ABSTRACT
The microstructure of a granular packing is directly related to its static and dynamic behavior. For instance strong interparticle forces in a cohesive powder stabilize extremely porous structures which are far from a random close packing, leading to bridging, channeling and other feeding problems associated to disturbances in industrial handling of fine powders (Jenike 1964; Tomas 2004; Yang et al. 2003). While macrostructural information is fairly accessible through experimental techniques, obtaining microstructural information in 3D is far from trivial. Any attempt to experimentally visualize structure and ordering of single particles in 3D requires techniques that penetrate the opacity of a powder packing, see for instance Sederman et al. (2001) or Wang et al. (2004). Spin-echo smallangle neutron scattering (SESANS) is such a technique (Bouwman et al. 2004). SESANS uses the penetrating ability of neutrons in bulk materials together with high sensitivity to extremely low angle scattering all together making it possible to study structures up to 10 µm in size, e.g. structure in superfine powders with discrete particle diameters between 1-10 µm. Further more the SESANS correlation function G(z) is a real space signal and directly related to structure and ordering of the particles (Krouglov et al. 2003a).
