Induced melts

Melting, a major physical event, has small, subtle effects on shock-compression wave profiles. The relatively small volume changes and limited mixed-phase regions result in modest, localized changes in loading wave speed. Consequently, shock-induced melting and freezing remains an area with little data and virtually no information on the influence of solid properties and defects on its kinetics. 

We can think of the strain as inducing melting. At the melting temperature TM we would expect the volume fraction of each phase to be equal to 0.5. We could argue that this happens where the storage and loss moduli are equal. Given these assumptions we can calculate the amount of solid and liquid-like material present as a function of strain. The apparent volume fraction of liquid is shown for a polyvinylidene fluoride latex in Figure 6.17. 

Some soHd compounds exhibit a significant melting point depression with CO2 pressure (induced melting) [125]. For example, the melting point of the complex 5b changes from 383 K (0.1 MPa) to 301 K (6.5 MPa). This phenomenon was taken into account by the development of a saturation cell for Hquids and solids that Hquefy. 

These measures of solute segregation are closely related to the spatial and temporal patterns of the flow in the melt. Most of the theories that will be discussed are appropriate for laminar convection of varying strength and spatial structure. Intense laminar convection is rarely seen in the low-Prandtl-number melts typical of semiconductor materials. Instead, nonlinear flow transitions usually lead to time-periodic and chaotic fluctuations in the velocity and temperature fields and induce melting and accelerated crystal growth on the typically short time scale (order of 1 s) of the fluctuations. 

Fig. 5.3 Schematic representation of drag-induced melt removal and pressure-induced melt removal mechanisms.

Removal of the melt, also discussed in Section 5.1, is made possible, in principle, by two mechanisms drag-induced flow and pressure-induced flow (Fig. 5.4). In both cases, the molten layer must be sheared, leading to viscous dissipation. The latter provides an additional, important source of thermal energy for melting, the rate of which can be controlled externally either by the velocity of the moving boundary in drag-induced melt removal or the external force applied to squeeze the solid onto the hot surface, in pressure-induced melt removal. 

Let us imagine a scenario where a chiral product of a given handedness has been formed by an absolute asymmetric synthesis. Episodic changes in temperature would induce melting of the system that comprises the chiral reactant product. Supplying additional substrate material and then reducing the temperature should result in additional crystallization of the reactant, but this... 

Rubin A. E., Ulff-M0ller F., Wasson J. T., and Carlson W. D. (2001) The Portales Valley meteorite breccia evidence for impact-induced melting and metamorphism of an ordinary chondrite. Geochim. Cosmochim. Acta 65, 323-342. 

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