Radiance Temperatures (in the Wavelength Range 521 to 1500 nm) of Rhenium and Iridium at Their Melting Points by a Pulse-Heating Technique

Abstract

The melting-point radiance temperatures (at seven wavelengths in the range 521 to 1500 nm) of rhenium and iridium were measured by a pulse-heating technique. The method is based on rapid resistive self-heating of the specimen from room temperature to its melting point in less than 1 s and on simultaneously measuring the specimen radiance temperature every 0.5 ms with two high-speed pyrometers. Melting was manifested by a plateau in the radiance temperature-versus-time function for each wavelength. The melting-point radiance temperatures for a given specimen were determined by averaging the measured temperatures along the plateau at each wavelength. The melting-point radiance temperatures for each metal were determined by averaging results for several specimens at each wavelength. The results are as follows.$\begin{gathered} Rhenium Iridium \hfill \\ \overline {2989 K at 521nm} \overline {2458 K at 523 nm} \hfill \\ 2916 K at 614 nm 2402 K at 617 nm \hfill \\ 2891 K at 656 nm 2380 K at 656 nm \hfill \\ 2853 K at 707 nm 2349 K at 711 nm \hfill \\ 2789 K at 807 nm 2297 K at 808 nm \hfill \\ 2719 K at 905 nm 2243 K at 906 nm \hfill \\ 2324 K at 1500 nm 1944 K at 1500 nm \hfill \\ \end{gathered}$ Based on estimates of the random and systematic errors arising from pyrometry and specimen conditions, the expanded uncertainty (two standard-deviation level) in the reported values is ±8K.