Redesigning combustion synthesis for coupled co-production of SiC and Si3N4 powders

Silicon carbide (SiC) and silicon nitride (Si₃N₄) powders are critical raw materials for advanced ceramics. However, traditional synthesis methods face four major challenges: difficulty in achieving SiC nanosizing, difficulty in realizing Si₃N₄ high purification, the need for external energy input for the weakly exothermic Si-C reaction, and the requirement of adding large amounts of diluents to enable the combustion synthesis of the strongly exothermic Si-N₂ reaction. Recently, a research team utilized the difference in heat release between the Si-N₂ and Si-C reactions. By means of chemical furnace encapsulation, the strong heat release from the Si-N₂ reaction was used to induce the combustion synthesis of the weakly exothermic Si-C reaction system. Through the regulation of the combustion reaction temperature field and the partial pressure of CO reducing gas, β-SiC powders with an average particle size of only 30 nm and high-purity pink β-Si₃N₄ powders with an oxygen content as low as 0.46 wt% were successfully synthesized.

The team published their work in Industrial Chemistry & Materials on October 10, 2025.

High-performance Si-based ceramics using nanoscale SiC and high-purity Si₃N₄ powders as raw materials exhibit significant application value in semiconductor processing, power electronics, and high-temperature engineering. “To obtain cost-effective ceramic powders, and based on a comprehensive consideration of production energy consumption, efficiency, and product cost-performance, we believe that combustion synthesis technology is the most promising method to achieve large-scale and low-cost manufacturing of high-quality Si-based ceramic powders. However, for the combustion synthesis of SiC and Si₃N₄, the existing technologies still have two prominent shortcomings, which urgently require innovative breakthroughs,” explains Jiangtao Li, a professor at the Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, China. 

The team proposes a simple and practical new approach for the coupled combustion synthesis of the two reaction systems (Si-C/Si-N₂): by utilizing the strong exothermic characteristic of the Si-N₂ reaction, this reaction is employed as a chemical furnace to compensate for the energy deficiency of the weakly exothermic Si-C reaction. Meanwhile, the Si-C main reactant system constructs a reductive atmosphere with low O₂ and high CO at high temperatures, which promotes the formation of high-purity and low-oxygen Si₃N₄. By adjusting the proportion of the Si-N₂ chemical furnace system to the Si-C main reaction system, the temperature field of the coupled combustion synthesis system is optimized. This not only ensures the complete reaction of Si-C but also reduces the amount of diluent used in the Si-N₂ reaction process, thereby significantly enhancing the quality and cost advantages of both products.

The synthesized SiC and Si₃N₄ powders exhibit excellent performance: the obtained nanoscale SiC powders have an average particle size of 30 nm and good dispersibility; the pink Si₃N₄ powders have an oxygen content of 0.46 wt%, which is 60% lower than that of Si₃N₄ powders (1.20 wt%) produced by UBE, a well-known international manufacturer. The residual Si in the Si₃N₄ product is also reduced from 10.4 wt% to 1.66 wt%.

Next steps will focus on the pilot-scale amplification of this experimental work, up to industrial production. The key technical issue to be addressed is the precise regulation of the temperature field and CO concentration field during the scaled-up synthesis process.

The research team includes Lujia Han, Huakang Zhang, Xiao Yang and Jiangtao Li from the Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, China; Yuanyuan Li and Yanhao Dong from Tsinghua University, China.

This research is funded by the National Natural Science Foundation of China (U24A2049 and 92263205).

Industrial Chemistry & Materials is a peer-reviewed interdisciplinary academic journal published by Royal Society of Chemistry (RSC) with APCs currently waived. ICM publishes significant innovative research and major technological breakthroughs in all aspects of industrial chemistry and materials, especially the important innovation of the low-carbon chemical industry, energy, and functional materials. Check out the latest ICM news on the blog.