National Repository of Grey Literature 54 records found  1 - 10nextend  jump to record: Search took 0.02 seconds. 
Titanium, Alloys and Intermetallics for Biological and Industrial Applications
Vespalec, Vítězslav ; Jech, David (referee) ; Čelko, Ladislav (advisor)
The creation of this Bachelor´s thesis was performed as a search retrieval, which includes basic information about titanium and its alloys. In the first chapter is stated history of titanium manufacturing. Following chapter include the most important property of pure titanium, such as alotropic modifications of the crystal grid, chemical, physical and technological characteristics, there is also space, that is assigned for using contemporary division of titanium alloys, detrimental effect of impurity, shape memory effect and intermetallics instance. Third part concern about selected application in industry. The conclusion pursue about biocompatibility factor and possibility use titanium and its alloys in implantology and dental applications.
High-temperature embrittlement of 14%Cr ODS ferritic steel in liquid lead environment
Dohnalová, Eva ; Čelko, Ladislav (referee) ; Hadraba, Hynek (advisor)
The thesis deals with the high-temperature embrittlement of 14%Cr ODS ferritic steel in liquid lead environment. The 14%Cr ferritic ODS steel ODM401 manufactured by powder metallurgy technology was used as an experimental material. The effect of the long-term annealing, surface corrosion attack in the melt Pb and Pb-Bi on the microstructure and mechanical properties was described. The subsequent microstructural changes were evaluated by means of scanning electron microscopy and transmission electron microscopy The mechanical behaviour of the experimental material was proven by means of microhardness test, impact test and static tensile test. The fractographical evaluation of fracture surfaces were performed on all samples. The surface attack and outstanding microstructural ganges were found after the long-time exposition of the steel in Pb/Pb-Bi melts at temperature 550°C/1000h and 500°C/1000h respectively. The embrittlement of the steel after exposition in Pb/Pb-Bi melts was comparable to the embrittlement after high-temperature annealing of the steel at temperature 650°C/1000h.
Advanced hydrophobic and hydrophilic surface treatments for non-nuclear energetics
Komarov, Pavel ; Ctibor,, Pavel (referee) ; Pawlowski, Lech (referee) ; Čelko, Ladislav (advisor)
V současnosti lze zaznamenat zvýšený zájem o studium pevných povrchů se specifickou smáčivostí (hydrofilní/superhydrofilní a hydrofobní/superhydrofobní) s ohledem na širokou škálu jejich potenciálních aplikací, mezi které patří například snížení aerodynamického odporu, ochrana proti námraze/odmrazování, korozní odolnost, ochrana proti biologickému znečištění, schopnost samočištění povrchů, apod. Způsoby přípravy takových povlaků však zahrnují sofistikované vícestupňové postupy, které jsou nákladné a neposkytují dostatečnou odolnost hydrofilního/hydrofobního chování takto modifikovaného povrchu. Předkládaná disertační práce je zaměřena na (i) vývoj technologického způsobu výroby hydrofilních/hydrofobních povlaků z materiálů odolných proti opotřebení s využitím technologie žárového nástřiku; a (ii) studium připravených povlaků, analýza jejich mechanických vlastností a kvality smáčivosti jejich povrchu. První část práce obsahuje úvod do teorie smáčivosti, volné povrchové energie, hydrofilních/superhydrofilních a hydrofobních/superhydrofobních povrchových úprav a přehled technologií žárových nástřiků. V rámci druhé, experimentální, části byly připraveny povlaky na bázi Al2O3, Cr2O3-SiO2-TiO2, YSZ a WC-Co-Cr a analyzováno jejich smáčivé chování s ohledem na topografii jejich povrchu. Dále byly studovány povlaky YSZ s lamelární a kolumnární mikrostrukturou, s ohledem na posouzení vlivu struktury povlaku na smáčivé chování. Prezentován je zde rovněž modifikovaný povlak s využitím vysokofrekvenčního plasmatu. V závěrečné fázi experimentů byly použity tři rozdílné prášky na bázi WC-Co-Cr pro výrobu povlaků odolných proti opotřebení s tzv. více stupňovou povrchovou topografií povrchu této aktivity. V rámci bylo zjištěno, že kombinace hrubého prášku s ultra jemnými (~500 nm) WC částicemi umožňuje vznik optimální povrchové topografie s velmi vysokou hydrofobností, kterou lze dále optimalizovat do superhydrofobního stavu pomocí dodatečné modifikace olejem na bázi Si. V poslední části práce byla u tohoto typu povlaku stanovena odolnost smáčivosti vzorků WC-Co-Cr pomocí testu odezvy na otěr v abrazivní suspenzi a testu odolnosti vůči kavitační erozi.
Structure and Properties of Coatings Produced by PVD Technology
Doubrava, Marek ; Horynová, Miroslava (referee) ; Čelko, Ladislav (advisor)
The submitted work is focused on study of 3rd generation DLC films produced by Platit a.s. company. Thin films are deposited utilizing filtered cathodic vacuum arc process (FCVA). The main goal of thesis was to find out the influence on film properties, caused by change of the substrate holders with different heat dissipation. The change of the substrate holders is motivated purely by economical effort to increase productivity of the deposition process. Teoretical part of the thesis is about the principles of PVD deposition process, characterization of the thin films, DLC thin films and materials used for cutting tools. Experimental part includes description of devices used for specimens analyses, including also the description of measuring process and used conditions. Acquiered results, not only the thin film thickness, adhesion or amount of sp^3 bonds, match with expected results.
Formation of Diffusion Barriers Using Chemical Vapour Deposition Process
Foltýnek, Jaroslav ; Němec, Karel (referee) ; Čelko, Ladislav (advisor)
Masters thesis deals with formation of diffusion barrier coatings by means of powder mixtures chemical vapor deposition. Its theoretical part is focused on the problems with diffusion barriers formation, where predominantly three most commonly used methods are introduced, i.e. CVD from powder mixtures, active gasses and slurries. The experimental part of master thesis deals with the formation of nickel-aluminide diffusion barriers on Inconel 713LC superalloy substrate, where was for aluminization used six different powder mixtures at the temperature of 800 °C and dwell of 0, 2 and 5 hours.
The use of surface modifications in recent technical practice
Červinka, Martin ; Čelko, Ladislav (referee) ; Klakurková, Lenka (advisor)
Bachelor's thesis deals with problems of surface treatment materials and their basic division. Work is detail focused on technology of thermal spray coatings. This work summarizes the basic information about the technology thermal spray coatings, their features and an overview of methods for their production. The aim of the project is to create an overview of methods of surface modifications used in recent practice and their application in different branches of industry.
Mechanical alloying and compactization of metallic composite powders
Husák, Roman ; Čelko, Ladislav (referee) ; Hadraba, Hynek (advisor)
Master´s thesis is focus on the proces of mechanical alloying. It is the proces of modifying a hetegeneous mixture of powder materials into a homogeneous composite powder. Experiments are focus on three types of composite materials. A magnetic soft alloy Permalloy, ODS steel based on commercially available powder steel 434 LHC and low-activation high-chrome ODS steel 14Cr-2W. On composite powders are made a series of mechanical tests and chemicel analysis. Based on this tests and analysis it was possible to confirm the milling time needed to create fully homogeneous composite powder. Next step is compaction of composite powder into compact volume and another mechanical tests ana analysis of microstructure. In these analyzes to determine whether i tis necessary to use protective atmosphere during mechanical alloying. All three type of materials succesfull prepared by mechanical alloying. It was found that for created of a fully homogeneous composite powder is necessary to perform mechanical alloying for 24 hours. When processing of corrosion resistant materials, i tis possible to perform mechanical alloying in an air atmosphere. During mechanical alloying materials which are subject to oxidation, i tis necessary to use protective atmosphere.
Influence of parameters of electrophoretic deposition on properties of ceramics
Husák, Roman ; Čelko, Ladislav (referee) ; Hadraba, Hynek (advisor)
Electrophoretic deposition is experimentally undemanding shaping method enabling preparation of ceramic material from stable suspension of ceramic particles by means of direct electric current. The aim of the work was to describe effect of electric current magnitude on velocity and final microstructural and mechanical properties of the ceramics. The alumina and zirconia layers were prepared by electrophoretic deposition from stable suspensions of ceramic particles in the isopropanol stabilised with monochloracetic acid. It was found that the real time dependance of particle deposition differs from the theoretical predisction for given electrical conditions. By precise measurement of kinetics of the electrophoretic deposition the actual electrophoretic mobility of the particles and the actual amount of particles taking part in the deposition process were found. It was found that with increasing the electrical current the actual electrophoretic mobility was decreased and actual amount of particles taking part in the deposition process was increased. The increasing velocity of particles under higher electrical currents led to the detorioration of particle arrangement in the elctrode and thus to the increasing of the pore sizes and final densities of the deposits. These microstructural changes reflected in the lowering of the hardness of the deposited ceramics of about 300HV5 in the case of alumina.
Unconventional Metals Hardsurfacing Technologies
Krejčí, Vojtěch ; Šárka,, Šimůnková-Houdková (referee) ; Čelko, Ladislav (advisor)
The main objektive of the bachelor thesis is to evolve problems of metalic surface welding and to implement the basic partition of the most expanded used technologies of surface welding. Sometimes we can see the term deposition metalic surface welding too but in practice is used technical term metalic surface welding. The introdution includes the basic acquaintance with problems and the characterization of the proces of surface welding including the summary of its advantages and disadvantages. In other chapters we aim on individual technologies of surface welding, its principle and using in technical practice. Simultaneously is worked out the overview of already unused or minimally used technologies of surface welding. After the presentation of individual technologies follows the section dealing with partition of materials used for surface welding by the basic material as well as surface welding materials at the present technical practice. In the experimental section of thesis follows selected examples of using the presented technologies of surface welding in practice at present.

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2 Čelko, Ladislav
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