Effect of supersaturation

Fig. 8. Morphological effects of supersaturations and temperature on vapor deposited materials (12).

Supersaturation has been observed to affect contact nucleation, but the mechanism by which this occurs is not clear. There are data (19) that infer a direct relationship between contact nucleation and crystal growth. This relationship has been explained by showing that the effect of supersaturation on contact nucleation must consider the reduction in interfacial supersaturation due to the resistance to diffusion or convective mass transfer (20). 

Parsiegla K, Katz J (1999) Calcite growth inhibition by copper (II) Effect of supersaturation. J Cryst Growth 200(l-2) 213-226... 

Figure 15.9. Effect of supersaturation on the rates of homogeneous and heterogeneous nucleation.

Effects of Supersaturation Degree on Period and Amplitude. The relation between the period of the oscillation curve and the supersaturation degree is shown in Figure 2. An increase in supersaturation degree brought about a considerable reduction in period. If a more supersaturated solution is used (there should be an operation restriction on the crystal growth), the period will be... 

Fig. 5.2.7 Effects of supersaturation quenching on the uniformity and mean size of the final products in the B-5 system. Samples B-5, B-5[ 1 ], B-5[2], and B-5[3] are those unquenched and quenched with a fixed amount of nitric acid after 80,100, and 120 min of aging, respectively. The added amount of nitric acid was 6 cm3 of 6.4 mol dm-3 HNOj to 24 cm3 of each sample B-5. (From Ref. 1.)...

Wang Q, Hikima T, Tojo K. Skin penetration enhancement by the synergistic effect of supersaturated dissolution and chemical enhancers. J Chem Eng Japan 2003 36 92-97. 

J.A.H. van Laarhoven, M.A.B. Kruft, and H. Vromans, Effect of supersaturation and crystallization phenomena on the release properties of a controlled release device based on eva copolymer, J. Controlled Release, 82(2-3) 309-317, August 2002. 

Jelen, P. and Coulter, S. T. 1973A. Effects of supersaturation and temperature on the growth of lactose crystals. J. Dairy Sci. 1182-1185. 

Figure 16.5. Supersaturation behavior, (a) Schematic plot of the Gibbs energy of a solid solute and solvent mixture at a fixed temperature. The true equilibrium compositions are given by points b and e, the limits of metastability by the inflection points c and d. For a salt-water system, point d virtually coincides with the 100% salt point e, with water contents of the order of 10-6 mol fraction with common salts, (b) Effects of supersaturation and temperature on the linear growth rate of sucrose crystals [data of Smythe (1967) analyzed by Ohara and Reid, 1973],...

Another theory that could account for the effect of supersaturation on contact nucleation is based on the view that nuclei formed cover a range of sizes that includes the critical nucleus. Since only the nuclei larger than the critical nucleus are stable, the relationship of the size of the critical nucleus to supersaturation reflects the dependence of contact nucleation on supersaturation. This concept, which has been referred to as a survival theory, seems to have been refuted by measurements of the sizes of crystals formed by collisions. These sizes are much larger than the critical nucleus, and the survival theory would have little influence on the number of nuclei that survive. 

Fig. 16 (a) Effect of supersaturation-temperature-structure relationship on the vapor deposited coatings, (b) the effect of free carbon on the morphology of the TiC deposition for a gas mixture of TiCI, CH and H, (1) cross-section of the TiC coating on WC-Co, and (2) surface morphology of the TiC whiskers. 

More commonly, the two metals A and B are only partially soluble in the solid state. The first additions of B to A go into solid solution in the A lattice, which may expand or contract as a result, depending on the relative sizes of the A and B atoms and the type of solid solution formed (substitutional or interstitial). Ultimately the solubility limit of B in A is reached, and further additions of B cause the precipitation of a second phase. This second phase may be a B-rich solid solution with the same structure as B, as in the alloy system illustrated by Fig. 12-2(a). Here the solid solutions a and P are called primary solid solutions or terminal solid solutions. Or the second phase which appears may have no connection with the B-rich solid solution, as in the system shown in Fig. 12-2(b). Here the effect of supersaturating a with metal B is to precipitate the phase designated y. This phase is called an intermediate solid solution or intermediate phase. It usually has a crystal structure entirely different from that of either a or P, and it is separated from each of these terminal solid solutions, on the phase diagram, by at least one two-phase region. 

Figure 4-1 Effect of supersaturation on growth rate and particle size.

Figure 4-4 Effect of supersaturation on free energy of cluster formation. 

Figure 4-10 Effect of supersaturation on growth characteristics of MgSO4 7H2O (after Clontz and McCabe (1971)).

Typically, using about 5 gm of monosized seed (usually a sieve fraction), and harvesting after several hours of operation, can produce an accurate and reproducible growth rate measurement. The effects of supersaturation (including the data in Fig. 4-20), impurity level in the mother liquors, and absolute temperature are easily determined. 

Figure 5-1 Effect of supersaturation on nucleation rate, growth rate, and nucleate particle size.

Figure 9.1 Schematic representation of the effect of supersaturation on particie growth.

Crystal Size Distribution. Crystal size was briefly mentioned in Section 14.2.3 Figure 14.7 gives a rough indication of the effects of supersaturation on growth rate, nucleation rate, and crystal size. 

Effect of supersaturation on crystal growth quality and type of nuclcation for MgSO THjO. (Adaptedfrom Ref. 5)... 

This equation, although it rests on incomplete data, gives results of the correct order and does refiect the very strong effect of supersaturation on nucleation. 

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