Small changes in particle-size distribution dramatically delay and enhance nucleation in hard sphere colloidal suspensions

We present hard-sphere crystallization kinetics for three samples with small differences in polydispersity. We show that an increase in polydispersity of 1% is sufficient to cause dramatic changes in the crystallization kinetics: Crystallization is delayed by almost one decade in time and quantitative and qualitative changes in the crystallization scenario are observed. Surprisingly the nucleation rate density is enhanced by almost a factor of 10. We interpret these results in terms of polydispersity limited growth, where local fractionation processes lead to a delayed but faster nucleation.

Figure 1

PSDs of the three fractions used. (a) XL65-A, $\sigma =5.8\%$, skewed; (b) XL65-B, $\sigma =5.3\%$, skewed; (c) XL65-C, $\sigma =4.8\%$, symmetric.

Figure 2

(Color online) Crystallization parameters for $\Phi =0.527$: Filled blue crosses XL65-A; open red circles XL65-B; filled black squares XL65-C. From top to bottom: Crystallinity, crystalline volume fraction, average linear dimension, absolute number of crystals, and nucleation rate densities.

Figure 3

(Color online) Nucleation rate densities of the main nucleation process $\Phi =0.527$: Filled blue crosses XL65-A; open red circles XL65-B; filled black squares XL65-C.

Figure 4

From top to bottom: —Induction time (closed circles) and crossing time (open circles), maximum crystal size (open circles) and final crystal size (closed circles), and average nucleation rate density (closed circles) and maximum nucleation rate density (open circles) as functions of polydispersity $\Phi =0.527$.