Densities of Molten and Solid Alloys of (Fe, Cu, Ni, Co)-S at Elevated Temperatures - Literature Review and Analysis

Abstract

Densities of solid and liquid Fe, Cu, Ni and Co, and their alloys both at the presence and absence of sulfur have been reviewed. Volumetric thermal expansions were used to estimate the densities at different temperatures. Densities of the alloys generally decrease with increasing temperature. For the pure metals the reduction in density as temperature rises from 25 oC to their respective melting point can be estimated to be about 7.05 ± 0.4 % just before melting and about 11.63 ± 0.92 on complete melting. According to the literature data and the analyzed results, at ambient pressure condition, density of the stoichiometric FeS changes from 4.615 g/cm3 at 25 oC to 3.8 g/cm3 at 1200 oC (17.7 %), density of the stoichiometric Cu2S changes from 5.65 g/cm3 at 25 oC to 5.18 g/cm3 at 1200 oC (8.3 %), density of the stoichiometric NiS changes from 5.5 g/cm3 at 25 oC to 5.025 g/cm3 at 1027 oC (8.5 ± 1.8 %) and density of the stoichiometric CoS changes from 5.45 g/cm3 at 25 oC to 4.88 g/cm3 at 1100 oC (10.45 %). A study on the Fe-S melts at 4GPa suggests that in sulfur-poor compositions, where solubility of sulfur is less likely to be affected by pressure, the density of the sulfides at isothermal conditions decreases in a similar fashion as under 1 bar, i.e., density decreases non-linearly with increasing composition of sulfur.