Drop size dependence of contact angles for liquid tin on silica surface: line tension and its correlation with solid-liquid interfacial tension

Using the sandwich drop method, advancing contact angles were measured for liquid tin on the silica (SiO2) surface under high vacuum (10(-5) Pa) at 1173 K. A drop size dependence for the measured contact angles was observed, i.e. the contact angle decreased as the drop's base radius was increased. In line with explaining similar observations for "low-energy" (i.e. organic) systems, the observed trend for the Sn-SiO2 (i.e. "high-energy") system was interpreted using the modified Young equation. It was found that the drop size dependence of contact angles can be interpreted as being due to a positive line tension. The line tension value obtained might seem to be large (155 mu J/m) in comparison with the line tension values of the order of 1 mu J/m for low-energy systems; however, a large line tension for the Sn-SiO2 system is in line with results from the low-energy systems which indicate a positive correlation between the line tension and the solid-liquid interfacial tension. (C) 1998 Elsevier Science B.V. All rights reserved.