The ZrC–C eutectic structure and melting behaviour: A high-temperature radiance spectroscopy

A fast spectro-pyrometer has been employed for radiance measurements of zirconium carbide samples laser-heated to very high temperature, for compositions 0.7≤C/Zr≤2.61 and in a spectral range 0.550 micron ≤ λ ≤ 0.900 micron. The ZrC–C eutectic temperature has been taken as the radiance reference. The measured normal spectral emissivity (NSE) ε of solid zirconium carbide is close to 0.6 at 0.650 micron, in agreement with previous literature. Its high-temperature behaviour, value in the liquid, carbon-content and wavelength dependences in the visible-near infrared range have been determined here for the first time. Liquid zirconium carbide seems to interact with electromagnetic radiation in a more metallic way than the solid. A considerable NSE increase has been observed at increasing carbon content, which can be interpreted on the basis of preferential growth along the “c” plane of the carbon lamellae in the eutectic structure.