<p>Pri proizvodnji kvalitetnog belog konzumnog &scaron;ećera iz &scaron;ećerne repe, srećemo se sa problemom prisustva makromolekularnih jedinjenja u soku &scaron;ećerne repe koja su &scaron;tetna pa ih je neophodno odstraniti. Uklanjanje ovih jedinjenja, koja čine oko 60 % od ukupno sadržanih nesaharoznih materija u soku &scaron;ećerne repe, zasniva se&nbsp; na principu taloženja uz primenu različitih koagulanata (najče&scaron;će jedinjenja koja sadrže pozitivne jone kalcijuma). Međutim, afinitet vezivanja kalcijuma sa nepoželjnim makromolekulima iz soka &scaron;ećerne repe je mali, pa su potrebne velike količine ovog jedinjenja u svakodnevnoj proizvodnji &scaron;ećera.</p><p>Cilj istraživanja obuhvaćenih ovom doktorskom disertacijom usmeren je ka primeni alternativnih koagulanata sa dvo- i trovalentnim katjonima, pre svega soli aluminijuma i bakra koja izlazivaju proces razelektrisavanja makromolekula soka &scaron;ećerne repe.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Merenjem elektrokinetičkih potencijala utvrđene su optimalne količine koagulanata potrebne za uspe&scaron;nu koagulaciju makromolekularnih jedinjenja iz soka &scaron;ećerne repe. Ispitivan je i uticaj drugih procesnih veličina kao &scaron;to su pH, koncentracija makromolekula i uticaj brzine me&scaron;anja na efikasnost taloženja makromolekula.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Predložen je mehanizam razelektrisavanja makromolekularnih jedinjenja kao i model dvojnogelektričnog sloja koji okružuje&nbsp; koloidne čestice u soku &scaron;ećerne repe.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Ispitivana su dva model-rastvora komercijalno raspoloživih pektina u koncentracijama koje odgovaraju koncentracijama u soku &scaron;ećerne repe kao i jedan model-rastvor proteinskog preparata. Ispitivani sistemi su tretirani rastvorima CuSO₄&nbsp;i Al2(SO₄)₃ i rastvorima njihovih sme&scaron;a u različitim odnosima.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Dokazano je, za sva tri ispitivana preparata, da su manje količine Cu⁺² jona u odnosu na Al⁺³^&nbsp;jone potrebne za sniženje vrednosti Zeta potencijala na nulu. Međutim, zbog mogućih nepoželjnih efekata CuSO₄&nbsp;u obradi hrane, Al(SO₄)₃ bi se mogao upotrebiti umesto tradicionalnog koagulanta CaO, kako zbog manje potro&scaron;nje koagulanta, tako i zbog očuvanja životne sredine.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Cilj eksperimenata sa sme&scaron;ama je ispitivanje mogućnosti pobolj&scaron;anja koagulacionih karakteristika često kori&scaron;ćene soli&nbsp;Al2(SO₄)₃, dodavanjem malih količina Cu⁺² jona. Međutim, čiste soli su pokazale bolja koagulaciona svojstva.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Istraživanja sa flokulantima, odnose se na odabiranje najpogodnijeg tipa i optimalne količine flokulanata, uz primenu predloženih koagulanata. Najveća efikasnost či&scaron;ćenja soka &scaron;ećerne repe, uočena je nakon primene anjonskog flokulanta koncentracije 3 mg/dm³. Dokazano je da ovaj tip flokulanata dodatno smanjuje vrednost Zeta potencijala prisutnih makromolekula čime se smanjuje potrebna količina ispitivanih koagulanata&nbsp;&nbsp;CuSO₄i&nbsp;Al(SO₄)₃.</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;</p><p>&nbsp;</p><p><br /><br />&nbsp;</p><p>&nbsp;</p> / <p>During production of full quality consumed white sugar from sugar beet, there is a problem of the presence<br />of macrom olecular compounds in sugar beet juice, which are harmful and we have to be removed.<br />Separation ofthese compounds, which make around 60% oflotal non-sucrose compounds in sugar beetjuice,<br />is done by the principle of sedimentation with different types of coagulants (mostly compounds with calcium<br />ion). However, affinity of calcium binding with undesirable macromolecules fiom sugar beet juice is not<br />significant and in that way it is necessary a lot of quantities of this compound throughout daily production of<br />sugar.<br />The aim of this doctoral thesis is to consider the application of alternative coagulants with divalent and<br />trivalent cations, especially the salt of aluminum and cooper, which cause the process of dischargeable<br />macromolecules in sugar beet juice.<br />Optimal quantities of coagulants needing for the efficient coagulation of macromolecules compounds from<br />sugar beet juice were determined by means of measuring of electrokinetic potentials. It was investigated the<br />influence of other process variables such as pH, concentration of macromolecules and the impact of speed<br />mixing on the efficiency of sedimentation of macromolecules.<br />Mechanism of discharge of macromolecules compounds as well as the model of double electric layer<br />surrounding colloidal particles in sugar beetjuice are suggested for sugar beetjuice clarification.<br />Two model solutions of pectin are investigated together with one model solution of protein. Their<br />concentration correspond to concentration of these macromolecules in sugar beet juice. All investigated<br />systems were treated by using both solutions of CuSO4 as well as Al2(SO4)3 and slutions of their mixtures in<br />different proportion.<br />It was proven for all three investigated samples that fewer quantities of Cu+2 ions compared to the values of<br />Al+3 ions are needed to reach zero Zeta potential. However, due to possible undesirable effects of CuSO4 on<br />food processing, Al2(SO4)3 is proposed instead of traditional coagulant CaO, not only because of lower<br />consumptions of coagulants but owing to protection of the environment.<br />The objective in the experiments with mixtures was to investigate enhancement of coagulated characteristics<br />with commonly used salt Al2(SO4)3 by adding small quantities of Cu+2 ions. It was proven that pure salts<br />showed better-coagulated properties.<br />Further investigation was focused to selection of the most appropriate type and optimal quantity of chosen<br />flocculants. The highest efficiency of clarification of sugar beet juice was noticed by applying anion<br />flocculants of concentration 3 mg/dm3. It was shown that this type of flocculants additionally decreased the<br />value of Zeta potential of present macromolecules which further reduce required quantity of investigated<br />coagulants CuSO4 and Al2(SO4)3.</p>

[pt] Os materiais nanoestruturados têm sido estudados ao longo das últimas décadas, por apresentarem propriedades particulares, promissoras propriedades térmicas, mecânicas e catalíticas, que muitas vezes não estão presentes no material não manométrico. Alguns avanços recentes têm mostrado que estas propriedades podem ser reforçadas pela inclusão de materiais com propriedades diferentes na sua estrutura, formando assim nanocompósitos. Por exemplo, as ligas de CuNi são muito dúcteis, mas a presença de nanopartículas de Al2O3 depositadas na matriz pode melhorar consideravelmente a dureza do material. Tal nanocompósito pode ser obtido, por exemplo, através de decomposição térmica nitratos, seguido por redução seletiva com hidrogênio. Nesse contexto, o presente trabalho tem como foco a síntese de ligas de CuNi e CuNi com adição de nanoparticulas de Al2O3, baseados na redução seletiva de CuO e de NiO com H2, e óxidos coformados com o óxido de alumínio por meio da decomposição térmica de seus nitratos metálicos. Cálculos termodinâmicos mostraram que a redução de Cu e Ni pode ser realizada a temperaturas relativamente baixas (400 mais ou menos 5 Graus C), e também que o processo se desenvolve seletivamente (apenas os óxidos de Ni e de Cu reagem nas condições impostas), resultando em compósitos de CuNi/Al2O3, que consiste na formação de uma liga CuNi contendo 1 por cento de Al2O3 como finas nanopartículas distribuídas homogeneamente. Precursores e amostras reduzidas foram caracterizados por difração de raios x (DRX) para determinar a natureza das fases individuais presentes (óxidos e ligas), microscopia electrónica de varredura (MEV) como uma primeira aproximação da morfologia das partículas e microscopia eletrônica de transmissão (MET). Os resultados obtidos indicam que a via química proposta resultou satisfatória para a elaboração das ligas CuNi contendo nanopartículas de Al2O3 homogeneamente distribuídas. Os resultados obtidos também indicam que, para as condições experimentais impostas tanto a decomposição dos nitratos como as reações de redução alcançaram conversões de 100 por cento. / [en] Materials containing nanostructured particles have been studied over the last decades in order to take advantage of their promising thermal, mechanical and catalytic properties. Some recent progress has shown that these properties can be further enhanced by the inclusion of materials with different properties in their structure, thereby forming nanocomposites. For instance, Ni-Cu alloys are highly ductile, but the presence of Al2O3 nanoparticles deposited inside the alloy matrix can considerably improve the material s hardness. Such a nanocomposite can be obtained, for example, through nitrate solutions thermal decomposition followed by selective reduction with hydrogen. In this context, the present work focuses on the synthesis of CuNi alloys and CuNi/Al2O3 composites based on the selective reduction of copper and nickel oxides with pure H2, co-formed with aluminum oxide through thermal decomposition of aqueous solutions of their metal nitrates. Thermodynamic computations showed that the Cu and Ni reduction can be accomplished at relatively low temperatures (400 plus or minus 5 C degrees), and also that the process develops selectively (only the oxides of Ni and Cu react at the imposed conditions), resulting in Cu-Ni-Al2O3 composites, consisting in a Cu-Ni alloy crystals containing 1 percent of Al2O3 as fine homogeneously distributed nanoparticles. Both the original (co-formed) and reduced oxide samples were characterized using x ray diffraction (XRD) for determining the nature of the individual phases present (oxides and alloys) and scanning electron microscopy (SEM) as a first approach to the investigation of the morphology of the particles. The results indicate that the proposed chemical route resulted in composite materials containing CuNi alloy and Al2O3 particles of controllable composition and homogeneously distributed among the samples. The achieved results also suggest that for the imposed experimental conditions both the nitrate decomposition as well as the reduction reactions could be conducted to 100 percent conversion.

Les raccords et connexions de caténaires ont un rôle important dans l’intégrité électrique et mécanique des caténaires. Ces pièces sont pour la plupart constituées d’un alliage de cuivre Cu-Ni-Si mis en forme par forgeage à chaud. Dans un contexte de fiabilisation du réseau ferroviaire, l’amélioration de leurs performances et de leurs procédés de fabrication est recherchée. Ces travaux se concentrent sur l’étape de mise en forme de ces pièces, et ont pour objectif de mieux comprendre les couplages matériaux-procédés des alliages Cu-Ni-Si.Une campagne expérimentale de compression est menée. Elle permet de développer un modèle rhéologique à base physique décrivant le comportement d’un alliage Cu-Ni-Si dans les gammes de température 800 - 950 °C et de vitesse de déformation 0.1 - 10 s−1. Il tient compte des phénomènes d’adoucissement par restauration et recristallisation dynamiques. Le modèle ainsi créé est ensuite implémenté dans un logiciel éléments finis.Un nouvel essai de formabilité est proposé. Il permet de reproduire les sollicitations mécaniques rencontrées lors d’un procédé de forgeage et vise à déterminer les conditions limites de formabilité d’un matériau. La mise en forme d’une pièce de référence est étudiée par le biais de cet essai. Sa caractérisation précise en matière de champ de déformations et de contraintes permet d’identifier les paramètres expérimentaux. Les résultats identifient une température limite de forgeage en-deçà de laquelle des fissures sont prédites dans la pièce. / Contact wire splices play a leading role in the electric and mechanical integrity of the catenary systems. Most of these parts are made of Cu-Ni-Si alloys and manufactured by a hot forging process. With the aim of increasing the reliability of the railway network, the improvement of their performances and their manufacturing processes is sought. This work is focused on the forming stage of these parts and aims to give a better understanding of the materials-processes couplings for the Cu-Ni-Si alloys.An experimental campaign including compression tests is conducted. It allows the development of a physically-based model to describe the rheological behavior of a Cu-Ni-Si alloy deformed in the temperature range between 800 °C and 950 °C, at strain rates in the range of 0.1 - 10 s−1. It takes into account the work-softening implied by dynamic recovery and dynamic recrystallization. The model thus created is then implemented in a finite element software.A new workability test is proposed. Its purpose is to reproduce the mechanical conditions encountered in a forming process and to determine the critical conditions of workability related to a material. The forging process of a reference part is studied by means of this test. An accurate characterization of the process in terms of strain magnitude and stress field allows the identification of the experimental parameters. The results lead to the identification of a limit temperature of workability below which fractures are predicted in the part.

Le nanoalliage cuivre-or (CuAu) pour la catalyse hétérogène fait l'objet d'un intérêt grandissant de la communauté scientifique. En effet, l'alliage de l'or, réputé être un élément stabilisateur, avec le cuivre, réputé très actif notamment vis-à-vis de l'oxygène, offre de très grandes possibilités, tant dans les réactions d'oxydation tel que l'oxydation du monoxyde de carbone, mais aussi dans les réactions d'hydrogénation, telle que l'hydrogénation sélective du butadiène. L'un des processus déterminant dans les réactions d'oxydation et d'hydrogénation est le processus d'adsorption et de dissociation des molécules d'O2 et de H2 par le catalyseur. Afin d'avoir une meilleure compréhension des processus mis en jeu, il est nécessaire d'identifier les sites actifs où a lieu l'adsorption et la dissociation éventuelle des molécules, mais aussi des mécanismes mis en jeu lors de ces processus. Mais aujourd'hui, il n'existe pas de consensus général, dans la communauté scientifique, concernant la localisation des sites actifs. C’est dans ce contexte que s’inscrit ce travail de thèse, mené au laboratoire Matériaux et Phénomènes Quantiques (MPQ) au sein de l'équipe Microscope électronique Avancée et NanoStructures (Me-ANS) dirigé par le professeur Christian Ricolleau. Les deux problématiques majeures auxquelles nous nous sommes intéressées sont (i) la stabilité structurale et morphologique des nanoparticules de Cu, Au et de Cu-Au dans le vide et en température et ce sur différents supports tels que le nitrure de silicium amorphe et le rutile-TiO2, (ii) la stabilité structurale et morphologique des nanoparticules de Cu, Au et de Cu-Au supportées sur rutile-TiO2, sous atmosphère de gaz oxydant (O2) et réducteur (H2). Les objectifs étant d'identifier les sites d'adsorption éventuels des molécules d'O2 et de H2 par les catalyseurs, et de mieux comprendre les mécanismes qui conduisent à l'évolution morphologique de ceux-ci en milieu réactif. / : Copper-gold nanoalloy (CuAu) for heterogeneous catalysis is of increasing interest in the scientific community. Indeed, the alloy of gold, known to be a stabilizing element, with copper, known to be very active with respect to oxygen particularly, shows interesting catalytic properties, in oxidation reactions such as oxidation of carbon monoxide, but also in hydrogenation reactions, such as the selective hydrogenation of butadiene. One of the rate determining step in oxidation and hydrogenation reactions is the process of adsorption and dissociation of O2 and H2 molecules by the catalyst. In order to have a better understanding of the processes involved, it is necessary to identify, the active sites where the eventual adsorption and dissociation of the molecules takes place, but also the mechanisms involved during these processes. However today, there is no general consensus in the scientific community towards the location of the active sites. It is in this context that this thesis work, conducted in the laboratory Materials and Quantum Phenomena (MPQ) within the team Advanced Electron Microscope and NanoStructures (Me-ANS) led by Professor Christian Ricolleau. The two major issues we have been interested in are (i) the structural and morphological stability, in vacuum and with temperature, of Cu, Au and Cu-Au nanoparticles deposited on different substrates such as amorphous silicon nitride and rutile -TiO2 nanorods, (ii) the structural and morphological stability of Cu, Au and Cu-Au nanoparticles supported on rutile-TiO2 under oxidizing (O2) and reducing (H2) atmospheres. The main goals being to identify the possible adsorption sites of the O2 and H2 molecules by the catalysts, and to better understand the mechanisms that lead to the morphological evolution of these NPs in a reactive medium.

Die Motivation zur Untersuchung ternärer und quaternären CuZr-Legierungen bestand in der Annahme, dass die Zugabe von Kobalt den Stabilitätsbereich von B2 CuZr bis zur Raumtemperatur erweitert und Aluminium einen signifikanten Effekt auf die Glasbildungsfähigkeit des CuZr-Systems hat. Die vorliegende Dissertation befasst sich mit der Herstellung und Charakterisierung von Cu50-xCoxZr50 (0 ≤ x ≤ 20) und Cu50-xCoxZr45Al5- (x = 2, 5, 10 und 20) Legierungen. Hierbei wurden die Phasenbildung, die thermische Stabilität, die Mikrostruktur, die Martensitbildung und die mechanischen Eigenschaften der Legierungen untersucht. Die Abhängigkeit der Phasenbildung von der Erstarrungsrate und der thermodynamischen Stabilität von Cu-Co-Zr-Legierungen zeigte, dass die Zugabe von Kobalt die Glasbildungsfähigkeit von Cu-Co-Zr-Legierungen absenkt und die stabilen kristallinen Produkte des Systems von Cu10Zr7 + CuZr2 zu (Cu,Co)Zr Phase mit einer B2 Struktur verändert. Die Ergebnisse weisen darauf hin, dass bei den schmelzgesponnene Bänder mit wenigstens 5 Atom-% Co das Glas direkt in B2 (Cu,Co)Zr kristallisiert, während Massivproben mit Co-Gehalten zwischen 0 ≤ x < 5 die monokline (Cu,Co)Zr Phase und Cu10Zr7 sowie CuZr2 beinhalten, wobei für x ≥ 10 die B2 (Cu,Co)Zr Phase bei Raumtemperatur im Gleichgewicht ist. Des Weiteren werden mit steigendem Co-Gehalt die Martensitumwandlungstemperaturen zu niedrigeren Werten verschoben. Die Phasenbildung im ternären System wird im pseudo-binären (Cu,Co)Zr-Phasendiagramm zusammengefasst, welches die Entwicklung neuer Formgedächtnislegierungen sowie metallischer Glas-Komposite bei Zugabe des Glasbildungselementes Aluminium vereinfacht. In den Vierstofflegierungen erhöht Al die Glasübergangs- und Kristallisationstemperaturen und verbessert dadurch die Glasbildungsfähigkeit des Systems. Die röntgenographische Analyse zeigte, dass die Kristallisationsprodukte der schmelzgesponnenen Bänder variieren: von Cu10Zr7 + CuZr2 + AlCu2Zr zu (Cu,Co)Zr + AlCu2Zr, wenn Co ≤ 5 und Co ≥ 10. Die Herstellung von Massivproben mit unterschiedlichen Durchmessern führte zu einem vollständig amorphen Gefüge, einem metallischen Glas-Komposit oder einem vollständig kristallinen Gefüge. Für Co ≤ 5 tritt neben (Cu,Co)Zr und AlCu2Zr ebenfalls Cu10Zr7 auf. Mittels Rasterelektronen (REM)- und Transmissionselektronenmikroskopie (TEM) erfolgte die Analyse des Einflusses von Al- und Co-Zugaben auf die Mikrostruktur von CuZr-Legierungen. Für die Cu-Co-Zr-Al-Legierungen sowie Cu30Co20Zr45Al5 (ø = 4 mm) und Cu45Co5Zr45Al5 (ø = 2 mm) wurden mikrostrukturelle Untersuchungen mittels TEM durchgeführt. Nachfolgend wurde die Heterogenität der Mikrostruktur in der Cu40Co10Zr45Al5 (ø = 2 mm) untersucht. Der Einfluss von Co auf die mechanischen Eigenschaften von rascherstarrten Cu50-xCoxZr50 (x = 2, 5, 10 und 20 Atom-%) Legierungen zeigt, dass das Verformungsverhalten der Stäbe unter Druckbeanspruchung stark von der Mikrostruktur der (Cu,Co)Zr Phase und somit von der Legierungszusammensetzung abhängt. Kobalt beeinflusst die Bruchfestigkeit der Gussproben. Weiterhin zeigen Proben mit martensitischem Gefüge eine Kaltverfestigung. Neben der Kaltverfestigung zeigen die Legierungen mit hohem Co-Gehalt eine verformungsinduzierte Martensitumwandlung und weisen zwei Streckgrenzen auf. Für die Vierstofflegierungen wurde der Einfluss der Kühlrate und der chemischen Zusammensetzung auf die mechanischen Eigenschaften untersucht. Für Cu48Co2Zr45Al5 (ø = 1.5, 2, 3 und 4 mm) und Cu45Co5Zr45Al5 (ø = 3 mm) wurde der Einfluss der Kühlrate und der Heterogenität diskutiert. Die Ergebnisse zeigen, dass die mechanischen Eigenschaften der Cu50-xCoxZr45Al5-Legierungen stark von der Makrostruktur und dem Volumenanteil der amorphen und kristallinen Phase abhängen. Die verformungsinduzierte Martensitumwandlung in Cu40Co10Zr50- und Cu40Co10Zr45Al5-Gussstäben wurde mittels hochenergetischer Röntgenstrahlung durchgeführt. Die In-situ- Druckversuche erfolgten weg- und kraftkontrolliert. Das makroskopische und mikroskopische Spannung-Dehnungs-Verhalten sowie die Phasenumwandlungskinetik wurden dabei betrachtet. Die relativen Veränderungen der vollständig integrierten Intensität der ausgewählten B2- und Martensitreflexe, die auf die Veränderungen der Volumenanteile der entsprechenden Phasen unter Verformung hinweisen, wurden als Phasenumwandlungsvolumen M/M+B2 beschrieben. / The fact that the presence of Co extends the stability range of B2 CuZr to room temperature, together with the significant effect of Al on improving the glass forming ability of the CuZr system was the motivation to investigate the ternary and quaternary CuZr alloys with the aim of synthesizing BMG composites containing B2 (Cu,Co)Zr crystals. This PhD thesis deals with preparation and characterization of Cu50-xCoxZr50 (0 ≤ x ≤ 20) and Cu50-xCoxZr45Al5 (x = 2, 5, 10 and 20) alloys. The phase formation, thermal stability, microstructure, martensitic transformation and mechanical properties of these alloys were investigated. The dependence of phase formation on solidification rate and the thermodynamically stability of Cu-Co-Zr alloys reveals that the addition of Co decreases the glass forming ability (GFA) of the Cu-Co-Zr alloys and changes the stable crystalline products of the system from Cu10Zr7 + CuZr2 to (Cu,Co)Zr phase with a B2 structure. The results indicate that for the melt-spun ribbons with at least 5 % Co, the glass crystallizes directly into B2 (Cu,Co)Zr, while in the case of bulk specimens, compositions with 0 ≤ x < 5 of Co contain the monoclinic (Cu,Co)Zr phase and Cu10Zr7 and CuZr2, whereas, for x ≥ 10, the B2 (Cu,Co)Zr phase is the equilibrium phase at room temperature. Furthermore, increasing the cobalt content decreases the martensitic transformation temperatures to lower temperatures. The phase formation in the ternary system is summarized in a pseudo-binary (Cu,Co)Zr phase diagram, that helps for designing new shape memory alloys, as well as bulk metallic glass composites with the addition of glass former elements. In the quaternary alloys, Al increases the glass transition and crystallization temperatures and hence improves the GFA of the system. The X-ray analysis illustrates that for the melt-spun ribbons, the crystallization products vary from Cu10Zr7 + CuZr2 + AlCu2Zr to (Cu,Co)Zr + AlCu2Zr when Co ≤ 5 and Co ≥ 10, respectively. Depending on the cooling rates, the bulk samples represent a fully amorphous structure or BMG composites or a fully crystalline structure. For Co ≤ 5, beside (Cu,Co)Zr and AlCu2Zr, Cu10Zr7 exists as well. Scanning (SEM) and transmission (TEM) electron microscopy investigations were done to investigate the effect of Al and Co addition to the microstructure of CuZr alloys. In the case of Cu-Co-Zr-Al alloys, Cu30Co20Zr45Al5 (ɸ = 4 mm) and Cu45Co5Zr45Al5 (ɸ = 2 mm) compositions were selected for the microstructure verification using TEM. Later, the heterogeneity of the microstructure in Cu40Co10Zr45Al5 (ɸ = 2 mm) alloy was considered. The effect of Co on the mechanical properties of rapidly solidified Cu50-xCoxZr50 (x = 2, 5, 10 and 20 at.%) alloys depict that the deformation behavior of the rods under compressive loading strongly depends on the microstructure, and as a results, on the alloy composition. Cobalt affects the fracture strength of the as-cast samples; and deformation is accompanied with two yield stresses for high Co-content alloys, which undergo deformation-induced martensitic transformation. Instead samples with a martensitic structure show a work-hardening behavior. For quaternary alloys, the effects of cooling rate and chemical composition on mechanical properties of the alloys were investigated. Cu48Co2Zr45Al5 (ɸ= 1.5, 2, 3 and 4 mm) and Cu45Co5Zr45Al5 (ɸ = 3 mm) compositions were selected to discuss the effect of cooling rate and heterogeneity, respectively. The results depict that the mechanical properties of Cu50-xCoxZr45Al5 alloys strongly depend on the microstructure and the volume fraction of the amorphous and crystalline phases. The deformation-induced martensitic transformation of Cu40Co10Zr50 and Cu40Co10Zr45Al5 as-cast rods, was studied by means of high-energy X-rays. The in situ compression measurements were performed in track control and load control modes. The macroscopic and microscopic stress-strain behavior, as well as the phase transformation kinetics were considered. The relative changes in the fully integrated intensity of the selected B2 and martensite peaks, which indicate the changes in volume fraction of the corresponding phases under deformation, was described as phase transformation volume, M/M+B2.

In dieser Arbeit wird die nanoskalige Struktur von Grenzschichten in binären metallischen Multischichten untersucht. Ausgangspunkt sind laserdeponierte Multischichten des mischbaren Systems Fe/Al und des nichtmischbaren Systems Co/Cu. Die Struktur der durch die hochenergetischen Teilchen bei der Deposition entstandenen Grenzschichten wird mit Hilfe von zahlreichen Analyseverfahren (RBS, CEMS, EXAFS, Röntgenverfahren, TEM, AES und magnetische Messungen), sowie Simulationsrechnungen auf Basis des ballistischen Mischens (TRIDYN) untersucht. Anschließend wird mit Hilfe von Ionenstrahlmischen und thermischem Anlassen die Grenzschichtstruktur weiter modifiziert.

Cette thèse s’inscrit dans le cadre général de la dépollution d’effluents gazeux faiblement chargés en Composés Organiques Volatils (COV). L’étude concerne l'oxydation de trois COV cibles (méthane, propène, et toluène) dans l'air à la pression atmosphérique dans d'une part un réacteur plasma de décharge à barrière diélectrique (DBD) pulsée et un réacteur catalytique utilisés séparément et d'autre part, dans un réacteur hybride associant le réacteur plasma aux catalyseurs dans deux configurations: le catalyseur au coeur de la décharge et le catalyseur en post-décharge. Les catalyseurs sont à base de Pd, Mn, Cu, et Co supportés sur des billes de Al2O3. Ils ont été caractérisés par ICP-OES, TEM/EDX, XRD, XPS, et DRIFTS. L’efficacité de conversion des COV, la sélectivité en CO/CO2, ainsi que la nature et les concentrations des produits formés pour les trois molécules avec les trois systèmes ont été étudiées en fonction de la température du gaz, de l'énergie injectée, de la concentration des COV, de la taille du support, du type de métal et sa teneur, et de la vitesse volumique horaire. Dans tous les cas, l’activation des catalyseurs à basse température a été démontrée quand ces derniers sont couplés au plasma et les principaux produits de réaction identifiés et quantifiés par spectroscopie infrarouge à transformée de Fourier. Le couplage plasma-catalyseur améliore de façon significative l’efficacité de conversion du méthane, du propène, et du toluène dans l’air ainsi que la sélectivité en sous-produits. L'effet de synergie entre le plasma et les catalyseurs pour la conversion des COV a été démontré dès lors que le plasma est généré directement au sein du réacteur catalytique. / The focus of this thesis is the application of non-thermal plasma and catalysis in chemical processing, in particular for the removal of Volatile Organic Compounds (VOC) diluted in air. In a first part, the oxidation of three pollutants (methane, propene, and toluene) is studied experimentally in a pulsed dielectric barrier discharge (DBD) reactor and in a catalyst reactor working independently. In a second part, a hybrid plasma-catalyst reactor either in a single-stage or in a two-stages configuration, in which the catalyst is located inside or downstream from the plasma reactor, respectively. Catalyst materials based on Pd, Mn, Cu, and Co supported on alumina beads were tested and characterized by ICP-OES, TEM/EDX, XRD, XPS, and DRIFTS. Products were analyzed and quantified by infrared spectroscopy. Achieved VOCs removal efficiencies and CO/CO2 selectivity, as well as nature and concentrations of the formed products, were evaluated as function of many factors, particularly the specific input energy, the gas temperature, the initial VOCs concentration, the nature of catalyst (size support, metal loading), and the hourly space velocity. It has been successfully demonstrated that the combination of plasma and catalyst in the both configurations has many benefits compared to traditional thermal-catalysis and plasma alone treatment including a lowering of the catalyst operating temperature, an improvement of the conversion of VOCs at similar temperatures, and a better end-products selectivity and energy efficiency. The mutual interaction lead to a synergistic effect in plasma-catalysis especially when the discharge is in direct contact with the catalyst whatever the VOCs studied.

This work deals with fatigue properties and stability of microstructure of ultrafine-grained (UFG) copper prepared by severe plastic deformation by means of equal channel angular pressing (ECAP) method. The effect of different fatigue loading regimes and thermal exposition on microstructural changes was investigated and the fatigue lifetime curves were experimentally determined. The research attention was focussed on localization of cyclic plastic deformation and fatigue crack initiation in UFG structure. Experimental results indicate that after stress-controlled fatigue loading (both symmetrical and asymmetrical) the microstructure remains ultrafine; no grain coarsening was observed. Contrary to this, strain-controlled fatigue loading results in formation of bimodal structure. Grain coarsening was observed also after thermal exposition at 250 °C for 30 minutes. Annealing at lower temperatures does not result in grain coarsening or development of bimodal structure. Fatigue loading results in development of surface relief in form of cyclic slip markings. Their density, distribution and shape differ for particular fatigue loading regimes. Differences in crack initiation mechanism in low- and high-cycle fatigue region were found. Nevertheless, the characteristic feature for all loading regimes was stability of UFG microstructure in the region of cyclic slip bands and fatigue cracks.

Selective laser melting (SLM) is an additive manufacturing technology. In this thesis, a heat-treatable Al-3.5Cu-1.5Mg-1Si alloy and related materials (composites and hybrid materials) have been successfully fabricated by selective laser melting and characterized in terms of densification, microstructure, heat treatment, mechanical properties as well as tribological and corrosion behavior. Firstly, the fully dense SLM Al-Cu-Mg-Si alloy was fabricated by SLM successfully. The alloy shows a higher yield strength than SLM Al-12Si alloy, and lower wear resistance and corrosion rate than commercial 2024 alloy before and after T6 heat treatment. Secondly, with the aim of designing new alloy compositions and to examine the phases and microstructures of SLM Al-Cu alloys and to correlate their microstructures with the observed mechanical properties, Al-xCu (x = 4.5, 6, 20, 33 and 40 wt. %) alloys have been synthesized in-situ by SLM from mixtures of Al-4.5Cu and Cu powders. The results indicate that the insufficient Cu solute diffusion during the layer-by-layer processing results in an inhomogeneous microstructure around the introduced Cu powders. With increasing Cu content, the Al2Cu phase in the alloys increases improving the strength of the material. These results show that powder mixtures can be used for the synthesis of SLM composites but the reaction between the matrix and the second-phase should be considered carefully. Thirdly, the TiB2/Al-Cu-Mg-Si composite was also designed and fabricated successfully by SLM and it shows a higher strength than the unreinforced SLM alloy before and after T6 heat treatment. Finally, an Al-12Si/Al-3.5Cu-1.5Mg-1Si hybrid with a good interface was fabricated successfully. This hybrid alloy shows a good yield strength and elongation at room temperature, indicating an effective potential of selective laser melting in the field of hybrid manufacturing.

As current environmental challenges are gaining increased attention, development of clean energy solutions is becoming one of the essential strategies to keep within the boundaries of established environmental policies. Solid oxide cell (SOC) technology can provide clean energy conversion and storage when hydrogen is the energy carrier. The high total energy conversion efficiency resulting from the high operation temperature of SOCs make the technology promising, but material costs must be reduced to make it commercially viable. Therefore, this thesis aims to study the long- term performance of a novel cost-optimized cell interconnect at 650 and 850 °C. At high temperatures, chromium evaporation from the interconnect result in electrode poisoning, which may be mitigated by application of a protective coating. The studied interconnect is an AISI 441 steel with some different pre-oxidized copper and iron spinel coatings. Sample analysis was made mainly with scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and X-ray diffraction. It was found that the most promising pre-oxidation treatment was 24 h at 750 °C and that chromium migration was restrained at 650 °C long-term treatment but not at 850 °C where it wasfound available for evaporation at the surface. / När samtida milljöutmaningar får ökad uppmärksamhet blir gröna energilösningar en av de viktigaste strategierna för att hålla sig inom satta gränser från etablerade miljöriktlinjer. Teknologin bakom fastoxidceller, eller solid oxide cells (SOCs), kan bidra med grön omvandling och lagring av energi när energibäraren är väte. Den höga totala omvandlingseffektiviteten, som kommer med den höga verkningstemperaturen, gör SOC till en lovande teknologi, men materialkostnaderna måste först reduceras innan den blir komersiellt gångbar. Därför syftar detta examensarbete till att undersöka prestandan av en ny, kostnadsoptimerad cellinterkonnektor på lång sikt i 650 och 850 °C. Vid höga temperaturer förångas krom från interkonnektorn, vilket leder till elektrodförgiftning, men kan mildras genom applicering av en skyddande beläggning. Den undersökta interkonnektorn är ett stål som betäcknas AISI 441 belagt med några olika föroxiderade beläggningar av koppar- och järnspinell. Proverna analyserades i huvudsak genom svepelektronmikroskopi kobinerat med energidispersiv röntgenspektroskopi och röntgendiffraktometri. Det visades att den mest lovande föroxideringsbehandlingen var 24 h i 750 °C och att krom förblev återhållet vid 650 °men inte vid 850 °C då det fanns tillgängligt för förångning vidytan.