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- 2008 (22) (entfernen)
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Schlagworte
- Bragg magnification (3)
- X-ray refraction (3)
- Coherent imaging (2)
- Holotomography (2)
- Microtomography (2)
- Non-destructive evaluation (2)
- Scintillator (2)
- Synchrotron instrumentation (2)
- Synchrotron-CT (2)
- Aerospace (1)
Eingeladener Vortrag
- nein (4)
X-ray refraction topography techniques are based on ultra-small angle scattering by micro-structural elements causing phase-related effects such as refraction and total reflection at a few minutes of arc as the refractive index of X-rays is nearly unity. The refraction contrast is several times higher than true absorption and results in images of cracks, pores and fibre debonding separations below the spatial resolution of the detector. In most cases the investigated inner surface and interface structures correlate to mechanical properties. For the exploration of micro structured materials the refraction technique has been improved by a 3D Synchrotron Refraction Computed Tomography test station. The specimen is placed in an X-ray beam between two single crystals, which suppresses all sample scattering. In addition, an asymmetric cut second crystal can magnify the image up to 50 times revealing nano meter resolution. The technique is an alternative to other attempts on raising the spatial resolution of CT machines.
Corrosion of steel reinforcement in concrete exposed to chloride containing
environments is a serious problem in civil engineering practice. Electrochemical
methods, e.g. potential mapping, provide information whether the steel reinforcement
is still passive or depassivation has been initiated. By applying such techniques no
information on the type of corrosion, its extent and distribution of corrosion products
is available. Particular the corrosion progress is a significant problem. Especially in
the case of element corrosion in reinforced concrete structures, the development at
the anode can not be separated into corrosion damage causing by element corrosion
or self-corrosion. Until now also in laboratory tests it is impossible to collect such
information without destroying specimens after electrochemical testing was
performed place. To overcome this problem it was tried to study the steel surface
within the mortar specimens by X-ray tomography (CT). Within the scope of these
investigations it could be shown, that X-ray tomography is suitable to make corrosion
pits visible which are embedded in a mortar with a cover thickness of about 35 mm.
In this publication the corrosion damage of reinforced steel is documented timedependent
by X-ray tomography.
Ein effektives Wassermanagement ist ein wichtiger Aspekt in der Entwicklung von Brennstoffzellen hinsichtlich Langzeitstabilität und Optimierung der Leistungsfähigkeit. Eine zentrale Rolle spielt dabei die Gasdiffusionslage, die für die gleichmäßige Verteilung der Reaktionsgase auf die elektrochemisch aktive Schicht (Katalysator) sorgen soll. In diesem Beitrag werden gemeinsame Forschungsaktivitäten des Helmholtz-Zentrums Berlin für Materialien und Energie (Entwicklung bildgebender Verfahren) sowie des Zentrums für Sonnenenergie- und Wasserstoff-Forschung (ZSW, Entwicklung von Brennstoffzellen) vorgestellt. Im Rahmen dieser Kooperation werden die Entstehung, die Verteilung und der Transport von flüssigem Wasser, kurz das Wassermanagement, unter Betriebsbedingungen untersucht. Mittels Synchrotronradiografie und -tomografie werden kleinste Wassercluster in der Gasdiffusionslage detektiert. Die gewonnenen Erkenntnisse dienen der Modifikation und einer gezielten Auswahl der eingesetzten Materialien.