Surface tension and adsorption in liquid silver-oxygen alloys

The influence of oxygen on surface tension of liquid silver has been studied in a pressure range from 10-20bar to 1 bar at 1100°C. For pure silver a surface tension ? = 890 [mNm-1] at its melting point and a surface entropy of -0.16 [mN m-1 K-1] have been found. Oxygen is highly surface active and segregates to the free liquid surface up to high partial pressures (-80 mbar). At this pressure a surface excess concentration ? = 18.8·10-6 [molem-2] has been calculated, which corresponds to a surface area per oxygen atom A = 8.8·10-2 [nm2atom-1], suggesting the presence of a Ag-O surface structure with the oxygen ions protruded towards the gas phase. Measurements made on vitreous carbon, alumina and silica supports demonstrated that the lower thermodynamic stability and faster decomposition kinetics of the latter oxide prevent accurate measurements below about 10-10 mbar. At the same time, in the high pO2 range, silicates form on the surface of liquid silver resting on silica supports