Visualization of the shear region in a cohesive powder by scanning with a polarized neutron beam

The flow of cohesive powder occurs by the formation of shear planes or zones. How these form and how particles microscopically behave in a shear zone is fundamental for understanding powder flow. In this work Neutron Depolarization has been used to study in-line particles in a powder sample. The Neutron Depolarization technique gives a unique insight in the particle rotations and width of the shear zone. It has been shown that rotation of particles during a normal consolidation becomes less when the sample is more compacted. Shear displacement experiments showed that particles rotate in a preferred direction. The width of the region in which the preferred rotation takes place is found to be at least 1000 to 2000 particle diameters.