RADIANCE TEMPERATURES AT 1500 NM OF NIOBIUM AND MOLYBDENUM AT THEIR MELTING-POINTS BY A PULSE-HEATING TECHNIQUE

Radiance temperatures at 1500 nm of niobium and molybdenum at their me lting points were measured by a pulse-heating technique. The method is based on rapid resistive self-heating of the strip-shaped specimen fr om room temperature to its melting point in less than 1 s and measurin g the specimen radiance temperature every 0.5 ms with a high-speed inf rared pyrometer. Melting of the specimen was manifested by a plateau i n the radiance temperature-versus-time function. The melting-point rad iance temperature for a given specimen was determined by averaging the measured values along the plateau. A total of 12 to 13 experiments wa s performed for each metal under investigation. The melting-point radi ance temperatures for each metal were determined by averaging the resu lts of the individual specimens. The results for radiance temperatures at 1500 nm are as follows: 1983 K for niobium and 2050 K for molybden um. Based on the estimates of the uncertainties arising from the use o f pyrometry and specimen conditions, the combined uncertainty (two sta ndard-deviation level) in the reported Values is +/-8 K.