국내 최대 기계 및 로봇 연구정보

기술보고서

기술보고서 게시판 내용
타이틀	Measuring Thermodynamic Properties of Metals and Alloys With Knudsen Effusion Mass Spectrometry
저자	Copland, Evan H.;; Jacobson, Nathan S.
Keyword	ENERGY OF FORMATION;; ENTHALPY;; FREE ENERGY;; ION CURRENTS;; KNUDSEN FLOW;; KNUDSEN GAGES;; MASS SPECTROSCOPY;; METALS;; MONOMERS;; PARTIAL PRESSURE;; THERMODYNAMIC PROPERTIES;; VAPOR PRESSURE;; VAPORS
URL	http://hdl.handle.net/2060/20110001597
보고서번호	NASA/TP-2010-216795
발행년도	2010
출처	NTRS (NASA Technical Report Server)
ABSTRACT	This report reviews Knudsen effusion mass spectrometry (KEMS) as it relates to thermodynamic measurements of metals and alloys. First, general aspects are reviewed, with emphasis on the Knudsen-cell vapor source and molecular beam formation, and mass spectrometry issues germane to this type of instrument are discussed briefly. The relationship between the vapor pressure inside the effusion cell and the measured ion intensity is the key to KEMS and is derived in detail. Then common methods used to determine thermodynamic quantities with KEMS are discussed. Enthalpies of vaporization, the fundamental measurement, are determined from the variation of relative partial pressure with temperature using the second-law method or by calculating a free energy of formation and subtracting the entropy contribution using the third-law method. For single-cell KEMS instruments, measurements can be used to determine the partial Gibbs free energy if the sensitivity factor remains constant over multiple experiments. The ion-current ratio method and dimer-monomer method are also viable in some systems. For a multiple-cell KEMS instrument, activities are obtained by direct comparison with a suitable component reference state or a secondary standard. Internal checks for correct instrument operation and general procedural guidelines also are discussed. Finally, general comments are made about future directions in measuring alloy thermodynamics with KEMS.