The effects of ultrasound on crystals: Sonocrystallization and sonofragmentation

Abstract

When ultrasound is applied to a solution for crystallization, it can affect the properties of the crystalline products significantly. Ultrasonic irradiation decreases the induction time and metastable zone and increases the nucleation rate. Due to these effects, it generally yields smaller crystals with a narrower size distribution when compared with conventional crystallizations. Also, ultrasonic irradiation can cause fragmentation of existing crystals which is caused by crystal collisions or sonofragmentation. The effect of various experimental parameters and empirical products of sonocrystallization have been reported, but the mechanisms of sonocrystallization and sonofragmentation have not been confirmed clearly. In this review, we build upon previous studies and highlight the effects of ultrasound on the crystallization of organic molecules. In addition, recent work on sonofragmentation of molecular and ionic crystals is discussed.