Investigating microstructure of concentrated suspensions of anisotropic particles under shear by small angle neutron scattering

The microstructure of dense suspensions of anisotropic particles that are ordered at rest is explored under shear as a function of particle anisotropy and shear rate using small angle neutron scattering. For suspensions containing spheres and mildly anisotropic heteronuclear dicolloids, after preshearing, long-range order is present in the form of randomly stacked hexagonally close packed layers. As the shear rate is increased, long-range directional order is lost. At even higher shear rates, long-range order is re-established in the form of hexagonally packed layers sliding over one another. Suspensions of ordered homonuclear dicolloids are polycrystalline at rest, and as the shear rate is increased, sliding hexagonally packed layers develop while at larger shear rates long-range order is lost. These results demonstrate surprisingly large effects of shear on the microstructures of suspensions containing particles with small changes in anisotropy. (c) 2007 The Society of Rheology.