Zirconium temperature measurements from the melting point to $4100$ K involving the use of blackbody models in the liquid state

The temperature ($2128$–$4100$ K) dependence of specific enthalpy $E$ at atmospheric pressure is obtained under conditions of fast (microseconds) pulsed electric heating of zirconium foil samples. The enthalpy dependence of the spectral density of radiation at the wavelength of $0.855\mu$m is measured for flat surfaces and for two blackbody models made of zirconium foil. The temperature is calculated by Planck's formula. The temperature plateau on the curve of the dependence of $T$ on $E$ in the melting of zirconium is used for calibration, and the value of the plateau temperature is taken to be equal to the equilibrium melting point of $2128$ K. The blackbody models are assembled of separate flat strips of zirconium. The objective of this study is to develop and experimentally verify a blackbody model suitable for both metals and graphite and to derive the temperature dependence of the thermal properties of liquid metals and liquid carbon at high temperatures under conditions of fast pulsed heating. A Tektronix TDS 754C four-channel digital oscilloscope was used in the measurements.