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129-Xe-NMR-spektroskopische Untersuchungen an Carbon Black und Graphit - 129Xe NMR Spectroscopy of Carbon Black and GraphiteSchmidt, Holger 24 February 2003 (has links)
Porous Carbon Blacks with specific surfaces of up to 1475 m²/g were examined and characterized by <sup>129</sup>Xe NMR spectroscopy. Graphite is regarded as a not-porous reference. The porosity of Carbon Blacks can be divided in three categories: inter-aggregate, intra-aggregate and intra-particle pores. A reciprocal behavior of the chemical shift to the middle pore radius has been found. Here the pressure and temperature dependence of the chemical shift are to be considered and only with pressures over 8-12 bar a characteristic limit value is reached. The diffusion coefficient of the intra-porous xenon atoms was determined with the help of the PFG NMR spectroscopy and lies with ambient temperature and a pressure from 10 to 12 bar within the range of 3·10<sup>-9</sup> to 3·10<sup>-8</sup>m²/s. The adsorption in micro-porous Carbon Blacks can be described by the pore filling theory of Dubinin and co-workers.
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Neue Methoden zur Feststoffanalytik unter Einsatz eines Induktiv gekoppelten Plasma-Massenspektrometers (ICP-MS) - New Methods in solid analysis for Inductively Coupled Plasma Mass Spectrometry (ICP-MS)Maibusch, Ralf 11 March 2003 (has links)
The main point of this thesis is the validation of SA-ICP-MS for routine analysis in the steel industry. Therefor a new interface-system is build up in order to measure transient siganls from the continuos ablation process of the spark device. Further more the coupling of an ETV oven for slurry analysis and a Laser Ablation for isitope ratio determination is discriebed. Some fundamental aspects in formation of interference in ICP-MS are pointed out at the end of this thesis.
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Direkte Bestimmung von Eisenspuren in Dichlorsilan mit Hilfe der Graphitrohrofen-Atomabsorptionsspektrometrie (GF-AAS) - Direct Determination of Trace Amounts of Iron in Dichlorosilane by Graphite Furnace Atomic Absorption Spectrometry (GF-AAS)Benninghoff, Claus 11 March 2004 (has links)
In the present thesis the development of an analytical method for the determination of trace amounts of iron in dichlorosilane by graphite furnace atomic absorption spectrometry with a modified autoprobe unit is described. An conceived gas inlet system enabled a nearly contamination free and constant gas injection. The analytical method is optimized and the iron concentration in dichlorosilane is quantitatively determined.
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Untersuchungen zur Auswirkung von anorganischen Zusätzen auf die sekundären Reaktionen der thermischen Dehydrochlorierung von Polyvinylchlorid - Studies on the influence of inorganic additives on the advanced reactions of the thermal dehydrochlorination of poly(vinyl chloride)Wylamrzy, Joerg 24 March 2004 (has links)
The context of this work examines the influence of zinc sulfide (ZnS) and other inorganic substances (Sb2O3, Sb2S3, Sn, Zn ) on the cross-linking reactions of the conjugated double bond sequences, which are generated as a consequence of thermal dehydrochlorination reactions of poly(vinyl chloride) (PVC). With increasing cross-linking grade, the flammability of the corresponding PVC would be decreased due to the suppression of fragmentation reactions. In this work element balances of thermal degrading PVC samples with inorganic additives are analyzed, as well as thermogravimetric investigations are consulted. Apart from qualitative views a kinetic model of the dehydrochlorination reactions is developed using multivariate nonlinear regression analysis of thermogravimetric data. The changes in the thermally stressed polymer samples under argon and under oxygen admission are observed using different analytic techniques (visual video monitoring, infrared spectrometry, and scanning electron microscopy). It can be shown that during the thermal degradation of PVC the cross-linking reactions can be increased by several inorganic additives.
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Probenahme und chemische Analytik korngrößenfraktionierten Immissions- und Emissionsaerosolen - Sampling and chemical analyses of size-fractionated aerosols in ambient air and emissionsJohn, Astrid Christiane 28 March 2002 (has links)
Within this thesis, instruments and methods were developed for sampling devices and chemical analysis of PM 10 and PM 2.5. These two particle size fractions are European standards for air quality monitoring since 1999. A specially designed "ambient air sampling system" for the direct collection of PM 10, PM 2.5 and PM 1 on TXRF-sample carriers for subsequent analysis by Total-Reflection X-Ray Fluorescence Analysis (TXRF) was constructed and calibrated in the laboratory. Additionally, a PM 1-Inlet for a High-Volume-Sampler was developed. As a result, the determination of mass concentrations as well as important chemical constituents (anions and cations, elemental and organic carbon, heavy metals, polycyclic aromatic hydrocarbons) is possible for the fine particle fraction PM 1. The newly developed instruments were used together with commercially available PM 10- and PM 2.5-samplers for a field campaign at a traffic-related measurement site. Data analyses showed good results concerning quality assurance and dem onstrated the complementarities of the different sampling systems. A detailed characterization of the ambient aerosols was obtained and a first source apportionment could be conducted. However, the results also showed that for an efficient air pollution reduction strategy, particle size fractionated emission measurements are necessary as well. Therefore, a PM 10/PM 2.5 in-stack cascade impactor was designed and calibrated. During measurements at various industrial plants, the newly developed instrument showed good results concerning reproducibility and plausible data in comparison with mass concentrations obtained with the plane filter device for the determination of total suspended particulates (TSP). A chemical characterization similar to the ambient air particles was conducted with TXRF for some of the samples. The results showed that size fractionated particle sampling together with multielemental analyses give characteristic patterns ("fingerprints") of emissions. In a next step, the information can be used for source apportionment by fingerprintmodelling and the quantification of the contribution of different sources to ambient air particle concentrations.
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Entwicklung, Anwendungen und Grenzen atomspektrometrischer Verfahren zur Spurenelementbestimmung in reaktiven Prozessgasen / Development, applications and limits of atomic spectrometric procedures for the determination of trace elements in reactive process gasesTelgheder, Ursula 12 April 2005 (has links)
The development of analytical procedures for the analysis of selected reactive process gases in order to use them in the production of semiconductors without sample preparation is the main task of the presented work. Different atomic spectrometric methods e.g. Electrothermal Atomic Absorption Spectrometry (ETAAS), Microwave Induced Plasma Atomic Emission Spectrometry (MIP-AES), Non dispersive Atomic Fluorescence Spectrometry and Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) have been used for the development of the procedures. The physico-chemical features of the matrix request a fitted sampling e.g. suitable, non corrosive material of the tubes and unions, and modified analytical system. The described ETAAS system with an automated sampling system allows the determination of Cu, Fe and Ni in gaseous HCl, Cl2, BCl3 and SiH2Cl2 without sample preparation. A comparison of calibration with standard aqueous solutions as well as standard additions and calibration with a gaseous standard has shown the negligible influence of the matrix on the calibration using the ETAAS system.
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Nickelspeziesanalyse im Cytosol humaner intestinaler Gewebeproben mittels online-Kopplung von Kapillarelektrophorese und induktiv gekoppeltem Plasma-Massenspektrometer - Nickelspeziesanalysis in the cytosol of human intestinal tissue with online coupling of capillary-electrophoresis with inductively coupled plasma mass spectrometryBonsack, Sven 30 April 2003 (has links)
This thesis deals with the nickelspecies-analysis in cytosol of human intestinal tissue. The aim was, to find the differences in nickelspecies between the cytosol of malignant and normal tissue of the same patient with CE/ICP-MS resp. SEC/ICP-MS coupling. The result was, that the area ratio of two nickelspecies in the cytosol of malignant tissue are significant higher than in the cytosol of normal tissue. Maybe the two nickelspecies can be an oncogenproduct.
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Thermische und photochemische Charakterisierung der Produkte einer Photo-Diels-Alder-Reaktion - Thermal and Photochemical Characterisation of the Products of a Photo-Diels-Alder-reactionKruse, Claudia 25 April 2002 (has links)
During the irradiation of 1-acetylnaphthaline in the presence of c,d-substituted olefines with a cyclic amine as a donor different products were generated. The reaction pathways were monitored by NMR-spectroscopy and it was proved that the main products were generated by a Photo-Diels-Alder-reaction. The c,d-olefines are added head-to-tail with the donor substituent in endo-position to the remaining aromatic system. Their structures could unambiguously be proven by single crystal x-ray structure analysis. Furthermore their thermal and photochemical properties were investigated: the activation enthalpies and activation entropies for their thermal decompositions were investigated and during their irradiation in solution with light of 254 nm a Di-<font face="Symbol">p</font>-methane-rearrangement could be observed.
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Nukleophile aromatische Substitution zur Synthese mehrzähniger Komplexliganden und Herstellung geordneter bimetallischer NanopartikelMuth, Oliver 13 May 2005 (has links)
Als Schlüsselreaktion zum Aufbau von para-chinoiden Triphenylenfarbstoffen mit komplexierungsfähigen Funktionalitäten für Metallionen sowie von Methylen- und Methin-verbrückten Oligopyridinen eignet sich hervorragend die nukleophile aromatische Substitution. Für die Synthese der funktionalisierten para-chinoiden pi-Systeme diente dabei ein Triarylmethylkation mit einem sterisch abgeschirmten zentralen Kohlenstoffatom und zweier peripherer Fluorsubstituenten an aromatischen Ringen, die bei der Umsetzung mit Nukleophilen als elektrophilen Bausteinen 2-Fluor- und 2,6-Difluorpyridin mit 2-Methyllithiumpyridin eröffnete den effizienten Zugang zur Familie der Methylen- und Methin-verbrückten mehrzähnigen Oligopyridin-Liganden in sehr guten Ausbeuten von meistens 90% und mehr. Die hieraus resultierenden Methylen-verbrückten Pyridin-Liganden konnten ihrerseits wieder als nukleophile Bausteine erfolgreich mit 2-Fluor- und 2,6-Difluorpyridin umgesetzt werden. Mit den hergestellten Pentakispyridinen wurden mehrere Kupfer(II)-Komplexe hergestellt. Der zweite Abschnitt der Arbeit befasst sich mit der Herstellung von geordneten FePt-Nanopartikeln. Dabei wurde eine literaturbekannte Herstellungsmethode ausgehend von Pt(acac)2, 1,2-Hexadecandiol...
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Diffusionsmessungen an Polyethylenglykolen mittels PFG-NMR-Spektroskopie und dynamischer Lichtstreuung / Diffusion measurements of poly(etylene glycol) in solution by Pulsed Field Gradient NMR spectroscopy and Dynamic Light ScatteringDunkhorst, Kirsten 06 May 2005 (has links)
The Pulsed Field Gradient (PFG) NMR spectroscopy was uesd to determine, via the diffusion coefficient, the molecular weights and the molecular weight distributions for sampels of poly(etylene glycol) (PEG) in D2O. Additional it was investigated, whether the components of mixtures of poly(ethylene glycol) with different molecular weights could be quantitatively determined by the differences in diffusion coefficient. The results of this study are compared with the result of the Dynamic Light Scattering (DLS) technique, the standard methode for the determination of molecular weights. The PFG NMR findings shows that the the molecular weights and the molecular weight distributions agreed well with values provided by the manufacturer. The mixtures could not be determined quantitativley, because of considerable overlaps in the molecular weight distributions. But it could be shown that the PFG NMR spectroscopy and the DLS technique complement one another.
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