Resistance, emissivities and melting point of tantalum

L. Malter, D. B. Langmuir

The relation between true and brightness temperatures of tantalum was determined by means of pyrometric observations on the inside and outside of a long thin-walled tube heated electrically. The brightness temperature as a function of heating current was determined by sighting on an electrically heated wire of known diameter. Potential leads of fine tungsten wire welded to tantalum filaments permitted a determination of the electrical properties as a function of temperature. The electrical properties at the melting point yielded a value for this quantity from the extrapolated temperature vs. electrical property relations. Value for the melting point determined is 3269 K.

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Materials
Curve 1
Temperature Range, K: 1000-3269 Composition (weight percent), Specifications and Remarks: Regular stock from Fansteel Metallurgical Corp.; tantalum was sealed in glass bulb, outgassed, flashed, sealed in clean bulb, and outgassed at 2023 K for 5 hrs with seven, interposed, 30 sec flashes at 2673 K; data calculated from total radiation intensity by means of Stefan-Boltzmann law.
Curve 1
Wavelength μ: 0.665 Temperature Range, K: 1000-3269 Geometry θ': ~0° Composition (weight percent), Specifications and Remarks: Regular stock from Fansteel Metallurgical Corp; tantalum was sealed in glass bulb, outgassed, flashed, sealed in clean bulb, and outgassed at 2023 K for 5 hrs with seven, interposed, 30 sec flashes at 2673 K; data extracted from smooth curve.