Spectrometry (XPS). The results show high stability of the surface phase composition after the mechanical and heat treatments. Results obtained from the surface analysis in micrometer depth (XRD, EDX, GDOES) do not show any changes after the different treatments. Iron oxides were detected in XPS and conversion electron Mössbauer spectra (CEMS) which analyze the surface composition in a nanometer scale. In addition to, fine changes in atomic ordering on the surface can be observed after mechanical and heat treatments in the CEMS spectra.

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