Molar Volume and Surface Tension of Liquid Bi–Cu Alloys

Abstract Bi–Cu alloys may potentially be used for thermal energy storage or as a catalyst for methane pyrolysis. For application research and simulations, it is necessary to know the reliable thermophysical properties of liquid alloys. Density of liquid Bi–Cu alloys (25, 50, 75 at. pct Cu) was measured with dilatometric method over the 971 K to 1500 K range. Density decreases linearly with temperature for all compositions. The molar volume calculated from measured densities shows positive excess molar volume. Surface tension was measured with maximum bubble pressure method over the 1125 K to 1500 K range. The data fitted with linear equations show that while the surface tension of 25 at. pct Cu decreases and that of 50 at. pct Cu alloy does not vary with temperature, the surface tension of 75 at. pct Cu alloy increases with temperature. The present results are confronted with literature data and several model calculations, part of which were performed in Pandat, and the reasons for positive excess molar volume and surface tension temperature coefficient are explained in terms of thermodynamics of Bi–Cu solutions.