Eco-friendly design of complex refractory aggregates as alternatives to the magnesia-chromite ones

Besides the good performance of electrofused magnesia-chromite aggregate (EMCA) in ceramic refractories, the generation of toxic Cr+6 after working conditions is driving its urgent replacement. Aiming at optimizing the search towards eco-friendly options, this work applied multiple electron-microscope-based techniques to assess its key microstructural features. BSE/EDS imaging coupled with thermodynamic calculations (CALPHAD) indicated that these aggregates were comprised of a periclase matrix where spinel precipitates (d50 & AP;15 & mu;m) were embedded, inducing microcracking due to the thermal expansion mismatch. EBSD technique highlighted its pattern, revealing a good fit with {110} planes, which agrees with the Zener-Stroh crack mechanism. Designing concepts of compositionally complex ceramics were applied to find eco-friendly EMCA alternatives. From the 154 simulated systems, the four most promising ones were experimentally produced and characterized. Although kinetics aspects must be addressed, Cr-free EMCA-inspired microstructures were obtained, highlighting that this design approach can be used to support the development of novel raw materials.

Automated summary

In this study, multiple electron-microscope-based techniques were applied to assess the microstructural features of electrofused magnesia-chromite aggregate (EMCA). The results showed that the aggregates were comprised of a periclase matrix with embedded spinel precipitates, which induced microcracking due to thermal expansion mismatch. By designing compositionally complex ceramics, eco-friendly alternatives to EMCA were found and successfully produced. This study highlights the potential of the design approach in supporting the development of novel raw materials.