Advancement in experimental methodologies to produce phase equilibria and thermodynamic data in multicomponent systems

One of the key aspects to develop sustainable metallurgical production is to ensure that the predictive power of thermodynamic tools is brought up to a new level of accuracy and reliability. Exploring new polymetallic processes, integrating primary and recycled materials, means utilising the uncharted areas within the Cu-Pb-Zn-Fe-Ca-Al-Mg-Si-O (major) – Cr-Na (slagging) – As-Sn-Sb-Bi-Ag-Au-Ni-Co (minor) slag-solids-metal-matte-speiss-sulfate system. This requires extensive integrated experimental and thermodynamic modelling study, which is underway at PyroSearch at the University of Queensland (UQ). Recent improvements in experimental methodology allowed: * Generating over a thousand equilibrium data points per annum by high-temperature (400–1750°C) equilibration, quenching, electron probe X-ray microanalysis (EPMA) technique at laboratory-controlled oxidation/reduction conditions. * Studying previously impossible systems by smart choice of substrates corresponding to system conditions, one example being rhenium foil for Sn- and Sb-rich slags. * Systematic updates in the properties of pure components/endmembers to provide self-consistent heat capacities from -273 to >3000°C in all phases, enthalpies of phase transition and melting points. The accuracy of measurements also increased. For instance, selected compounds with well-known stoichiometry were systematically used as a set of secondary standards. Also, effects of secondary X-ray fluorescence were addressed. As the experimental techniques improve, new areas of compositions are revealed, which are not necessarily easy to describe using the existing thermodynamic model frameworks. Examples of these areas are: miscibility gaps in silicate systems, many of which never accurately measured before; multicomponent 4-phase liquid equilibria slag-matte-metal-speiss; liquidus temperatures for extremely high melting oxides CaO, MgO, NiO and SnO2.