Abstract
The crystal nucleation rate of sodium chloride in ethanol was investigated by measuring the induction time at various supersaturation ratios under silent and ultrasound irradiation at frequencies between 22-500 kHz. Under silent conditions, the data follows the classical nucleation theory showing both the homogeneous and heterogeneous regions, giving an interfacial surface tension of 31.0 mJ/m2. Sonication led to a non-linearity in the data and was fitted by a modified classical nucleation theory to account for the additional free energy being supplemented by sonication. For 98 kHz, this free energy increased from 1.33 x 108 to 1.90 x 108 J/m3 for sonication powers of 2 to 15 W, respectively. It is speculated that the energy is being supplemented by the localized bubble collapse and collisions. Increasing frequency from 22 to 500 kHz revealed a minimum induction time obtained at frequencies between 44 and 98 kHz, which has been attributed to the overall collapse intensity being the strongest at these frequencies.