Introduction to proceedings of the workshop on Knudsen Effusion Mass Spectrometry

Abstract The collected papers in this Special Edition are from a Workshop on one of the most informative methods of experimental thermodynamics, “Knudsen Effusion Mass Spectrometry” (KEMS). This international workshop was held in Julich, Germany in October of 2017. KEMS is based on the near equilibrium conditions between a condensed phase and a vapor that is achieved in a Knudsen cell. The well-defined orifice on the Knudsen cell forms a molecular beam, which is directed to a mass spectrometer. The measured ion intensities from each vapor species can be converted to partial pressures. These partial pressures give a full picture of the vapor composition and thermochemistry of the formed vapor species. For a multi-component sample, thermodynamics of the condensed phase can be attained as well. The measured partial pressures of each species allow a wealth of thermodynamic information to be collected: enthalpy, entropy, Gibbs energy, Helmholtz energy, activity of component i, equilibrium constants, and others. The widely used thermochemical tables contain many data entries from KEMS measurements. KEMS measurements are also used extensively in Calphad assessments. The 2017 KEMS workshop cover a wide range of applications for KEMS—thermodynamics of alloys, ceramics, and organic compounds for nuclear, chemical process, energy storage, aerospace propulsion, and geological fields. The wide versatility of KEMS was demonstrated—from low temperature alloys and organic compounds (700 K) to very high temperature oxides (2500 K). Vaporization and solution properties of both organic and inorganic compounds (halides, oxides, hydroxides, nitrides, carbides, etc.) were discussed. Papers on instrumentation development and improved sampling were also presented. There were discussions of new KEMS instruments and facilities under construction. It was shown that KEMS in conjunction with modeling is a valuable tool in thermodynamics. KEMS measurements have been used as an input to Calphad models and KEMS measurements have been used to guide and check first principles calculations.