Sonocrystallization
HIU-induced crystallization was carried out using an ultrasound
generator (model Q125; QSonica, LLC, Newtown, CT., U.S.A.) at 20 kHz and
125 W and a 1/8′′ ultrasound probe (model CL-18). Liquid MKF (5 mL) was
put into a 15 mL centrifuge tube and placed in a water bath set at 70 °C
for 10 min to completely melt the sample. Then it was poured into a
specially designed glass cell (Ueno et al., 2003) jacketed by
circulating water and connected to a thermostat. The temperature of the
sample inside the glass cell was maintained at 25 ± 0.5 °C by water
circulation. When the sample temperature reached 25 °C, the timing was
started and HIU was applied for 5 s and the sample was allowed to
crystallize for 60 min. During that period, the crystallization of the
sample was followed using different techniques. The HIU amplitude was
varied from 30% to 50% and 70% of the maximum value (180 µm). During
sonication the sample temperature increased to approximately 25.7, 29.2
and 32.8 °C for the HIU amplitudes of 30, 50 and 70%, respectively,
before decreasing to 25 °C.