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Weiche Materie Vortrag: Fr., 10:20–10:40 F-V48
Tomographic small-angle x-ray scattering of nanostructured soft-matter
materials
Marion Kuhlmann 1 , Stephan Volker Roth 1 , Rainer Gehrke 1 , Christian
G. Schroer 2 , Ulrich Nöchel 3 , Armando Almendarez-Camarillo 3 , Norbert
Stribeck 3
1 HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Germany – 2 Institut für Strukturphysik,
TU Dresden, D-01062 Dresden, Germany – 3 University Hamburg, Institute
TMC, Bundesstr. 45, D-20146 Hamburg, Germany
Scanning microscopy is performed in combination with small angle x-ray scattering
(SAXS), exploiting the SAXS contrast inside the sample. This is especially useful for
samples, where classical absorption tomography fails. The result is an invasive but
non-destructive analytic tool to determine the local microstructure on the nanometre
scale inside a specimen. The tomographic reconstruction yields the SAXS pattern in
the direction of the rotation axis at each location of a virtual slice through a sample.
In case of rotationally symmetric specimen the full reciprocal space information can be
reconstructed [1]. These reconstructed SAXS patterns can be analysed in order to track
the variations of the nanostructure inside the sample. Many nanostructured soft-matter
materials exhibit rotational symmetry, e.g. natural fibres, polymer fibres, wood. The
method is demonstrated by data from polyethylene rods made by injection moulding
[2], a freeze dried arabidopsis flower stalk, and rat tail collagen. The experiments were
performed at the beamline BW4 at the DORIS III storage ring of HASYLAB / DESY.
The monochromatic synchrotron radiation was focused by parabolic refractive lenses
made of beryllium [3]. In case of a polyethylene rod a spatial resolution of ≈80 µm has
been resolved in the reconstructed slice. A 2D detector at distances >1800 mm allowed
to cover a q-range from 0.06 nm −1 to 2 nm −1 . The primary, the directly transmitted,
and the scattered intensity were measured for projections of slices through the specimen
over a full rotation of the sample to allow for tomographic reconstruction. Currently,
single pattern acquisition times are of 20 s up to 360 s, this leads to days of required
beamtime for one tomogram. Technical developments are discussed to minimize such
limitations.
[1] C.G. Schroer et al., Appl. Phys. Lett. 88, (2006) 164102
[2] N. Stribeck et al., Macromol. Chem. Phys. 205, (2004) 1445
[3] B. Lengeler et al., J. Phys. D: Appl. Phys. 38, (2005) A218