Title of the PhD thesis: 

Development of advanced eco-friendly spinel-containing materials to replace chromite-based refractories

Abstract: 

Until the 1990s, the use of electrofused magnesia-chrome aggregates (EMCA) was widespread in refractory linings for the steel industry. Despite their efficiency and low cost, it was discovered that these materials generate toxic byproducts. Consequently, MgAl₂O₄-containing refractories emerged as the main alternative, though their performance has not yet reached equivalent levels. This thesis combined computational and experimental tools to design and evaluate non-toxic compositions, focusing on their thermomechanical, chemical and microstructural properties. Initially, the substitution of MgO with ZnO as a spinel-forming additive in alumina-based refractory castables was investigated. Additionally, introducing ZnO enabled microwave-assisted sintering of these materials. Nonetheless, zinc volatilization above 1300 °C revealed its limitations. Therefore, the study focused on more deeply characterizing the EMCA. Inspired by the findings, four chromium-free compositions were designed and produced via fusion or sintering, both at a laboratory scale. Dilatometry and thermal conductivity tests demonstrated the promising performance of the novel compositions and the potential to tailor their properties through minor compositional adjustments. Finally, the industrial interest in the results of this thesis enabled a partnership with a refractory manufacturer. In collaboration, pilot-scale tests are currently being conducted to develop industry-applicable technology capable of reducing the environmental impact associated with chromium-containing refractories.

Link for the PhD thesis (in Portuguese): https://repositorio.ufscar.br/handle/20.500.14289/21472