National Repository of Grey Literature 8 records found  Search took 0.01 seconds. 
Nanomechanical testing of an a-C:N nanolayer prepared by ion beam assisted deposition on Ti.sub.6./sub.Al.sub.4./sub.V alloy
Vlčák, P. ; Šepitka, J. ; Horaždovský, T. ; Jirka, Ivan ; Gregora, Ivan ; Němec, M.
We applied ion beam assisted deposition for preparing a-C:N nanolayers on Ti6Al4V alloy. A Hysitron TI 950 TriboIndenter (TM) nanomechanical test instrument was used to assess the depth profiles of the mechanical properties on modified titanium substrates. Two methods were employed : a) quasistatic partial unload, and b) dynamic Continuous Measurement of X (CMX). The average nanoindentation hardness increased from HIT similar to 5GPa for a reference sample to HIT similar to 8.6 GPa for a sample coated by an a-C nanolayer, and to HIT similar to 11.5 GPa for a sample coated by an a-C:N nanolayer. The average storage modulus of the sample coated by a-C:N increased from E' similar to 130 GPa (reference sample) to E' similar to 155 GPa. The storage modulus of the sample coated by the a-C nanolayer was less than the storage modulus of the titanium substrate.
Study of cerium oxide-metal interaction with gases - carbon monoxide oxidation and methanol decomposition
Kolářová, Tatiana ; Nehasil, Václav (advisor) ; Čech, Vladimír (referee) ; Jirka, Ivan (referee)
Title: Study of cerium oxide-metal intraction with gases - carbon monoxide oxidation and methanol decomposition Author: Tatiana Kolářová Department: Department of Surface and Plasma Science Supervisor: Doc. RNDr. Václav Nehasil, Dr., Department of Surface and Plasma Science Abstract: Dissertation thesis is focused on the study of two catalytic systems on the basis of cerium oxide-metal. The systems were characterized by various methods of surface analysis. The first part of the work concerns influence of the preparation parameters on the character of gold nanoparticles deposited onto the sputtered cerium oxide layers from a solution. Catalytic activity of prepared Au/CeOx/(C)/Si systems, containing particles with the mean sizes of 4- 10 nm, was tested toward CO oxidation at atmospheric pressure. The results show that with increasing amount of gold present on the samples, also the productivity of CO2 during the reactions grows. The work is further focused on the preparation of an inverse model CeOx/Pt(111) system. On this system, adsorption of methanol at low temeperatures and its decomposition during a heating was studied. It is apparent from presented results that the decomposition of methanol on the inverse CeOx/Pt(111) systems behaves in a different way than on a clean platinum sample or a thick...
Interaction of simple molecules with reducible oxides: model studies of H2O/CeOx and CO/CuOx
Dvořák, Filip ; Mysliveček, Josef (advisor) ; Jirka, Ivan (referee) ; Švec, Martin (referee)
The thesis is focused on the investigation of fundamental catalytic properties of two model catalysts-CeOx/Cu(111) and CuOx/Cu(111)-by means of advanced surface science techniques. The investigations performed on CeOx are devoted to the study of the relationship between the surface structure and the surface activity of ceria. We develop the preparation method leading to growth of epitaxial CeOx(111) thin films with the adjustable morphological parameters-the step density and the ordering of surface oxygen vacancies. By using the CeOx(111) films with precisely controlled structure we identify the role of the step edges and of the oxygen vacancies in the interaction of water with ceria. The investigation performed on CuOx is focused on the microscopic characterization of the reduction process of Cu2O(111) on the molecular level directly under a near ambient pressure of CO. In direct microscopic study we identify the active initiation centers, the intermediate oxide phases, and the kinetics of the reduction reaction of Cu2O(111).
Interaction of bone and vascular cells with materials constructed for tissue replacement and drug delivery system
Vandrovcová, Marta ; Bačáková, Lucie (advisor) ; Smetana, Karel (referee) ; Jirka, Ivan (referee)
Interactions between biomaterials and cells play an important role in tissue engineering. It has been repeatedly shown that the cell behaviour strongly depends on physical and chemical properties of the material surface. In our study we focused on materials used for the construction of bone implants and replacements to support cell adhesion, growth and osteogenic diferenciation and to lead to an integration between an implant and a bone tissue. First we tested an influence of different micrpattern of fullerens' C60 and composites' C60/Ti films to adhesion of bone cells MG 63, their initial spreading, growth, viability and formation of cytosceletal protein actin. Some of these films were additionally iradiated with Au+ ions, which led to the conversion of some C60 molcules into amorphous carbon (a-C). We confirmed that pattern influenced the distribution of cells without decrease viability. Thus, the production of patterns could be used to direct cell adhesion. In the second study, we also observed the influence of the thickness of coated layer. We found that more selective cell growth can be achieved by depositing of thicker fullerens' film. Our study with osteoblast-like MG 63 cells cultured on PLGA films revealed, that surface coated with chosen components of extracellular matrix (colagen I and...
Study of the structure and of interaction with gas molecules of Rh-Sn and Rh-SnO2
Janeček, Petr ; Nehasil, Václav (advisor) ; Jirka, Ivan (referee) ; Bartoš, Igor (referee)
In this work we present the results of the analysis of the surface structures and absorption properties with respect to the CO and O2 molecules of the Sn/Rh and Rh/SnO2 model systems. In the part dedicated to the Sn structures on Rh surfaces with two different orientations - Rh(110) and Rh(111) - we have investigated the development of the core electron levels and valence band during the development of surface reconstructions and absorption of CO molecules. The surface reconstructions of the Sn/Rh(110) systems were studied for the first time. Difference in behaviour w.r.t. Sn/Rh(111) was observed and explanation offered. Finally, on in-situ prepared epitaxial SnO2 layers, the surface reconstruction (4×1) was observed. The CO adsorp- tion properties of Rh on polycrystalline and epitaxial SnO2 layers were also studied and difference in behaviour explained.
Bouša, Milan ; Kalbáč, Martin ; Jirka, Ivan ; Kavan, Ladislav ; Frank, Otakar
The transfer of graphene prepared by Chemical Vapor Deposition (CVD) from metal catalyst to target substrate is an important step in preparing desirable nanoscale structures in various fields of science, and thus searching for fast, cheap and clean method attracts great interest. Investigation of mechanical properties of graphene, which are crucial for applications in flexible electronics, performed on bendable synthetic materials, requires a transfer technique using polymers soluble in aliphatic solvents harmless for target polymer substrates. In this study we explore a dry technique using polydimethylsiloxane (PDMS) as stamping polymer and polyisobutylene (PIB) layer as graphene-support polymer. After the transfer PDMS is peeled off and PIB is dissolved in hexane, hence this method fulfils the above mentioned prerequisite. The effectiveness of this transfer was examined by scanning electron microscopy, optical microscopy and Raman microspectroscopy including micro-mapping, and finally by X-ray photoelectron spectroscopy. With all methods carried out, it was found that this sort of stamp-technique is suitable for a high precision transfer of small grains of CVD graphene onto polymer substrates with large yields and similar purity compared to poly(methylmethacrylate) (PMMA)based transfer methods. However, it introduces substantial quantity of surface discontinuities, and therefore this is not a proper method for large scale applications.
Vlastnosti vrstev na elektroerodovaném povrchu implantátů
Peřina, Vratislav ; Havránek, Vladimír ; Starý, V. ; Bačáková, Lucie ; Zemek, Josef ; Jirka, Ivan ; Jehlička, J. ; Vorlíček, Vladimír ; Fencl, J.
Plasma sprayed and in oil electroeroded implant surfaces were studied by various surface analytical techniques including cell adhesion.
Application of Electron Spectroscopy for Chemical Analysis (ESCA) in Solid State Chemistry
Jirka, Ivan
Possibilities of extraction of the chemical information from the photoelectron and auger spectra of insulators is oveviewed. The examples based on original experiments proceeded in our laboratory are presented.

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