Measurement of Thermal Conductivity from High Temperature Pulse Diffusivity and Calorimetry Measurements

Abstract

The measurement of the thermal conductivity of small samples over an extended temperature range is discussed. Experimental data on thermal diffusivity obtained by the laser pulse technique are combined with specific heat data, obtained either by differential scanning calorimetry or by vaporization calorimetry, to derive the thermal conductivity. An an example of the use of this technique, data are reported on the conductivity of an ASTM A517 steel over the temperature range 100–1200°C. The thermal diffusivity was derived from temperature vs time data obtained from a laser pulse diffusivty system designed and constructed at Sandia. A data reduction technique was used which simultaneously corrects for finite pulse time effects and sample heat losses by radiation. The specific heat was measured directly at temperatures below 680°C using a commercial differential scanning calorimeter. For temperatures up to 1200°C, the specific heat was determined by differentiating a curve fit to the measured sample enthalpy. The enthalpy was measured using a liquid argon vaporization calorimeter developed at Sandia. The thermal conductivity of the A517 steel was then calculated over the entire temperature range. A classical Curie transition was observed during measurements of both the diffusivity and enthalpy. The effect of this transition on the measured thermal conductivity is discussed.