Temperature dependence of surface tension of liquid Sn-Ag, In-Ag and In-Cu alloys

It is usually known that the surface tension of liquid metals and alloys decreases with increasing temperature, i.e., the temperature dependence of the surface tension is negative. We found, however, that some liquid alloys, which have large difference of the surface tension of pure components, show positive temperature dependence in certain composition ranges. Some Pb-free alloys, for which information on the surface tension is indispensable to be developed as environmental-friendly material, can be listed in this special category. The experimental results and the thermodynamic analysis of the temperature dependence of those alloys are discussed in the paper.