Nucleation simultaneous with growth

The growth step in a phase transformation begins once an embryo has exceeded the critical size, r, and becomes a stable nnclens. Note that nucleation will continne to occur simultaneously with growth of the new-phase particles of course, nucleation cannot occur in regions that have already transformed into the new phase. Furthermore, the growth process will cease in any region where particles of the new phase meet because here the transformation will have reached completion. 

Both the evolution of the atomic fractions in the solution and of the chemical shift of all species (Fig. 9(b)-(e)) allow four steps in the formation of A1P04—CJ2 induction, dissolution, nucleation and crystal growth. During the induction period, a constant amount of A1 atoms in the solution is observed during the set up of the pH synthesis. The dissolution step, which is quasi simultaneous with the induction period, is characterized by an increase of the amount of A1 species in the solution (Fig. 9(b)-(c)). During this period, the different NMR results show the development of the right solution composition for the formation of soluble reactive species, the development of supersaturation conditions (with an increase of the soluble species concentration) and the formation of the solution species involved in the crystallization. 

Iron oxide samples often display a wide range of particle sizes indicating that nucleation and erystal growth took place simultaneously over the bulk of the reaetion. In recent years, attention has been foeussed on the production of oxides with different shapes and also with a narrow range of particle sizes, so-ealled monodispersed products (see Fig. 10-6). This... 

At very low crystallization temperatures (Fc < 75°C), the growth of iPB crystals in the blends proceeds simultaneously with the crystallization of iPP. The presence of iPB crystals may induce additional nucleation of iPP at the interface between the two polymers thus, two populations of spherulites can appear in the blends small iPB spherulites nucleated inside the iPB-rich phase and iPP spherulites nucleated at the interfaces. As a consequence of the above phenomena, the size of iPP spherulites in blends decreases at large undercooling, while it increases at low undercoolings, as compared with plain iPP crystallized at the same Fc [60]. 

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