A novel tar–silica sol bonded no-cement Al2O3–SiC–C castable with improved carbon dispersion and SiC whisker formation

This study prepared a novel carbon–silica (C–S) suspension, incorporating tar as the carbon source and silica sol as the binder. With robust bonding capabilities, it replaced conventional spherical bitumen in Al₂O₃–SiC–C (ASC) (where SiC is silicon carbide) refractory castables. Two key advantages were identified: improved carbon dispersion and in situ generation of SiC whiskers. This work advances the development of no-cement castables by using silica sol as a binder, avoiding the drawbacks of traditional cement systems and enhancing high-temperature performance. The effects of tar additions on the microstructure, phase composition, high-temperature properties, oxidation behavior, and slag erosion resistance of C–S–ASC castables were systematically investigated. Results showed that 4 wt.% tar addition led to more uniform carbon distribution than conventional castables. Industrial Computed tomography (CT) analysis revealed a notable increase in matrix density, indicating effective SiC whisker formation. Consequently, thermal modulus of rupture, oxidation resistance, and slag erosion resistance were significantly improved. Specifically, thermal shock resistance (residual strength ratio = 61.1%) increased by 24% and oxidation resistance (ω = 69.5%) by 20.9%, compared to castables with traditional carbon sources.