Some Factors of Effective Distribution Coefficient in Zone Melting

Abstract

The effective distribution coeMcient in zone melting operation depends on such factors as zone travel rate, stirring of the melt-zone and entrapping of melted liquid in grown-up crystals. Part of melted liquid is occluded, when dentrites project from the solid-liquid interface. This occulusion decreases the separation effect in zone melting.
In this work the ratio of occlusion was estimated in order to find a relation between the effective distribution coeMcient and the factors mentioned above.
Samples used were naphthalene containing about 3 wt f5e of B-naphthol (k1) and phenol containing m cresol (1k). A glass tube of 18 mm 1. D. and 240 mm in packed length was used as a container. The melt-zone was stirred by a device equipped with an electromagnet and a rotor The zone travel rate(V)was fixed at 20, 40, 60, 80 and 100mm/hr, and the stirring rate was varried in a range of ON200 rpm at each zone travel rate.
The concentration profiles after single zone pass shewed effeetiveness of stirring (Figs. 1, 2 and 3). The effective distribution coeMeient (k) was expressed by the following equation

where p is the ratio of occlusion, r is the stirring rate and a is a constant. The effectivedistribution coeMcients estimated by the equation above were in good agreement with the experimental results (Tables 1 and 2).