The distribution of dislocation activities among crystals in sucrose crystallization

Abstract

The growth kinetics of sucrose crystals from aqueous solutions has been studied using a photomicroscopic technique in an isothermal, continuous-flow chamber. The phenomena of size-independent growth and growth rate dispersion (GRD) are observed in the experiments. These results indicate that the constant crystal growth (CCG) model is applicable in the studied crystallization system. The dislocation activity of a crystal is incorporated in a modified two-step model to account for the existence of GRD in the CCG model. The experiments have been conducted to eliminate the resistance to crystal growth due to the volume diffusion by increasing the solution flow rate through the growth chamber. Thus, the crystal growth process becomes surface reaction-controlled and the effects of the sole surface reaction step on the growth kinetics can be investigated. The activation energy of 66.6 kJ/mol is obtained for the surface reaction process in sucrose crystal growth. In addition, it is found that the distribution of the dislocation activities among crystals mainly falls within the range of 50–150% of the average dislocation activity.