Directional solidification important parameters

In some cases, it may be possible to isolate the active ingredients as a melt, so providing options to carry out the finishing process directly from the melt, if necessary in combination with other substances. Important parameters for the selection of a suitable process are the properties of the melt, including melt viscosity and solidification behavior. 

While this may appear even more cumbersome than Eq. (3.41), it contains some parameters that are directly measurable such as the interfacial surface energy, y, and the heat of fusion, AH, but more importantly, it contains the temperature difference (T, — T), which is the degree of undercooling—that is, how far the temperature is below the melting (solidification) point ... 

The oil-water interface is one of the most important systems. The liqnid-liquid interface constitutes a phase separation where two different molecules meet. We can directly measure the magnitude of the surface tension, with rather high precision. It wonld thns seem that much useful information can be obtained if we could measure a dynamic parameter of the interface, such as the freezing phenomenon. It is widely known that liqnids can be cooled below their freezing temperature without solidification (snpercooled fluid) and that they can be heated above their boiling temperature without vaporization (snperheated liquid). 

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