The surface tension of pure Zn measured by means of the maximum bubble pressure method

Abstract

[EN] The surface tension sigma of pure Zn and its temperature coefficient have been measured by means of the maximum bubble pressure technique over the temperature range [Tm, m , Tm+250 m +250 degrees C], where Tm m is the melting temperature. Alumina and quartz capillaries of various radii were used. Alumina capillaries were coated with boron nitride to discard possible wetting and high purity argon was used as bubbling gas. In addition, sigma was measured while heating, cooling, or introducing the capillaries in the melt at several chosen temperatures. All measurements with alumina capillaries showed a negative temperature coefficient while those with quartz capillaries gave a positive temperature coefficient. These results are compatible with Nogi et al. conclusion in the sense that positive temperature coefficients reported in the literature should be ascribed to oxygen and/or impurity effects enhanced in volatile metals. In particular we argue that the positive temperature coefficient is a consequence of the concomitant action of several factors, namely, vaporization of Zn, oxygen traces in the bubbling gas, and the oxygen and Si produced in the chemical reactions involving quartz and liquid zinc.