Large- and Small-Aperture Fixed-Point Cells of Cu, Pt–C, and Re–C

Abstract

Extending the application of metal (carbide)-carbon eutectic fixed-point cells to radiometry, e.g., for measurements in irradiance mode, requires fixed-point cells with large apertures. In order to make large-aperture cells more readily usable in furnace systems with smaller furnace tubes commonly used for small-aperture fixed-point cells, a novel cell design was developed. For each of Cu, Pt-C, and Re-C fixed points, two types of fixed-point cells were manufactured, the small-and largeaperture cell. For Pt-C and Re-C, the large-aperture cells were filled with a hypereutectic metal-carbon mixture; for the small cells, a hypo-eutectic mixture was used for filling. For each material, the small and large cells were compared with respect to radiometric differences. Whereas plateau shape and melting temperature are in good agreement for the small-and large-aperture Cu cells, a larger difference was observed between small-and large-aperture cells of Pt-C and Re-C, respectively. The origin of these observations, attributed to the temperature distribution inside the furnace, ingot contamination during manufacture, and non-uniform ingot formation for the larger cells, is discussed. The comparison of measurements by a radiation thermometer and filter radiometer of the Re-C and Pt-C large-aperture cells showed large differences that could be explained only by a strong radiance distribution across the cavity bottom. Further investigations are envisaged to clarify the cause.123 970 Int J Thermophys (2008) 29:969-983

Construction and validation of a platinum–carbon eutectic fixed point

“…PTB/NMIJ/Pt-C had itself been validated by comparison with other cells at the NMIJ, where it showed an agreement in the melting temperature of better than 30 mK and had a melting range of less than 250 mK, with the melting range defined as the plateau with limited slope around the inflection point [18].…”

Camera-based investigation of high-temperature fixed points for radiometric application

“…Radiance mode measurements are realized by radiation thermometers, while filter radiometer realize irradiance mode measurements. However, earlier investigations of such large aperture cells revealed a difference in the plateau shape when measured with instruments of different fields of view, indicating a possible problem in the radiance distribution across the cavity opening as the phase transformation progresses [1].…”

“…To enable the calibration of devices with different fields of view and measuring spot sizes, the calibration sources used must generate homogeneous radiation over a considerably large area. Recently, large area high-temperature fixed-points based on metal(carbide)-carbon and metal-carbon (M(C)-C) eutectics with radiating cavity diameters of 8 mm to 10 mm have been developed especially for radiometric applications [1][2][3]. The relatively large cavity diameter of these fixed-point sources allows instruments with different fields of view to be used, e.g.…”

Dissemination of thermodynamic temperature using Fe-C and Pd-C high-temperature fixed point cells

“…As a result of this research, robust manufacturing procedures have been established [ 7 , 8 ], different xed point cell designs with applications in radiation thermometry, contact thermometry and radiometry have been developed [ 9 ] and for a number HTFPs the thermodynamic temperature during the melt (de ned as the point-of-in ection (POI) during the melting plateau) and their liquidus temperature was determined. Development with respect to thermodynamic temperature determination initially focused on three different metal-carbon alloys Co-C, Pt-C, Re-C [ 10 ].…”