Effect of synthesis temperature on the carbothermal reduction of silicon carbide from rice husk with copper additive

The synthesis of silicon carbide from rice husk typically requires temperatures above 1500°C due to limitations in solid-state diffusion. In this study, a Cu-catalyzed carbothermal reduction route was investigated using a rice husk–silica gel mixture at a fixed mass ratio of 1:1.4 over the temperature range of 900–1300°C. After HF purification, a high SiC content of 88.47% (ISO 21068-2:2008) was achieved at 1300°C, which is approximately twice that obtained by non-catalytic pyrolysis (40–60% at 1600°C). Three distinct kinetic regimes were identified: 900–1100°C, characterized by a gradual increase in SiC yield (4.63% per 100°C); 1100–1200°C, showing a sharp increase (8.48% per 100°C after purification); and 1200–1300°C, where the reaction approached saturation. The presence of Cu promotes a Vapor–Liquid–Solid mechanism via the formation of a low-temperature Si–Cu eutectic (~ 800°C), thereby significantly enhancing atomic diffusion between the liquid and solid phases. XRD analysis confirmed the formation of 3C- and 4H-SiC polytypes, while FTIR spectra revealed characteristic Si–C vibration bands at 809 and 624 cm⁻¹. HF treatment effectively removed residual SiO₂ and Cu oxides, as evidenced by SEM/EDX analysis. The combined catalytic assistance and selective post-purification enable high-purity SiC formation at significantly reduced temperatures, demonstrating an efficient pathway for converting biomass-derived precursors into advanced ceramic materials.