Влияние кинетики роста новой фазы и давления на распределение компонентов при фазовых переходах

The relationship between the kinetics of the addition of solution particles to a new phase, the change in the amount of motion of the component at the interface, and the diffusion of the components in the phases is shown. This interaction significantly affects the distribution of the concentration of components in the phases. The proposed theory explains the dependence of the effective distribution coefficient on the concentration in the zone cleaning of solutions.

The Dependence of Effective Distribution Coefficient on Growth Rate and Mass Transfer Coefficient for P-Xylene in Solid-Layer Melt Crystallization

The solid-layer growth kinetics and resulting crystal purity for a well-mixed p-xylene (PX) melt with impurity of o-xylene (OX) or ethylbenzene (EB) were studied in this work at various cooling temperatures. A correlation based on the energy balance was adopted to describe the dependence of growth rate on the temperature gradient between melt and cooling medium. An empirical equation based on the mass balance was proposed to relate the effective distribution coefficient with growth rate, mass transfer coefficient, and impurity mole fraction. By fitting the proposed empirical equation with the experimental effective distribution coefficients, the mass transfer coefficients for the PX/OX and PX/EB mixtures were retrieved respectively.

DETERMINATION OF EFFECTIVE DISTRIBUTION COEFFICIENT OF IMPURITIES DURING ZONE REFINING OF TELLURIUM

Knowledge of distribution coefficient values is essential in estimating the refining efficiency, and plays an important role during the purification process, typically zone refining. The effective distribution coefficient "K eff " of impurities Se , Fe , Cr and Pb in tellurium was determined in the present study and found to be 0.48, 0.05, 0.25 and 0.19, respectively. The results are validated by comparing with the available published data, and we observed a difference of less than one order, which was reasonably comparable. The influence of "K eff " on zone refining efficiency was examined and it was noticed that the effective distribution coefficient increases with respect to the translation rate, which is minimum at an optimum lower translation rate (= 30 mm/h ). The relative solute concentration C/C0 is determined experimentally, which shows the best fit of experimental values with Pfann's equation. The impurity profile along the length of the zone refined ingot is also discussed.

Czochralski growth of Yb3+ and Pr3+ doped Ca-fluoroapatite

Pure, Pr3+, and Yb3+ doped Ca-fluoroapatite (Ca-FAP) crystals were grown by the Czochralski method. The effective distribution coefficient keff for Yb3+ was 0.5. For Pr3+ a very high keff of 1.4 was obtained. Values for keff are discussed in terms of an elastic model accounting for the strain energy originating from the difference in the size of Ln3+ ions. The Ln3+ concentrations were measured by absorbance spectroscopy, by inductively coupled plasma optical emission spectroscopy, and by electron microprobe analyses.

Surface Morphology and Lattice Misfit in Yig and La: Yig Films Grown by Lpe Method on GGG Substrate

ABSTRACTY3Fe5O12(YIG) and La-doped YIG films were grown on the {111} GGG substrate using the PbO-B2O3 flux system. Pb, La incorporation and lattice misfit and annealing behaviors were studied. In the case of LPE growth of YIG film, lead ions from flux are substituted inevitably, and they play an important role in controlling film misfit. For a complete lattice matching, high supercooling is necessary in pure YIG growth, but this induces high defect concentration. In this experiment, La ions were added in the solution to sufficiently increase lattice parameter of the film grown under low supercooling. The concentration of substituted Pb and La were increased as the growth temperature was lowered and growth rate increased. The effective distribution coefficient of La was about 0.2 at a supercooling of 30 °C. The optimum growth conditions which bring about very small misfit were determined by measuring the misfit by double crystal diffractometer. Strain distributions of pre-annealed and annealed samples were investigated by triple crystal diffractometer.