국내 최대 기계 및 로봇 연구정보

기술보고서

기술보고서 게시판 내용
타이틀	Long Term Measurement of the Vapor Pressure of Gold in the Au-C System
저자	Copland, Evan H.
Keyword	EUTECTICS;; GOLD;; VAPOR PRESSURE;; KNUDSEN FLOW;; MASS SPECTROSCOPY;; GIBBS FREE ENERGY;; GRAPHITE;; PHASE DIAGRAMS;; SENSITIVITY ANALYSIS;; PARTIAL PRESSURE;;
URL	http://hdl.handle.net/2060/20090027867
보고서번호	E-16808;; NASA/CR-2009-215498
발행년도	2009
출처	NTRS (NASA Technical Report Server)
ABSTRACT	Incorporating the Au(s,l) graphite reference in component activity measurements made with the multiple effusion-cell vapor source mass spectrometry (multicell KEMS) technique provides a fixed temperature defining ITS-90 (T(sub mp)(Au) = 1337.33K) and a systematic method to check accuracy. Over a 2 year period delta H sub鵪)Au was determined by the 2nd and 3rd law methods in 25 separate experiments and were in the ranges 362.2 plus or minus 3.3 kJmol(sup -1) and 367.8 plus or minus 1.1 kJmol(sup -1), respectively. This 5 kJmol-1 discrepancy is transferred directly to the measured activities. This is unacceptable and the source of this discrepancy needs to be understood and corrected. Accepting the 2nd law value increases p(Au) by about 50 percent, brings the 2nd and 3rd law values into agreement and removes the T dependence in the 3rd law values. While compelling, there is no way to independently determine instrument sensitivities, S(sub Au), with T in a single experiment with KEMS. This lack of capability is stopping a deeper understanding of this problem. In addition, the Au-C phase diagram suggests a eutectic invariant reaction: L-AuƔ.7at%C) = FCC-AuƐ.08at%C) C(graphite) at T(sub e) approximately 1323K. This high C concentration in Au(l) must reduce p(Au) in equilibrium with Au(s,l) graphite and raises some critical questions about the Gibbs free energy functions of Au(s,l) and the Au fixed point (T(sub mp)(Au) = 1337.33K) which is always measured in graphite.