Multiple-gas cooling method for constant-pressure heat capacity measurement of liquid metals using aerodynamic...

Until now, heat capacity measurements performed with levitation techniques have required accurate knowledge of the sample's emissivity beforehand. For a sample levitated using an aerodynamic levitator, it experiences both radiative and forced convective heat loss. The sample's emissivity only allows for the calculation of the radiative heat loss term, and a model has yet to be developed to accurately describe the total combined heat loss for aerodynamic levitation (ADL). In this study, we will introduce a novel multiple-gas cooling method for heat capacity measurement for ADL where two types of inert levitation gases (Ar and Kr) with different thermal conductivities were used to generate two cooling curves for the same sample. For samples being cooled at different cooling rates, the total heat loss is the same. The radiative heat loss was expressed using Stefan-Boltzmann's law, and the convective heat loss using Ranz-Marshall's equation. The two independent parameters (i.e., emissivity and heat capacity) of one given sample could then be solved using the two independent cooling curves. The heat capacities of gold, copper, nickel, iron, and palladium around the melting point were measured using this method. The multiple-gas cooling method for heat capacity measurement introduced in this study is the first heat capacity measurement method available for ADL and can be performed for materials with unknown emissivity. This newly developed method is important for the study of the thermophysical properties of high-temperature liquids, especially molten oxides with low electrical conductivity.