Simultaneous measurements of heat capacity, electric resistivity, and hemispherical total emittance of an alloy of niobium, tantalum, and tungsten in the range 1500 to 2800 K

Abstract

Simultaneous measurements of the heat capacity, electric resistivity, and hemispherical total emittance of an alloy of niobium, tantalum, and tungsten (nominal composition: 80 mass per cent Nb, 10 mass per cent Ta, and 10 mass per cent W) in the temperature range 1500 to 2800 K by a sub-second-duration transient technique are described. Estimated inaccuracies of measured properties are: 3 per cent for heat capacity, 5 per cent for hemispherical total emittance, and 0.5 per cent for electric resistivity. Properties of the alloy are compared with the properties of the constituent elements. The measured heat capacities are approximately 2.6 per cent (on the average) higher than the values computed according to Kopp's additivity law. Although this difference is within the combined estimated inaccuracies, it is higher than the combined estimated imprecision of the measurements. Therefore, the alloy probably departs from Kopp's law. The electric resistivities indicate a significant departure from Matthiessen's law. Like the major constituent niobium, the alloy showed a negative departure from linearity in the plot of electric resistivity against temperature.