Uncertainty evaluation for density measurements of molten Ni, Zr, Nb and Hf by using a containerless method

We report on high-temperature density measurements of nickel (Ni), zirconium (Zr), niobium (Nb), and hafnium (Hf) in supercooled and stable liquid states by using an electrostatic levitator (ESL) and evaluation of their associated uncertainties. More specifically, this work demonstrates a detailed description of our non-contact measurement method (i.e. schematics of the instrumentation, levitation procedure and density calculation from droplet images). We find that the main contribution of the uncertainties come from measuring sample temperature and mass, aspect ratio of the sample shape, pixel-calibration factors for two-dimensional (2D) detector, and order of the fitting function for calculating the volume. The measurements are typically made with combined uncertainties less than 0.5% and 2.1% for two different types of pyrometers that are used in low temperature (600 K similar to 2800 K) and high temperature (1000 K similar to 3800 K) ranges each operating at a wavelength of 1.6 mu m and 0.9 mu m, respectively. At melting temperatures, the combined uncertainties of the density measurements of liquid metals are measured less than +/- 1.4% for low temperature and +/- 2.2% for high temperature cases.