Expansion and crystallization of a sediment of charged colloidal spheres

Abstract
An amorphous sediment of charged colloidal particles in a nonaqueous solvent was prepared by centrifugation. The evolution of sediment height and volume fraction profile to equilibrium were studied with light scattering. A simple sedimentation–diffusion equation allows the experimental data to be modeled quantitatively. The top of the sediment crystallizes within a week, whereas the lower part of the sediment does not show any sign of crystallization after several months, indicating a strong concentration dependence of crystallization rate.