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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 41 (1985), S. 434-440 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The Fourier diffraction method of Warren-Averbach, developed to measure external stress-induced strains of polycrystalline materials, can also be applied to analyse internal distortions of microparacrystals. In one case a function that is proportional to the distance p2 can be obtained whilst in the second case a function proportional to |p| in the physical space can be derived. More complicated problems arise when both types of distortions occur at the same time, which happens if microparacrystals are exposed to external stresses. This is discussed here for examples of unannealed extruded polyethylene and composite material such as carbon resin fibres. The Warren plot shows that the microparacrystals under investigation suffer rheological transformations, which can no longer be explained by a convolution integral of the reflection profiles with the distribution function of their mean net-plane distance s. The measured function of p can satisfactorily be derived from an empirically detected formula being applied to the convolution product of reciprocal values of the two distortions 1/g2p and 1/ε2p2, the physical meaning of which still remains an open question.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 43 (1987), S. 506-513 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Very thin equatorial small-angle scattering of Cu Kα radiation is observed from metallic wires, glass fibres and hard elastic polypropylene which can be explained quantitatively as a refraction phenomenon if the excess refractive indices n = 1 - ε of the samples are smaller than unity. For Cu Kα radiation and SiO2 glass ε has a value of 7.2 × 10-6. The intensity Is of reflection within a total reflection angle δ = 3.8 × 10-3 = 13' is negligibly small compared with the intensity of refraction IB. In addition to refraction, diffraction by gaps and holes in strained polypropylene was observed. The scattering of 60 μm particles of Li-Ba silicate glass powders [Nau & Brückner (1971). Kolloid Z. Z. Polym. 244, 223-233] can be explained by transforming the observed scattering of spheres to cylinders yielding the refraction IB as calculated.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 47 (1991), S. 446-447 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The absorption of X-rays scattered by isotropic random multiphase materials is shown theoretically to depend not only on volume fraction, linear absorption coefficient and mean particle size of each phase but also on the shape of the scattering particles. The absorption effect is remarkably enhanced with increasing polydispersity and irregularity of the scattering phase.
    Type of Medium: Electronic Resource
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