What do ultrasound velocity and attenuation tell us about crystal nucleation

Akulichev and Bulanov showed that a coupling between ultrasound and crystals in equilibrium with their melt would occur leading to high attenuation. This phenomenon is well established. However, what happens in circumstances such as in the induction period where critical fluctuations occur and crystal embryos appear and disappear, i.e. under non-equilibrium circumstances? Evidence is presented that the mean solution adiabatic compressibility is altered by these transient phenomena, providing a unique insight into a poorly understood and industrially crucial process step. Fluctuations in adiabatic compressibility observed as a result of the high measurement rates available with high frequency pulsed ultrasound provide further insight into the early stages of crystal growth phenomena. Later on, when individual crystals begin to interact and sinter a frame modulus emerges which necessitates a semi-phenomenological interpretation.