Chemie und Prozesstechnik
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Eingeladener Vortrag
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Contamination of natural bodies of water with oil and lubricants (or generally, hydrocarbon derivatives such as petrol, fuel and others) is a commonly found phenomenon around the world due to the extensive production, transfer and use of fossil fuels. The timely identification of these contaminants is of utmost importance, since they directly affect water quality and represent a risk for wildlife and human health even in trace amounts.
In this work, we develop a simple system for the on-field detection of total petroleum hydrocarbons (TPH) in water and soil, the "Spectrocube". The test is based on the measurement of the fluorescence signal emitted by the molecular rotor 4-DNS-OH dye. This dye is embedded in a hydrophobic polymeric matrix (PVDF), avoiding interactions of water with the dye and providing a robust support for use in test-strip fashion. The test-strip’s fluorescence intensity increases linearly at low concentrations of TPH, reaching a saturation value at higher concentrations.
For excitation and evaluation of the test-strip fluorescence, a simple miniature optical system was designed. The system works semi-quantitatively as solvent-free TPH detection kit, as well as quantitatively when using a simple cyclopentane extraction step. To simplify the fluorescence read-out, the device is coupled to a tablet computer via Bluetooth, running a self-programmed software ("app").
A brief perspective of BAM on nanocarriers is presented including examples with special emphasis on the characterization of such materials and underlying challenges. In this respect, also ongoing activities at BAM on different types of core/shell nanomaterials and related systems are briefly summarized.
Die metallischen Verunreinigungen in Metallen lassen sich mittels hochauflösender Massenspektrometer relativ einfach ermitteln. Die Glimmentladungs-Massenspektrometrie (GD-MS) stellt hierfür eine schnelle Multielementmethode dar. Aufgrund ihrer höheren Anregungs- und Ionisationsenergien ist die Bestimmung von Nichtmetallen eine weit größere Herausforderung. Außerdem fehlt es an für die direkte Feststofftechnik notwendigen Kalibrierstandards z.B. in Form zertifizierter Referenzmaterialien. Für die quantitative Bestimmung von Verunreinigungen wurden mit Standards dotierte Pulverpresslinge und dotierte, gesinterte Materialien auf ihre Eignung als Kalibrierstandards für die GD-MS untersucht. Dabei kamen unterschiedliche Plasmabedingungen (gepulster/ kontinuierlicher Betrieb; verschiedene Plasmagase) zum Einsatz. Ein Überblick über analytische Kenngrößen und Grenzen der verwendeten Kalibrierstrategien wird gegeben. Zur Validierung des Verfahrens wurde die hochauflösende Continuum Source Absorptionsspektrometrie (HR-CS-MAAS) verwendet. Die analytische Nutzung der Molekül-absorptionsspektrometrie zur Bestimmung von Halogenen basiert auf der Bildung insitu-generierter zweiatomiger Moleküle (AlCl, GaF). Die entstehenden Molekülspektren werden im Echelle-Spektrometer aufgespalten und mittels CCD-Array detektiert, was eine sehr empfindliche Messung und präzise Quantifizierung ermöglicht.
The technique of painting on the reverse side of a glass panel was rediscovered by German artists at the beginning of the 20th century. They appreciated the impressive gloss, luminosity, and depth of colours in this genre. Compared to stained glass, the distinctive properties of this technique are: (1) the paint is applied “cold”, hence, it doesn’t involve a firing step, (2) reverse paintings on glass are framed and always viewed in reflected light and (3) the reverse paint stratigraphy is different from canvas paintings, starting with the front most layer and ending with the backing layer. In 1908 several artists, including Gabriele Münter, Wassily Kandinsky, Heinrich Campendonk, August Macke and Franz Marc of the “Der Blaue Reiter” (the Blue Rider) collective took an interest in this technique and started to share their interest with other colleagues in Europe. Our pioneering project is tracing this transfer of knowledge by a multidisciplinary approach in terms of art history, paint technology and material science. More than 100 artists and >1000 reverse paintings on glass were identified during the project. This high number of objects clearly points out that this technique was by far more important for modern art than previously assumed. In-situ, non-invasive measurements (XRF, Raman, VIS, DRIFTS) on a well-considered selection of 67 paintings reveal the broad palette of colorants ranging from traditional to experimental. Special attention is paid to the impact of synthetic organic pigments (SOP) in artists palette. Demonstrative examples by W. Kandinsky, L. G. Buchheim and F. Jespers are used to discuss analytical challenges and highlights.
A variety of materials of technological interest change their properties through contact with reactive media. Solid-gas reactions lead to a variety of reaction products on the surfaces and internal interfaces. The observation of nucleation and growth processes in the environment where they occur (in situ) from a chemical-structural perspective is especially challenging for aggressive atmospheres. The talk presents innovative approaches to study corrosion mechanisms using advanced X-ray methods. Using energy dispersive X-ray diffraction and X-ray absorption spectroscopy in different tailor made environmental reaction chambers, valuable insights into high temperature oxidation and sulfidation processes were gained. Fe-based alloys were exposed to hot and reactive atmospheres containing gases like SO2, H2O and O2 at 650°C. During the gas exposure the tailor made reaction chambers were connected to a high energy diffraction end station at the synchrotron. The crystallization and growth of oxide and sulfide reaction products at the alloy surfaces were monitored by collecting full diffraction pattern every minute. Careful examination of shape and intensity of phase-specific reflections enabled to a detailed view on growth kinetics. These studies showed, oxides are the first phases occurring immediately after experimental start. As soon as reactive gas media enter the chamber, the conditions change and different reaction products, such as sulfides start to grow. A comparison of different gas environments applied, illustrated the differences in the type of reaction products. The in situ observation of high temperature material degradation by corrosion made it possible to study the contribution of phases, which are not stable at room temperature. For instance, wuestite (Fe1-xO), was frequently observed at high temperatures in humid gases on Fe with 2 wt.% and 9 wt.% chromium, but not at room temperature. The strength of the occurrence of this phase additionally explains why, despite a higher Cr content, ferritic alloys with 9 wt.% Cr in a challenging atmosphere prevent the intrinsic formation of protective layers. The in situ observations were supplemented by careful considerations of thermodynamic boundary conditions and detailed post characterization by classical metallographic analysis. Additionally, the structure and chemistry of the dominant oxide layers were evaluated using X-ray absorption near edge structure spectroscopy. The talk will give an overview about chances and challenges for studying high temperature corrosion phenomena by advanced X-ray methods.