In-situ synthesis of Al4Si2C5 platelets via AlF3-assisted vapor transport for enhanced performance of Al2O3-SiC-C castables

To meet the requirements of enhanced-performance Al 2 O 3 -SiC-C (ASC) refractories driven by larger modern blast furnaces, a novel in-situ approach to synthesize Al 4 Si 2 C 5 platelets within ASC was developed. Combined thermodynamic and experimental studies demonstrated the formation of Al 4 Si 2 C 5 platelets via AlF 3 -facilitated vapor-phase transport of Si sources to carbon at 1300–1600 °C. First-principles calculations indicate its growth initiates via SiC heterogeneous nucleation on C(002), followed by vapor adsorption of Al 2 O (g) , SiO (g), and SiOF 2(g). With 0.2 wt% AlF 3 , ASC castables exhibited markedly enhanced overall performance, including superior mechanical strength, improved thermal shock resistance, and significantly better oxidation and slag corrosion resistance. These enhancements arise from pore-filling by Al 4 Si 2 C 5 platelets and their role in forming a protective barrier during oxidation, which jointly hinder oxygen/slag penetration and crack propagation. This work provides fundamental insights into the low-temperature synthesis and reinforcement mechanisms of Al 4 Si 2 C 5 , offering a theoretical basis for designing high-performance refractories.