Oxidation behavior of Al2O3-SiC-C castable with highly wettable SiC@C composites

Abstract

Graphite-based composite materials have emerged as a crucial alternative to traditional flake graphite for optimizing the performance of Al₂O₃-SiC-C (ASC) castables after decarburization. In this paper, high wetting SiC@C composites powder was prepared via a sol-gel method combined with a carbothermal reduction reaction, and its effect on the oxidation behavior of ASC castables is explored. The results showed that SiC@C composites was synthesized under microwave conditions at 1000 °C, forming a structure where SiC whiskers are coated. And its contact angle with water decreases from 107° to 35°. Upon incorporation into ASC castables, the SiC whiskers within the sample continued to grow and develop with increasing addition of graphite-based composite materials. At a 2 wt% addition, the SiC whiskers began to form a cylindrical structure. Simultaneously, both the cold crushing strength and cold modulus of rupture exhibited a gradual increase. At the optimal 2 wt% addition, these values reached their maximum, 79.5 MPa and 11.4 MPa, respectively. The substitution of graphite-based composite materials also conferred good oxidation resistance to the ASC samples. Under oxidizing atmosphere conditions, the SiC whiskers on the composite material's surface facilitated the formation of a SiO₂ coating layer, which impeded the contact between oxygen and graphite, thereby enhancing the oxidation resistance of the material. Consequently, the oxidation index was reduced from 75.58 % to 42.71 %.