Sessile drop evaluation of high temperature copper/spinel and slag/spinel interactions

Metal droplets sticking to spinel solids, present in metallurgical slag systems, play an important role in hindering the sedimentation of copper in slags. To understand this phenomenon, the interaction between spinel particles with Cu on one hand and with slag, on the other hand, was evaluated. A dedicated approach was applied, using an industrially relevant synthetic slag system PbO-FeO-SiO2-CaO-Al2O3-Cu2O-ZnO, pure copper and MgAl2O4 substrates to represent the industrial slag, the entrained copper droplets and the spinel solids, respectively. Both the copper-MgAl2O4 and the slag-MgAl2O4 interaction were studied using sessile drop measurements, combined with an extensive microstructural analysis. Additionally, the effect of time on the slag-MgAl2O4 interaction was studied using immersion experiments. Copper displayed a non-wetting behaviour on MgAl2O4, whereas slag displayed a reactive wetting and an interaction layer of (Mg, Fe, Zn)(Al, Fe)2O4 spinel was formed at the interface, which was also observed in the immersion experiments. Moreover, the diffusion of MgO and Al2O3 from the spinel substrate into the slag droplets was noted.