Noncontact surface tension and viscosity measurements of rhenium in the liquid and undercooled states

Surface tension and viscosity of liquid rhenium, which have hardly been measured due to the extremely high melting temperature of rhenium, were measured using an electrostatic levitation method combined with the oscillation drop technique. Sample position instability problems caused by the photon pressure of the heating lasers and by sample evaporation were solved by modifying the electrodes design. Good sample stability allowed the measurements of the surface tension and the viscosity over wide temperature ranges including the undercooled states. Over the $2800–3600\mathrm{K}$ interval, the surface tension of rhenium was measured as $\sigma \left(T\right)=2.71\times {10}^3-0.23\left(T-T_m\right)$ , where $T_m$ is the melting temperature, $3453\mathrm{K}$ . At $T_m$ , the datum agrees well with the literature values. Similarly, on the same temperature range, the viscosity was determined as $\eta \left(T\right)=0.08\exp \left[1.33\times {10}^5∕\left(\mathrm{RT}\right)\right]\left(\mathrm{mPa}\mathrm{s}\right)$ .