Thermal Diffusivity of Metals at High Temperatures

Abstract

A modified Ångström method for measuring thermal diffusivity and hence thermal conductivity of metals has been developed. Like previously reported dynamic methods, this method uses a heat source, whose temperature varies sinusoidally with time, located at one end of an effectively infinite rod. Unlike these methods, only one period of the heat pulse is required to eliminate the unknown coefficient determining the heat lost by radiation since both velocity and amplitude decrement of the heat pulse are measured. In addition to providing greater reliability at high temperatures by using only one period, the new method is faster in taking data and simpler in computation. The thermoelectric potentials from two thermojunctions are amplified and plotted on a Brown electronic recorder in order to obtain a permanent record of all necessary data for computing the thermal diffusivity. Results for copper, nickel, and thorium over the temperature range 0–500°C are given.