A new approach to measuring liquid metal density at high pressure and high temperature using aerodynamic levitation

Accurate knowledge of liquid metal density and its temperature dependence is essential for understanding phase transformations, thermophysical behavior, and the safe design of high-temperature engineering systems. While numerous techniques have been developed to measure the density of liquids at high temperature, conventional contact methods suffer from significant limitations, including sample contamination and poorly constrained heat losses, which restrict their applicability at extreme temperatures. Non-contact techniques, particularly levitation-based methods, have, therefore, become indispensable for characterizing metals in the liquid state at very high temperatures. However, all kinds of levitation techniques are limited in temperature by the systematic evaporation of the sample close to the boiling point, introducing temperature limitations and additional sources of uncertainty in volume determination. We employ aerodynamic levitation combined with high-power laser heating to measure the density of liquid iron at temperatures up to the boiling point. Although aerodynamic levitation minimizes sample deformation and eliminates container-related artifacts, measurements at high temperature remain also challenged by intense evaporation, which has historically limited reliable density data for iron to below 2400 K. To overcome this barrier, experiments are conducted under high-pressure helium (9.2 MPa), effectively controlling evaporation and enabling stable measurements at substantially higher temperatures. Using high-speed imaging and contour-based volume reconstruction, we report precise density measurements of liquid iron up to 3100 K, representing an important leap forward in the field of levitation techniques and thermophysical characterization. This breakthrough technique unlocks new possibilities for high-temperature measurements by providing enhanced control over evaporation.