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

• Published in: Materials letters 2019-04, Vol.240, p.229-232
• Main Authors: Pei, Dejian, Li, Yu, Cang, Daqiang
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Anorthite; Bend strength; Calcium oxide; Ceramics; Hematite; High temperature; In situ XRD; Magnesium oxide; Materials science; Mechanical properties; Phase transformation; Pyroxenes; Red mud; Silicon dioxide; Sintering; Solidification; X-ray diffraction
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/j.matlet.2019.01.019

•In situ XRD was applied to study the sintering of SiO2-Al2O3-CaO-MgO ceramic.•Generated anorthite played the role of flux to reduce sintering temperature.•Generated pyroxene acted as the main skeleton phase to improve bending strength.•Slow cooling favored the precipitation of more pyroxene and less anorthite. 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 °C (1080 °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.