Nanoscale SiC powder synthesized by NaCl-assisted combustion and its formation mechanism
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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 performanceof SiC is significantly influenced by its particle size and purity. This paper employs the combustion synthesis method toproduce SiC using a magnesium thermal reduction-based technique, which is characterized by simple equipment, low energyconsumption, and suitability for large-scale production. In the SiO2-C-Mg system, utilizing combustion synthesis with NaClas a diluent effectively prevented particle growth caused by excessive combustion temperatures, thereby enabling the scalableproduction of high-purity nano SiC. Experimental results demonstrated that the addition of NaCl significantly reduced theproduct particle size, achieving a minimum of 26 nm. As a diluent, NaCl influenced the nucleation and growth processes ofSiC, further regulating the particle sizes. During nucleation, NaCl absorbed heat through phase change, effectively loweringthe adiabatic temperature of the system, increasing undercooling, and enhancing the nucleation rate. During growth, NaClacted as a dispersant to inhibit the growth of particles. In addition, NaCl provided a liquid phase environment that acceleratedmass transfer and heat transfer processes, and exhibited a high solubility for active species, the formation of SiC followed thedissolution-precipitation mechanism. Large-scale production of high-purity nano SiC can lay the foundation for the high-endapplications of SiC-based materials.
Abstract
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 performanceof SiC is significantly influenced by its particle size and purity. This paper employs the combustion synthesis method toproduce SiC using a magnesium thermal reduction-based technique, which is characterized by simple equipment, low energyconsumption, and suitability for large-scale production. In the SiO2-C-Mg system, utilizing combustion synthesis with NaClas a diluent effectively prevented particle growth caused by excessive combustion temperatures, thereby enabling the scalableproduction of high-purity nano SiC. Experimental results demonstrated that the addition of NaCl significantly reduced theproduct particle size, achieving a minimum of 26 nm. As a diluent, NaCl influenced the nucleation and growth processes ofSiC, further regulating the particle sizes. During nucleation, NaCl absorbed heat through phase change, effectively loweringthe adiabatic temperature of the system, increasing undercooling, and enhancing the nucleation rate. During growth, NaClacted as a dispersant to inhibit the growth of particles. In addition, NaCl provided a liquid phase environment that acceleratedmass transfer and heat transfer processes, and exhibited a high solubility for active species, the formation of SiC followed thedissolution-precipitation mechanism. Large-scale production of high-purity nano SiC can lay the foundation for the high-endapplications of SiC-based materials.