|
|
|
| The Development of the Co-C Eutectic High-temperature Fixed-point |
| WANG Jian-hua1,XIAO Chang-zhi1,2,DONG Wei2,WANG Tie-jun2,LIU Zhi-feng1 |
1.Beijing University of Technology, Beijing 100124,China
2.National Institute of Metrology, Beijing 100013,China |
|
|
|
|
Abstract A new construction method based on an extended graphite sleeve and pre-forming eutectic is describedIn order to improve the temperature gradient along the HTFP cell and avoid thermal stress concentration in the process of phase transition, the crucible is designed hybrid structure, namely, placing the high purity graphite foil with anisotropic thermal conductivity between the graphite sleeve and crucible.Meanwhile it can reduce the filling times effectively which can decrease the introduced external contaminants by using the extended graphite sleeve.CCT-WG5 (Consultative Committee for Thermometry, Working Group 5: Radiation Thermometry) for the definition of thermodynamic temperature with the highest level of Co-C eutectic HTFP demands the repeatability is better than 20 mK and the difference between the initial temperature and the end temperature of melting is less than 120 mK.A new Co-C eutectic HTFP was constructed based on the new filling method, and the preliminary results show that the phase transition temperature is 1324.054oC, short-term repeatability is better than 9 mK, and the difference between the initial temperature and the end temperature of melting is less than 110 mK, which meet the CCT-WG5 requirements for the HTFPs.
|
|
|
|
|
|
|
|
［1］ Preston-Thomas H.The International Temperature Scaleof 1990 (ITS-90)［J］.Metrologia, 1990, (27): 107-116.
［2］ Woolliams E, Machin G, Lowe D, et al.Metal(carbide)-carbon eutectics forthermometry and radiometry: a review of the first seven years［J］.Metrologia,2006, (43): 11-28.
［3］ Bloembergen P, Yamada Y.Measurement of Thermodynamic TemperatureAbove the Silver Point on the Basis of the Scheme n = 2［J］.Int J Thermophys, 2011,(32): 45-67.
［4］ Lowe D, Anhalt K, Hartmann J.Construction and validation of a platinum-carbon eutectic fixed point［J］.Metrologia, 2008, (45): 325-329.
［5］ Battuello M, Florio M, Sadli M,et al .Investigations on Two Co-C Fixed-Point Cells Prepared at INRIM and LNE-Cnam［J］.Int J Thermophys, 2011, (22): 168-177.
［6］ Yamada Y, Wang Y.Long Term Stability of Metal-Carbon Eutectic Fixed Point Cells［J］.计量学报, 2008, 29 (5A): 46-51.
［7］ Wang T, Bai C, Dong W.Results of Long-Term Stability Tests Performed for the Eutectics Co-C and Pt-C［J］.Int J Thermophys, 2011, (32): 348-356.
［8］ Yuan Z, Lu X, Wang J, et al.Realization of ITS-90 above Silver Freezing Point at NIM［J］.Int J Thermophys, To be published.
［9］ Massalski B T.Binary Alloy Phase Diagrams, Materials Park［M］.Ohio: ASM International, 1990, 1323-1329.
［10］ Dong W, Wang T, Bloembergen P, et al.The Eutectic Pt-C: Deriving the Liquidus Temperature at the Eutectic Concentration from Freezing Experiments by Extrapolation to Zero Freezing Rate［J］.Int J Thermophys, To be published. |
|
|
|
2011, Vol. 32 
