The influence of temperature on the separation rate of Sn-Pb melts in capillaries

Abstract

Objective. When holding binary metal melts in vertical capillaries, the effect of their partial functional stratification can be observed.The equilibrium height distribution of a heavy component corresponds to the barometric dependence and is achieved in less than 2 hours. A further increase in the duration of the stratification process does not lead to an increase in the degree of achieved segregation. It is shown that the obtained distribution can be well described by the Landau parametric equation for a mixture of two types of particles with different densities. The particle size determined by the approximation of experimental data for Sn-Pb melts by the Landau equation corresponds to clusters containing 8.000-10.000 atoms.  

The speed of the stratification process depends on many factors: the height and the diameter of the capillary, the inclination of the capillary, the composition of the mixture, the interaction of the melt with the material of the capillary, and other parameters. It is known that the temperature is the main determining factor of the molecular kinetic motion of particles in a liquid. For example, an increase in temperature leads to an increase in diffusion and a decrease in viscosity. Therefore, if the process of stratification is associated with the molecular-kinetic movement, the increase in temperature should result in the acceleration of the stratification process. The aim of the experiment was to study the dependence of the current concentration difference at the ends of the capillary on the duration of stratification (stratification rate) at different temperatures.

Methods and methodology. The process of stratification of Sn-Pb eutectic mixtures was carried out in inclined capillaries of the same length and diameter at different temperatures. The comparison of the obtained transition curves showed that the processes of stratification reach equilibrium in the same time for all given temperatures (from 210 to 450˚C). This indicates that the stratification rate is independent of the process temperature.

Conclusion. Therefore, it can be concluded that the mechanism of the stratification process of metal melts in capillaries is not related to the classic molecular kinetic motion of atoms in the system. This result is crucial for the study of properties of the liquid state and requires the development of a special theory to explain it.

SOURCE OF FINANCING

The reported was supported by the Russian Foundation for Basic Research (grant No. 16-01-00662а).

CONFLICT OF INTEREST

The authors declare the absence of obvious and potential conflicts of interest related to the publication of this article.

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