EXPANSION AND CRYSTALLIZATION OF A SEDIMENT OF CHARGED COLLOIDAL SPHERES

An amorphous sediment of charged colloidal particles in a nonaqueous s olvent was prepared by centrifugation. The evolution of sediment heigh t and volume fraction profile to equilibrium were studied with light s cattering. A simple sedimentation-diffusion equation allows the experi mental data to be modeled quantitatively. The top of the sediment crys tallizes within a week, whereas the lower part of the sediment does no t show any sign of crystallization after several months, indicating a strong concentration dependence of crystallization rate.