Thermodynamic parameters of liquid cobalt‐palladium alloys by computer‐aided Knudsen cell mass spectrometry

Abstract

AbstractThe computer‐aided Knudsen cell mass spectrometry has been applied for the determination of the molar thermodynamic excess properties of liquid binary Co‐Pd alloys. Thermodynamic evaluation followed the “Digital Intensity‐Ratio” (D.I.R.)‐method. Two‐parameter thermodynamically adapted power (TAP) series are used for the algebraic representation of the molar excess properties. Liquid Co‐Pd alloys are characterized by exothermic molar heats of mixing HE, slight negative molar excess entropies, and negative molar excess Gibbs energies GE. At 1850 K the minimum HE value is −13000 J/mol (55.1 at.% Pd), the minimum SE value is −4 J/(mol K) (52.7 at.% Pd), and the minimum GE value is −5700 J/mol (57.9 at.% Pd). At 1850 K the thermodynamic activities of both components, Pd and Co, show slight negative deviations from Raoult's law over the entire range of composition. The Co activities of the Co‐richest alloys (xPd<0.14) are nearly ideal.