Submitted by Ronildo Prado (ronisp@ufscar.br) on 2017-08-23T17:56:30Z No. of bitstreams: 1 DissPSS.pdf: 2648669 bytes, checksum: ac3f76c4b2b9666e9decfa0e9745dece (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-23T17:56:38Z (GMT) No. of bitstreams: 1 DissPSS.pdf: 2648669 bytes, checksum: ac3f76c4b2b9666e9decfa0e9745dece (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-23T17:56:44Z (GMT) No. of bitstreams: 1 DissPSS.pdf: 2648669 bytes, checksum: ac3f76c4b2b9666e9decfa0e9745dece (MD5) / Made available in DSpace on 2017-08-23T17:56:49Z (GMT). No. of bitstreams: 1 DissPSS.pdf: 2648669 bytes, checksum: ac3f76c4b2b9666e9decfa0e9745dece (MD5) Previous issue date: 2017-03-10 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / With the increase in life expectancy, there has been a raise in the use of prostheses due to the need to replace parts of the human body. To avoid tissue rejection, metal alloys from implants should be biocompatible. The Ti-6Al-4V alloy is widely used in prostheses, however, aluminum presents tissue irritation and inflammation issues and vanadium oxide is unstable, with a high probability of being cytotoxic. Thus, the search for new alternatives has reached the Ti-β alloys, whose properties are more similar to those of the human bone and its structure can present stable or metastable phases according to the quantity of the alloying elements. Unfortunately, Ti prosthesis have a high price compared to the 316L and 316L stainless steel ones, as the later do not have the biocompatibility characteristics of Ti. It seems an interesting research topic about how to use a Ti alloy coating in stainless steel for biomedical application. To be able to deposit the metal alloy, magnetron sputtering is a good choice, since this technique is largely used to obtain thin films due to the quality of the formed films, their high deposition rate, low pressure work and less intense electron bombardment of the substrate. Consequently, it has been used in the manufacture of thin films of Ti and its alloys for biomedical applications. There is no notice of another research group working in this theme. In this project, the objective is to study the influence of the surface change on the deposition of the thin films and if there is difference in the composition when performing chemical cleaning before spraying. / Com o aumento da expectativa de vida, houve um aumento no uso de próteses devido à necessidade de substituir alguma parte do corpo humano. As ligas metálicas utilizadas em implantes devem ser biocompatíveis, para evitar a rejeição pelo corpo. Uma liga muito utilizada é a Ti-6Al-4V, entretanto o alumínio possui problemas de irritação e inflamação de tecidos e o óxido de vanádio é instável, com alta probabilidade de ser citotóxico. Assim, a procura de novas alternativas chegou-se as ligas de Ti-β, cujas propriedades são mais parecidas com as do osso humano e sua estrutura pode apresentar fases estáveis ou metaestáveis de acordo com a quantidade dos seus elementos de liga. Entretanto, próteses de Ti tem um preço alto em relação as de aço inoxidável 316 e 316L. Como estas não possuem as características de biocompatibilidade do Ti, é interessante utilizar um recobrimento de liga de Ti em aço para uso biomédico. Para a deposição da liga metálica, o processo de pulverização magneto-catódica é de grande interesse. Essa técnica consagrou-se na deposição de filmes finos devido a sua alta taxa de deposição, trabalho a baixas pressões, bombardeamento menos intenso de elétrons no substrato e qualidade do filme formado. Consequentemente, passou a ser utilizada na fabricação de filmes finos de Ti e suas ligas para aplicações biomédicas. O objetivo deste projeto é estudar a influência da alteração da superfície na deposição dos filmes finos, ou seja, se há diferença na composição ao se realizar limpeza química antes da pulverização. É importante notar que não se tem notícia de outro grupo de pesquisa trabalhando no mesmo tema.

Novel type of catalyst for proton exchange membrane fuel cells anode is demonstrated. It is based on magnetron sputtered Pt-CeO2 a Pt-Sn-CeO2 mixed oxides. It is shown, that these materials allow to significantly decrease amount of platinum in the anode catalyst. The preparation method yields high amount of platinum in ionized form, especially Pt2+ , which is related to the high activity. Stability of these catalytic layers were investigated under conditions similar to fuel cell anode (humidified hydrogen at elevated temperature). Also interaction of hydrogen a water under UHV conditions were studied, demonstrating high stability of the Pt2+ species. In the last part of the work sputtered Pt-Co mixed catalyst were investigated to be used in the PEMFC cathode. It is demonstrated that at right conditions, the sputtered alloy catalyst improves mass activity on cathode by factor more than two.

Les oxydes conducteurs transparents (TCO) sont une classe importante de matériaux possédant de nombreux domaines d’application, telles que les revêtements à faible émissivité ou comme électrodes transparentes pour les panneaux photovoltaïques et écrans plats. Parmi les matériaux TCO possibles, le ZnO dopé à l'Al (AZO) est couramment étudié notamment à cause de son coût relativement faible et de l'abondance en matières premières des éléments qui le compose. Les films minces d'AZO sont généralement produits par l’intermédiaire de procédés de dépôts physiques en phase vapeur, tels que la pulvérisation cathodique magnétron. Cependant, l’une des limitations de ces techniques repose sur l’homogénéité des films en utilisant la pulvérisation magnétron réactive (DCMS). Ce problème d'homogénéité peut être lié au bombardement du film en croissance par des ions négatifs d'oxygène, lesquels peuvent induire la présence de défauts accepteurs supplémentaires et la formation de phases secondaires isolantes. Dans ce travail, les films d'AZO sont déposés par pulvérisation cathodique magnétron en régime d’impulsions haute puissance (HiPIMS), un procédé dans laquelle des densités de courant instantanées élevées sont obtenues par l’intermédiaire de courtes impulsions de faible rapport cyclique. Dans la première partie de cette thèse, la possibilité d'améliorer l'homogénéité des films AZO par HiPIMS est démontrée. Cette amélioration peut être liée à un important taux de pulvérisation instantanée pendant chaque impulsion HiPIMS, de sorte que le processus puisse avoir lieu en régime métallique. Ceci permet de réduire l’impact du bombardement en ions d'oxygène pendant la croissance du film, évitant ainsi la formation de phases secondaires. Un autre problème de l'AZO est la stabilité des propriétés intrinsèques dans des environnements humides. Pour évaluer ce problème, la dégradation des propriétés électriques après une procédure de vieillissement a été étudiée pour des films déposés à la fois par DCMS et HiPIMS. Une méthode a été proposée pour restaurer les propriétés des films qui consiste en un recuit à basse température sous atmosphère de N2. L'amélioration des propriétés électriques des films peut être liée à un processus de diffusion dans lequel l’eau est évacuée hors des films. Ensuite, l'influence de la température du substrat sur les propriétés des films d'AZO déposés par HiPIMS a été étudiée. Les propriétés électriques, optiques et structurelles ont été améliorées avec l'augmentation de la température du substrat jusqu'à 600°C. Cette amélioration peut s’expliquer par l'augmentation de la qualité cristalline et le recuit des défauts. Dans une dernière partie, le dépôt de films d'AZO sur des substrats flexibles de PET a été étudié. Les films se développent sous la forme d'une couche épaisse, poreuse et composés de colonnes orientées de manière préférentielle selon l’axe c au-dessus d’une fine couche de départ. L’analyse de la résistance électrique après déformation mécanique a permis de déterminer une relation de proportionnalité inverse ou la résistance électrique augmente avec la diminution du rayon de courbure, cette dernière étant moins prononcée pour des films plus épais / Transparent conducting oxides (TCOs) are an important class of materials with many applications such as low emissivity coatings, or transparent electrodes for photovoltaics and flat panel displays. Among the possible TCO materials, Al-doped ZnO (AZO) is studied due to its relatively low cost and abundance of the raw materials. Thin films of AZO are commonly produced using physical vapour deposition techniques such as magnetron sputtering. However, there is a problem with the homogeneity of the films using reactive direct current magnetron sputtering (DCMS). This homogeneity problem can be related to the bombardment of the growing film with negative oxygen ions, that can cause additional acceptor defects and the formation of insulating secondary phases. In this work AZO films are deposited by high power impulse magnetron sputtering (HiPIMS), a technique in which high instantaneous current densities are achieved by short pulses of low duty cycle. In the first part of this thesis, the possibility to improve the homogeneity of the deposited AZO films by using HiPIMS is demonstrated. This improvement can be related to the high instantaneous sputtering rate during the HiPIMS pulses, so the process can take place in the metal mode. This allows for a lower oxygen ion bombardment of the growing film, which can help to avoid the formation of secondary phases. Another problem of AZO is the stability of the properties in humid environments. To assess this problem, the degradation of the electrical properties after an aging procedure was investigated for films deposited by both DCMS and by HiPIMS. A method was proposed, to restore the properties of the films, using a low temperature annealing under N2 atmosphere. The improvement of the electrical properties of the films could be related to a diffusion process, where water is diffusing out of the films. Then, the influence of the substrate temperature on the properties of AZO films deposited by HiPIMS was studied. The electrical, optical and structural properties were found to improve with increasing substrate temperature up to 600°C. This improvement can be mostly explained by the increase in crystalline quality and the annealing of defects. Finally, the deposition of AZO films on flexible PET substrates was investigated. The films are growing as a thick porous layer of preferentially c-axis oriented columns on top of a thin dense seed layer. The evolution of the sheet resistance of the films after bending the films with different radii was studied. There is an increase in the sheet resistance of the films with decreasing bending radius, that is less pronounced for thicker films

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-09-19T20:22:47Z No. of bitstreams: 1 IgorOliveiraNascimento_TESE.pdf: 5575757 bytes, checksum: c19dabd04c4f5dd3dd95968e649af7af (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-09-20T21:21:32Z (GMT) No. of bitstreams: 1 IgorOliveiraNascimento_TESE.pdf: 5575757 bytes, checksum: c19dabd04c4f5dd3dd95968e649af7af (MD5) / Made available in DSpace on 2017-09-20T21:21:32Z (GMT). No. of bitstreams: 1 IgorOliveiraNascimento_TESE.pdf: 5575757 bytes, checksum: c19dabd04c4f5dd3dd95968e649af7af (MD5) Previous issue date: 2017-06-23 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Filmes finos de nitreto de tit?nio foram depositados em superf?cies de sil?cio e de vidro, utilizando as t?cnicas de deposi??o: descarga em Gaiola Cat?dica e Magnetron Sputtering, a fim de verificar a influ?ncia da corrente e da temperatura na taxa de deposi??o, na estequiometria dos filmes finos e nas propriedades estruturais dos filmes finos. As deposi??es por Gaiola Cat?dica foram realizadas nas configura??es gaiola alta, gaiola baixa e por uma inova??o da t?cnica utilizando a gaiola dupla, em atmosfera gasosa composta de 75% de hidrog?nio e 25% de nitrog?nio, sob temperaturas de 300?C e 350?C, e tempos de deposi??es de 2 e 4 horas. As deposi??es foram realizadas em Magnetron Sputtering em atmosfera gasosa composta de 75% de arg?nio e 25% de nitrog?nio, utilizando correntes de 0,40 A e 0,50 A, nos tempos de deposi??es de 2 e 4 horas. Para a caracteriza??o dos filmes finos de nitreto de tit?nio, utilizou-se a espectroscopia Rama (RAMAN) que forneceu a medida direta das energias dos nodos da primeira ordem dos ?tomos constituintes dos filmes finos. Os espectros mostraram interdifusividade at?mica que comprovaram a forma??o de nitreto de tit?nio o que permitiu o c?lculo da raz?o da concentra??o N/Ti, As an?lises de difra??o de raios-X (DRX) comprovaram que os filmes finos obtidos s?o compostos por TiN, apresentando varia??es nos planos cristalinos indicando a n?o exist?ncia de um plano preferencial para o crescimento dos filmes, A espectroscopia de energia de dispers?o (EDS) analisou quantitativamente a composi??o dos filmes finos de nitreto de tit?nio, A microscopia eletr?nica de varredura (MEV) evidenciou a estrutura dos filmes finos de nitreto de tit?nio e foi poss?vel calcular as espessuras dos mesmos, A microscopia de for?a at?mica (AFM) mostrou algumas caracter?sticas microestruturais como a diferen?a entre picos e vales da topografia dos filmes finos de nitreto de tit?nio. De maneira geral, os filmes finos de nitreto de tit?nio depositados por Gaiola Cat?dica apresentaram menor cristalinidade devido ? baixa quantidade de nitrog?nio na atmosfera e, evidenciaram que quanto mais elevada a temperatura, maior ser? a espessura do filme fino. Os filmes finos depositados por Magnetron Sputtering apresentaram crescimento na espessura com o aumento da corrente e s?o mais estequiom?tricos. / Thin films of titanium nitride deposited on silicon surfaces and glass deposition techniques using: Download cathodic cage and Magnetron Sputtering to verify the influence of flow and temperature in the deposition rate in stoichiometry of thin films and structural properties of thin films. Deposits of cathodic cage was carried out in high cage configurations and cage low an innovation of the technique using atmospheric gas double cage consisted of 75% hydrogen and 25% nitrogen to temperatures of 300 ? C and 350 ? C Y deposits both 2 and 4 hours. The deposits were made in an atmosphere of sputter gas Magnetrons consisting of 75% argon and 25% nitrogen using current 0.40 A and 0.50 A in the deposition time of 2 and 4 hours. Rama spectroscopy (Raman), which makes available for the characterization of thin layers of titanium nitride direct measurement of the energy of the node of the first order of the constituent atom of the thin films. The spectra showed interdifusivity atomic of the titan nitride formation that the calculation of the concentration ratio N / Ti, X-ray diffraction analysis (XRD) showed that the thin films obtained from TiN is composite with variations of the crystal planes indicating the non-existence of preference plan for The growth of films, microscopy of the energy dispersion spectroscopy (EDS) quantitatively analysed the composition of the thin films of titanium nitride, electron scanning (MEV) structure highlight thin films of titanium nitride was able to calculate the thickness thereof, the scanning force microscopy (AFM) showed microstructural properties, Which is the difference between the peaks and valleys of the topography of the thin films of titanium nitride. In general, thin films deposited by cathodic titanium nitride cage deposited a lower crystallinity due to the small amount of nitrogen in the atmosphere, and showed that the higher the temperature, the greater the thickness of the thin film. Thin films deposited by Magnetron Sputtering have increased thickness with increasing current and are stoichiometric.

Lors de ce projet, des revêtements de CrN-WC ont été étudiés en temps que matériaux hybrides durs et résistants. L'association d'un carbure et d'un nitrure résistants bien à la corrosion et obtenus dans des conditions optimales de dépôt permettra d'avoir des matériaux de protection contre l'usure, la corrosion mais aussi des dépôts servant de couches tampon à du diamant nanocristallin dont l'adhérence est mauvaise. Tout d'abord nous avons déterminé la faisabilité du système de CrN-WC et son utilisation comme couche intermédiaire pour du diamant nanocristallin. En faisant varier les paramètres de dépôt, nous avons optimisé la microstructure, les caractéristiques chimiques, mécaniques et tribologiques de nos couches. Si le système CrN-WC adhère relativement bien sur silicium, ce ne fut pas le cas sur acier. Les propriétés mécaniques de ces dépôts ont été par ailleurs plus faibles que celles que nous attendions. Nous avons ensuite étudié l'influence de la température sur nos dépôts de CrN-WC. En effet, le fait de chauffer lors du dépôt permet d'augmenter l'adhérence des couches et d'améliorer leurs propriétés mécaniques. Les revêtements obtenus à haute température ont bien montré une amélioration marquée de leurs diverses caractéristiques par rapport aux dépôts obtenus sans chauff. / For this project, CrN-WC coatings are investigated as a hybrid hard and tough material. The use of a hard-carbide with a corrosion-resistant nitride may produce tailored coatings with the desired combination of properties for use as a stand-alone protective coating, or as a basis for nanocrystalline diamond deposition. The work is divided into three stages. The initial study determined the viability of the CrN-WC system, and its use as an interlayer for nanocrystalline diamond. This successful study was followed by a variation of deposition conditions at low deposition temperature. By varying the deposition parameters, the microstructure, chemical, mechanical, and tribological behavior may be optimized. While the system has relatively good adhesion to silicon substrates, its adhesion to steel was lacking. Additionally, the system showed lower than expected mechanical properties. The final step increased the deposition temperature. The aim here was to increase adhesion and improve the mechanical properties. Prior results with other systems show consistent improvement of mechanical properties at elevated deposition temperatures. The high deposition temperature coatings showed marked improvement in various characteristics over their low deposition temperature cousins.

Title: Study of 3-phase catalytic layers for polymer electrolyte fuel cells and electrolysers Author: Šimon Fuka Department: Department of Surface and Plasma Science Supervisor: doc. Mgr. Iva Matolínová, Dr., Department of Surface and Plasma Science Abstract: The diploma thesis focuses on the study of catalytic layers for Proton Exchange Membrane Fuel Cells (PEMFC) or electrolyzers based on the mixture of platinum and cerium oxide. These layers are prepared by using magnetron sputtering, their properties are studied depending on the deposition parameters or the choice of the substrate by using SEM, AFM, XPS and then tested as an anode in the fuel cell. In addition to the morphology of the catalytic layers, it has been shown that the dispersion of very small nanoparticles of the catalyst with a size of 1-2 nm has a great effect on PEMFC performance. Most of the prepared samples gave maximal and maximal specific performance much higher than the state of art values published for Pt-CeOx system. By studying properties of the layers used as the anode catalysts, this work contributes to the understanding of PEMFC fuel cell behavior and, consequently, to its potential commercialization. Keywords: Fuel cell, cerium oxide, platinum, catalyst, magnetron sputtering

Les films minces sont couramment employés pour apporter de nouvelles fonctionnalités au verre plat. Dans une grande gamme de produits industriels pour le bâtiment et l'automobile, l'isolation thermique est améliorée par le dépôt de films nanométriques d'Ag qui sont suffisamment minces pour la transparence optique mais suffisamment épais pour refléter l'infrarouge. Ces revêtements bas-emissifs sont des empilements complexes de films minces qui sont déposés à l'échelle industrielle par pulvérisation cathodique sur les panneaux de verre. Le démouillage ou la délamination peuvent réduire la performance optique et la durabilité du produit en raison de l'adhésion médiocre entre l'Ag et les couches adjacentes. Le film d'Ag est par conséquent pris en sandwich entre des couches texturées {0001} de ZnO qui se trouve être le meilleur candidat pour améliorer la cristallisation et l'adhésion. Des couches dites bloqueurs de métaux de transition tels que le Ti sont également ajoutées à l'interface. Dans ce cadre industriel, cette thèse s'est penchée sur divers aspects fondamentaux des interfaces métaux/ZnO en combinant des approches de science des surfaces sur des monocristaux et des films pulvérisés. Plusieurs stratégies de mesure et systèmes modèles ont été employés pour aborder les questions du contact électrique à l'interface Ag/ZnO, du contrôle de la polarité dans les films pulvérisés de ZnO et de l'évolution de la chimie à une interface enterrée Ti/ZnO lors d'un traitement thermique. / Thin films are a common way to add functionality to flat glass. In a wide range of commercial products for building materials and automotive industry, thermal insulation is improved by the deposition of a continuous nanometric film of Ag which is thin enough to ensure optical transparency but thick enough to reflect infra-red light. The low-emissive coatings consist of complex stacks of thin films deposited at the industrial scale by magnetron sputtering on window-sized glass plates. Dewetting or delamination may impact the performance and lifetime of the product due to a poor adhesion of Ag. Therefore, Ag is sandwiched in between ZnO{0001}-textured films which turned out to be the best candidate to improve Ag crystallization and adhesion. Blocker layers of transition metals, such as titanium, are also added at the interface. In this industrial context, the present thesis focused on several fundamental aspects of metal/ZnO interfaces by combining surface science approaches on single crystals and model sputtered films. Several original measurement strategies and model systems have been employed to tackle the questions of: (i) the Ag/ZnO electrical contact, (ii) the control of the polarity of sputtered ZnO films on amorphous substrates, and (iii) the evolution of the chemistry of buried Ti/ZnO interface during thermal treatment.

P-type transparent conductors are needed for a wide range of applicationssuch as solar cells and electrochromic smart windows. Solar power is animportant form of energy in today’s society as the threat of global warmingpushes the world towards fossil free energy. Hence a lot of solar cell typeshave been developed, among them tandem cells which are to different typesof solar cells stacked on top of each other. If one of the cells is based ona perovskite, a transparent p-type thin film electrode is needed as a holeconductor and electron blocking layer between the two cells. Nickel oxide(NiO) is a good candidate for this application as it has desired propertiessuch as good hole conduction, a high band gap and a matching work functionto the perovskite. The transmittance of as deposited NiO films by reactivemagnetron sputtered is limited so post deposition annealing is used to increasethe transmittance. This is not possible in this solar cell application as parts ofthe solar cell stack is temperature sensitive.Electrochromic smart windows contain a layer that can change its opticalproperties with the application of a voltage. Such windows are used inbuildings to increase energy efficiency and they contain an electrochromicdevice where NiO is used as an electrode as it has electrochromic properties,but just like with the solar cells, the transmittance of NiO is limited. Thisstudy investigates whether it is possible to make as deposited NiO by reactivemagnetron sputtering transparent, eliminating the need for post depositionannealing. Such a deposition process was found using different sputtermachines with the process point on the edge between metal and oxide modein terms of oxygen flow. This resulted in highly transparent and highlyresistive NiO films with a much higher deposition rate than in oxide mode.

Title: Study of new catalytic materials for proton exchange membrane fuel cells Author: Petr Homola Department: Department of Surface and Plasma Science Supervisor: Prof. RNDr. Vladimír Matolín, DrSc. Abstract: Submitted thesis deals with study of thin layers based on platinum and cerium oxides in order to use them in fuel cells with polymer membrane (PEM- FC). A set of samples with different amount of platinum was prepared by means of magnetron sputtering. Samples were investigated by X - ray Photoelectron Spectroscopy (XPS) and results were confronted with sputtering parameters. It was found out that chemical state of platinum is related to its amount in thin layer. The less platinum was contained in thin layer, the less amount of Pt0 state was observed and amounts of Pt2+ and Pt4+ states increased. Furthermore the temperature stability of prepared layers in the interval from room temperature to 250 ◦ C was studied by means of XPS. The adsorption of carbon monoxide was measured by infrared absorption spectroscopy (IRAS). Increasing degree of adsorption on sample probably related to platinum reduction with increased tem- perature was observed. Measurements of other samples were devaluated by strong contamination with nickel carbonyls. Keywords: PEMFC, cerium oxide, magnetron sputtering, XPS, CO adsorption

Presented work is focused on the deposition and characterization of thin and ultrathin plasma polymer films, then also on the preparation of nanocomposites metal/plasma polymer. The characterization of plasma polymer films was partly done in-situ without exposing the samples to the atmosphere. The thickness of prepared films was measured by spectral ellipsometry, the chemical composition was measured by XPS. The morphology and optical properties of deposited films were measured ex-situ. It is shown that during the initial stages of growth the properties of plasma polymer films depend on their thickness and also on the material of the substrate. Many interesting applications were explored for prepared nanocomposites metal/plasma polymer. They can be used as superhydrophobic coatings, gradient coatings, substrates for Raman spectroscopy or as antibacterial coatings. Moreover, special optical properties of prepared nanocomposites were studied in detail. Presented work has an experimental character.