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 influenc e of oxygen on the surface tension of zirconium. During electromagnetic lev itation the surface oscillations of liquid drops were recorded by CCD-imagi ng with a digital camera. The integrated pixel intensity versus time signal was analysed by fast Fourier transformation. The first effects of oxygen o n surface tension were found at a concentration of 740 ppm (parts per milli on by weight) oxygen in the undercooled melt at temperatures below 1700 deg rees C (T-m= 1852 degrees C). Further addition of oxygen to 945 ppm decreas es the surface tension above the melting point, and greatly decreases the s urface tension in the undercooled region. In both cases the sign of the tem perature dependence of surface tension changes from negative to positive. F urther 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 liq uid surface producing a constant positive slope of surface tension versus t emperature with the further result of a common point of intersection with t he curve of the pure material. (C) 1999 Elsevier Science B.V. All rights re served.