Thermophysical properties of thoriated tungsten above 3600 K by a pulse-heating method

Year: 1996

Authors: Righini F., Spisiak J., Bussolino GC., Rosso A., White GK.

Autors Affiliation: CNR Istituto di Metrologia G. Colonnetti, Strada delle Cacce 73, 10135 Torino, Italy; Institute of Physics, Slovak Academy of Sciences, Bratislava, Slovakia; CSIRO Division of Applied Physics, Lindfield, NSW 2070, Australia

Abstract: Thoriated tungsten (tungsten, 98% thorium oxide, 2%) is a widely used electrode material for inert-gas are-welding. A subsecond pulse-heating technique was applied to rod specimens; radiance temperature was measured by highspeed pyrometry. Literature values of the temperature dependence of the normal spectral emissivity of tungsten were used to obtain true temperatures, with the melting point of thoriated tungsten as a calibration point. Experimental results obtained in the temperature range from 3600 K to the melting point (3693 K) are presented and discussed, along with data obtained during the initial part of the free cooling period. The electrical resistivity results show a regular behavior up to the melting point, indicating that thoria remains an insulator up to 3680 K. During heating, a heat capacity anomaly is found near 3666 K, interpreted as the melting point of thoria. During cooling, two anomalies are found, the first one with a peak near 3660 K and a second one (possibly a Frenkel disorder) with a peak near 3148 K.

Journal/Review: INTERNATIONAL JOURNAL OF THERMOPHYSICS

Volume: 17 (5)      Pages from: 1025  to: 1036

KeyWords: Electrical resistivity; Frenkel disorder; Heat capacity; Melting point; Thoria; Tungsten; Welding electrodes
DOI: 10.1007/BF01441991

Citations: 4
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