Other Factors Affecting Crystallization

Other factors that affect crystallization processes include pressure and stress. Increasing the static pressure has the effect of raising Tm as shown by the Clapeyron equation  

Stress, on the other hand, where deformation is involved, has a considerable effect on crystallization kinetics and morphology. Polymer molecules become oriented during deformation. If the temperature is reduced enough before the molecules relax, then they may crystallize in this oriented state. For polymer melts it is not so easy to create stress-induced crystallization. However, if the product of the relaxation time, k, and the time, t, for the melt temperature to drop to Tx is approximately equal to 1.0, then we can expect the crystallization of oriented molecules. 

FIGURE 5.23 Physical properties of PET yams wound at various speeds. (Data are from Huisman and Henvel, 1978.) 

FIGURE 5.24 Physical properties of PET as a function of the drawing ratio. (Adapted from Van der Meer, 1971.) 

One way to incorporate the effect of stress on crystallization is described here (Katayama and Yoon, 1985). One starts with the generalized Avrami equation  

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Other factors affecting the choice of a crystal are its reflecting power and resolving power. These properties are discussed later. 

In addition to the periodicity of the crystal lattice, there are other factors affecting the diffraction quality of the crystal, i.e. the type of the ordered atoms have a significant influence on the diffraction power of the crystal. The heavier (more electrons)... 

From the data presented in this Table, it appears that in contrast to binary blends without a compatibilizer, the crystallization of the minor component in compatibilized blends cannot be solely explained by the size of the dispersion [Ikkala et al., 1993 Flaris et al., 1993 Tang and Huang, 1994a Holsti-Miettinen et al, 1995]. Other factors affecting the crystallization are the type of compatibilizer and its degree of miscibility with one or both of the blend components, the amount of compatibilizer added, the amount of interface created, and other effects. 

Lees, R. (1965). Factors Affecting Crystallization in Boiled Sweets, Fondants and Other Confectionery, Brit. Food Manuf. Ind. Res. Assoc., Scientific and Technical Survey No. 42, Leatherhead. 

Salting out by the addition of substances that may contain a common ion with the crystallized substance, thereby reducing its solubility, or by changing other factors affecting the ability of the solvent to solvate the material... 

The Equilibrium Thermodynamic Functions, 275 Other Factors Affecting the Meiting Process of Polymer Crystals, 277... 

OTHER FACTORS AFFECTING THE MELTING PROCESS OF POLYMER CRYSTALS... 

The nature of the deposit and the rate of nucleation at the very beginning of the deposition are affected, among other factors, by the nature of the substrate. A specific case is that of epitaxy where the structure of the substrate essentially controls the structure of the deposit.Plb lP ] Epitaxy can be defined as the growth of a crystalline film on a crystalline substrate, with the substrate acting as a seed crystal. When both substrate and deposit are of the same material (for instance silicon on silicon) or when their crystalline structures (lattice parameters) are identical or close, the phenomena is known as homoepitaxy. When the lattice parameters are different, it is heteroepitaxy. Epitaxial growth cannot occur if these stmctural differences are too great. 

Except for the factors mentioned above, such as the reactant ratio employed, variation of lanthanide and transition metal, crystallization conditions, and the presence of a secondary ligand, there are several other factors that can affect the controllable assembly of the lanthanide-transition metal-amino acid cluster compounds. 

We have also seen (Sec. VI,A) that the position of the Fermi level on the surface of the crystal ,+ is determined, other conditions being equal, by its position inside the crystal e +. An increase of e + entails an increase of ,+, and a decrease of a decrease of e.+. We are thus led to the conclusion that the factors which shift the Fermi level in the bulk of the crystal, i.e., which affect the electrical conductivity, will also shift the Fermi level on the surface (in the same direction) i.e., they will affect the catalytic activity. Furthermore we come to the conclusion that the factors directly displacing the Fermi level on the surface without affecting its position in the bulk (i.e., the factors affecting the degree of bending of the bands) will also affect both the electrical conductivity and the catalytic activity simultaneously. 

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

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