Investigations of the influence of oxygen on the surface tension of zirconium by the oscillating drop technique

The oscillating drop technique has been applied to investigate the influence of oxygen on the surface tension of zirconium. During electromagnetic levitation the surface oscillations of liquid drops were recorded by CCD-imaging with a digital camera. The integrated pixel intensity versus time signal was analysed by fast Fourier transformation. The first effects of oxygen on surface tension were found at a concentration of 740 ppm (parts per million by weight) oxygen in the undercooled melt at temperatures below 1700 degrees C (T-m= 1852 degrees C). Further addition of oxygen to 945 ppm decreases the surface tension above the melting point, and greatly decreases the surface tension in the undercooled region. In both cases the sign of the temperature dependence of surface tension changes from negative to positive. Further addition of oxygen up to 1675 ppm does not yield an increased effect. This situation was interpreted as a limit of oxygen saturation on the liquid surface producing a constant positive slope of surface tension versus temperature with the further result of a common point of intersection with the curve of the pure material. (C) 1999 Elsevier Science B.V. All rights reserved.