The Normal Spectral Emissivity at a Wavelength of 684.5 nm and Thermophysical Properties of Liquid Zirconium Up to the End of the Stable Liquid Phase

Abstract

It is very difficult to determine normal spectral emissivity under pulse‐heating conditions in the liquid state. Nevertheless normal spectral emissivity is an important quantity for temperature determination when measuring thermophysical properties. In the 80s Azzam [1] developed a laser polarimeter for the determination of optical parameters without any moving parts. Recently such a polarimeter was adapted for pulse‐heating experiments, which are performed in a sub‐microsecond time‐scale, and integrated into the existing measurement setup. The behavior of normal spectral emissivity for liquid metals at 684.5 nm can be illustrated by three groups: a) increasing, b) decreasing, or c) constant emissivity values as a function of temperature in the liquid phase. To achieve reliable thermophysical properties of liquid metals involves the measurement of normal spectral emissivity in conjunction with the radiometric temperature. Within this paper recent results of normal spectral emissivity at 684.5 nm as well as thermophysical properties for zirconium at melting and for the liquid phase are reported.