Measurement of normal spectral emissivity of liquid copper

Abstract

The normal spectral emissivity of copper in solid and liquid states was measured at 1 273 to 1 673 K with wavelength during 400 to 850 nm. The ratio of radiation intensity to that at a reference wavelength of 650 nm was measured in order to avoid the difficulty of simultaneous measurement of the radiation intensity from a black body. The emissivity of copper increases in solid state and decreases in liquid state with increasing temperature and decreases with increasing wavelength in both states. At the melting point of 1 358 K, the emissivity at 650 nm discontinuously increases from 0.123 in solid to 0.143 in liquid.