MEASUREMENT OF THE HEAT OF FUSION OF TANTALUM BY A MICROSECOND-RESOLUTION TRANSIENT TECHNIQUE

The heat of fusion of tantalum was measured using a microsecond-resolu tion pulse-heating technique. The technique is based on rapid (about 1 00-mus) resistive self-heating of a specimen by a high-current pulse f rom a capacitor discharge system and measuring the current through the specimen, voltage across the specimen, and radiance temperature of th e specimen as functions of time. Melting of a specimen is manifested b y a plateau in the radiance temperature versus time function. The time integral of the power absorbed by the specimen during melting yields the beat of fusion. Measurements gave a value of 34.8 kJ . mol-1 for t he heat of fusion of tantalum, with a total uncertainty of +/- 6%. Ele ctrical resistivity of solid and liquid tantalum at its melting temper ature was also measured.