Effect of mullite microcrystal on phase change mechanism of anorthite-based ceramics at low temperatures using...

Electrolytic manganese residue (EMR) has caused severe pollution due to its high concentration of water-soluble contaminants, posing a major obstacle to the sustainable development. To address the low utilization of EMR and its associated pollution, mullite-enhanced anorthite ceramics were successfully prepared at temperatures below 1200 °C by using EMR and calcined kaolin (CK). Different EMR/CK ratios, sintering temperatures, and holding times were investigated. The optimal bending strength of 65.09 MPa was obtained at 1160 °C for 60 min with EMR/CK ratio of 1:1. The enhanced mechanical strength originates from the altered crack propagation path caused by in-situ synthesis of mullite microcrystals. Phase composition, microstructure, and thermal analysis revealed that CaO reacts with α-SiO₂ to form wollastonite and gehlenite, ultimately synthesizing anorthite above 1100 °C. The spinel-like intermediate during the mullite formation provides most of aluminum source and part of silicon source for anorthite synthesis. This study offers a sustainable solution for solid waste co-disposal and heavy metal pollution control.