  The structural evolution of a nano-powder by repeated dispersion and settling
can lead to characteristic fractal substructures. This is shown by numerical
simulations of a two-dimensional model agglomerate of adhesive rigid particles.
The agglomerate is cut into fragments of a characteristic size l, which then
are settling under gravity. Repeating this procedure converges to a loosely
packed structure, the properties of which are investigated: a) The final
packing density is independent of the initialization, b) the short-range
correlation function is independent of the fragment size, c) the structure is
fractal up to the fragmentation scale l with a fractal dimension close to 1.7,
and d) the relaxation time increases linearly with l.
