Silicon Carbide Powder Purity via Silicon Dioxide Mediator

Silicon dioxide (SiO2) is introduced as an intermediary substance that mediates the reaction between carbon and silicon. The SiO2 reacts with residual carbon to form CO gas, and with residual silicon to form SiO gas, thereby controlling the stoichiometric ratio and preventing contamination of the final SiC product. This intermediary mechanism resolves the contradiction by enabling precise stoichiometric control while maintaining high purity.

The invention converts the potentially harmful effect of excess carbon or silicon into a beneficial process. Residual carbon and silicon, which would normally decrease product purity, are intentionally allowed to remain in the reaction mixture and then reacted with SiO2 to form gaseous products (CO and SiO) that are easily removed. This transforms the harmful presence of residual reactants into a controlled purification mechanism.

Silicon dioxide serves as a simple intermediary additive that enables the direct reaction process to achieve high purity. The SiO2 is mixed with carbon and silicon sources and reacts with any residual carbon or silicon during the direct synthesis, converting them into gaseous products that escape the reaction zone. This maintains the simplicity of the direct reaction approach while achieving the purity level previously requiring more complex multi-step processes.

The invention changes the compositional parameter of the reaction mixture by introducing silicon dioxide at a specific molar ratio (0.01:1 to 0.3:1 relative to silicon and carbon sources). This parameter change enables the direct reaction to proceed while simultaneously providing the mechanism to remove residual reactants, thus achieving both ease of manufacture and high manufacturing precision.