In the frame of this thesis different calix[4]resorcin- and calix[4]pyrogallolarene derivatives were used as platform for the synthesis of novel star polymers and dendritic structures. The objectives of this work can be portrayed under the following points: First: Synthesis and modification of calix[4]resorcin- and calix[4]pyrogallolarenes with a varying number and varying type of functional sites and their precise characterization by modern NMR techniques and single crystal X-ray diffraction. Second: Synthesis of well-defined star polymers and dendrimers with different number of arms and accordingly dendrons, based on calix[4]resorcin- and calix[4]pyrogallolarenes, via convenient polymerization and generation growth reactions and analysis of the obtained products by different methods (MALDI-TOF-MS, SEC-RI and SEC-MALLS, NMR).

<p>Heavy-duty trucks are in idle operation during long periods of time, providing the vehicles with electricity via the alternator at standstill. Idling trucks contribute to large amounts of emissions and high fuel consumption as a result of the low efficiency from fuel to electricity. Truck manufacturers are working to develop equipment using auxiliary power units to supply the trucks with electricity, which operate independently of the main engine. Fuel cell-based auxiliary power units could offer high efficiencies and low noise and vibrations. The hydrogen required for the fuel cell can be generated in an onboard fuel reformer. This thesis is devoted to hydrogen generation from dimethyl ether, DME, by autothermal reforming focusing on the application of fuel cell auxiliary power units. In the search for alternative fuels, DME has lately been identified as a promising diesel substitute.</p><p>The first part of the thesis gives an introduction to the field of DME reforming with a literature survey of recent studies within the area. Included are also results from thermodynamic equilibrium calculations.</p><p>In the following parts of the thesis, experimental studies on autothermal reforming of DME are presented. A reformer constructed to generate hydrogen to feed a 5 kW_e polymer electrolyte fuel cell is evaluated with emphasis on trying to work close to a practically viable process, i.e. without external heating and using gas mixtures resembling real conditions. Additional experiments have been conducted to investigate the use of catalytic oxidation of dimethyl ether as a heat source during startup. The results of these studies are presented in Paper I.</p><p>In the second experimental study of this thesis, which is presented in Paper II, Pd-based monolithic catalysts are evaluated at small scale for use in autothermal reforming of DME. A screening of various catalyst materials has been performed followed by a study of the influence on the product composition of varying operating parameters such as oxygen-to-DME ratio, steam-to-DME ratio, and temperature.</p>

The structure and magnetism of selected compounds of the pnictides iron based superconductors with chemical formula LnO{1-x}FeAsFx (Ln = La,Sm and Ce), commonly known as 1111, and of rare earth iron borates RFe3(BO3)4 (R = Tb, Gd, Nd and Y), were studied by means of hard x-ray diffraction. For the 1111 pnictides compounds, Rietveld refinement of powder x-ray diffraction measurements at room temperature reveals, that the ionic substitution of O by F has no effect on the structure of the FeAs layers of tetrahedra, whereas the major changes takes place in the LnO layer. These changes are reflected as a shrinkage of the crystal lattice, specially in the c direction. Additionally, a study of the temperature dependent structure of the Sm and Ce-1111 compounds was performed and an estimation of the the structural transition temperature was obtained. The results of the structural measurements, combined with electrical resistivity and µSR, were used to construct the Sm and Ce-1111 phase diagrams. These phase diagrams are characterized by two regions, consisting of a spin density wave (SDW) state and a superconducting state, which are sharply separated upon doping. Considering the different Ln ion, upon F doping the transition temperatures are more efficiently suppressed in Ce-1111 as compared to Sm-1111. More intriguingly, for the Ce case, a coexistence region between static magnetism and superconductivity without an orthorhombic distortion has been observed. Further analysis of the width of the Bragg peaks reveals strong lattice fluctuations towards phase transitions, which are reflected in magnetic and transport properties. Moreover, a strong damping of the lattice fluctuations is observed at Tc for superconducting Sm-1111 samples, giving experimental evidence of competing orders towards phase transitions in the iron pnictides. Regarding the iron borates, non-resonant x-ray scattering studies have shown several new diffraction features, from the appearance of additional reflections that violate the reflection conditions for the low temperature crystal structure, to the emerging of commensurate superlattice peaks that appear below TN. A detailed analysis of the structure factors and q dependencies of the earlier reflections, demonstrate their magnetic nature. Additional resonant x-ray magnetic scattering experiments on NdFe3(BO3)4 were performed at the Nd L2,3 and Fe K edges. The results show that the magnetization behavior is different for the Nd and for the Fe sublattices. Moreover, we find that the magnetization of the Nd sublattice is induced by the Fe magnetization. The temperature dependent measurements also show a commensurate to incommensurate transition where the magnetic structure changes from a commensurate collinear structure, where both Nd and Fe moments align in the hexagonal basal plane, to an incommensurate spin helix structure that propagates along c. When a magnetic field is applied, the spin helix is destroyed and a collinear structure is formed where the moments align in a direction perpendicular to the applied magnetic field. Moreover, the critical field at which the spin helix is destroyed is the same field at which the magnetic induced electric polarization is maximum, thus, showing that the spin helix is not at the origin of the electric polarization.

Materials based on fullerenes and carbon nanotubes are very much different from most “traditional” materials, primarily because they are built from nanosized molecules with highly symmetry-dependent properties. Being the subject of a very active research field over the last twenty years, carbon nanostructures proved to be indeed extraordinary. Their splendid mechanical properties attract a great interest among material scientists. Their wide range of electrical properties, from ballistic conductors to insulators, makes them ideal candidates for future, better electronics. The possibilities seem to be nearly unlimited, with proposed applications ranging from quantum computing to medicine. However, in order to make it all happen one day, we first need to explore and understand the physics and chemistry of carbon nanomaterials. This work focuses on production and characterization of materials and structures in which fullerenes and/or carbon nanotubes are the main ingredients, and which can be produced or modified under high-pressure – high-temperature (hp-hT) conditions. Raman and photoluminescence spectroscopy, X-ray diffraction and scanning probe microscopy were employed for characterization of the samples. The research presented in this thesis is spread over a rather wide range of carbon nanomaterials. To highlight some of the main results – the first hp-hT polymerization of C60 nanorods and the C60-cubane compound is reported. The polymerization mechanism in the latter case was identified to be radically different from that in pure C60. The pressure-temperature diagram of C60-cubane is presented. A comparative study of C60 and C70 peapods under extreme p-T conditions reveals how the confinement affects the fullerenes’ ability for polymerization. Finally, in situ resistance measurements on Rb4C60 under high pressure show that the semiconducting character of this material persists at least up to 2 GPa, contradicting earlier reports on the existence of an insulator-to-metal transition and providing an insight into conduction mechanisms in this anomalous intercalated compound.

Land disposal of solid waste is a vital component of any solid waste management system. Design, operation and closure of municipal solid waste (MSW) landfills are required by regulations to control leachate and gases generated during the life, closure,and post-closure of the facility. Clogging of leachate drainage and removal systems in landfills is a common phenomenon and has been acknowledged in several landfills throughout the United States and abroad. This project was conducted in two phases. Phase I was completed in February of 2005 and Phase II was completed in August of 2006. Leachate characteristics data obtained in Phase I was processed and analyzed, along with supplementary data obtained in Phase II on liquid and solid phase testing. Leachate samples from the landfill and lysimeters indicated the presence of iron and sulfate-reducing bacteria. These bacteria are known to facilitate biologically induced precipitate formation.The mechanism by which biologically ind uced precipitate may form begins with oxidizing acetate by iron and sulfate-reducing bacteria, reducing sulfate to sulfide and ferric iron to ferrous, and then forming calcium carbonate, iron sulfate, and possibly dolomite and other minerals.The results show that the clogging mechanism is driven by two major processes: transformation of volatile acids to substrates by iron and sulfate-reducing bacteria causing local pH and total carbonate to increase, which accelerate calcium carbonate precipitation, and thermodynamically favored reactions in supersaturated conditions based on saturation indices of calcium, sulfide, iron, and other species with respect to minerals. For each 1 mg of consumed volatile acids there were 1.7 mg of calcium, 0.28 mg of sulfate, and 0.03 mg of iron removed. Field and lysimeter precipitate samples were analyzed (using X-Ray Diffraction, Scanning Electron microscopy, and Electron Dispersive Spectroscopy) and correlated with geochemical modeling of leachate const ituents. Precipitate analyses showed the presence of calcium carbonate, brushite (calcium phosphate),and dolomite, where as geochemical modeling showed that calcium carbonate, hydroxyapatite (complex of calcium phosphate), dolomite, pyrite, and siderite may be formed from field and lysimeter leachate constituents. The results also showed that submerged and stagnant conditions in the leachate collction systems accelerate the precipitation process.

Die vorliegende Arbeit fokussiert auf die Synthese von organisch/anorganischen Hybridmaterialien mit multifunktionalen Eigenschaften unter ausschliesslicher Darstellung dieser Materialen mit Hilfe des „wet chemistry“ Zugangs. Ausgehend von der Darstellung und Charakterisierung von isomorphen bzw. isostrukturellen Hybridmaterialien der allgemeinen Zusammensetzung catena-{[Me3NH][MCl3·2H2O]}n (Mtac) (MII = Mn, Co, Ni, Cu, tac = [Me3NH]Cl3·2H2O]) speziell mittels IR und UV/vis Spektroskopie ist beschrieben, wie sich aus diesen entsprechende bi-, tri-, und auch tetra-heterometallische Koordinationspolymere der allgemeinen Zusammenseztung {MxM´ytac}n, {MxM´yM´´ztac}n, {MxM´yM´´zM´´´ttac}n (MII = M ≠ M´≠ M´´≠ M´´´≠ M´´´´ und x, y, z, t als prozentualer Metallgehalt) herstellen lassen und welche limitierende Faktoren zu berücksichtigen sind. Leifähigkeitsmessungen an Einkristallen ausgewählter Koordinationspolymere werden vorgestellt. Zusätzlich werden die durch Rekristallisation von Nitac erhaltenen zwei verschiedenen Koordinationspolymere der Formel {[Me3NH]3{NiCl4}{NiCl3}}n und {[(Me3NH]{NiCl3}}n in Bezug auf ihre ungewöhnlichen strukturellen und magnetischen Eigenschaften vorgestellt und beschrieben. Die durch Austausch von [Me3NH]+ Kationen gegen [Et3NH]+ bzw. protonierten aromatischen N-haltigen Kationen wie [2,2’-bipyH2]2+, [4,4’-bipyH2]2+ and [1,10-phenH2]2+ erhaltenen Reaktionsprodukte aus Umsetzungen mit Hilfe des “wet chemistry” Zugangs werden im Hinblick auf ihre Festkörperstrukturen beschrieben. Die erfolgreiche Darstellung einer neuen Familie von perylentetracarboxylato-basierenden Komplexen, die teilweise hervorragende Löslichkeiten besitzen, wird beschrieben sowie die strukturellen, magnetischen und lumineszierenden Eigenschaften ausgewählter Vetreter. / The thesis presented here is focused on the synthesis of organic/ inorganic hybrid materials with multifunctional properties by means of the “wet chemistry” approach. The synthesis and characterization of hybrid materials with the general composition catena-{[Me3NH][MCl3·2H2O]}n (Mtac) (MII = Mn, Co, Ni, Cu, tac = [Me3NH]Cl3·2H2O]) is described. Due to their isomorphic and/ or isostructural character, bi-, tri-, and even tetra-heterometallic chains of the general formula {MxM´ytac}n, {MxM´yM´´ztac}n, {MxM´yM´´zM´´´ttac}n (MII = M ≠ M´≠ M´´≠ M´´´≠ M´´´´ and x, y, z, t is the percentage of each metal content) were synthesized and characterized. Limitating factors of the synthesis of these types of heterometallic coordination polymers are discussed. Furthermore, the conductive properties of selected representatives were investigated. Additionally, the products obtained from recrystallization of Nitac, two different novel 1D coordination polymers of the formula {[Me3NH]3{NiCl4}{NiCl3}}n and {[(Me3NH]{NiCl3}}n are described with respect to their structural and magnetic properties. Efforts to replace the [Me3NH]+ cations of Mtac compounds by [Et3NH]+ cations as well as by protonated aromatic amines as [2,2’-bipyH2]2+, [4,4’-bipyH2]2+ and [1,10-phenH2]2+ are reported next with respect to the structural exploration of obtained hybrid materials by the “wet chemistry” approach. Finally, the synthesis of a new family of perylene tetracarboxylate (ptc) based soluble complexes is reported. Structural, magnetic and luminescence properties of selected representatives of this new series of soluble ptc derivatives are reported.

Die vorliegende Arbeit fokussiert auf die Synthese von organisch/anorganischen Hybridmaterialien mit multifunktionalen Eigenschaften unter ausschliesslicher Darstellung dieser Materialen mit Hilfe des „wet chemistry“ Zugangs. Ausgehend von der Darstellung und Charakterisierung von isomorphen bzw. isostrukturellen Hybridmaterialien der allgemeinen Zusammensetzung catena-{[Me3NH][MCl3·2H2O]}n (Mtac) (MII = Mn, Co, Ni, Cu, tac = [Me3NH]Cl3·2H2O]) speziell mittels IR und UV/vis Spektroskopie ist beschrieben, wie sich aus diesen entsprechende bi-, tri-, und auch tetra-heterometallische Koordinationspolymere der allgemeinen Zusammenseztung {MxM´ytac}n, {MxM´yM´´ztac}n, {MxM´yM´´zM´´´ttac}n (MII = M ≠ M´≠ M´´≠ M´´´≠ M´´´´ und x, y, z, t als prozentualer Metallgehalt) herstellen lassen und welche limitierende Faktoren zu berücksichtigen sind. Leifähigkeitsmessungen an Einkristallen ausgewählter Koordinationspolymere werden vorgestellt. Zusätzlich werden die durch Rekristallisation von Nitac erhaltenen zwei verschiedenen Koordinationspolymere der Formel {[Me3NH]3{NiCl4}{NiCl3}}n und {[(Me3NH]{NiCl3}}n in Bezug auf ihre ungewöhnlichen strukturellen und magnetischen Eigenschaften vorgestellt und beschrieben. Die durch Austausch von [Me3NH]+ Kationen gegen [Et3NH]+ bzw. protonierten aromatischen N-haltigen Kationen wie [2,2’-bipyH2]2+, [4,4’-bipyH2]2+ and [1,10-phenH2]2+ erhaltenen Reaktionsprodukte aus Umsetzungen mit Hilfe des “wet chemistry” Zugangs werden im Hinblick auf ihre Festkörperstrukturen beschrieben. Die erfolgreiche Darstellung einer neuen Familie von perylentetracarboxylato-basierenden Komplexen, die teilweise hervorragende Löslichkeiten besitzen, wird beschrieben sowie die strukturellen, magnetischen und lumineszierenden Eigenschaften ausgewählter Vetreter. / The thesis presented here is focused on the synthesis of organic/ inorganic hybrid materials with multifunctional properties by means of the “wet chemistry” approach. The synthesis and characterization of hybrid materials with the general composition catena-{[Me3NH][MCl3·2H2O]}n (Mtac) (MII = Mn, Co, Ni, Cu, tac = [Me3NH]Cl3·2H2O]) is described. Due to their isomorphic and/ or isostructural character, bi-, tri-, and even tetra-heterometallic chains of the general formula {MxM´ytac}n, {MxM´yM´´ztac}n, {MxM´yM´´zM´´´ttac}n (MII = M ≠ M´≠ M´´≠ M´´´≠ M´´´´ and x, y, z, t is the percentage of each metal content) were synthesized and characterized. Limitating factors of the synthesis of these types of heterometallic coordination polymers are discussed. Furthermore, the conductive properties of selected representatives were investigated. Additionally, the products obtained from recrystallization of Nitac, two different novel 1D coordination polymers of the formula {[Me3NH]3{NiCl4}{NiCl3}}n and {[(Me3NH]{NiCl3}}n are described with respect to their structural and magnetic properties. Efforts to replace the [Me3NH]+ cations of Mtac compounds by [Et3NH]+ cations as well as by protonated aromatic amines as [2,2’-bipyH2]2+, [4,4’-bipyH2]2+ and [1,10-phenH2]2+ are reported next with respect to the structural exploration of obtained hybrid materials by the “wet chemistry” approach. Finally, the synthesis of a new family of perylene tetracarboxylate (ptc) based soluble complexes is reported. Structural, magnetic and luminescence properties of selected representatives of this new series of soluble ptc derivatives are reported.

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