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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 2912-2914 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Because the refractive index for hard x rays is slightly different from unity, the optical phase of a beam is affected by transmission through an object. Phase images can be obtained with extreme instrumental simplicity by simple propagation provided the beam is coherent. But, unlike absorption, the phase is not simply related to image brightness. A holographic reconstruction procedure combining images taken at different distances from the specimen was developed. It results in quantitative phase mapping and, through association with three-dimensional reconstruction, in holotomography, the complete three-dimensional mapping of the density in a sample. This tool in the characterization of materials at the micrometer scale is uniquely suited to samples with low absorption contrast and radiation-sensitive systems. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5878-5886 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 34 (2001), S. 602-607 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A new technique, `topo-tomography', suitable for the characterization of the three-dimensional defect structure in bulk crystals, is proposed. The technique consists of the combination of diffraction topography and microtomography. It is applicable to high-quality single crystals, provided that the `direct image' is the dominant contrast mechanism. In this case, crystal defects give rise to locally enhanced intensity compared with the perfect-crystal matrix. The additional intensities sum along the diffracted-beam direction and yield projections of the local Bragg reflectivity. Like in the case of absorption tomography, the three-dimensional distribution of this reflectivity can be reconstructed from a large number of projections. The first experimental results of this technique, applied to a synthetic diamond crystal, are presented.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 5 (1998), S. 376-378 
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Experimental data with unprecedented submicrometre resolution obtained in a phase-contrast radiography experiment in a magnifying configuration are presented. The term `phase contrast' here indicates that the phase retardation of coherent light in matter was utilized as the contrast mechanism. The coherent and divergent beam exiting an X-ray waveguide was used in a lensless configuration to magnify spatial variations in optical path length up to several hundred times. The defocused image of a nylon fibre was measured with a resolution of 0.14 µm at the object. Sufficient contrast was found for exposure times of 0.1 s, i.e. in the regime for real-time studies.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 33 (2000), S. 1149-1153 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The distribution of inverted ferroelectric domains on the surface and within the bulk of a periodically poled KTA (KTiOAsO4) single crystal has been observed using a simple X-ray diffraction imaging setup which takes advantage of the highly coherent beams available at a third-generation synchrotron source, such as the ESRF. This technique allows one to reveal the phase difference between the waves that are Bragg diffracted from adjacent domains via free-space propagation (Fresnel diffraction). The phase difference of the diffracted waves is mainly produced by the difference in phases of the structure factors involved, and contains precise structural information about the nature of the domain walls.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Reliability of functionally graded metal matrix composites (FGMMCs) for automotive components is still dependent on the detailed knowledge of the mechanisms of the microstructural build-up, for instance on the mechanisms leading to the distribution and relative positions of the reinforcing particles. In order to assess the influence of the SiC particle size on the 3-D inter-particle connectivity in functionally graded Al/SiCp composites produced by centrifugal casting, X-raymicrotomography experiments were performed at the ID19 beamline in ESRF (European Synchrotron Radiation Facility). The FGMMCs consisted of an Al-10Si-2Mg alloy matrix, reinforced by an average SiC particle volume fraction of 0.10; two different average sizes were used: 37 µm and 12 µm. The holographic modification of the X-ray CMT (Computer Micro- Tomography) method allowed to obtain neatly contrasted images, as opposed to classical CMT.Good agreement was found between the particle size evaluated by CMT and by laser interferometry. Particle clustering has been evaluated in number and volume, showing that a lowermean particle size is related to more clustering. Such an adverse effect relies on the importance of particle/liquid alloy surface tension. Also, the mean particle size has been evaluated as a function of particle number within a cluster: as expected, the larger a cluster, the larger the particles inside it
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 519-521 (July 2006), p. 1367-1372 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper generally presents different techniques available to image the microstructure ofmaterials in three dimensions (3D) at different scales. It then focuses on the use of the moreversatile of these techniques for aluminum alloys : X-ray tomography. The paper describes therecent improvements (spatial and the temporal resolution, grain imaging). Electron tomography isalso presented as a promising technique to improve the spatial resolution
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1662-0356
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Natural Sciences in General , Technology
    Notes: This paper provides a brief overview of the possibilities offered by X-ray computedmicrotomography, and particularly synchrotron radiation X-ray microtomography, regarding metalmatrix composite characterization, emphasis being placed in the case of Al-based functionallygraded materials. Examples are provided concerning the characterization of the reinforcementpopulation, interfacial properties, in-situ transformation and damage evolution. The specific needsof the technique and limitations to its widespread use are mentioned
    Type of Medium: Electronic Resource
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