Wettability and Mechanical Properties of Red Mud–Al2O3 Composites

Abstract

In 2023, the global production of new red mud is expected to reach nearly 200 million tons, but less than 10% of it is currently being utilized in an environmentally friendly manner. To reduce the sintering temperature of alumina ceramics, a sintering aid method is used, as high-purity alumina ceramics require a solid-phase sintering temperature of over 1700 °C. The metal oxides present in red mud are necessary components for high-performance composite alumina ceramics. Composites were obtained by mixing and sintering red mud and Al2O3. This study focused on the mechanical properties and wettability of these composites. The results indicated that the 10% red mud–Al2O3 composite exhibited the highest hardness (20.12 GPa) and flexural strength (346 MPa). This is attributed to the formation of a mineral phase dominated by CaAl12O19, generated by the red mud during the sintering process, which filled the pores and reduced porosity. The surface energy of the red mud–Al2O3 composite was the highest at room temperature and high temperature, reaching 49.60 mJ·m−2 and 1164.7 mJ·m−2, respectively, indicating that it has better stability at both room and high temperatures. This study provides an important fundamental basis for the application of red mud–alumina composites to replace alumina-based composites in the field of construction materials, molten metal filters, ceramic cleavers, etc.