A Couette–Taylor (CT) crystallizer was used to demonstrate the unique fluid dynamic properties of a Taylor vortex for the phase transformation of sulfamerazine (SMZ). With a conventional Rushton mixing tank (MT) crystallizer, the phase transformation from a metastable crystalline phase to the stable crystalline phase took more than 60 h with acetonitrile (ACN) as the solvent and an agitation rate of 3000 rpm. Using a CT crystallizer, this phase transformation occurred within 3–7 h with rotation speeds in the CT crystallizer of 300–1000 rpm. Increasing the rotation speed of the CT crystallizer also significantly enhanced the phase transformation, whereas adding water to the solvent increased the solubility difference between the two polymorphs and accelerated the phase transformation in both crystallizers. The phase transformation in the CT crystallizer was always many times faster than that in the MT crystallizer. Nucleation and mass-transfer models were used to describe the nucleation induction time of the stable crystal form and the transformation of metastable crystals into stable crystals. The influence of the fluid motions of the periodic Taylor vortex and random eddy in the CT and MT crystallizer, respectively, on the induction time was correlated by the nucleation enhancement factor, which was expressed as function of energy dissipation. The resulting induction and transformation times correlated well with the experimental data in terms of the energy dissipation and solubility difference across the whole range of phase transformation conditions, including rotation speeds, water fractions, and temperatures.

We have investigated by imaging ellipsometry (IE) the crystallization of amorphous silicon (a-Si) at low temperature by Ni-silicide-mediated crystallization on a glass substrate. We observed a significant difference in the ellipsometric image between polycrystalline silicon (poly-Si) and a-Si and confirmed that annealing for longer time leads to increasing area of poly-Si domain. The progress of crystallization is modeled as the growth of a disk in a two-dimensional surface since the crystallized region expanded as a disk shape. The rate of increasing radius of the disk and the average distance between initial nucleus points were obtained by fitting the change of the area of the disk measured by the IE with annealing time.

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