The novel possibilities of phase feature detection in radiography at a third generation synchrotron radiation source are used to image, both in projection and in computed tomography, a cracked silicon single crystal and metal matrix composites strained in tension. Through an instrumentally very simple technique, based on Fresnel diffraction, phase jumps related to the interface between the matrix and the reinforcing phases of the composites are detected even when these phases show very similar x-ray attenuation. Strain-induced cracks with openings below the micrometer range are also visible through the phase modulation they introduce, illustrating the potential of the technique for assessing damage in materials with improved resolution and sensitivity.
Particularly high coherence of the x-ray beam is associated, on the ID19 beamline at ESRF, with the small angular size of the source as seen from a point of the sample (0.1-1 µrad). This feature makes the imaging of phase objects extremely simple, by using a `propagation' technique. The physical principle involved is Fresnel diffraction. Phase imaging is being simultaneously developed as a technique and used as a tool to investigate light natural or artificial materials introducing phase variations across the transmitted x-ray beam. They include polymers, wood, crystals, alloys, composites or ceramics, exhibiting inclusions, holes, cracks, ... . `Tomographic' three-dimensional reconstruction can be performed with a filtered back-projection algorithm either on the images processed as in attenuation tomography, or on the phase maps retrieved from the images with a reconstruction procedure similar to that used for electron microscopy. The combination of diffraction (`topography') and Fresnel (`phase') imaging leads to new results.
The aim of this paper is to present a methodology for 2D and 3D characterization of different foams using X‐ray microtomography with a resolution of 30 micrometer. 2D and 3D quantitative image analyses have been performed to obtain information about the cells. The main parameters of interest are the cell size, the cell size distribution, morphology of the cells, connectivity of the cells, and fraction of matter at the edges. We use morphological operations such as opening granulometry to separate cells when they are not perfectly closed. This characterization was performed on Alporas, IFAM, and Norsk‐Hydro foam.
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