Graphen und Graphit als Vertreter sp2-hybridisierter Kohlenstoffmaterialien weisen sehr gute elektronische Eigenschaften auf, die sich in vielen Fällen durch Adsorption oder Interkalation von Metallatomen weiter verbessern lassen. In dieser Arbeit wird die atomare Struktur von nickelinterkaliertem Graphit sowie von nickelbesetztem Mono- und Bilagen-Graphen und deren Stabiität mittels Dichtefunktionaltheorie berechnet und untereinander verglichen. Durch Untersuchung des Einflusses der Nickelatomdichte sowie von Anzahl und Abstand der Kohlenstofflagen werden verallgemeinerte Vorhersagen für Graphitmaterialien mit Nickelinterkalation und deren Verhalten bei externen Verspannungen möglich. Abschließend wird der Einfluss der Nickelatome auf die elektronischen Eigenschaften anhand der Bandstruktur untersucht. Aufgrund zusätzliche Bänder in der Nähe der Fermienergie kann eine Verbesserung des elektrischen Transportes angenommen werden.:Abbildungsverzeichnis Tabellenverzeichnis Abkürzungsverzeichnis Symbolverzeichnis 1. Einleitung 2. Überblick zu Kohlenstoffmaterialien 2.1. Formen des Kohlenstoffs 2.2. Interkalation 2.3. Elektronische Eigenschaften 3. Dichtefunktionaltheorie 3.1. Motivation 3.2. Das Hohenberg-Kohn-Theorem 3.3. Berechnung der Elektronendichte 3.4. Abschätzung der Austausch-Korrelations-Energie 3.4.1. Lokale Dichtenäherung 3.4.2. Verallgemeinerten Gradientennäherung 4. Simulationsmethodik 4.1. Modellsystem 4.2. Software und Rechenparameter 5. Ergebnisse 5.1. Gleichgewichtspositionen 5.1.1. Nickelbesetztes Graphen 5.1.2. Interkalierte Systeme 5.1.3. Betrachtung höherer Nickeldichten 5.2. Einfluss des Lagenabstandes und Stabilitätsbetrachtungen 5.3. Elektronische Eigenschaften 5.3.1. Einfluss der geometrischen Struktur 5.3.2. Bandstruktur von nickelbesetztem Graphen 5.3.3. Bandstrukturen der interkalierten Systeme 6. Zusammenfassung und Ausblick A. Einfluss der Nickeldichte B. SCAN-Funktional und ebeneWellen C. Energielandschaften bei konstantem Lagenabstand D. Spineffekte in der Bandstruktur E. Fette Bandstruktur der weiteren Systeme Literaturverzeichnis Selbstständigkeitserklärung

Thema der vorliegenden Arbeit ist die Untersuchung ausgewählter niederdimensionaler Schichtgittersysteme, wobei das Hauptinteresse in der Erforschung der elektronischen Struktur im Zusammenhang mit Interkalationsexperimenten liegt. Einkristalline Graphit-, TiSe2- und TaSe2-Proben wurden vor und nach der Interkalation mit winkelaufgelöster Photoemission, Fermi- und Isoenergieflächenmessungen und Elektronenbeugung (LEED) analysiert. Als Interkalationsmaterialien wurden U, Eu, Gd und Cs verwendet. Die experimentellen Daten wurden mit Ergebnissen von LDA-LCAO-Bandstrukturrechnungen und Simulationen im Rahmen eines Single-Impurity-Anderson-Modells verglichen. Neben dem Einfluß unterschiedlicher Valenzelektronen der interkalierten Atome auf den Einlagerungsprozeß werden Fragen zum Lokalisierungsverhalten von 4f- und 5f-Zuständen und zu den Veränderungen in der Dimensionalität der Verbindungen durch die Einlagerung diskutiert. Ein weiterer Schwerpunkt dieser Arbeit befaßt sich mit Untersuchungen zur temperaturabhängigen Ausbildung von Ladungsdichtewellen in 1T-TaSe2. / Subject of the present thesis are investigations of selected low-dimensional layered lattice systems, with the principal goal to study the electronic structure in relation to intercalation experiments. Single-crystalline graphite-, TiSe2 - and TaSe2- samples were analyzed by angle-resolved photoemission, Fermi- and isoenergy-surface measurements, and low energy electron diffraction experiments before and after intercalation. U, Eu, Gd, and Cs were used as materials for the intercalation process. The experimental results were compared with theoretical LDA-LCAO band-structure calculations and with simulations in the framework of a single-impurity Anderson model. In addition to the influence of different numbers of valence electrons from intercalated atoms, questions concerning the localization of 4f and 5f states and changes in the dimensionality of the compounds due to the intercalation process are discussed. Investigations of the temperature dependent formation of charge density waves in 1T-TaSe2 complete this work.

Much study has been carried out to determine the properties of Lamellar Graphite Iron (LGI) or grey iron and their relations to factors such as the cooling rate, the dendrite morphology, the pouring temperature, and so on. However, there hasn’t been much comprehensive study on the properties of LGI outside the generally used and accepted composition, with 1 to 3% Silicon. The scope of this study is to measure and evaluate the thermal conductivity and tensile strength of LGI, for a higher concentration of  Si and different carbon contents. The concentration of Si aimed for was 4% but the concentration obtained after spectroscopy was between 4.1% to 4.15%. There are two hypereutectic, one near-eutectic and three hypoeutectic samples considered and these six chemical compositions were cast under different cooling conditions . The cooling time has been varied by providing different molds of 30mm, 55mm, and 80mm diameter cylinders respectively, for all the six sample compositions. The microstructure analysis carried out studies the segregation of Si, the graphite morphology, primary austenite morphology. These factors are then compared to the thermal and tensile behavior measured in this study. It can be observed that the thermal conductivity studied in the present work has a direct correlation for a higher Si content and tends to be greater than the thermal conductivity values observed from other studies with lower content Of Si. However, the conductivity shows an inverse relation with the cooling rate and is maximum for the samples with the lowest cooling rate. The tensile strength, on the other hand, seems to have a lower value than that observed in previous studies for LGI with 1 to 3% Si, but shows a direct correlation with the cooling rate. The mean area fraction of dendrites obtained and the mean interdendritic hydraulic diameter is also measured and their influence on the properties are also studied. The addition of more Si has greatly favored the thermal behavior positively but has also reduced the tensile strength.

Abstract This study concerns the Swedish artist Roj Friberg (1934–2016). The essay is based on a study of technique and materiality used by Friberg. He is quite marginalized and slightly forgotten in the Swedish art history and when mentioned merely described as a painter from the 1960´s who used graphite mixed with French turpentine, in order to work on the surface with an eraser attached to an electric drill. However, Friberg used other different and more complex painting techniques in his work, something this essay will notice and highlight. The used method is a biographical, dealing with the references to Friberg. To explain why he was considered an “outsider” in Swedish art, the theory of social capital by Pierre Bourdieu is applied. Also, Wolfgang Kemps concept of reception history, which focus on the arts beholder, rather than the artists itself. From the middle of 1970 Friberg also used an ancient painting technique called encaustic, heated beeswax mixed with pigment. Paintings which have received very little attention; therefore, the focus is on his use of encaustic in combination with his other techniques, such as melted graphite, melted wax crayons or drawn with wax crayons and graphite. The work with lasered layers and the typical method of working from darkness to light in Friberg´s pictures shows resemblance with the ancient encaustic portraits from Fayum, in the 50 AD.

Im ersten Teil wurde Probenvorbereitungs-Methoden und instrumentelle Methoden zur Organofluor-Bestimmung verglichen, um Vor- und Nachteile bei der Summenparameter-Analytik von per- und polyfluorierten Alkylverbindungen (PFAS) zu identifizieren. Daher wurden Oberflächenwasserproben aus der Spree in Berlin und Industrieabwasserproben mit zwei PFAS-Summenparametern analysiert – dem extrahierbaren (EOF) und dem adsorbierbaren organisch gebundenen Fluor (AOF). Beide PFAS-Summenparameter wurden mit zwei fluorsensitiven Detektionssystemen analysiert – Hochauflösender Kontinuumstrahler-Graphitofen Molekülabsorptionsspektrometrie (HR-CS-GFMAS) und combustion Ionenchromatographie (CIC). HR-CS-GFMAS erwies sich im Vergleich zu CIC als der empfindlichere und schnellere Ansatz mit höherer Präzision. Im zweiten Teil wurde eine neue Methode zur PFAS-Summenparameteranalyse und EOF-Bestimmung in Bodenproben auf Basis von HR-CS-GFMAS entwickelt und optimiert. EOF-Massenanteile wurden bei mehrfacher Extraktion und Nutzung der Festphasenextraktion (SPE) zur Entfernung anorganischen Fluors untersucht. Bei einem Vergleich der optimierten Methode mit und ohne SPE zeigte sich eine drastische Diskriminierung von Organofluor-Verbindungen mittels SPE. Im dritten Teil wurden Organofluor-Massenbilanzen in aquatischen Systemen anhand von Oberflächenwasser- und Schwebstoffproben (SPM) untersucht. SPM-Proben wurden mit vier komplementären Analysemethoden analysiert – target und non-target, direct total oxidizable precursor assay (dTOPA) und EOF. Daher wurden drei Organofluor-Massenbilanzansätze für die räumlich und zeitaufgelöste SPM-Probenanalyse verwendet: (I) Identifizierung von oxidierbaren PFAS-Vorläufer, (II) Identifizierung des Anteils der identifizierten und nicht identifiziertes EOF und (III) PFAS-target, PFAS dTOPA, non-target-Screening und EOF-Analyse, um das nicht identifizierte EOF aus Ansatz (II) weiter zu entschlüsseln. / In the first part, a comparison of sample preparation and instrumental methods for organofluorine determination was used to identify advantages and disadvantages in sum parameter analysis of per- and polyfluoroalkyl substances (PFASs). Therefore, surface water samples from the Spree River in Berlin, Germany and industrial effluent samples were analyzed using two PFAS sum parameters – the extractable (EOF) and adsorbable organically bound fluorine (AOF). Both PFAS sum parameters were analyzed using two fluorine sensitive detection systems – high-resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) and combustion ion chromatography (CIC). HR-CS-GFMAS turned out to be the more sensitive and faster approach accompanied with higher precision compared to CIC. In the second part, a new method for PFAS sum parameter analysis and EOF determination in soil samples based on HR-CS-GFMAS was developed and optimized. EOF mass fractions were investigated upon multiple extraction and utilization of solid phase extraction (SPE) for inorganic fluorine removal. In a comparison of the optimized method with and without SPE, a highly biased discrimination of organofluorines using SPE was shown. In the third part, organofluorine mass balances were investigated in aquatic systems using surface water and suspended particulate matter (SPM) samples. SPM samples were analyzed using 4 complementary analytical methods – target and non-target HRMS, direct total oxidizable precursor assay (dTOPA) and EOF. Therefore, 3 organofluorine mass balance approaches were used for SPM sample analysis in spatial and time resolved manner: (I) Identification of oxidizable PFAS precursors, (II) Identification of the proportion of identified and unidentified EOF and (III) PFAS target, PFAS dTOPA, non-target screening and EOF analysis to further unravel the unidentified EOF from approach (II).

La stratégie de la tectonique moléculaire a montré durant ces dernières années son utilité dans la construction de nouveaux matériaux. Elle repose sur l’auto-assemblage spontané de molécule dite intelligente appelée tecton. Ces molécules possèdent l’habilité de se reconnaitre entre elles en utilisant diverses interactions intermoléculaires. L'assemblage résultant peut donner lieu à des matériaux moléculaires avec une organisation prévisible. Cette stratégie exige la création de nouveaux tectons, qui sont parfois difficiles à synthétiser et nécessitent dans la plupart des cas de nombreuses étapes de synthèse, ce qui empêche ou limite leur mise en application pratique. De plus, une fois formées, les liaisons unissant le corps central du tecton avec ces groupements de reconnaissance moléculaire ne peuvent plus être rompues, ce qui ne permet pas de remodeler le tecton par une procédure synthétique simple. Afin de contourner ces obstacles, nous proposons d’utiliser une stratégie hybride qui se sert de la coordination métallique pour construire le corps central du tecton, combinée avec l'utilisation des interactions plus faibles pour contrôler l'association. Nous appelons une telle entité métallotecton du fait de la présence du métal. Pour explorer cette stratégie, nous avons construit une série de ligands ditopiques comportant soit une pyridine, une bipyridine ou une phénantroline pour favoriser la coordination métallique, substitués avec des groupements diaminotriazinyles (DAT) pour permettre aux complexes de s'associer par la formation de ponts hydrogène. En plus de la possibilité de créer des métallotectons par coordination, ces ligands ditopiques ont un intérêt intrinsèque en chimie supramoléculaire en tant qu'entités pouvant s'associer en 3D et en 2D. En parallèle à notre étude de la chimie de coordination, nous avons ii examiné l'association des ligands, ainsi que celle des analogues, par la diffraction des rayons-X (XRD) et par la microscopie de balayage à effet tunnel (STM). L'adsorption de ces molécules sur la surface de graphite à l’interface liquide-solide donne lieu à la formation de différents réseaux 2D par un phénomène de nanopatterning. Pour comprendre les détails de l'adsorption moléculaire, nous avons systématiquement comparé l’organisation observée en 2D par STM avec celle favorisée dans les structures 3D déterminées par XRD. Nous avons également simulé l'adsorption par des calculs théoriques. Cette approche intégrée est indispensable pour bien caractériser l’organisation moléculaire en 2D et pour bien comprendre l'origine des préférences observées. Ces études des ligands eux-mêmes pourront donc servir de référence lorsque nous étudierons l'association des métallotectons dérivés des ligands par coordination. Notre travail a démontré que la stratégie combinant la chimie de coordination et la reconnaissance moléculaire est une méthode de construction rapide et efficace pour créer des réseaux supramoléculaires. Nous avons vérifié que la stratégie de la tectonique moléculaire est également efficace pour diriger l'organisation en 3D et en 2D, qui montre souvent une homologie importante. Nous avons trouvé que nos ligands hétérocycliques ont une aptitude inattendue à s’adsorber fortement sur la surface de graphite, créant ainsi des réseaux organisés à l'échelle du nanomètre. L’ensemble de ces résultats promet d’offrir des applications dans plusieurs domaines, dont la catalyse hétérogène et la nanotechnologie. Mots clés : tectonique moléculaire, interactions intermoléculaires, stratégie hybride, coordination métallique, diffraction des rayons-X, microscopie de balayage à effet tunnel, graphite, phénomène de nanopatterning, calculs théoriques, ponts hydrogène, chimie supramoléculaire, ligands hétérocycliques, groupements DAT, catalyse hétérogène, nanotechnologie. / In recent years, molecular tectonics has been a useful strategy in the construction of new materials. It relies on the spontaneous self-assembly of molecules called tectons. These molecules have the ability to recognize themselves using various intermolecular interactions. The resulting assembly can produce molecular materials with predictable organization. This strategy requires the creation of new tectons, which are sometimes difficult to synthesize and require in most cases many synthetic steps, which prevents or limits their practical application. Moreover, once formed, the bonds joining the central core of the tecton with the groups used for molecular recognition cannot be broken, which means that it is not possible to recycle or reform the tecton by simple synthetic procedures. To avoid these obstacles, we propose to use a hybrid strategy that uses metal coordination to build the central core of the tecton, combined with the use of weaker interactions to control the association. We call such entities metallotectons due to the presence of metal. To explore this strategy, we constructed a series of ditopic ligands containing either pyridine, bipyridine or phenanthroline to promote metal coordination, substituted with diaminotriazinyl groups (DAT) to allow inter-complex association by the formation of hydrogen bonds. In addition to the possibility of creating metallotectons by coordination, these ditopic ligands have an intrinsic interest in supramolecular chemistry as entities that can associate in 3D and 2D. In parallel to our study of coordination chemistry, we examined the association of ligands by X-ray diffraction (XRD) and scanning tunneling microscopy (STM). The adsorption of these molecules on the graphite surface at the liquid-solid interface results in the formation of different networks through a process of 2D nanopatterning. To understand the details of iv molecular adsorption, we systematically compared the 2D organization observed STM with the 3D structures determined by XRD. We also simulated the adsorption by theoretical calculations. This integrated approach is essential to characterize the molecular organization in 2D and to understand the origin of the observed preferences. These studies of the ligands themselves may therefore serve as a reference when we study the association of metallotectons derived by ligands coordination. Our work demonstrates that the strategy combining coordination chemistry and molecular recognition is a rapid and an efficient method to create supramolecular networks. We verified that the strategy of molecular tectonics is also effective in leading the organization in 3D and 2D, which often shows a significant homology. We found that our heterocyclic ligands have unexpected ability to adsorb strongly on the graphite surface, creating networks organize in nanoscale. Together, these results provide promising applications in several fields, including heterogeneous catalysis and nanotechnology. Keywords : molecular tectonics, intermolecular interactions, hybrid strategy, metal coordination, X-ray diffraction, scanning tunneling microscopy, graphite, nanopatterning phenomenon, theoretical calculations, hydrogen bonds, supramolecular chemistry, ligands, DAT groups, heterogeneous catalysis, nanotechnology.

We have measured the optical properties of films of the organic semiconductors PTCDA (3,4:9,10-perylene-tetracarboxylic dianhydride) and HBC (peri-hexabenzocoronene), prepared by Organic Molecular Beam Expitaxy (OMBE), on different substrates by means of Differential Reflectance Spectroscopy (DRS). The optical setup enables us to directly follow the thickness dependent optical properties of the organic films, starting from submonolayer coverage up to thicker films on the order of 20 monolayers (ML) film thickness. Due to the different optical nature of the different substrates used, i.e., mica, glass, Au(111), and HOPG, the direct interpretation of the DRS signal is not feasible. Therefore, we have proposed a method by which the calculation of the optical constants n (index of refraction) and k (absorption index) of thin films on arbitrary substrates from just one spectral measurement (in our case the DRS) becomes possible. The results fulfill a priori a Kramers-Kronig consistency and no specific model is needed to express the spectral behavior of the optical constants. Based on our method, we have successfully calculated the optical constants, and therefore the absorption behavior, of films of different thickness of PTCDA on mica, glass, Au(111), and HOPG, as well as of HBC on mica, glass, and HOPG. Extrinsic effects due to island growth or the presence of a polarizable substrate (screening) have been accounted for. We have introduced a finite dipole model which considers the extended geometry and anisotropy of the organic molecules. The calculated absorption behavior is discussed in great detail in terms of spectral changes with varying film thickness, different growth modes, degree of ordering of the films, interactions with the substrates and oscillator strength. A direct observation of a monomer-dimer transition in solid films could be observed for the first time. Our results indicate an exciton delocalization over about 4 molecules for both molecules.

La stratégie de la tectonique moléculaire a montré durant ces dernières années son utilité dans la construction de nouveaux matériaux. Elle repose sur l’auto-assemblage spontané de molécule dite intelligente appelée tecton. Ces molécules possèdent l’habilité de se reconnaitre entre elles en utilisant diverses interactions intermoléculaires. L'assemblage résultant peut donner lieu à des matériaux moléculaires avec une organisation prévisible. Cette stratégie exige la création de nouveaux tectons, qui sont parfois difficiles à synthétiser et nécessitent dans la plupart des cas de nombreuses étapes de synthèse, ce qui empêche ou limite leur mise en application pratique. De plus, une fois formées, les liaisons unissant le corps central du tecton avec ces groupements de reconnaissance moléculaire ne peuvent plus être rompues, ce qui ne permet pas de remodeler le tecton par une procédure synthétique simple. Afin de contourner ces obstacles, nous proposons d’utiliser une stratégie hybride qui se sert de la coordination métallique pour construire le corps central du tecton, combinée avec l'utilisation des interactions plus faibles pour contrôler l'association. Nous appelons une telle entité métallotecton du fait de la présence du métal. Pour explorer cette stratégie, nous avons construit une série de ligands ditopiques comportant soit une pyridine, une bipyridine ou une phénantroline pour favoriser la coordination métallique, substitués avec des groupements diaminotriazinyles (DAT) pour permettre aux complexes de s'associer par la formation de ponts hydrogène. En plus de la possibilité de créer des métallotectons par coordination, ces ligands ditopiques ont un intérêt intrinsèque en chimie supramoléculaire en tant qu'entités pouvant s'associer en 3D et en 2D. En parallèle à notre étude de la chimie de coordination, nous avons ii examiné l'association des ligands, ainsi que celle des analogues, par la diffraction des rayons-X (XRD) et par la microscopie de balayage à effet tunnel (STM). L'adsorption de ces molécules sur la surface de graphite à l’interface liquide-solide donne lieu à la formation de différents réseaux 2D par un phénomène de nanopatterning. Pour comprendre les détails de l'adsorption moléculaire, nous avons systématiquement comparé l’organisation observée en 2D par STM avec celle favorisée dans les structures 3D déterminées par XRD. Nous avons également simulé l'adsorption par des calculs théoriques. Cette approche intégrée est indispensable pour bien caractériser l’organisation moléculaire en 2D et pour bien comprendre l'origine des préférences observées. Ces études des ligands eux-mêmes pourront donc servir de référence lorsque nous étudierons l'association des métallotectons dérivés des ligands par coordination. Notre travail a démontré que la stratégie combinant la chimie de coordination et la reconnaissance moléculaire est une méthode de construction rapide et efficace pour créer des réseaux supramoléculaires. Nous avons vérifié que la stratégie de la tectonique moléculaire est également efficace pour diriger l'organisation en 3D et en 2D, qui montre souvent une homologie importante. Nous avons trouvé que nos ligands hétérocycliques ont une aptitude inattendue à s’adsorber fortement sur la surface de graphite, créant ainsi des réseaux organisés à l'échelle du nanomètre. L’ensemble de ces résultats promet d’offrir des applications dans plusieurs domaines, dont la catalyse hétérogène et la nanotechnologie. Mots clés : tectonique moléculaire, interactions intermoléculaires, stratégie hybride, coordination métallique, diffraction des rayons-X, microscopie de balayage à effet tunnel, graphite, phénomène de nanopatterning, calculs théoriques, ponts hydrogène, chimie supramoléculaire, ligands hétérocycliques, groupements DAT, catalyse hétérogène, nanotechnologie. / In recent years, molecular tectonics has been a useful strategy in the construction of new materials. It relies on the spontaneous self-assembly of molecules called tectons. These molecules have the ability to recognize themselves using various intermolecular interactions. The resulting assembly can produce molecular materials with predictable organization. This strategy requires the creation of new tectons, which are sometimes difficult to synthesize and require in most cases many synthetic steps, which prevents or limits their practical application. Moreover, once formed, the bonds joining the central core of the tecton with the groups used for molecular recognition cannot be broken, which means that it is not possible to recycle or reform the tecton by simple synthetic procedures. To avoid these obstacles, we propose to use a hybrid strategy that uses metal coordination to build the central core of the tecton, combined with the use of weaker interactions to control the association. We call such entities metallotectons due to the presence of metal. To explore this strategy, we constructed a series of ditopic ligands containing either pyridine, bipyridine or phenanthroline to promote metal coordination, substituted with diaminotriazinyl groups (DAT) to allow inter-complex association by the formation of hydrogen bonds. In addition to the possibility of creating metallotectons by coordination, these ditopic ligands have an intrinsic interest in supramolecular chemistry as entities that can associate in 3D and 2D. In parallel to our study of coordination chemistry, we examined the association of ligands by X-ray diffraction (XRD) and scanning tunneling microscopy (STM). The adsorption of these molecules on the graphite surface at the liquid-solid interface results in the formation of different networks through a process of 2D nanopatterning. To understand the details of iv molecular adsorption, we systematically compared the 2D organization observed STM with the 3D structures determined by XRD. We also simulated the adsorption by theoretical calculations. This integrated approach is essential to characterize the molecular organization in 2D and to understand the origin of the observed preferences. These studies of the ligands themselves may therefore serve as a reference when we study the association of metallotectons derived by ligands coordination. Our work demonstrates that the strategy combining coordination chemistry and molecular recognition is a rapid and an efficient method to create supramolecular networks. We verified that the strategy of molecular tectonics is also effective in leading the organization in 3D and 2D, which often shows a significant homology. We found that our heterocyclic ligands have unexpected ability to adsorb strongly on the graphite surface, creating networks organize in nanoscale. Together, these results provide promising applications in several fields, including heterogeneous catalysis and nanotechnology. Keywords : molecular tectonics, intermolecular interactions, hybrid strategy, metal coordination, X-ray diffraction, scanning tunneling microscopy, graphite, nanopatterning phenomenon, theoretical calculations, hydrogen bonds, supramolecular chemistry, ligands, DAT groups, heterogeneous catalysis, nanotechnology.

This thesis focuses on the effect of microstructural variation on the mechanical properties and deformation behavior of ductile iron. To research and determine these effects, two grades of ductile iron, (i) GJS-500-7 and (ii) high silicon GJS-500-14, were cast in a geometry containing several plates with different section thicknesses in order to produce microstructural variation. Microstructural investigations as well as tensile and hardness tests were performed on the casting plates. The results revealed higher ferrite fraction, graphite particle count, and yield strength in the high silicon GJS-500-14 grade compared to the GJS-500-7 grade. To study the relationship between the microstructural variation and tensile behavior on macroscale, tensile stress-strain response was characterized using the Ludwigson equation. The obtained tensile properties were modeled, based on the microstructural characteristics, using multiple linear regression and analysis of variance (ANOVA). The models showed that silicon content, graphite particle count, ferrite fraction, and fraction of porosity are the major contributing factors that influence tensile behavior. The models were entered into a casting process simulation software, and the simulated microstructure and tensile properties were validated using the experimental data. This enabled the opportunity to predict tensile properties of cast components with similar microstructural characteristics. To investigate deformation behavior on micro-scale, a method was developed to quantitatively measure strain in the microstructure, utilizing the digital image correlation (DIC) technique together with in-situ tensile testing. In this method, a pit-etching procedure was developed to generate a random speckle pattern, enabling DIC strain measurement to be conducted in the matrix and the area between the graphite particles. The method was validated by benchmarking the measured yield strength with the material’s standard yield strength. The microstructural deformation behavior under tensile loading was characterized. During elastic deformation, strain mapping revealed a heterogeneous strain distribution in the microstructure, as well as shear bands that formed between graphite particles. The crack was initiated at the stress ranges in which a kink occurred in the tensile curve, indicating the dissipation of energy during both plastic deformation and crack initiation. A large amount of strain localization was measured at the onset of the micro-cracks on the strain maps. The micro-cracks were initiated at local strain levels higher than 2%, suggesting a threshold level of strain required for micro-crack initiation. A continuum Finite Element (FE) model containing a physical length scale was developed to predict strain on the microstructure of ductile iron. The material parameters for this model were calculated by optimization, utilizing the Ramberg-Osgood equation. The predicted strain maps were compared to the strain maps measured by DIC, both qualitatively and quantitatively. To a large extent, the strain maps were in agreement, resulting in the validation of the model on micro-scale. In order to perform a micro-scale characterization of dynamic deformation behavior, local strain distribution on the microstructure was studied by performing in-situ cyclic tests using a scanning electron microscope (SEM). A novel method, based on the focused ion beam (FIB) milling, was developed to generate a speckle pattern on the microstructure of the ferritic ductile iron (GJS-500-14 grade) to enable quantitative DIC strain measurement to be performed. The results showed that the maximum strain concentration occurred in the vicinity of the micro-cracks, particularly ahead of the micro-crack tip. / Denna avhandling fokuserar på effekten av variationer i mikrostrukturen på mekaniska egenskaper och deformationsbeteende hos segjärn. För att undersöka dessa effekter, två olika sorter av segjärn, (i) GJS-500-7 och (ii) högkisellegerad GJS-500-14, gjutits till plattor av olika tjocklekar för att generera mikrostrukturvariationen. Mikrostrukturundersökning, samt drag- och hårdhetsprov gjordes på de gjutna plattorna. Resultaten visade att en högre ferritfraktion, grafitpartikelantal och sträckgräns i den högkisellegerade GJS-500-14-sorten jämfört med GJS-500-7. För att studera förhållandet mellan mikrostrukturell variation och spännings-töjningsbeteendet på makroskala, modellerades detta med hjälp av Ludwigson-ekvationen. De erhållna spännings-töjningsegenskaperna modellerades baserat på mikrostrukturell karaktäristika genom multipel linjärregression och variansanalys (ANOVA). Modellerna visade att kiselhalt, grafitpartikelantal, ferritfraktion och porfraktion var de viktigaste bidragande faktorerna. Modellerna implementerades i ett simuleringsprogram för gjutningsprocessen. Resultatet från simuleringen validerades med hjälp av experimentella data som inte ingick i underlaget för regressionsanalysen. Detta möjliggjorde att prediktera spännings-töjningsbeteendet och dess variation hos gjutna segjärns komponenter med liknande sammansättning och gjutna tjocklekar som användes i denna studie. För att kunna undersöka deformationsbeteendet på mikroskala utvecklades en metod för kvantitativ mätning av töjning i mikrostrukturen, genom DIC-tekniken (digital image correlation) tillsammans med in-situ dragprovning. I denna metod utvecklades en grop-etsningsprocess för att generera ett slumpvis prickmönster, vilket möjliggjorde DIC-töjningsmätning i matrisen och i området mellan grafitpartiklarna med tillräcklig upplösning. Metoden validerades genom benchmarking av den uppmätta sträckgränsen mot materialets makroskopiska sträckgräns mätt med konventionell dragprovning. Det mikrostrukturella deformationsbeteendet under dragbelastning karakteriserades. Under elastisk deformation avslöjade töjningsmönstret en heterogen töjningsfördelning i mikrostrukturen, och bildandet av skjuvband mellan grafitpartiklar. Sprickbildning initierades vid låg spänning och redan vid de spänningsnivåer som ligger vis ”knät” på dragprovningskurvan, vilket indikerar energidissipering genom både begynnande plastisk deformation och sprickbildning. Den lokala töjningen vis sprickinitiering skedde då den lokala töjningen översteg 2%, vilket indikerar att detta skulle kunna vara en tröskelnivå för den töjning som erfordras för initiering av mikro-sprickor. En kontinuum Finita Element (FE) modell utvecklades för att prediktera töjningen hos ett segjärn och dess fördelning i segjärns mikrostruktur. Materialparametrarna för denna modell optimerades genom att anpassa parametrarna i Ramberg-Osgood ekvationen. De predikterade töjningsfördelningarna jämfördes med de experimentell uppmätta töjningsmönstren uppmätta med DIC, både kvalitativt och kvantitativt. Töjningsmönstren överensstämde i stor utsträckning, vilket resulterade i att modellerna kunde anses vara validerade på mikronivå. För att kunna mäta töjningsmönster under dynamiska förlopp på mikronivå utvecklades en metod för att skapa prickmönster och att utföra in-situ CT provning i ett svepeletronmikroskop (SEM). Prickmönstret skapades genom avverkning med en fokuserad jonstråle (FIB), och provades på det ferritiska segjärnet (GJS-500-14 grad). Resultaten visade att maximal töjningskoncentration fanns i närheten av mikrosprickorna, framförallt framför sprickspetsen.

The diploma thesis is divided into two main parts. The first part describes the production of chrome and cobalt tips for SP-STM with subsequent testing of chrome tips on the Fe-Ir system (111). Furthermore, the first results from the growth studies of niobium on iridium(111) are presented. In the second part is described in detail the experimental LT-STM microscope of the Faculty of Physical Engineering. The chapter deals with the development of the microscope and its testing on a HOPG sample under atmospheric and vacuum conditions. The chapter describes the biggest problems which were solved when the microscope was puting into operation state. The second part also introduces the design of a new vacuum transport system, which consists of a tip and sample transport pallet. At the end of the second part is described the testing of cooling systems for LT-STM and the design of their modifications.