Optimizing capillary channels via particle distribution to fabricate low-residual-silicon reaction-bonded SiC composites

Reaction-bonded silicon carbide composites exhibit high strength and excellent resistance to corrosion and wear; however, their performance and maximum operating temperature are constrained by the presence of residual silicon. This study applies an orthogonal experimental design combined with variance analysis to optimize the SiC particle-size distribution, thereby enhancing mechanical properties and reducing the amount of residual silicon. The results indicate that a 7:3:2 ratio of coarse, medium, and fine SiC particles yields a high packing density, effectively fills internal pores, and promotes uniform silicon infiltration. This optimized distribution results in a residual silicon content of 9.9 vol%, a bulk density of 3.09 g cm⁻³, and a bending strength of 402.2 MPa. Furthermore, the study demonstrates that the trimodal particle-size distribution improves the packing density of the green body, decreases pore size, and refines capillary channels, thereby significantly enhancing mechanical strength. These findings offer valuable guidance for the fabrication of high-performance SiC composites with refined microstructures and reduced residual silicon content.