Thermodynamic temperature assignment to the point of inflection of the melting curve of high-temperature fixed points.

The thermodynamic temperature of the point of inflection of the melting transition of Re-C, Pt-C and Co-C eutectics has been determined to be 2747.84 ± 0.35 K, 2011.43 ± 0.18 K and 1597.39 ± 0.13 K, respectively, and the thermodynamic temperature of the freezing transition of Cu has been determined to be 1357.80 ± 0.08 K, where the ± symbol represents 95% coverage. These results are the best consensus estimates obtained from measurements made using various spectroradiometric primary thermometry techniques by nine different national metrology institutes. The good agreement between the institutes suggests that spectroradiometric thermometry techniques are sufficiently mature (at least in those institutes) to allow the direct realization of thermodynamic temperature above 1234 K (rather than the use of a temperature scale) and that metal-carbon eutectics can be used as high-temperature fixed points for thermodynamic temperature dissemination. The results directly support the developing mise en pratique for the definition of the kelvin to include direct measurement of thermodynamic temperature.

Report on the CCT Supplementary Comparison S1 of Infrared Spectral Normal Emittance/Emissivity.

The National Measurement Institutes (NMIs) of the United States, Germany, France, Italy and Japan, have joined in an inter-laboratory comparison of their infrared spectral emittance scales. This action is part of a series of supplementary inter-laboratory comparisons (including thermal conductivity and thermal diffusivity) sponsored by the Consultative Committee on Thermometry (CCT) Task Group on Thermophysical Quantities (TG-ThQ). The objective of this collaborative work is to strengthen the major operative National Measurement Institutes' infrared spectral emittance scales and consequently the consistency of radiative properties measurements carried out worldwide. The comparison has been performed over a spectral range of 2 µm to 14 µm, and a temperature range from 23 °C to 800 °C. Artefacts included in the comparison are potential standards: oxidized inconel, boron nitride, and silicon carbide. The measurement instrumentation and techniques used for emittance scales are unique for each NMI, including the temperature ranges covered as well as the artefact sizes required. For example, all three common types of spectral instruments are represented: dispersive grating monochromator, Fourier transform and filter-based spectrometers. More than 2000 data points (combinations of material, wavelength and temperature) were compared. Ninety-eight percent (98%) of the data points were in agreement, with differences to weighted mean values less than the expanded uncertainties calculated from the individual NMI uncertainties and uncertainties related to the comparison process.

Thermophysical properties of rhodium obtained by fast pulse-heating.

The so-called platinum metals are Ru, Rh, Pd, Os, Ir and Pt. Our workgroup has already published data on Pd, Ir and Pt. The present work will focus on measurements of the thermophysical properties of rhodium, which have been carried out recently. The scarce literature data available emphasize the need for new measurements. Using a rapid pulse-heating technique, wire-shaped specimens are ohmic-heated by the passage of a large current pulse. This fast heating drives the sample from room temperature up into the liquid phase in typically 50 µs and thus prevents chemical reactions and gravitational distortions. Enthalpy, electrical resistivity and volume expansion can be obtained as a function of temperature. From these results, heat of fusion, heat capacity and change of density can be calculated as a function of temperature. A set of data of the mentioned quantities will be presented and the comparison to literature values will be discussed within this study. Additionally we will contrast the results for rhodium with the respective results for Pd, Ir and Pt. The conformity of data published decades ago with our new measurements is fairly high. Rhodium does not show unexpected behaviour regarding the comparison to Pd, Ir and Pt.