Growth rate of crystal

Growth rates of crystals under satisfactory conditions are in the range of 0.1-... 

High-pressure freezing Specimens are subjected to a pressure of 2100 bar, which depresses the melting point of water, reduces the formation of ice nuclei, and retards the growth rate of crystals... 

Here the so called ideal growth rate of the crystal layer is a calculated one. It is calculated from the linear dependence between the cooling rate of the surface and the resulting growth rate. The measured growth rate of crystal layer v includes all pos-... 

The growth rates of crystals with partially broken surfaces or with fines adhered to it were larger in both directions than those of smooth surface. Further, the optical purities of crystals with broken surfaces and with fines adhered on the surfaces were lower than those with smooth surfaces. From these results, the kinetics of growth of D-SCMC crystals and the mechanism of inclusion of impurity during their growth process was considered. 

Curie s concept [7], which considered that the normal growth rates of crystal faces are proportional to the surface free energies and... 

It should be noted that there may be other possible factors affecting the normal growth rate of crystal faces. 

Figure 10.4. Growth rates of crystal faces in synthetic quartz [l]-[3] = normal growth rate of crystal faces = growth rate in weight A = reference data.

The growth rates of crystals depend on their instantaneous surface and the linear velocity of solution past the surface as well as the extent of supersaturation, and are thus represented by the... 

Growth rates of crystals also must be measured in the laboratory or pilot plant, although the suitable condition may be expressed simply as a residence time. Table 16.3 gives a few growth rate data at several temperatures and several extents of supersaturation for each substance. In most instances the recommended supersaturation measured as the ratio of operating to saturation concentrations is less than 1.1. It may be noted that at a typical rate of increase of diameter of 10 7 m/sec, the units used in this table, the time required for an increase of 1 mm is 2.8 hr. 

TABLE 16.3. Mean Overall Growth Rates of Crystals (m/sec) at Each Face8... 

Growth Rate of Crystals with Preferred Thicknesses. 50... 

Cimmino et al. [25] reported that the radial growth rates of crystallization G, measured in sPS/PPE blends, decrease strongly with increase in PPE content (Figure 20.3). This effect might arise from an increase in the transport free energy of crystalline segments in the melt, due the larger Tg of the blend compared with pure sPS, or to a decreased capability of sPS to nucleate, induced by its dilution in PPE. 

Adapted from Reference 22. n, index of Avrami s equation z, rate constant in Avrami s equation C, linear growth rate of crystal sperulite I, sporadic nucleation rate in time d, width of crystal fibril r, crystal radii. 

In an anti-solvent recrystallization process, then, particle size and particle size distribution is determined by the interaction between the nucleation rate and the growth rate of crystals, on one hand, and by the rate of creation of supersaturation, on the other hand all three are influenced by the manner of addition of the anti-solvent. Figure 5 is a qualitative picture of simultaneous events that occur when an anti-solvent is added to a solution of a solute that is to be recrystallized. The three zones shown in Figure 5, designated I, II, and III, denote three areas of supersaturation. Zone I is for a supersaturation less than 1, i.e., for actual solute concentrations less than saturation. No growth of particles will occur in this zone (and in fact if there are any particles that are "somehow" present, they will dissolve). In Zone II, the supersaturation is less than the critical value discussed earlier, but "some" nucleation can occur particles that are present in this... 

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