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Paper des Monats
- ja (77)
Stiffness analysis of epoxy interphase on copper micro-structures by scanning force microscopy
(2004)
Einfluss hoher Temperaturen und Drücke auf die Ultraschalleigenschaften eines Komposit-Prüfkopfes
(2004)
Volatile organic compounds (VOC) were investigated at a dry-cleaning facility of a former military site in Germany. VOCs have leaked into the unsaturated soil zone consisting of sandy aggragated material and fine to medium sand.
The groundwater table is located at 1.50 to 2.00 m.
The following investigations were performed:
·Soil sampling using an open window sampler, layer specific determination of VOC in the soil using gas chromatography after the following sample preparation procedure
- extraction with methanole
- extraction with pentane
- multiple headspace extraction (MHE) [1]
·Soil gas measurements, sampling using concentrating steps [2]
The various extraction procedures for VOC analysis in soil have yielded different
results. The results will be discussed with an emphasis on risk assessment, and recommendations for the procedure will be presented.
References
[1 ] DIN EN ISO 10301: 08.97: Wasserbeschaffenheit - Bestimmung leichtflüchtiger halogenierter Kohlenwasserstoffe - Gaschromatographische Verfahren
[2] VDI-Richtlinie 3865:06.98: Messen organischer Bodenverunreinigungen, Blatt 3: Gaschromatographische Bestimmung von niedrigsiedenden organischen Verbindungen in Bodenluft nach Anreicherung an Aktivkohle oder XAD-4 und Desorption mit organischen Lösungsmitteln
The determination of the pollutant transfer from the soil with leachate into the groundwater is of fundamental importance for the assessment of the risk potential posed by contaminated sites.
Following the German Federal Soil Protection and Contaminated Sites Ordinance (BBodSchV) the leachate forecast is allowed to perform among others on the basis of material testing in the laboratory (elution) or in-situ investigations in the transition area from the unsaturated to the water saturated zone (place of assessment).
In this study the leaching behaviour of PAH through two lysimeters in laboratory scale was monitored under unsaturated conditions using a PAH contaminated soil from a former tar works site. The glass columns (30 cm in diameter) containing about 30 kg of contaminated soil were irrigated weekly with 300 ml of water. PAHs, pH value, DOC, turbidity, conductivity were determined for periodically taken eluates.
The different leaching behaviour of the various PAHs will be presented by examples on the poster.
After relatively high initial leachate loads of high-water-solubility PAHs the release adjusts relatively quickly to a constant low level. Released concentrations decrease with increasing molecular size. The results indicate a low availability of the studied contaminants after 270 days since only a minor fraction of the initial amount of PAHs was released from the soil during the experiment.
This method seems to be reliable of providing data on leachate amounts of PAHs under field-like conditions over a long period of time.
Emissions OECD guidelines
(2004)
Laser-Induced Breakdown Spectroscopy for On-Site Determination of Chloride and Sulfur content
(2004)
Termites in Hamburg
(2004)
Flame Retardant Mechanisms of Red Phosphorus and Magnesium Hydroxide in High Impact Polystyrene
(2004)
The flame retardant mechanisms of red phosphorus, magnesium hydroxide and red phosphorus combined with magnesium hydroxide were studied in high impact polystyrene by means of comprehensive decomposition studies and combustion tests. The study is intended to illuminate prerequisites and the potential of red phosphorus as a fire retardant for hydrocarbon polymers in the condensed phase and in the gas phase. Thermal and thermo-oxidative decomposition, decomposition kinetics and the product gases evolved were characterized using thermogravimetry coupled with Fourier transform infrared spectroscopy and mass spectroscopy, respectively. Fire behaviour was investigated with a cone calorimeter using different external heat fluxes, whereas the flammability was determined by limited oxygen indices. The combustion residues were analysed using XPS. Red phosphorus reduced the heat release in HIPS due to radical trapping in the gas phase. Magnesium hydroxide influenced fire behaviour by heat sink mechanisms, release of water and the formation of a magnesia layer acting as a barrier. The combination of both flame retardants in HIPS nearly resulted in a superposition. A slight synergy in barrier characteristics was due to the formation of magnesium phosphate, whereas a slight anti-synergism occurred in flammability and in the gas phase action. The latter effect is controlled by a decreased fuel rate due to the barrier layer rather than by an initiation of red phosphorus oxidation in the condensed phase.
The fracture toughness in the fiber-matrix composite by means of the single fiber pull-out test can be achievable, if it is possible to measure the compliance of partial debonded fiber, which necessitates a stable crack propagation and the determination of the corresponding crack length. A combination of high stiff test equipment and a simultaneous monitoring of the photo-elastic pattern of the embedded fibers with the help of polarization microscope enables to measure crack length and determination of Gc [Hampe, A and Marotzke, C. (1997). The Energy Release Rate of the Fiber/Polymer Matrix Interface: Measurement and Theoretical Analysis, J. Reinf. Plast. and Compo., 16: 341-352.]. This method is well-known for glass fiber-amorphous polymer composite. In this investigation, we tried to implement the same technique to C-fiber with amorphous and semi-crystalline polymer composites. The energy release rate (ERR) of the fiber-matrix interface was evaluated for the carbon fiber-reinforced in polycarbonate (PC) by interfacial crack propagation arising in the single fiber pullout test. Further, the crack propagation at the fiber-matrix interface with different matrix morphology was discussed with the use of photo-elastic pattern observed with the aid of polarization microscope.
Spectral fluorescence standards for the traceable characterization of fluorescence measuring systems
(2004)
Estimates of the uncertainty of lattice parameters refined from neutron powder diffraction data
(2004)
Nickel base alloys are frequently applied in safety-relevant fields such as chemical plant construction or power plant engineering. Particularly on account of their cubic face-centered solidification characteristic, these materials are frequently susceptible to metallurgy-specific hot cracking during fusion welding. A classification of these materials according to their hot cracking resistance in the MVT-Test (Modified Varestraint Transvarestraint Test) is carried out by the example of a series of base and welding filler materials. Moreover, it has been proven by the MVT Test that the hot cracking resistance of nickel base alloy (Alloy 602 CA) can be improved by selecting appropriate shielding gases.
Acceptance Tests
(2003)
Proposals for perfomance demonstration and modular reliability assessment for humanitarian demining
(2003)
Konzepte zur Quantifizierung des Restrisikos bei der Minensuche und in der zerstörungsfreien Prüfung
(2003)