Study on the promotion mechanism of SiC formation at the reaction interface by structural evolution of silica under the action of K2CO3

In the production process of metallurgical-grade silicon (MG-Si), silicon carbide (SiC), as a key intermediate product, has a generation efficiency that directly affects the yield and energy consumption level of MG-Si. This study systematically investigates the influence mechanism of the structural evolution of silica on the formation of SiC at the reaction interface under the action of K2CO3, using a silica-coal diffusion couple system. The diffusion couple results indicate that after the addition of K2CO3, the diffusion layer thickness and average concentration of Si element on the coal side increased by 11.4% and 29.2%, respectively, while the regional enrichment degree and average concentration of C element on the silica side increased, with the latter rising by 25.0%. Overall, the addition of K2CO3 effectively promoted the formation of SiC at the reaction interface, accompanied by a 163% increase in the volume shrinkage rate on the silica side after the reaction. Mechanism analysis reveals that K2CO3 can react with SiO2 to form low-melting-point potassium silicate and gaseous products, significantly increasing the number and size of pores on the silica side. Simultaneously, the formation of potassium silicate weakens the lattice stability of SiO2, reduces the energy barrier for crystal phase transformation, and promotes the transition of quartz to its polymorphs. Thus, the synergistic effect of pore structure development and crystal phase transformation collectively enhances the high-temperature reactivity of silica, thereby improving the efficiency of SiC formation at the interface. This study reveals an effective method and mechanism for modifying silica raw materials, providing a new theoretical basis and practical reference for intensifying MG-Si smelting based on raw material optimization.