MICROWAVE SINTERING APPLIED TO CAC-BONDED ALUMINA-BASED CASTABLES CONTAINING ZnO

Even though MgO-containing castables are broadly applied as commercial refractories, recent studies have pointed out that ZnO can also induce spinel-like phase formation in alumina-based compositions, giving rise to gahnite (ZnAl₂O₄). Compared to MgO, ZnO-containing castables present lower spinelization temperature, similar cold modulus of rupture and enhanced thermal shock damage resistance. Furthermore, the high microwave absorption of zincite arises the likelihood of applying microwave sintering to refractories comprising this oxide. In the present work, microwave and conventional sintering at several temperatures were applied to ZnO-containing alumina-based castables. Although a partial gahnite decomposition was detected by the microwave heated samples due to the reducing atmosphere induced by the oxidation of SiC microwave susceptors, higher densification, enhanced mechanical properties at room temperature, 26-times faster sintering procedure, and a rough-estimated 70%-lower energy consumption, were attained. Thus, if properly adjusted, the microwave technique could be applied to sinter some refractory compositions, potentially leading to environmental and performance enhancements.