Determination of the Mixing Thermodynamic Properties of LiquidTernary Alloys by Fitting the Knudsen Effusion Mass Spectrometric Datato the Redlich-Kister-Muggianu Sub-Regular Solution Model

摘要

FWe discuss the vaporisation of four liquid ternary-alloy systems, namely, Cu-In-Sn, Ag-In-Sn, Al-Cu-Sn andCu-Sb-Sn, on the basis of our previous Knudsen effusion mass spectrometric (KEMS) investigations of these systems.The thermodynamic activities and the thermodynamic functions (Gibbs energy, enthalpy, entropy) of mixing weredetermined using selected standard KEMS procedures (i.e., Simple Pressure Calibration Method (SPC), OligomerComposition Change Method (OCC), Isothermal Evaporation Method (IEM) and Gibbs-Duhem Ion Intensity RatioMethod (GD-IIR)). In addition, the same thermodynamic quantities, as well as the so-called ternary interaction (L-)parameters, were also obtained from the composition dependence of the measured ion-intensity ratios using a newmathematical procedure (RKM-KEMS). The essence of this new procedure is the fitting of the measured intensity-ratiodata were to the Redlich-Kister-Muggianu (RKM) sub-regular solution model, and this model is valid for many liquidternary alloys, including the systems reviewed here. A full description of the mathematical derivation of RKM-KEMS isgiven in this work. The primary and intermediate data, obtained directly from the multiple-regression as output data, arethe RKM ternary interaction L-parameters. From these quantities, the integral molar excess Gibbs energy, the excesschemical potentials, the activity coefficients and the activities were evaluated in this order. In addition, using thetemperature dependence of activities, the integral and partial molar excess enthalpies and entropies could also bedetermined. The thermodynamic data obtained with the above-mentioned conventional KEMS methods and with the newRKM-KEMS procedure were compared and a good agreement was obtained for the systems studied.