Preformed and in-situ spinel-containing alumina castables: Effect of in situ ZnAl2O4 formation

The effect of in situ ZnAl₂O₄ formation by the addition of ZnO on the properties of preformed and in situ MgAl₂O₄ spinel-containing cement-bonded alumina castable has been investigated. 2 wt.% ZnO was added in the 10 and 20 wt.% spinel in preformed and 2.8 and 5.6 wt.% MgO in in situ spinel-containing alumina castables, respectively. Calcium aluminate cement was employed as a binder, and the flow consistency of the castables was adjusted using the Dinger–Funk model with distribution coefficients of.21 and.29. All the samples were assessed for densification and strength studies after heat treatment at different temperatures. 1550°C fired samples were evaluated for phase development, microstructure with EDAX, and slag corrosion study. ZnO-containing alumina spinel castables were finally compared against the compositions without additives. The results revealed that the formation of ZnAl₂O₄ has significantly improved the densification, mechanical, thermomechanical, and corrosion properties. Microstructural studies show that the in situ formed ZnAl₂O₄ phase makes a solid solution with the spinel (MgAl₂O₄) phase in the composition.