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  • 1
    Digitale Medien
    Digitale Medien
    Displacements from Cu4Ti in a Cu–Ti single crystal using small-angle and diffuse X-ray scattering: a synchrotron radiation study (2000)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 33 (2000), S. 928-937 
    Details
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: Single crystals of Cu–2.5 at.% Ti have been studied by small-angle and large-angle X-ray scattering to determine the displacements induced by the formation and the coarsening of ordered Cu4Ti precipitates. The variation of the atomic scattering factor of Cu near its absorption edge was used to confirm the nature of the precipitates and to show that the scattering appearing near Bragg peaks was due to the displacements of the atoms from their ideal positions, induced by the formation of the precipitates, and not to the segregation of the Ti atoms. The displacement field was found to be dependent on the precipitate mean size, with a single component aligned along a soft 〈100〉 direction: it is composed of a region of dilatation, where the Cu-atom positions follow the increase of the atomic distance induced by the Cu4Ti precipitate formation, followed by a region of contraction. This effect is responsible for the pile-up of the precipitates along the soft directions: the interaction between precipitates is repulsive at long distances and attractive at shorter distances.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0021889800003071
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  • 2
    Digitale Medien
    Digitale Medien
    Determination of anomalous scattering factors for zinc and silver in Al–Zn–Ag alloys (1985)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 18 (1985), S. 181-183 
    Details
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: The anomalous scattering factors of zinc and silver in samples of Al-rich Al–Zn–Ag have been measured near their K-absorption edges. EXAFS spectra obtained from the Stanford Synchrotron Radiation Laboratory were converted to the imaginary part of the atomic scattering factor f′′ using the optical theorem. With a knowledge of f′′(E), f′, the real part of the atomic scattering factor, was determined from the Kramers–Kronig dispersion relation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S002188988501007X
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  • 3
    Digitale Medien
    Digitale Medien
    A comparison of the merits of isotopic substitution in neutron small-angle scattering and anomalous X-ray scattering for the evaluation of partial structure functions in a ternary alloy (1985)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 18 (1985), S. 230-236 
    Details
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: Solute partitioning during decomposition of a ternary alloy may be evaluated through the inversion of a system of linear equations, obtained by performing at least three independent small-angle scattering experiments. The merits of neutron scattering (with isotopic contrast) and of anomalous X-ray scattering (near the absorption edges) are compared. It appears that neutron scattering, although having good contrast, is not suited to these studies since slight structural differences between the three samples may lead to erroneous results. On the other hand, the use of the same sample in anomalous scattering avoids this problem, but with the drawback of a more ill-conditioned system. Nevertheless, the possibility of performing more than three anomalous experiments may improve the results and a new analysis of data is proposed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0021889885010196
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  • 4
    Digitale Medien
    Digitale Medien
    The nature of the scattering tail in Cu–Ni–Fe and Invar alloys investigated by anomalous small-angle X-ray scattering (1991)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 24 (1991), S. 1027-1034 
    Details
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: A large rapidly decreasing intensity called the `scattering tail' is generally observed at the smallest recorded angles during small-angle measurements of metallic alloys. Since this tail was interpreted as caused by a bimodal phase separation in Cu–Ni–Fe alloys and by long-wavelength concentration fluctuations in Invar alloys, these two systems were re-examined with anomalous X-ray scattering. The variation of the alloying atomic contrasts allows a discrimination between the different types of particles or defects. In neither of the two systems can the tails be interpreted as caused by large-scale concentration fluctuations. In Cu–Ni–Fe alloys, the tail is due to some kind of superficial defect (surface roughness etc.). In Invar alloys, the tail is probably due to residual impurity particles.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0021889891007811
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  • 5
    Digitale Medien
    Digitale Medien
    Morphology of encapsulated iron nanoparticles obtained by co-sputtering and implantation: a GISAXS study (2000)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 33 (2000), S. 437-441 
    Details
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: A grazing incidence small-angle X-ray scattering (GISAXS) study is presented on the morphology of iron nanoparticles buried in carbon matrices, obtained either by ion-beam sputtering co-deposition or by ion-implantation. It is shown that, depending on the experimental synthesis conditions, the shape of the iron nanoparticles is either spherical or elongated perpendicularly to the substrate. The possible growth mechanisms are examined in terms of volume and surface diffusion, defect density, interfacial energy and residual stress.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0021889899014181
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  • 6
    Digitale Medien
    Digitale Medien
    Determination of specific volumes in multilayers by anomalous X-ray scattering (1988)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 21 (1988), S. 317-321 
    Details
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: X-ray diffraction in multilayer structures is determined by the electronic concentration profile, which depends both on the atomic concentration and on the specific volume. Probing with photons of different wavelengths in the vicinity of an absorption edge (anomalous X-ray scattering) produces a variation of the scattered intensity, which allows the separation of both contributions. A test of the feasibility of this method on several multilayer samples is presented. The technique appears to be sensitive enough to measure specific volume ratios with a precision of about 5%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S002188988800247X
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  • 7
    Digitale Medien
    Digitale Medien
    Anomalous small-angle X-ray diffraction of an Nd-Fe multilayer (1991)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 24 (1991), S. 156-163 
    Details
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: The Bragg peak intensities, related to the electronic concentration profile, depend both on atomic concentrations and on specific volumes. Anomalous dispersion, using synchrotron radiation, produces a variation of the scattered intensity, which in principle allows a separation of the two contributions. The kinematic approximation for diffraction of thick multilayers allows an easy evaluation of the ratio of specific volumes, but the entire reflectivity curves and their deformations with photon wavelength can be explained by the interferences between the Kiessig fringes and diffraction maxima in a kinematic approximation. A full optical treatment confirms the previous analysis. Finally, the relaxations occurring during Nd–Fe interdiffusion are too small to be measured in our experimental conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0021889890011633
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  • 8
    Digitale Medien
    Digitale Medien
    Determination of displacements from nanoprecipitates in a Cu–Ni–Fe single crystal using anomalous small-angle and large-angle X-ray scattering (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 34 (2001), S. 484-492 
    Details
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: Single crystals of Cu–41.5 at.% Ni–16 at.% Fe have been studied by small-angle and large-angle X-ray scattering in order to determine the displacements induced by the disc-like precipitates formed during decomposition. The small-angle X-ray scattering (SAXS) patterns gave information on the size and the organization of the precipitates, while the scattering near Bragg peaks allows a determination of the distortions of the lattice created by these precipitates. The variations of the atomic scattering factors of Fe, Ni and Cu (for the large-angle measurements) were used to determine both the partial structure functions (`chemical' data) and the partial displacements. The precipitates were found to be enriched in Fe and Ni, which induced a contraction of the lattice, while the depleted matrix (mainly Cu) was dilated. This succession of compressed and dilated regions is very stable and prevents a single precipitate from growing much in this direction during coarsening. This can explain why a single precipitate tends to grow mainly in the orthogonal directions, where the extension of the displacements is smaller than the precipitated region.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0021889801008809
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  • 9
    Digitale Medien
    Digitale Medien
    Anomalous small-angle-X-ray scattering on Al–Zn and Al–Zn–Ag alloys (1985)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 18 (1985), S. 480-486 
    Details
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: Anomalous small-angle scattering (ASAXS) spectra from Al–Zn and Al–Zn–Ag alloys have been recorded at the Stanford Synchrotron Radiation Laboratory (SSRL). The data were obtained at different energies close to the Zn absorption edge. For the binary alloy, the ASAXS intensities follow quantitatively the variation in the atomic scattering factor of zinc. For the ternary alloys, the anomalous effect decreases when the Zn content decreases. Although only weighted sums of the partial structure functions could be determined, it is shown that the results are consistent with the `two-phase' unmixing model and the direction of tie lines of the metastable miscibility gap has been determined. A new method for analyzing ASAXS data for two absorption edges is proposed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0021889885010743
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  • 10
    Digitale Medien
    Digitale Medien
    A multilayer analyser suitable for linear detection of anomalous small-angle X-ray scattering (1992)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 25 (1992), S. 785-788 
    Details
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: Measurements of anomalous small-angle X-ray scattering often include a strong fluorescent background. The separation of the elastic scattering from the background is usually performed at the time of analysis. This paper presents an alternative experimental method using a multilayer analyser compatible with a linear position-sensitive detector and, for a test case, compares the resulting structure factors with those obtained by the usual technique. The technique achieves the proposed goal but at the expense of counting rate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0021889892007064
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