In situ XRD study on sintering mechanism of SiO2-Al2O3-CaO-MgO ceramics from red mud

The sintering mechanism of novel SiO2-Al2O3-CaO-MgO ceramics obtained from red mud was studied using two batches of ceramics mixed with 50 wt% red mud. The sintering behavior and mechanical properties were studied, and crystal evolution was investigated using X-ray diffraction (XRD), especially in situ XRD. Results showed that anorthite with Na+-solidification played the role of flux to reduce the optimal sintering temperature of ceramics by about 50 degrees C (1080 degrees C for ceramic sample #2), whereas hematite, residual quartz, and generated pyroxene formed the skeleton phase in ceramics during high temperature sintering. Formation of more pyroxene in ceramics improved the bending strength (115.88 MPa for ceramic sample #1). Slow cooling was beneficial to precipitate more pyroxene and less anorthite during sintering. This research is of special interest for the utilization of red mud in ceramics. (C) 2019 Published by Elsevier B.V.