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Mecanismos de transporte de cargas injetadas por canhão de elétrons de baixa energia em meios dielétricos. / Low energy electron beam injected charge and its transport mechanisms in dieletrics.Dante Luis Chinaglia 23 April 1999 (has links)
Neste trabalho realizamos uma série de medidas de correntes elétricas através de amostras de polímeros isolantes submetidos a radiação por feixe eletrônico, amostras essas inserida em um circuito em modo de corrente. A energia do feixe incidente foi sempre tal que não atravessava totalmente a amostra, depositando em seu interior excesso de carga negativa. A polaridade dessa carga foi determinada pela curva de emissão secundária. Como a energia do feixe foi sempre muito superior à energia EII (abaixo dessa energia o número de elétrons injetados pelo feixe é menor que os arrancados para fora da amostra, e acima desse valor o contrário ocorre), as amostras usadas (polifluoretileno-propileno, polietileno de alta densidade e polietileno de baixa densidade) foram carregadas negativamente. Devido à radiação parcialmente penetrante, cada amostra foi dividida em duas regiões distintas: irradiada e não-irradiada. Na região não-irradiada permanece a condutividade intrínseca do material, enquanto na irradiada a condutividade foi muito aumentada devido à geração de portadores secundários pela radiação. As curvas de corrente foram medidas durante e após a irradiação sob diferentes campos elétricos aplicados externamente. Vários modelos teóricos foram aplicados para explicar os resultados de correntes medidas. O mais simples foi o Modelo Caixa, onde a penetração dos primários era um valor fixo r, dividindo a amostra em condutividade induzida g1 de 0 a r, e condutividade intrínseca gi, de r a L, sendo g1 gi (L é a espessura da amostra). O modelo mais sofisticado levou em conta uma região Δr em torno de r pois considera que o freamento dos elétrons não ocorre todos no mesmo ponto, mas tem uma dispersão em tomo de um ponto r. Por esse motivo a condutividade induzida é dependente da posição, e num caso mais geral depende também do tempo. Durante a irradiação da amostra inserida no circuito de medida, pode ocorrer injeção pelos eletrodos alterando, em determinadas circunstâncias, a polaridade do excesso de carga. Como resultado dos ajustes teórico-experimentais vários parâmetros elétricos dos materiais foram obtidos. / This work presents several electric current measurements in dieletric polymers under irradiation by electron beam. The samples were irradiated in a current mode circuit. The energy of the beam provided a negative charge profile charge in the bulk o the sample. The polarity of the deposited charge was determined by a secundary emission curve. Since the energy of the beam was always bigger tham EII (which defines the balance between the injected electrons and the emitted ones; below EII the sample became positively charged, while above it is negatively charged) the samples (polyethylene propylene, high density polyethylene and low density polyethylene) were always negatively charged. Each irradiated sample was divided in two regions: the irradiated region and the non-irradiated one. Due to the secondary generated carries, the condutivity of the irradiated region gi was orders of magnitude higher than the intrinsic condutivity g1. The eletric currents were measured during and after the irradiation, under different external electric fields. Several theoretical models were used to explain the experimental results. The simplest one, the box models, considers the induced condutivity gb from 0 to r, and the intrinsic condutivity gi from r to L (L being the sample thickeness). The more sophisticated model, on the other hand, considers a range value Δr around the point r. It means that the stopping power is not abruptly but rather is distributed in a region Δr around the point r. For this reason the induced conductivity depends on the position, and in a more general framework, also in time. During the irradiation, carriers are injected to the sample by the electrodes, and in certain conditions the excess of charge has its polarity inverted. From the theoretical-experimental fittings important electrical parametes of the materials were obtained.
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Vliv trajektorie elektronového svazku na vlastnosti povrchu oceli 42CrMo4 / Influence of the electron beam trajectory on the surface properties of steel 42CrMo4Mikuš, Tomáš January 2018 (has links)
The thesis deals with surface quenching of steel 42CrMo4 by electron beam. Influence of technologic parameters and beam deflection on properties and structure of prepared layers is studied. Electron beam surface quenching was applicated with and without melting of the surface. Structures of layers made by electron beam quenching were compared with structures made by laser and electromagnetic induction. Structures and phases were analysed by optical microscopy, SEM and roentgen diffraction. Hardness was measured on hardened layers.
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Rotační bleskové kalení s pomocí elektronového svazku a laserového paprsku / Rotary flash hardening with help of electron beam and laser radiationKlusáček, Martin January 2019 (has links)
This master thesis deals with surface hardening of steels, especially with rotary flash hardening of 42CrMo4 steel (WNr 1.3563, ČSN 15142). In this method homogenous heating of whole surface occurs during a very fast rotation of the component. In the theoretical part of this thesis the most common methods of surface hardening are described, with focus on laser and electron beam technologies. In the experimental part special device for this application was constructed. Rotary flash hardening was done using different radiation source and experimantal device parameters. The hardened surface layer of maximal thickness of 0,7 mm and width of 5,6 mm was achieved using laser beam. Results with electron beam were way better, because this technology allows to control the distribution of power along the beam width in order to improve the width/thickness ratio of hardened layer. Using this method maximal layer thickness of 1,4 mm and width of 13,4 mm was achieved.
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Elektronová pinzeta / Electron tweezerŠtubian, Martin January 2020 (has links)
Táto práca sa zaoberá novým spôsobom manipulácie mikro a nano objektov, konkrétne tekutých AuGe ostrovčekov pomocou elektrónového zväzku. V prvej časti je diskutovaný mechanizmus manipulácie, je popísaný princíp a ďalej sú uvedené experimenty a simulácie potvrdzujúce tento princíp. Druhá časť práce sa zaoberá využitím uvedenej manipulácie k tvorenie mikro/nano štruktúr.
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Příprava a charakterizace nanostruktur s funkčními vlastnostmi v oblasti plazmoniky / Fabrication and characterization of nanostructures with functional properties in the field of plasmonicsBabocký, Jiří January 2020 (has links)
Tato dizertční práce se zabývá výrbou a charakterizací plasmonických nanostruktur. Její první část začíná krátkým úvodem do plasmoniky s navazujícím přehledem metod, které jsou v dnešní době nejčastěji používány k výrobě a charakterizaci plasmonických nanostruktur. Druhá část se pak zaměřuje na samotný výzkum, který byl v rámci PhD studia realizován. Cílem prvních experimentů bylo prozkouat možnosti použití elektronové litografie za variabilního tlaku v procesní komoře pro výrobu plasmonických nanostruktur na nevodivých substrátech jako je např. sklo. Jelikož se jedná o materiály, které jsou velice často používány k přípravě plasmonických struktur pacujících v oblasti viditelného světla. Druhá sekce pak diskutuje některé specifické aspekty přípravy plasmonických mikrostruktur elektronovou litografií pro THz oblast. Poslední část se pak zaměřuje na funkční vlastnosti plasmonických nanostruktur, převážně pak na kvantitativní charakterizaci fáze dalekého pole indukovaného plasmonickými nanostrukturami a jejich aplikacemi v oblasti optických metapovrchů - uměle připravených povrchů, které mohou být použity jako planární optické komponenty. Práce demonstruje a diskutuje různé experimentální přístupy použití mimoosové holografické mikroskopie pro jejich charakterizaci.
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Effect of Beam Characteristics and Process Parameters on the Penetration and Microstructure of Laser and Electron Beam Welds in Stainless Steel and TitaniumHochanadel, Joris Erich January 2020 (has links)
No description available.
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Porovnání navařování svazkem elektronů a plazmou / Comparison of cladding by the electron beam and plasma processRudyk, Martin January 2014 (has links)
This diploma thesis deals with plasma cladding and electron beam cladding. The theoretical part is divided into several chapters which is focused on description of these methods of cladding process. In the practical part the particular experiment of electron beam cladding (EBC) and plasma cladding (PC) is described. In the conclusion overall results were assessed, both methods were compared each other and possible exploitation in industry was described.
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Modifikace vrstev deponovaných technologiemi HVOF a cold spray pomocí technologie elektronového paprsku / Modification of HVOF and cold spray deposited coatings via electron beam technologyVacek, Petr January 2016 (has links)
The aim of this thesis was to modify microstructure and coating-substrate interface of CoNiCrAlY coatings deposited by HVOF and cold spray on Inconel 718 substrates. Electron beam remelting and annealing in a protective atmosphere were used to modify the coatings. Microstructure, chemical and phase composition were analyzed. The effect of beam current, transversal velocity and beam defocus on remelted depth was evaluated. As-sprayed microstructure and chemical composition of coatings were analyzed and compared with remelted samples. The effect of annealing of the as-sprayed and remelted samples was evaluated. Remelted layers exhibited dendritic structure. Chemical composition changed only after remelting of interface and part of a substrate. When only the coating was remelted, chemical composition remained the same. Phases coarsened after the annealing. Chemical composition changed after annealing due to the diffusion.
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Vodíkem modifikované grafenové struktury pro polem řízené tranzistory / The hydrogen modification of the graphene structures for field effect transistorsKurfürstová, Markéta January 2016 (has links)
This master’s thesis is focused on the subject of graphene modified with atomic hydrogen and its electronic transport properties. Structural and electronic properties of graphene and hydrogenated graphene are compared in the theoretical part of the thesis. The Raman spectroscopy technique is described, including characterization of typical Raman spectra of both unmodified and modified graphene. Samples used during experimental part of the thesis are prepared via laser and electron lithography, and are set to be measured in a vacuum chamber. Subsequently, electronic transport properties are measured before and after hydrogen modification of graphene. Finally, hydrogenated graphene is irradiated using electron beam and changes in its structure are analyzed with Raman spectroscopy techniques.
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8. Chemnitzer Symposium Füge- und Schweißtechnik 2012: Tagungsband, 20. November 2012Mayr, Peter 30 November 2012 (has links)
Im Rahmen des Symposiums gaben Vertreter weltweit agierender Konzerne, wie Audi AG, voestalpine Gießerei Linz, Alstom AG und SITEC GmbH Einblick in ihre Forschungsaktivitäten im Bereich Mobilität, Energietechnik, Medizintechnik und Sondermaschinenbau.
Die schweißtechnischen Institute der Universitäten Aachen, Braunschweig, Clausthal, Dresden, Magdeburg und Graz gaben einen Überblick über universitäre Forschungsaktivitäten.
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