Изследвания върху зараждането и растежа на кристалите
Studies on the nucleation and growth of crystals

Summary/Abstract: Crystallization is occurring frequently in nature (and already in the antiquity has been used for production of cooking salt). As science and technology developed the crystallization to the current status, it has become one of the basic processes in a number of large-scale industries. This mini review describes some novel achievements in the research on the nucleation and growth of crystals. The thermodynamics and kinetics of these processes are considered, with a special focus on the Bulgarian contribution to the science of the crystallization. The relation between the sizes of the critical nucleus and the stable nucleus (which dissolution probability is zero) is calculated. Considered is the logistic functional dependence of the nucleation kinetics and its consequences for the crystal size distribution (CSD) of the grown crystals. Calculation of the crystal nuclei number per unit volume as a function of both nucleation time and supersaturation is enabled by recently devised formula. It has been shown that the polydispersity of the crystals occurs already at the stage of their nucleation (and the initial enlargement of the nucleated crystals) and is amplified during their subsequent growth to macroscopic dimensions. Pointed are two (gravity instigated) effects which amplify crystal polydispersity during the crystal growth in unstirred solutions. Special attention is paid to the growth of crystals in solutions with a preset concentration. In doing so, it is shown that the average size of the crystals reached at any time is reversely-proportional to the root third of the number of crystals in a unit volume. The review ends with practical instructions for achieving the desired characteristics of the crystallizing product.

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