Density Determination of Liquid Copper, Nickel, and Their Alloys

A method for the determination of the density of electromagnetically levitated metallic liquids has been developed. This method employs an enlarged beam of parallel laser light to produce a shadow image of the sample. The shadow is recorded by a digital CCD-camera, and the images are analyzed using an edge detection algorithm. The circumference is fitted by Legendre polynomials that can be used for calculations of the volume of the sample. The method has been tested successfully on various alloys of copper-nickel (NixCuy), as well as on the pure elements, Cu and Ni. Densities were measured for each sample at different temperatures below and above the melting point, and a linear behavior was observed. At the melting point the densities for copper and nickel were 7.9 and 7.93 g ·cm−3, respectively. For T=1270°C liquid copper has a density of 7.75 g ·cm−3 which strongly increases up to roughly 8.1 g ·cm−3 if a small amount (10–40 at.%) of nickel is added to the system. For nickel concentrations larger than 50 at.% the density remains nearly constant.