Graphene nanosheets hydrothermally armored with nano-MgAl hydrotalcite: A synergistic nanocomposite boosting high-temperature properties of alumina-spinel castables

Flake graphite (FG) limits the development of high-performance carbon-containing castables due to its inherent hydrophobicity. In this study, a graphene nanosheet/nano-MgAl hydrotalcite (GN/MAH) composite powder was successfully synthesized via a hydrothermal method. Under optimal conditions, the water contact angle of the composite powder was reduced from 103.6° for GNs to 44.6°, indicating significantly improved hydrophilicity. The incorporation of the GN/MAH composite powder markedly enhanced the mechanical performance of the castables after heat treatment at 1600 °C. Compared with the reference sample (0#), the cold modulus of rupture and hot modulus of rupture increased by 77.22 % and 54.91 %, respectively. Furthermore, the uniform dispersion of GNs within the castable matrix facilitated the maintenance of superior high-temperature performance even with a reduced carbon content of ∼0.15 wt%. As a result, the residual strength ratio of the castable after thermal shock increased by 13.69 %, while the slag corrosion index decreased by 43.26 %.