Can A Foreign Particle Cause Surface Instability?

The occurrence of foreign bodies on growing surfaces of crystals will serve as precursors for heterogeneous two-dimensional (2D) nucleation so that at relatively low supersaturations, it will promote rapid growth at the regions where the foreign particles are in contact with the crystal surface. This leads to so-called particle-induced surface instability. At high supersaturations, due to the limitation of effective transport, heterogeneous 2D nucleation will become kinetically unfavorable. Foreign particles have no effect on crystal growth. A heterogeneous 2D nucleation model is put forward to analyze this special type of surface instability. To check the model, we examined a naphthalene crystal-melt system experimentally. A novel phenomenon of a needlelike pattern of surface instability caused by solid-particle-induced growth was observed. This particle-induced surface instability occurs in a completely different regime of G/R from the dendritic-like surface instability. The theoretical predictions are confronted with the measured kinetic relations of the both normal and induced growth. The results turn out to be in excellent agreement with the predictions. I