Melting recrystallization process

An example of the use of a ternary eutectic diagram for the assessment of a melt recrystallization process (for nitrotoluene isomers) is given in section 8.2.1. 

The relatively large crystallite thicknesses that were deliberately developed for these dilatometric experiments (12) assured that melting-recrystallization processes did not complicate this particular study of the fusion process. Consequently, none of the well-known effects of melt-recrystallization reported previously... 

Thus, the present work resrrlts have shown that the fractal dimension of space, in which rranocomposites stractrrre is formed, is defined by their crystalline polymer phase morphology and does not depend on crystallinity degree. The indicated dimension defines rmeqrrivocally partial melting-recrystallization process at nanocomposites deformation and irrfluences strongly on their mechanical characteristics. 

Irreversible transformations, from more disordered toward more ordered modifications of a given form have been, for instance, observed for the a form of i-PP [39,40,43,44] (see Sect. 2.4), as well as for the most common form of i-PS [74], In these cases the transitions occur by recrystallization processes in the respective melting regions. 

Exothermic events, such as crystallization processes (or recrystallization processes) are characterized by their enthalpies of crystallization (AHc). This is depicted as the integrated area bounded by the interpolated baseline and the intersections with the curve. The onset is calculated as the intersection between the baseline and a tangent line drawn on the front slope of the curve. Endothermic events, such as the melting transition in Fig. 4.9, are characterized by their enthalpies of fusion (AHj), and are integrated in a similar manner as an exothermic event. The result is expressed as an enthalpy value (AH) with units of J/g and is the physical expression of the crystal lattice energy needed to break down the unit cell forming the crystal. 

Siekmann B. and Westesen K., Thermoanalysis of the recrystallization process of melt-homogenized glyceride nanoparticles, Colloids Surf. B, 3, 159, 1994. 

The chemical shift lineshape changes observed for the crystalline fraction of melt-recrystallized PTFE from /L14°C to w28°C (Figure 6) are due to reorientation about an axis essentially parallel to Ozz (which is tilted VL2° from the molecular chain axis). The temperature dependence of the line-shape changes can be simulated as an increase in the rate of rotational diffusion about this axis (Figure 6) and this process has an activation energy of 48+11 kcal/mole. In addition, the... 

Cables via the powder-in-tube (PIT) method The approach is especially suited to processing Bi-2223 into leads and cables for power applications. A silver or silver alloy tube, filled with the partially reacted precursor powders formulated to yield Bi-2223, is drawn down to a wire 1-2mm diameter. The wire is rolled into a tape if that is the required form, usually with a width-to-thickness ratio of approximately 10 1. The composite is then heated to 800-900 °C when the powder partially melts. The recrystallization process is controlled and the pure Bi-2223 phase develops with large grains oriented so that the Cu-O planes lie parallel to the silver surface to optimize Jc. 

When the mixture has cooled to room temperature, add in 65 milliliters (2.2 fluid oz.) of more water (cold water this time), and then stir the entire mixture for about 30 minutes at room temperature, and then allow the entire mixture to stand (no stirring) for several hours at room temperature. Afterwards, filter-off the precipitated solid, and then vacuum dry or air-dry it. Finally, reciystalhze this dry solid from 100 milliliters (3.4 fluid oz.) of acetone, and after the recrystallization process, vacuum dry or air-dry the filtered-off crystals. The result will be about 3 grams (0.1 oz.) of the desired piperine compound with a melting point of 128 Celsius. 

Additionally, the process from which the material was generated may also play an important role in the melt onset. The recrystallization processes, including the solvent and mechanical systems utilized to manufacture the material, may greatly affect the crystallinity of the material. This would directly influence the amorphous content in the presumably high crystalline material through the production of an impurity, which would lower the melt onset of the material (39). Although there has been recent interest (40) in investigating these phenomena, their impact on the characterization of materials is not yet fully understood. 

---