Optical properties (at 684.5 nm) and radiance temperatures at the melting point of group VIIIb transition metals cobalt, nickel, palladium, and platinum
Claus Cagran, Boris Wilthan, Gernot Pottlacher
Optical constants (index of refraction n and extinction coefficient k) and normal spectral emissivities of liquid cobalt, nickel, palladium, and platinum were measured with a division-of-amplitude photopolarimeter (DOAP) operating at 684.5 nm. The polarimeter is part of a pulse-heating apparatus using resistive self-heating of conducting specimens from room temperature to the upper limit of the liquid state in less than 50 μs. The temperature during the experiments (except for nickel) was simultaneously determined with a fast optical pyrometer operating at 650 nm. Additionally, radiance temperatures at melting at 684.5 nm calculated from emissivity and the melting temperature are presented for all four materials. The melting-point emissivities (normal spectral)/radiance temperatures at 684.5 nm, obtained by averaging several experimental results from each material, are: 0.346/1623.1 K for cobalt, 0.365/1595.8 K for nickel, 0.360/1678.8 K for palladium, and 0.364/1858.9 K for platinum. The results for all determined optical properties are given as melting-point values as well as linear least-squares fits to the liquid state. The uncertainty for emissivity and optical constants (with a coverage factor of k* = 2) is estimated and reported.