Crystal growth kinetics in binary mixtures of model charged sphere colloids

From the formation of crystalline materials from their melts is at the heat of many important industrial processes. A rigorous and comprehensive understanding of the crystallization process, however, is still lacking, and its experimental and theoretical investigation has remained a considerable challenge. We studied the crystal growth velocities v of random composition body centred cubic (rc-bcc) colloidal crystals formed from a shear molten binary mixture of charged colloidal spheres suspended in deionized water. We used Bragg microscopy at constant particle number density n and as a function of the number fraction of large particles p. With increasing p the growth velocity v first drops steeply, then more slowly to yield an overall trapezoidal composition dependence. This dependence is not expected from the Wilson-Frenkel growth law for reaction limited growth which on the other hand correctly describes the number density dependence. The deviation possibly indicates a change in the kinetic prefactor.