National Repository of Grey Literature 35 records found  beginprevious24 - 33next  jump to record: Search took 0.01 seconds. 
Selective growth of metallic materials on clean and oxidized substrates.
Koňáková, Kateřina ; Cháb, Vladimír (referee) ; Čechal, Jan (advisor)
The diploma thesis deals with morphology of cobalt thin film on clean Si(111) and on silicon dioxide thin film on Si(111) studied by AFM and XPS. It is also study of selective growth of cobalt on lattice made by focused ion beam and electron lithography. In the last part, the growth of metals (Fe, Co) on surface oxide on Ni3Al(111) was studied.
The influence of cobalt additive on parameters of positive electrode for Ni-Cd accumulators
Svoboda, Michal ; Svoboda, Vít (referee) ; Špičák, Petr (advisor)
The Master´s thesis deals with description of the influence of cobalt additive on positive electrode parameters for Ni-Cd accumulators. Trough the use of Electrochemical Quartz Crystal Microbalance are analysed the effects which decline effective life of positive electrode during accelerated cycling. Theoretical part describes important characteristics of Ni-Cd accumulators, the working principle and effects which are in progress on positive electrode during cycling. The next part deals with description of system EQCM and the pricnciples of doping active mass with cobalt additive. Practical part consists of EQCM system calibration and electrochemical measurements. The principal aim is detection of the influence of cobalt additve on active mass during cycling in different electrolytes. From the results of measurements is set the optimal amount of cobalt additive.
Microdetermination of cobalt by methods of molecular and atomic absorption spectrometry
Charuza, Martin ; Řezáčová, Veronika (referee) ; Sommer, Lumír (advisor)
This diploma thesis is focused on microdetermination of cobalt by UV-VIS spectrophotometry with organic agents and comparison with atomic absorption spectrometry. In the first part properties, occurance and importance of cobalt in the environment are desribed, complete with as a part of vitamine B12. Attention is also given to cobalt compounds, especially in the oxidative states +II and +III. Methods of preconcentration and preparation cobalt determination in real samples are adduced. In this thesis are described some optical analytical methods with accept on spectrophotometric agents for determination of cobalt. The experimental part of this thesis icludes optimalization of the spectrophotometric determination of cobalt with choosen organic agents 4-(2-pyridylazo)resorcin and 2-(5-Brom-2-pyridylazo)-5-diethylaminophenol and optimalization of atomic absorption spectrometry for cobalt determination. All of real samples of water (surface, underground, mineral and waste) were measured by both 4-(2-pyridylazo)resorcin and 2-(5-Brom-2-pyridylazo)-5-diethylaminophenol via UV-VIS and via atomic absorption spectrometry. Results of determinations were compared. A sample of vitamine B12 was measured too by all techniques.
Deposition of Cobalt nanodots using EBID and optimalization of their chemical composition and morphology
Vyroubal, Ondřej ; Průša, Stanislav (referee) ; Kolíbal, Miroslav (advisor)
This bachelor's thesis deals with deposition of metal nanostructures by EBID. Several deposition parameters are described and it is shown how they infuence the process of deposition. The atomic composition of cobalt structures was veried by EDX. Additionally, the optimized geometries of nanostructures for future practical applications are shown as well.
Preparation and characterization of samples for a study on the effect of surface plasmon polaritons on island growth on surfaces
Závodný, Adam ; Kolíbal, Miroslav (referee) ; Čechal, Jan (advisor)
This bachelor's thesis deals with preparation and analysis of cobalt thin films and determination of the thermal stability of Al2O3/Au/SiO2/Si multilayer. The films are formed on the crystalline silicon with oxide surface layer, i.e. SiO2/Si(111) and Al2O3/SiO2/Si(111). Thin films are prepared using an effusion cell and their growth is studied as a function of substrate temperature, type and layer thickness. Prepared samples are studied by the X-ray Photoelectron Spectroscopy, Scanning Electron Microscopy and Atomic Force Microscopy.
Preparation of Ag/Co/Ag Trilayers
Burda, Pavel ; Kolíbal, Miroslav (referee) ; Čechal, Jan (advisor)
The Bachelor's thesis is aimed to the preparation of silver and cobalt ultrathin films. The films are formed on modified surfaces of crystalline silicon substrates (SiO2/Si(111), Si(111) ?H, Si(111) 7×7) and amorphous SiO2 in a form of a quartz glass. Thin films are grown using an effusion cell for Molecular Beam Epitaxy (MBE). Surface modified surfaces are covered subsequently by a silver, cobalt and silver thin layer. The individual film thickness is 6 nm. Consequently the samples are studied by the X-ray Photoelectron Spectroscopy (XPS) and the Atomic Force Microscopy (AFM). The morphology of thin films and growth modes are compared among the substrates. Growth modes change with the surface modification type. Complete trilayer system Ag/Co/Ag was prepared on SiO2/Si(111) and Si(111) 7×7. Such system can be employed in plasmonics in order to allow the control of surface plasmon polariton properties by an external magnetic field.
The circulation of cobalt in the environment
Charuza, Martin ; Mládková, Zuzana (referee) ; Sommer, Lumír (advisor)
This bachelor thesis deals with importance of cobalt in the environment, especially as a component of B12 vitamin. Vitamin B12 is a complex, that is necessary for proper formation of blood corpuscules and DNA, except that affects many others procesess in the body. Cobalt forms many complex compounds, which are discussed in this work. The most common oxidation number in compounds are +II and +III. The second part describes spectrophotometric determination of cobalt with suitable reagents. There are a lot of spectrophotmetric reagents for cobalt determination in a sample. The most widely used spectrophotometric reagents for determination of cobalt are 4-(2-pyridylazo)resorcinol (PAR), 1-(2-pyridylazo)-2-naphtol (PAN), 2-(5-Brom-2-pyridylazo)-5-diethylaminophenol (5-Brom-PADAP), 4-(2-thiazolylazo)resorcinol (TAR) a 2-(2-thiazolylazo)-4-methoxyphenol (TAMP). All of theese reagents are heterocyclic azodyes. Cobalt is bonded on this azodyes by coordination covalent bond and forms stable complex.
RESPONSE OF SURFACE MORPHOLOGY IN COBALT-FULLERENE MIXTURE FILMS UPON VARIATION OF THE METAL CONTENT
Lavrentiev, Vasyl ; Lavrentieva, Inna ; Vacík, Jiří
The morphology and roughness of the films show great change around some critical composition x(c) of the mixture film (x(c) approximate to 3). The films with lower Co content (x < 3) is rather smooth and the roughness is rather low. However, if x >= 3, the roughness of the CoxC60 films dramatically increases and sharp protrusions appear on the surface that reflects an important phase transformation in the film structure. The obtained AFM results define the concentration interval of the Co solubility in solid C-60 (x < 3), which was found to be narrower than that evaluated from spectroscopic experiments (see the text). This interval suggests a formation of the Co1C60 and Co2C60 fullerides in the CoxC60 mixtures where the Co atoms occupy the tetrahedral holes in the fullerene lattice. The dramatic change of the surface morphology at x >= 3 reflects the pronounced Co clustering which likely occurs due to numerical filling the octahedral pores. Formation of the protrusions on the surface of the supersaturated CoxC60 mixture films (x > 3) is a consequence of the compressive stress arising in the film due to the Co clustering.
Effect of Precursor Synthesis on Catalytic Activity of Co3O4 in N2O Decomposition
Chromčáková, Ž. ; Obalová, L. ; Kovanda, F. ; Pacultová, K. ; Kukutschová, J. ; Michalik, S. ; Kustrowski, P. ; Jirátová, Květa
The correlation between methods of preparation, phase composition of precursors, catalytic properties of the related oxide catalysts, and the role of the cobalt ions as catalytic active sites is discussed.
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Study of Influence of Segregated Impurities on Magnetism of Grain Boundaries and Free Surfaces in FCC Nickel and Cobalt
Všianská, Monika ; Vémolová, H. ; Šob, Mojmír
We present an ab initio study of segregation of 12 nonmagnetic sp impurities (Al, Si, P, S, Ga, Ge, As, Se, In, Sn, Sb and Te) at the Sigma5(210) grain boundary (GB) and (210) free surface (FS) in ferromagnetic fcc nickel and cobalt. We analyze their effect on structure, magnetic and mechanical properties. We determine the preferred segregation sites of the impurity atoms, their segregation enthalpies and strengthening/embrittling energies with their decomposition into the chemical and mechanical components. In this contribution, we focused on the influence of segregated impurities on the magnetic moments of neighbouring atoms, the changes in the density of states and why the magnetically dead layers may be present in nickel but not in the cobalt.

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