Experimental investigation of the phase relations in the system Cu-Ni-S in the temperature range 1200 C to 700 C

Abstract

Phase relations in the ternary system Cu-Ni-S were investigated using 275 samples in evacuated quartz-glass tubes. A comparative statistical evaluation was made between areas (0.12 mm2 ) analysed using EDS (Energy Dispersive Spectrometry) with a Scanning Electron Microscope (SEM) and spot analyses on a grid pattern using WDS (Wavelength Dispersive Spectrometry) with the Electron Microprobe (EMP). EDS analyses of areas were found to give more reproducible and statistically more meaningful results. Averaged area analyses of phases in equilibrium phase assemblages were used for construction of the l 200°C, 1100°C, 1000°C, 900°C, 800°C and 700°C isothermal sections. From the combined results of the isothermal sections, the liquidus phase diagram could be determined. This diagram, together with the liquid compositions of invariant phase equilibria from the isothermal sections, were used to determine the crystallisation paths of the Cu-Ni-S system. Converter matte that is slow-cooled in the beneficiation process of Cu, Ni, and platinum group elements usually contains elements other than Cu, Ni, and S in small amounts. Of all these elements Fe probably has the greatest effect on the phase diagram, especially when present in concentrations greater than the typical ~3wt% and the envisaged effects of Fe on the phase diagram is discussed. It is, however, reasonable to assume that the Cu-Ni-S system represents converter matte composition sufficiently well and the Cu-Ni-S phase