DYNAMICS OF CRYSTALLIZATION IN HARD-SPHERE SUSPENSIONS

Density fluctuations are monitored by small-angle light scattering dur ing the crystallization of 0.22-mu m-radius, hard colloidal spheres. M easured structure factors show an intensity maximum at finite-scatteri ng vectors. The shape of the intensity distribution scales at early ti mes during nucleation and growth and again at large times during ripen ing. A1 intermediate times there is a crossover region where scaling c eases to be valid, Both dir amplitude and the position of the maximum intensity show quasi-power law behavior In time. The values of the obs erved exponents are within the range expected for classical growth mod els. The breadth of the intensity distribution increases with increasi ng volume fraction, suggesting greater crystal polydispersity with inc reasing volume fraction. The power volume fraction intensity distribut ions suggest that crystals have a compound or internal structure, whil e the observed decrease in characteristic length in the crossover time regime may indicate breakup of crystals to this smaller internal stru cture. The results of measurements are compared with results calculate d fur nucleation and growth of crystals in suspensions of hard spheres , Results also are compared with earlier measurements made on samples containing 0.50-mu m radius spheres. Differences in the two systems ar e discussed in terms of interparticle potential, polydispersity, and g ravitational effects.