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Progressive Amorphous Carbon Alloys Synthesized in Low-Temperature Plasma
Bránecký, Martin ; Trunec, David (referee) ; Kylián,, Ondřej (referee) ; Čech, Vladimír (advisor)
Atomic/plasma polymerization technology is widely used in various technical fields. This work is focused to use the PE-CVD technology in the field of formation of interphase and adhesive layers, which are developed into layered nanostructures. To ensure reproducible chemical and physical properties of the materials, the deposition process was monitored by mass spectrometry. Vapours of the pure tetravinylsilane, or a mixture of these vapours with oxygen, was used as a precursor for atomic polymerization, which results in the thin films with a large variability of properties. Physical and chemical properties were varied by the effective power delivered to the plasma discharge. The deposited films were analyzed from different perspectives using several methods (in situ spectroscopic ellipsometry, FTIR, nanoindentation, AFM). The removal of hydrogen atoms from the carbon-silicon network results in increased crosslinking of the material, which controls the mechanical and optical properties of the deposited layers. From the precisely defined a-CSi:H and a-CSiO:H materials, layered nanostructures composed of 3 and 7 individual layers was subsequently constructed. These nanostructures were analyzed by XPS and RBS to determine the atomic concentrations of carbon, silicon, oxygen and their binding states.
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Deposition and characterization of SA layers from vinyltriethoxysilane
Veverka, Miroslav ; Veselý, Michal (referee) ; Čech, Vladimír (advisor)
Development of composite material is very much progressive sector and leads to evolution of material with new property. This type of material has one, but important deficiency. It is small adhesion armature to matrix. My study is sight on improvement adhesion the surface by deposition self assembled (SA) monolayer from organosilanes. Property of this layer, like thickness, surface tension, homogenity and wettability, was evaluated by the contact angle measurement and spektroscopical elipsometri.
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Functional organic-inorganic nanostructures
Kelíšek, Petr ; Zmeškal, Oldřich (referee) ; Čech, Vladimír (advisor)
Diploma thesis deals with preparation of multilayered organic-inorganic nanostructures via PECVD technology and analysis of optical properties of these layers by spectroscopic ellipsometry. The theoretical part handles the definition of thin layers, layered and gradient nanostructures, plasma enhanced chemical vapor deposition and principles of spectroscopic ellipsometry. In the experimental part, used materials and chemicals are described, afterwards follow a complete description of the apparatus used for sample preparation and a description of the sample preparation procedure. The results part consists of methodology of preparing material models necessary for ellipsometric measurements and evaluation of optical properties of deposited nanolayers.
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Plasmachemical processing of fibrous reinforcements for polymer composites
Knob, Antonín ; Lapčík, Ĺubomír (referee) ; Čech, Vladimír (advisor)
The diploma thesis is aimed at coating of glass fibers using tetravinylsilane as a monomer by Plasma-Enhanced Chemical Vapor Deposition (PECVD). The surface modified fibers were used as reinforcements for unsaturated polyester resin to form composites of controlled interphase. Chemical and mechanical properties of thin films were controled by the effective power. Determination of fiber-matrix adhesion and an influence of polymer-interface on mechanical properties of composites were characterized by Scanning Electron Microscopy (SEM) and microindentation technique using Interfacial Testing System (ITS) enabling to measure the interfacial shear strength.
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Inteligent Controller of Active Magnetic Bearing
Turek, Milan ; Čech, Vladimír (referee) ; Ondrůšek, Čestmír (referee) ; Březina, Tomáš (advisor)
The PhD thesis describes control design of active magnetic bearing. Active magnetic bearing is nonlinear unstable system. This means it is not possible to use classic methods of control design for linear time invariant systems. Also methods of nonlinear control design are not universal and theirs application is not easy task. The thesis describes usage of simple nonlinear compensation which linearizes response of active magnetic bearing and allows usage of classic methods of control design for linear time invariant systems. It is shown that CARLA method can significantly improve parameters of designed controller. First part of thesis describes derivation of model of controlled active magnetic bearing and nonlinear compensation which linearizes response of controlled active magnetic bearing on input signal. Following part contains description of methods of state control design methods, selected methods of robust control design and most common methods of artificial intelligence used for control design and implementation. Next part describes hardware of used experimental device and its parameters. It also contains experimental derivation of model of electromagnetic force because the parameters are not available from manufacturer. Last part describes control design of active magnetic bearing. Several different approaches are described here. The approaches vary from completely experimental approach, through using Ziegler-Nichols method, state control design to methods for robust control design. During design is heavily used CARLA method which is very suitable for usage for online learning in real controller due its principle.
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Characterization of electronic properties of nanowires for electrochemistry
Kovařík, Martin ; Čech, Vladimír (referee) ; Kolíbal, Miroslav (advisor)
Elektrochemické metody nacházejí využití v mnoha aplikacích (např. senzorice, skladování el. energie nebo katalýze). Jejich nespornou výhodou je nízká finanční náročnost na přístrojové vybavení. Abychom lépe porozuměli procesům probíhajícím na elektrodách, je dobré znát elektronickou pásovou strukturu materiálu elektrody. Úkolem této práce je vyhodnotit výstupní práci a pozici hrany valenčního pásu nových materiálů pro elektrody, konkrétně cínem dopovaného oxidu india pokrytého nanotrubicemi sulfidu wolframičitého. Ultrafialová fotoelektronová spektroskopie a Kelvinova silová mikroskopie jsou metody použité pro tuto analýzu. Zvláštní důraz je kladen na přípravu vzorků elektrod pro měření, aby nedošlo k nesprávné interpretaci výsledků vlivem vnějších efektů jako je např. kontaminace nebo modifikace povrchu.
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Mechanical properties of glass fibers
Ševnina, Marija Vladimirovna ; Svěrák, Tomáš (referee) ; Čech, Vladimír (advisor)
The bachelor thesis deals with the examination of mechanical properties of unsized glass fibers and commercially sized glass fibers. The main objective is to determine the tensile strength, modulus of elasticity, and ductility for the fibers depending on the surface modification. To determine these properties, fiber diameters were measured using an Olympus BX 50 optical microscope followed by a tensile test on the Universal Testing Machine, ZWICK / Z010 / TH2A.
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Polymer composites with controlled interphase
Zvonek, Milan ; Knob, Antonín (referee) ; Čech, Vladimír (advisor)
Cieľom diplomovej práce je príprava polymerných kompozitov vyztužených sklenenými vláknami s riadenou medzifázou za použitia metódy plazmochemickej depozície z plynnej fáze a monomeru tetravinylsilanu. Teoretická časť je zameraná na literárnu rešerš o plazme, plazmovej polymerácií, tenkých vrstvách a kompozitoch. Experimentálna časť popisuje použité materiály a aparaturu použitú na povrchovú modifikáciu sklenených vlákien a prípravu vláknom vyztužených kompozitov. Povrchová úprava sklenených vlákien prebiehala za rôznych depozičných podmienok. Chemické a mechanické analýzy vytvorenej medzivrstvy prebiehali za použitia FTIR spektrometrie a vrypového testu. Vliv povrchovej úpravy bol zistený pomocou získanej interlaminárnej šmykovej sily použítím testu krátkych trámečkov.
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Deposition and characterization of GaN nanocrystals with a metal core
Čalkovský, Vojtěch ; Čech, Vladimír (referee) ; Mach, Jindřich (advisor)
Tato diplomova prace se zabyva prpravou a charakterizac GaN nanokrystalu s kovovym jadrem. V teoreticke casti teto prace je predstaven material GaN se svymi vlastnos- tmi a aplikacemi. Dale jsou uvedeny substraty pro rust a jednotlive mechanismy rustu GaN nanokrystalu. V dalsm jsou popsany kovove nanocastice a jejich opticke vlastnosti umoznujc zesilovan fotoluminiscence na zaklade interakce plasmonu a GaN. Experi- mentaln cast se zabyva prpravou GaN nanokrystalu s Ag jadrem ve ctyrech krocch. Prvne jsou Ag nanocastice naneseny na substrat Si(111). Nasledne se nechaj zoxidovat. Tretm krokem je depozice Ga a poslednm je nitridace. Jednotlive kroky byly opti- malizovany a analyzovany ruznymi metodami, jako je XPS, SEM, fotoluminiscence a Ramanova spektroskopie.
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Surface topography and mechanical properties of thin films on tetravinylsilane basis
Plichta, Tomáš ; Klapetek, Petr (referee) ; Čech, Vladimír (advisor)
Proposed diploma thesis is focused on preparation and characterization of the plasma polymer thin films based on tetravinylsilane monomer (TVS). Plasma enhanced chemical vapour deposition (PECVD) method involving pulse and continual plasma discharge modes were used for thin film deposition on silicon wafer pieces. Reactive plasma composition was containing pure TVS or mixtures of TVS and argon or oxygen gas. Atomic force microscopy was used for surface topography and roughness characterization. Cyclic nanoindentation was involved to measurements to determine the Young’s modulus and hardness of prepared films and scratch test was performed to evaluate the degree of adhesion. Special attention was drawn to the characterization of films with a Young’s modulus below 10 GPa. Tip geometry of indenter influence on scratch test was also commented. Surface and mechanical properties of thin films in relation to the deposition conditions were correlated to the obtained results and final analysis of deposition conditions influence is proposed.
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