Migration Of Liquid Inclusions Research Articles

Fractional crystallization on cooled walls: Separation efficiency with a growing crystal layer, its diffusion washing, and partial melting

The redistribution of components in the crystal layer-melt system at the main stages of fractional crystallization on cooled walls is studied. Mathematical solutions that can be used for calculating the fraction of trapped melt and the value of effective distribution (partition) coefficient in the crystallization of systems of different types are obtained. The kinetics of diffusion of impurities and migration of liquid inclusions under the action of temperature gradients at the growth and diffusion-washing stages of a two-phase crystal layer is studied. Simple relations for calculating the holdup of a melt and the maximal degree to which the main component can be purified in the partial melting (sweating) of crystal layers are derived. The theoretical results are compared with the experimental data obtained in the fractional crystallization of organic mixtures and freezing of aqueous solutions. Comparative analysis of the efficiency of the studied stages of fractional crystallization is accomplished and some practical recommendations are formulated.

Migration of liquid inclusions in a solid under asymmetric temperature oscillations

The existence of a new type of thermal migration has been found—the migration of the layer of a liquid phase between two substrates possessing different properties (e.g., two different cuts of a crystal) occurring under the action of asymmetric temperature oscillations. The effect can arise if three following conditions are simultaneously fulfilled: (1) the kinetic properties of the solid-liquid interfaces should be different, (2) the dependence of the growth (dissolution) kinetics on supersaturation should be nonlinear at least at one of the interfaces, and (3) the temperature oscillations should be asymmetric. It is shown that both sign and absolute value of the migration velocity depend on the shape of temperature oscillations. The velocities of migration for liquid layers of various thicknesses as functions of the amplitude of thermal oscillations, their shape, and frequency are calculated for the model Si-Al system.

The entrapment and migration of liquid inclusions during growth of FeGe 2 single crystals from the melt

Abstract The processes at the interface leading to the periodic entrapment of flat liquid inclusions are described. The impurity-rich inclusions are migrating towards the interface as liquid zones in temperature gradient zone melting. The parameters of the macrostep structure and the velocity of the inclusions are evaluated. The experiment have shown that different dopants (cobalt, tin) and the variation of the growth rate influence considerably the pecularities of the crystal microstructure.

On the influence of dislocations on the thermal migration of liquid inclusions

On the influence of dislocations on the thermal migration of liquid inclusions

On the influence of dislocations on the thermal migration of liquid inclusions

On the influence of dislocations on the thermal migration of liquid inclusions

Migration of brine cavities in rock salt

Small quantities of brine trapped in ‘negative crystals’ (cavities) exist in most rock salt (halite) and have been found to migrate toward a heat source. The theory of Hoekstra and others on the migration of liquid inclusions in ice crystals was modified for predicting the migration rates of brine cavities in salt. The driving force for the migration is the difference in solubility between the warm and colder sides of the brine cavity. The theoretical model indicates that the migration rate is a function of temperature and is directly proportional to the temperature gradient. Calculated cavity migration rates for a 1°C/cm gradient ranged from about 0 at 20°C to 7.7 cm/yr at 300°C. The theoretical predictions were found to be in reasonable agreement with migration rates measured in the laboratory, although there was considerable spread in the experimental data. Specimens consisted of relatively pure salt crystals from the Hutchinson, Kansas, mine, about 2½ cm on a side, containing brine cavities between 2 and 10 mm in maximum dimension. Thirty-one rate measurements (on twelve separate cavities) were obtained, covering the temperature range of 75°–244°C, with gradients ranging from 4 to 34°C/cm. Migration periods varied from about 20 to 358 hours, and the observed distances of migration ranged from 0.8 to 8 mm. The theoretical predictions also tended to confirm the approximate (but difficult to measure) rates of brine migration into a number of heated holes (salt wall temperatures up to 200°C) located in the Kansas mine.

Comment on paper by P. Hoekstra, T. E. Osterkamp, and W. F. Weeks, ‘The migration of liquid inclusions in single ice crystals’

Comment on paper by P. Hoekstra, T. E. Osterkamp, and W. F. Weeks, ‘The migration of liquid inclusions in single ice crystals’

The migration of liquid inclusions in single ice crystals

Abstract : The migration of brine pockets of KCl and NaCl under the influence of a temperature gradient was investigated in single ice crystals. The observed migration velocities are compared with velocities calculated from a simple diffusion model using the data on electrolytic solutions available in the literature. Although the relative movements of KCl and NaCl pockets were consistent with the diffusion theory, the observed velocities were always less than the calculated. Neither the direction of the gravitational field nor the crystallographic orientation of the host crystal significantly influenced the rate of migration. It was also shown that the migration of solid KCl particles occurs at temperatures below the eutectic point. Two mechanisms are proposed that would impede the mechanical differentiation of salts that crystallize at high temperatures relative to salts that remain in the brine of sea ice. These mechanisms explain recent field observations that the SO4/Cl ratio of sea ice does not increase with the age of the ice. (Author)