Abstract. Melting and freezing plateaus were observed with type-R thermocouples for the metal-carbon eutectics Pd-C, Ni-C, and Fe-C. For Pd-C, no apparent difference between the melting and freezing temperatures was observed at a heating/cooling rate of 3 °C/min. For Ni-C, the difference was 0.4 °C, and for Fe-C, 1.6 °C. The freezing temperature for Fe-C showed dependence on cooling rate, and the difference between the melt and the freeze decreased to 0.5 °C, though still significant, at a heating/cooling rate of 0.1 °C/min. The melting temperatures, measured with type-R thermocouples, were 1491 °C, 1329 °C, and 1153 °C, respectively, for Pd-C, Ni-C, and Fe-C eutectics, which agreed to within 1 °C with the values previously measured by radiation thermometers or the literature values. The crucibles, being made from graphite, were able to withstand heating cycles without breaking. The three metal-carbon eutectics, with melting temperatures between the copper point and the palladium point, are potentially useful practical reference points for calibration and evaluation of high-temperature thermocouples.

Print publication: Issue 1 (February 2000)