University of Siegen
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Publication Access status: Open Access , Mineralogisch-chemische Untersuchungen zur Archäometrie elamischer Keramiken aus Khouzestan, Iran(2008)The main purpose of our identification is the characterization of old ceramics' textures and the determination of the technical process, as well as the crystallization sequences, during ceramic fabrication in the ancient world. The origin of the material examined is related to areas of the Elamite period (1500 B.C.) in the south-west of Iran. Examinations in the area of material science are absolutely necessary for ancient ceramics as the process by which they were created, can be categorised as function of their chemical-mineralogical composition. Many ceramics' constituents were classified as Ca-rich ceramics. They will be classified in the system SiO2-Al2O3-(CaO+MgO). The main paragenesis is Diopside-Gehlenite-Anorthite-Quartz. In some cases, the Ca variation depends on the calcareous rocks which have been used in the pottery production. The crystalline phase composition was determined by quantitative X-Ray diffraction measurements with the Rietveld refinement method. The results have been matched with microscopic methods in order to come to a chemical-petrological conclusion about phase segregation. Quartz, Calcite and Pyroxene are the main temper constituents. Feldspars and Calcite are flux materials in the ceramic body. Kaolinitization and sericitization prove a high dehydration during the fabrication process which favored with respect to the K+/Al3+ ratios. The element distribution of the grain-interface-matrix structure was determined by EDX-measurements and enhanced with the physico-chemical properties of these structures. SFM measurements were carried out at adequate points: here either AFM with the use of pulsed force mode or scattering and absorption properties with SNOM were studied. The firing temperature during the process was also studied by thermoanalytical methods and is approximately 900-1010°C. Examinations determine also that local raw material has been used for ceramic fabrication and the technology in this region was also local technology.Source Type:Doctoral Thesis1 4 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Experimentelle Untersuchung der Wechselwirkung von Flüssigkeiten und Gasen mit Oberflächen von Magnetspeicherplatten(2007)In this thesis the adsorption behaviour of surfaces of hard disks for magnetic storage devices was simulated with the use of a Quartz Crystal Microbalance (QCM). Investigations of the influence of sputter parameters, aging and the effect of lubrication with perfluorinated polyethers (“lubricants”) showed that oxidation and the diffusion of metal ions of the magnetic storage layers onto the surface of the protecting carbon overcoat (COC) are the key players for the different amounts of nonpolar contaminations adsorbed on the surfaces of such hard disks. Experiments with sulphur dioxide led to a patent for the recycling of hard disks substrates made of glass and to further investigations of corrosive liquids like sodium hypochlorite. The data out of spectra of lubricants on hard disk surfaces generated by Time of Flight-Secondary Ion mass Spectrometry (TOF-SIMS) were analyzed with statistical approaches. The “Principal Component Analysis” (PCA) defines clusters of samples with the same surface properties and identifies the relevant peaks responsible for the differences between the clusters. The “Partial Least Squares” method (PLS) additionally gives quantitative data about the thickness of lubricant films. This enables the researcher to measure inhomogeneities in the lubricant distribution on a hard disk in the range below 1 nm in a safe and reproducible way.Source Type:Doctoral Thesis2 4 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Synthesis and studies of annelated quinolizinium derivatives as versatile constructs for fluorescent probes and ligands for triple-helical and abasic DNA structures(2006)In the present Thesis, various annelated derivatives of the quinolizinium ion, i.e. polycyclic compounds with a bridgehead quaternary nitrogen atom, were synthesized and investigated as fluorescent probes for the detection of biomacromolecules and as ligands for triple-helical DNA and abasic DNA structures. Along these lines, 9-donor-substituted acridizinium (benzo[ b ]- quinolizinium) derivatives represent a versatile construct for the development of fluorescent probes. Especially promising are the substituted N -aryl-9-aminoacridizinium salts, the fluorescence of which is susceptible to the microviscosity of the medium. Such compounds may be used for the fluorimetric detection of biomacromolecules, like DNA and proteins. A series of unsubstituted and methyl-substituted diazoniapenthaphenes, as well as the isomeric diazoniaanthra[1,2- α ]anthracenes and diazoniahexaphene were prepared by the cyclodehydration synthesis. These extended derivatives diazoniapolycyclic salts represent novel lead structures, in which preferential, high-affinity binding to the triple-helical DNA may be achieved in the absence of an additional alkaline side chains. Two isomeric acridizinium-adenine conjugates, as well as three acridizinium-9-carboxamides, were prepared. Their affinity towards regular and abasic-site containing DNA structures was investigated by thermal denaturation experiments with synthetic oligodeoxyribonucleotides. Acridizinium- adenine conjugates and aminoalkyl-substituted acridizinium-9-carboxamides are capable of selective binding to abasic DNA sites. They readily induce the photo-damage of plasmid DNA, however, without selectivity towards abasic DNA structures.Source Type:Doctoral Thesis3 8 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Control of molecular Spontaneous Emission in an optical lambda/2-microresonator(2006)Control of molecular Spontaneous Emission in an optical λ/2-microresonator In this thesis, the influence of a planar optical λ/2-microresonator on the Spontaneous Emission rate of embedded molecules and the implications on the microresonator-controlled emission is investigated by means of scanning confocal optical microscopy and spectroscopy. The experimental results obtained for molecular ensembles as well as for single molecules are compared with calculations and computer simulations based on existing theoretical models.Source Type:Doctoral Thesis3 7 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Multi-component metallo-supramolecular assemblies(2005)The key-results of the present thesis are: (1) Mechanistic Insight into the HETPHEN ( het eroleptic phen anthroline complexes) Approach. (2) Synthesis of a Variety of Rigid Bisphenanthrolines and Study of their Self-Assembly Behavior in Solution, in the Solid state and at Solid-Liquid Interfaces. (3) Multicomponent Self-Assembly Using a Nanoscale Macrocycle. (4) The HETTAP ( het eroleptic t erpyridine a nd p henanthroline complexes)Concept.Source Type:Doctoral Thesis1 12 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Beiträge zur Strukturchemie von Chalkogenotetrelen, Mercuraten und supramolekularen Netzwerken mit Quecksilber : Darstellung, Kristallstrukturen und elektronenmikroskopische Untersuchungen(2006)Based on optimized solid state syntheses (e.g. controlled thermal decomposition of azides) new chalcogenotetrels and -mercurates are prepared and characterized by solid state chemical methods. More advanced aspects of the new compounds are discussed with reference to the structural chemistry of related solids. The following new mixed valence chalcogenotetrels of alkali metals were obtained starting from alkali metal chalcogenides (A 2 X, A: alkali metal, X: chalcogenides) which were prepared before in separate reactions: K 2 Sn 4 S 8 , K 2 Sn 3 GeS 8 , K 2 Sn 2 Ge 2 S 8 and K 2 SnGe 3 S 8 . The new compounds show typical coordination polyhedra for the tetrel atoms in accordance with their oxidation states (e.g. tetrahedral or φ-trigonal bipyramidal coordination for the four and two valent states). Systematic evaluations of results from single crystal structure analyses did not show any evidence for a substitution of Sn(II) by Ge and the existence of K 2 Ge 4 S 8 (corresponding to K 2 Sn 4 S 8 ). Based on investigations of the quasi binary sections A 2 X-HgX (A = Na, K; X = S, Se, Te) the crystal structure of K 2 Hg 3 Se 4 was redetermined. The structure of this solid is characterized by one dimensional infinite HgSe 4/2 (HgSe 2/2 ) 2 -chains, which form pseudo layers via secondary chemical bonding interactions. The layers are separated by alkali metal atoms. In the field of mercury containing host-guest-compounds the two new compounds [Hg 6 Z 4 ](InBr 6 )Br (Z = As, Sb) could be obtained and were structurally characterized. They are isotypic to [Hg 6 Sb 4 ](SbBr 6 )Br. The cationic networks of these solids are based on a three dimensional connection of ethane analogous Z 2 Hg 6/2 -units. In the case of the cationic networks of the new compounds [Hg 2 Sb]MCl 4 (M = Al, Ga) corner sharing (SbHg 4/2 + )- tetrahedra are observed. The tetrahedral anions are located in suitable holes of the network and are reoriented as consequence of a first order phase transition. The compound [Hg 6 Sb 4 ](Ga 2 Br 7 )Br crystallizes in a new structure type. Its cationic network consists of a combination of (SbHg 4/2 + )-tetrahedras and Sb 2 Hg 4/2 E 2 -units (E = free electronpair) formally analogous to the molecule hydrazine.Source Type:Doctoral Thesis345 433 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , The use of supercritical carbon dioxide in solid state chemistry and basic structural investigations with chalcogenide halides of the third main group(2005)Abstract als PDF-DokumentSource Type:Doctoral Thesis2 48 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Design, synthesis and studies of radical and radical ion probes : from enzyme investigations to electroactive surfactants(2004)The present work is centered at understanding the mechanistic details of the coenzyme B 12 dependent enzymes such as diol and glycerol dehydratase that are known to involve radical and radical ionic intermediates in transforming vicinal diols to carbonyl compounds. The work aims on translating such reactive intermediates to relatively long lived ones (making use of beta cleavage leading to persistent radical or electron transfer processes) thereby enabling their spectroscopic detection. A number of modified enzyme substrates attached with groups such as ferrocene, quinone and 2,2,6,6-tetramethylpiperidinoxy were synthesised and were investigated. The efficacies of electrophores to probe radical ions at the active site of the enzyme inherently rely on the electron transfer process. Modulation of the oxidising/reducing property of radical cation/radical anion formed at the active site invariably effects the trapping efficiency of the electrophore. Cyclic voltammetry investigations on the model compounds based on Fuson enols revealed that hydrogen bonding can indeed alter oxidation potentials of enols by up to 500 mV Fc cathodically. The concept was also tested in solution by generating and trapping radical cations in solution via inter as well as intramolecular electron transfer from ferrocene as a donor to enol/enol ether radical cation. Use of stable and reversible redox systems can set a precedent to the development of not only radical ion clocks, they can additionally prove pivotal in areas of nano-technology requiring transfer of small volumes (nano litre range) of solutes in a well defined manner. Thus a couple of redox active compounds were synthesised and investigated for their surfactant property, electrochemical and chemical stability.Source Type:Doctoral Thesis3 13 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Bestimmung der Löslichkeit von Metallchelaten in überkritischem Kohlendioxid(1999)In the present work the bases for a direct reactive extraction of the metals palladium and rhodium were determined. The metals were converted thereby by addition of suitable ligands into chelates. Enormous differences in solubility of the chelates formed with the ligands DPDC and THD could be determined which is a basis for the selective extraction of metals. The most important basis for a selective extraction of a mixture of metal chelates is the knowledge of the solubility of the individual chelates in the extracting agent. For the investigation of this basis a dynamic-spectroscopic method was developed for the solubility determination of metal-organic compounds in supercritical carbon dioxide. The equipment used consisted in its core of a modified MPS 225 of the company Suprex, which was connected to a scanning UV detector. The calibration took place via an off-line quantification. With this equipment the solubility of chelates was determined as a function of the temperature and the density of the supercritical fluid. The temperatures, at which the isotherms were measured, were 50, 60 and 70 °C. The examined area of the reduced density extended from 1,1 to 1,9. The used model substances were chelates of the heavy metals palladium, rhodium and lead. As ligands 2.2.6.6 Tetramethylheptandione (THD), Diisopropyldithiocarbamate (DPDC) and the Methylthioglykolate (MTG) were selected.Source Type:Doctoral Thesis1 5 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Design von Baustoffen am Beispiel eines Putzes und eines Betons mit Glaszuschlag(2000)Die Arbeit gliedert sich in zwei Teile. Die beide Teile beschäftigen sich mit verschiedenen Baustoffsystemen, werden andererseits durch das Thema der gezielten Entwicklung eines Baustoffes für eine bestimmte Anforderung verbunden. Im Rahmen des ersten Teils wurde ein geeigneter Fassadenputz zur Sanierung von Ziegelmauerwerk entwickelt. Für die Restaurierputze wurden zwei Bindemittelsysteme, zum einen hydraulischer Kalk mit Hochofenzement, zum anderen Weißkalkhydrat mit Hochofenzement untersucht. Zusätzlich wurden Hydrophobierer, Kunststoffdispersion und Methylcellulose eingesetzt, um die Dauerhaftigkeit und Resistenz gegen Umwelteinflüsse zu erreichen, aber auch um die Verarbeitbarkeit zu verbessern. Der systematische Einsatz der verschiedenen Zusätze erlaubt Aussagen über deren Einfluss auf die Mörteleigenschaften. Im zweiten Teil der Arbeit wurde zur optischen Gestaltung von Sichtbeton farbiger Glasbruch als Betonzuschlag eingesetzt. Da eine Reaktion zwischen Glas und Zementstein im Beton bekannt ist, war es erforderlich, die Eignung dieses Zuschlags, seinen Einfluss auf die Betoneigenschaften sowie mögliche Schädigungen der Betonteile zu untersuchen. Es wurde der Einfluss von Zusatzmitteln wie Hydrophobierer, Fließmittel, Kunststoffdispersion, Glasmehl, Mikrosilica und Luftporenbildner auf Ausmaß und Art der entstehenden Schädigung unter verschiedenen Umweltbedingungen untersucht. Mit der Verwendung von drei unterschiedlichen Glasarten und verschiedener Glasgehalte wurde der Einfluss der im Glas befindlichen Alkalien auf die Reaktion beobachtet werden.Source Type:Doctoral Thesis414 239