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

Abstract 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.