In the copper smelting processes, the viscosity of the matte and the slag is an important factor for establishing efficiency. Impurities in the concentrates affect the viscosity not only by changing the melt structure but also by promoting precipitation of solid phase which sharply rises it. In this master thesis, a comprehensive methodology was established to study the MgO effects on the properties of a copper smelting slag. Thus, glassy samples were obtained and after confirmation of the composition and the glassy structure with EDS, SEM, and XRD analysis, they were examined through Ramanspectroscopy to study their glassy structure. Moreover, Mössbauer spectroscopy was used to determine the amount of Fe3+ in the samples. Models from the literature were compared to the experimental data. Coherence with the literature was found with the effect of MgO as a network modifier of the oxide melt structure and a promoter of high coordinated structures. Estimations through models were performed to study the iron redox equilibria of the melt and were compared with experimental data, but it was not possible to find the limit of Fe3+ at which precipitation of solid phase initiates. / I kopparsmältningsprocesserna är mattans och slaggens viskositet en viktig faktor för att uppnå effektivitet. Föroreningar i koncentraten påverkar viskositeten inte bara genom att ändra smältstrukturen utan också genom att främja utfällning av fast fas som kraftigt höjer den. I denna magisteruppsats fastställdes en omfattande metod för att studera MgO-effekterna på egenskaperna hos en kopparsmältningsslagg. Således erhölls glasiga prover och efter bekräftelse av kompositionen och den glasiga strukturen med EDS-, SEM- och XRD-analys undersöktes de genom Ramanspektroskopi för att studera deras glasstruktur. Dessutom användes Mössbauerspektroskopi för att bestämma mängden Fe3+ i proverna. Modeller från litteraturen jämfördes med experimentella data. Överensstämmelse med litteraturen hittades med effekten av MgO som ett nätverksmodifierare av oxidsmältstrukturen och en promotor för högkoordinerade strukturer. Uppskattningar genom modeller utfördes för att studera smältans järnredoxjämvikter och dessa jämfördes med experimentella data, men det var inte möjligt att hitta gränsen för Fe3+ vid vilken utfällning av fast fas initierades.

Dans cette étude, nous proposons d’utiliser la compression in situ dans le MET afin de caractériser les propriétés mécaniques de nanoparticules céramiques dont la taille caractéristique est de l’ordre de quelques dizaines de nanomètres. Nous appliquerons cette méthode à des nanocubes monocristallins de MgO, une céramique modèle dont la plasticité est bien connue dans le matériau massif. Les essais de nanocompression montrent que les nanocubes de MgO se déforment de façon homogène jusqu’à de grandes déformations (>50%) sans fissure apparente. L’analyse des résultats est assistée par des méthodes de corrélation d’images numériques et simulations de type dynamique moléculaire. Le mécanisme de déformation et l'effet de taille sur la limite élastique sont identifiés. Dans une deuxième partie de la thèse, nous présentons une étude sur des nanoparticules d’alumine de transition compactée en CED (Cellule à Enclumes en Diamant) à température ambiante, sous plusieurs pressions (5 GPa, 15 GPa et 20 GPa). Des lames minces préparées par FIB ont été étudiées en MET. Des images HRTEM montrent une texture cristallographique qui devient plus importante à des pressions plus élevées. Une orientation cristallographique préférentielle est observée, avec les plans {220} de la phase gamma de l’alumine la plupart du temps parallèles à la surface de contact avec une particule voisine. Ce comportement mécanique est cohérent avec un système de glissement, connu pour les structures spinelles. Une corrélation de ce comportement avec les tests in situ MET réalisés sur des nanoparticules similaires, par Emilie Calvié lors de sa thèse, est présentée. Enfin, des clichés de diffraction de type Debye Scherrer sont réalisés sur ces lames minces de nanoparticules d’alumine de transition compactées en CED à différentes pressions. L’analyse quantitative de ces clichés montre une transformation de phase de ces nanoparticules d’alumine de phase gamma en phase delta, de manière croissante avec la pression. / In this study, we propose an innovative mechanical observation protocol of ceramics nanoparticles in the 100nm size range. This Protocol consists of in situ TEM nanocompression tests of isolated nanoparticles. Load–real displacements curves, obtained by Digital Image Correlation, are analyzed and these analyses are correlated with Molecular Dynamics simulations. By this protocol a constitutive law with its mechanical parameters (Young modulus, Yield stress...) of the studied material at the nano-scale can be obtained. In situ TEM nano-compression tests on magnesium oxide nanocubes are performed. Magnesium oxide is a model material and its plasticity is very well known at bulk. The MgO nanocubes show large plastic deformation, more than 50% of plastic strain without any fracture. The TEM results are correlated to MD simulations and the deformation mechanism can be identified.The size effect and the electron beam effect on the yield strength are investigated. In a second part of the dissertation, we present a study on transition alumina nanoparticles compacted in a Diamond Anvil Cell at different uniaxial pressures. Thin Foils of these compacted nanoparticles are prepared by FIB for HRTEM Observations. Their analysis reveals the plastic deformation of the nanoparticles. The crystallographic texture observed inthese compacted nanoparticles in DAC shows a preferred orientation of the {110} lattice planes, orientated perpendicular to the compression direction. This is compatible with the slip system. This argument was reinforced with a preferred orientation of slip bands observed during in situ TEM nano-compression tests. Moreover, electron diffraction patterns (Debye Scherrer) analysis on these compacted transition alumina nanoparticles reveals the decrease of the presence of gamma-alumina and the increase of delta-alumina with increasing pressure. This reveals the phase transformation with increasing pressure from gamma to delta* alumina.

The synthesis and characterization of bis(ketoiminato)magnesium(II) complexes of composition [Mg(OCR2CH2CHR1NCH2CH2X)2] (X = NMe2: 3a, R1 = R2 = Me; 3b, R1 = Me, R2 = Ph. X = OMe: 3c, R1 = R2 = Me) are reported. Complexes 3a–c are accessible by the reaction of C(O)R2CH2CHR1N(H)CH2CH2X (X = NMe2: 1a, R1 = R2 = Me; 1b, R1 = Me, R2 = Ph. X = OMe: 1c, R1 = R2 = Me) with MgnBu2. The structure of 3b in the solid state was determined by a single crystal X-ray diffraction study, confirming that the Mg(II) ion is hexa-coordinated by two ketoiminato ligands, while each of the latter coordinates with its two N- and one O-donor atom in an octahedral MgN6O2 coordination environment in the OC-6-33 stereo-isomeric form. The thermal behavior of 3a–c was studied by TG and DSC under an atmosphere of Ar and O2 respectively. The respective Me-substituted complexes 3a,c decompose at lower temperatures (3a, 166 °C; 3c, 233 °C) than the phenyl derivative 3b (243 °C). PXRD studies indicate the formation of MgO. Additionally, TG-MS studies were exemplarily carried out for 3a, indicating the release of the ketoiminato ligands. Vapor pressure measurements were conducted at 80 °C, whereby 3a,c possess with 5.6 mbar (3a) and 2.0 mbar (3c) significantly higher volatilities than 3b (0.07 mbar). Complexes 3a–c were used as MOCVD precursors for the deposition of thin MgO films on silicon substrates. It was found that only with 3a,c thin, dense and rather granulated MgO layers of thicknesses between 28–147 nm were produced. The as-deposited MgO layers were characterized by SEM, EDX, and XPS measurements and the thicknesses of the as-deposited layers were measured by Ellipsometry and SEM cross-section images. Apart from magnesium and oxygen a carbon content between 3–4 mol% was determined.

The synthesis of complexes [M(OCHMeCH2NMeCH2)2] (5, M = Mg; 7, M = Zn) is described. Treatment of MeHNCH2CH2NMeH (1) with 2-methyloxirane (2) gave diol (HOCHMeCH2NMeCH2)2 (3), which upon reaction with equimolar amounts of MR2 (4, M = Mg, R = Bu; 6, M = Zn, R = Et) gave 5 and 7. The thermal behavior and vapor pressure of 5 and 7 were investigated to show whether they are suited as CVD (= chemical vapor deposition) and/or spin-coating precursors for MgO or ZnO layer formation. Thermogravimetric (TG) studies revealed that 5 and 7 decompose between 80–530 °C forming MgO and ZnO as evidenced by PXRD studies. In addition, TG-MS-coupled experiments were carried out with 7 proving that decomposition occurs by M–O, C–O, C–N and C–C bond cleavages, as evidenced from the detection of fragments such as CH4N+, C2H4N+, C2H5N+, CH2O+, C2H2O+ and C2H3O+. The vapor pressure of 7 was measured at 10.4 mbar at 160 °C, while 5 is non-volatile. The layers obtained by CVD are dense and conformal with a somewhat granulated surface morphology as evidenced by SEM studies. In addition, spin–coating experiments using 5 and 7 as precursors were applied. The corresponding MO layer thicknesses are between 7–140 nm (CVD) or 80 nm and 65 nm (5, 7; spin-coating). EDX and XPS measurements confirm the formation of MgO and ZnO films, however, containing 12–24 mol% (CVD) or 5–9 mol% (spin-coating) carbon. GIXRD studies verify the crystalline character of the deposited layers obtained by CVD and the spin-coating processes.

Die vorliegende Dissertation präsentiert eine detaillierte quantenchemische Untersuchung der H-Abstraktion von Methan durch MgO und Li dotiertes MgO. Motiviert wurde die durch das UniCat-Excellenz-Cluster, welches sich zum Ziel gesetzt hat, die oxidative Kupplung von Methan (OCM) im Detail zu verstehen. Basierend auf der Hypothese, dass Li+O•– Spezies für den H-Abstraktion Schritt verantwortlich sind, wurden kleine kationische MgO- und Li dotierte MgO-Cluster (die O•– Sites modellieren) untersucht. Zur Erstellung von möglichst realen Gasphasen-Modell-Systemen, wurde die globalen Minima der Gasphasencluster mittels eines genetischen Algorithmus bestimmt. Zum Vergleich wurden auch die Strukturen von neutralen MgO-Cluster bestimmt, um eventuelle strukturelle Unterschiede zu erkennen. Anschließend wurden die optimierten Cluster in Bezug auf ihre Eignung zur C-H-Bindungsaktivierung von Methan untersucht. Die Verwendung von kleinen Cluster-Größen ermöglicht es, die Reaktion im Detail zu studieren und verschiedene Methoden der Berechnung zu vergleichen. Die Ergebnisse für die kleinen Cluster wurden anschließend mit realistischeren Modellen verglichen, die eine genauere Beschreibung der Li dotierten Oberflächen ermöglichen, wie zum Beispiel non-embedded und embedded-Cluster und slab Modelle. Unerwartete Ergebnisse für die Betrachtung der Li+O•– Spezies haben zur Untersuchung von zusätzliche Arten von Defekten in MgO (wie niedrig koordinierten O2-Seiten, O-Leerstellen mit unterschiedlicher Ladung und Verunreinigungen) geführt, die als aktive Zentren in OCM fungieren können. Insbesondere wurden morphologische Defekte und verschiedene Arten von F Zentren untersucht. Die Aktivierung von Methan an defekten MgO-Oberflächen wurde innerhalb eines Cluster-Ansatzes untersucht und durch periodische Berechnungen mittels periodic slab models verifiziert. Die Ergebnisse wurden mit vorhandenen experimentellen Daten verglichen. / This work presents a detailed quantum chemical (mostly DFT) study of H abstraction from methane by MgO and Li doped MgO. It is motivated by the UniCat effort to understand the oxidative coupling of methane (OCM). Based on the hypothesis that an Li+O•– species is responsible for the H abstraction step in OCM small cationic MgO and Li doped MgO clusters (which model O•– sites) were investigated. Because we were interested in real gas phase model systems the global minimum structures of (MgO)n+ and LiO(MgO)n-1 clusters were first determined (by means of genetic algorithm) and then used in subsequent reactivity studies. To check if there are any structural differences between neutral and cationic MgO clusters the neutral species were studied as well. After structure determination, the activation of methane by the O•– radical sites was investigated. The small cluster sizes enabled to study the reaction in detail and to compare different methods of calculations. The results were verified by comparison with more realistic models that mimic Li doped MgO surface, like non-embedded and embedded clusters and slab models. However, unexpected results for the Li+O•– sites led to the consideration of additional types of sites in MgO that may be active for OCM – such as low-coordinated O2- sites, O vacancies with different charge and impurity defects. In particular morphological defects and different types of F centers were investigated. Methane activation by defective MgO surface was studied by a cluster approach and then followed by periodic calculations on periodic slab models. The results were compared to existing experimental data.

Die Erzeugung spinpolarisierter Ladungsträger in einem Halbleiter gilt als Grundvoraussetzung zur Realisierung spintronischer Bauelemente. Einen möglichen Ansatz zu deren Realisierung stellen Ferromagnet/Halbleiter(FM/HL)-Hybridstrukturen dar, deren Herstellung jedoch mit einigen Schwierigkeiten verbunden ist. Durch die Vermischung des ferromagnetischen Materials mit dem Halbleiter werden die elektronischen Eigenschaften der Hybridstruktur verändert und die Spininjektionseffizienz stark verringert. Durch das gezielte Einfügen einer dünnen Oxidschicht in den FM/HL-Grenzübergang kann die Diffusion unterdrückt, die Kristallqualität verbessert und die Effizienz der Struktur erhöht werden. Diese Arbeit beschäftigt sich mit dem Wachstum und der Charakterisierung dünner Oxidschichten, hergestellt mittels Molekularstrahlepitaxie. Zwei Seltenerdoxide, La2O3 und Lu2O3, werden auf GaAs-Substraten gewachsen und die Kristallqualität der Schichten miteinander verglichen. Mit der Heusler-Legierung Co2FeSi als Injektorschicht wird eine FM/Oxid/HL-Hybridstruktur auf Basis einer La2O3/GaAs(111)B-Struktur realisiert und magnetisch und elektrisch charakterisiert. Ein häufig verwendetes Barrierenmaterial in FM/HL-Hybridstrukturen ist Magnesiumoxid (MgO). In dieser Arbeit werden dünne MgO-Schichten auf GaAs(001) an der PHARAO-Wachstumsanlage am BESSY II erzeugt. Dies geschieht durch getrenntes Verdampfen von metallischem Mg bzw. Einleiten von molekularem Sauerstoff in die Wachstumskammer. Um die Oxidation des Halbleitersubstrats zu verhindern, wird vor dem MgO-Wachstum eine dünne Mg-Schicht abgeschieden. Abhängig von der Dicke dieser Schicht sind zwei in-plane-Orientierungen des MgO relativ zum GaAs kontrolliert einstellbar. Darüber hinaus werden Hybridstrukturen mit Eisen Fe als Injektorschicht und schrittweise erhöhter MgO-Schichtdicke gewachsen. Die Eindiffusion von Fe in das GaAs-Substrat nimmt mit zunehmender MgO-Schichtdicke um mehrere Größenordnungen ab. / The generation of spin-polarized charge carriers in a semiconductor is a basic building block for the implemention of spintronic devices. A feasible approach to their implementation are ferromagnet/semiconductur(FM/SC) hybrid structures, whose fabrication is associated with some issues. The intermixing of the ferromagnetic material with the semiconductor leads to distortion of the electrical properties of the hybrid structure and the spin injection efficiency is reduced. By intentionally inserting a thin oxide layer into the FM/SC interface diffusion can be suppressed while the crystal quality and the spin injection efficiency of the structure are both increased. In this thesis the growth and characterization of thin oxide films fabricated by molecular beam epitaxy are discussed. Two rare earth oxides, La2O3 and Lu2O3, are grown on GaAs substrates and their crystal qualities are compared. Based on La2O3/GaAs(111)B full FM/SC hybrid structures are grown with the Heusler alloy Co2FeSi as injection layer and characterized by magnetic and electrical means. Another material used as a barrier in FM/SC hybrid structures is magnesium oxide (MgO). Here, thin MgO layers are grown on GaAs(001) at the PHARAO system at BESSY II. The growth is conducted by the separated evaporation of metallic Mg and introducing molecular oxygen into the growth chamber. To avoid oxidation of the semiconducting substrate a thin Mg layer is deposited prior to the MgO growth. Depending on the Mg layer thickness two different MgO in-plane orientations can be achieved with respect to the GaAs substrate. Furthermore, FM/SC hybrid structures with iron Fe as injection layer are grown while the MgO layer thickness is increased gradually. The indiffusion of Fe into the GaAs substrate is suppressed by several orders of magnitude with increasing MgO layer thickness.

At present, the use of other sources of energy other than energy source from crude oil has accelerated. This is due to limited resources of fossil fuel, increasing prices of crude oil and environmental concerns. Alternative fuels such as biofuel are becoming more important because it can serve as a replacement for petroleum diesel due to its comparable fuel properties and cleaner emission. For use in a standard diesel engine, biodiesel can be blended (mixed) with petroleum diesel at any concentration. In this study, transesterification of waste cooking oil with methanol was catalyzed by heterogeneous catalyst TiO2-supported-MgO and the biodiesel produced was characterised. Waste cooking oil (WCO) was used because it is regarded as one of the cheapest feedstock for biodiesel production in that most oils from oil crops are used as food. Waste cooking oil is available in vast amounts each day in every restaurants and fast food outlets worldwide. The waste cooking oil used in this study was laboratory prepared by the addition of 5 wt. % of oleic acid into 95 wt. % of soybeans oil.10 wt. % of titanium-supported-magnesium oxide catalyst (MgO/TiO2) used was prepared by incipient wetness impregnation and characterized using XRF, BET and XRD. These materials were tested with the catalyst for the conversion of waste vegetable oil to biodiesel in presence of methanol and hexane co-solvent. Methanol to oil mole ratio of 18:1 was employed in the transesterification process. When hexane was used as cosolvent, methanol to oil mole ratio of 18:1 and methanol to hexane mole ratio of 1:1 was used. The effects of reaction time, reaction temperature and hexane co-solvent on the waste vegetable oil conversion has been established. The 1HNMR analysis was used to estimate the structure of FAME produced. It was observed that the oil conversion increases with the increased reaction time, reaction temperature and use of hexane as co-solvent. / Chemical Engineering / M. Tech. (Chemical Engineering)

At present, the use of other sources of energy other than energy source from crude oil has accelerated. This is due to limited resources of fossil fuel, increasing prices of crude oil and environmental concerns. Alternative fuels such as biofuel are becoming more important because it can serve as a replacement for petroleum diesel due to its comparable fuel properties and cleaner emission. For use in a standard diesel engine, biodiesel can be blended (mixed) with petroleum diesel at any concentration. In this study, transesterification of waste cooking oil with methanol was catalyzed by heterogeneous catalyst TiO2-supported-MgO and the biodiesel produced was characterised. Waste cooking oil (WCO) was used because it is regarded as one of the cheapest feedstock for biodiesel production in that most oils from oil crops are used as food. Waste cooking oil is available in vast amounts each day in every restaurants and fast food outlets worldwide. The waste cooking oil used in this study was laboratory prepared by the addition of 5 wt. % of oleic acid into 95 wt. % of soybeans oil.10 wt. % of titanium-supported-magnesium oxide catalyst (MgO/TiO2) used was prepared by incipient wetness impregnation and characterized using XRF, BET and XRD. These materials were tested with the catalyst for the conversion of waste vegetable oil to biodiesel in presence of methanol and hexane co-solvent. Methanol to oil mole ratio of 18:1 was employed in the transesterification process. When hexane was used as cosolvent, methanol to oil mole ratio of 18:1 and methanol to hexane mole ratio of 1:1 was used. The effects of reaction time, reaction temperature and hexane co-solvent on the waste vegetable oil conversion has been established. The 1HNMR analysis was used to estimate the structure of FAME produced. It was observed that the oil conversion increases with the increased reaction time, reaction temperature and use of hexane as co-solvent. / Chemical Engineering / M. Tech. (Chemical Engineering)

The present thesis describes the synthesis and characterization of magnesium, copper, and iron complexes and their application in the MOCVD (Metal-Organic Chemical Vapor Deposition) process, as well as the synthesis and characterization of yttrium and gadolinium complexes and their use as spin-coating precursors for metal oxide thin layer formation. The objective of this scientific work is the development of the family of bis(β-ketoiminato) magnesium(II) complexes and a series of heteroleptic β-ketoiminato copper(II) precursors for the formation of magnesium oxide and copper/copper oxide layers by using the MOCVD process. Modifications of the ketoiminato ligands affect the physical and chemical properties of the respective complexes. Another central theme of this work is the development of β-diketonato iron(III) complexes for the deposition of carbon-free gamma- and alpha-Fe2O3 layers via MOCVD. The thermal behavior and vapor pressure of the precursors could be influenced by the variation of the β-diketonate ligands. In addition, the synthesis and characterization of yttrium and gadolinium β-diketonates and their use as spin-coating precursors are described. Field-effect transistors were successfully fabricated by the deposition of carbon nanotubes on top of the Y2O3 films.

Ce travail de thèse s’est inscrit dans un cadre fondamental d’étude de la formation contrôlée d’oxydes en couches ultra-minces. Un bâti ultra-vide dédié à la croissance contrôlée de ces oxydes et à leur analyse in-situ (STM-STS, AES et LEED) a été développé. Par une méthode originale de phases alternées de dépôt d’une monocouche atomique de Mg et oxydation à RT, les mécanismes impliqués dans la formation de deux systèmes à fort potentiel applicatif : MgO/Si(100) et MgO/Ag(111) ont été étudiés .Le système MgO/Si(100) a révélé la formation d’une couche ultra-mince de Mg2Si à l’interface entre le MgO et le substrat. En bon accord avec les calculs thermodynamiques réalisés, une cristallisation de cette couche interfaciale dans un processus de dissociation partielle du Mg2Si en MgO à température ambiante a été observée. Identifiée ex-situ par TEM, la relation d’épitaxie associée à cette cristallisation a permis de conclure à la formation d’une hétérostructure MgO / Mg2Si (11-1) / Si(001), témoignant d’une grande qualité d’interface avec le silicium et de la formation d’une couche ultra-mince et amorphe de MgO homogène et isolante (gap de 6 eV).Pour le système MgO/Ag(111), nos résultats expérimentaux couplés aux calculs ab initio de nos partenaires du LAAS ont révélé l’absence de formation d’un alliage de surface ainsi qu’une croissance « liquid-like » du magnésium à RT. Un double empilement O/Mg/O/Mg/Ag(111) suivi d’un recuit UHV à 430°C a ensuite permis la stabilisation d’une couche ultra-mince polaire de MgO(111) qui a été caractérisée par LEED et STM-STS. Les propriétés physico-chimiques et origines possibles de stabilité de cet oxyde polaire ont ensuite été discutées. / This PhD work was dedicated to studying the fundamental mechanisms driving the controlled growth of ultra-thin oxide films. An experimental set-up was designed to finely control the growth parameters under UHV conditions while allowing the study of such oxide layers in situ with STM-STS, AES and LEED. Using an original method based on alternate cycles of Mg monolayer adsorption and RT oxidation, we focused on the formation of systems exhibiting a wide range of potential applications: MgO/Si(100) and MgO/Ag(111). The MgO/Si(100) system revealed the growth of an ultra-thin Mg2Si layer at the interface between the MgO and the silicon. In agreement with thermodynamic calculations, a crystallization of this interlayer driven by a partial decomposition of the Mg2Si to a MgO oxide was shown to occur at RT. From ex situ TEM experiments, the involved epitaxial relationship highlighted the formation of an MgO / Mg2Si (11-1) / Si(001) heterostructure. A sharp interface with the silicon was formed, as much as an ultra-thin and amorphous MgO layer exhibiting both a good homogeneity and a high insulating character (bandgap of 6 eV).In the MgO/Ag(111) system, no interfacial alloy formation and a « liquid-like » growth for the Mg were evidenced at RT, using our experimental results coupled with the ab initio calculations performed by our co-workers at LAAS laboratory. Later, a double-layering O/Mg/O/Mg/Ag(111) grown at RT followed by UHV annealing at 430°C resulted in the stabilization of a polar MgO(111) ultra-thin film, which was characterized using LEED and STM-STS. The physicochemical properties of this polar oxide and the potential origin of its stability were discussed.