Silicon carbide (SiC) is a high-melting-point carbide that exhibits properties such as high-temperature ablation resistance, high thermal conductivity, and excellent thermochemical stability. As a high-temperature structural material, the performance of SiC is significantly influenced by its particle size and purity. This paper employs the combustion synthesis method to produce SiC using a magnesium thermal reduction-based technique, which is characterized by simple equipment, low energy consumption, and suitability for large-scale production. In the SiO₂-C-Mg system, utilizing combustion synthesis with NaCl as a diluent effectively prevented particle growth caused by excessive combustion temperatures, thereby enabling the scalable production of high-purity nano SiC. Experimental results demonstrated that the addition of NaCl significantly reduced the product particle size, achieving a minimum of 26 nm. As a diluent, NaCl influenced the nucleation and growth processes of SiC, further regulating the particle sizes. During nucleation, NaCl absorbed heat through phase change, effectively lowering the adiabatic temperature of the system, increasing undercooling, and enhancing the nucleation rate. During growth, NaCl acted as a dispersant to inhibit the growth of particles. In addition, NaCl provided a liquid phase environment that accelerated mass transfer and heat transfer processes, and exhibited a high solubility for active species, the formation of SiC followed the dissolution-precipitation mechanism. Large-scale production of high-purity nano SiC can lay the foundation for the high-end applications of SiC-based materials.

Keywords: Nano SiC, Combustion synthesis, Diluent, Formation mechanism.