基于绿色催化剂的α-Si3N4粉体燃烧合成新技术及气相氮化反应机制研究

本项目旨在发展一种过程稳定、清洁的燃烧合成α-Si3N4粉体制备新技术。以光伏切割“废硅”为原料，利用细Si粉表面SiO2膜作为气化反应的绿色催化剂，同时采用H2除去Si3N4稀释剂表面SiO2膜，通过促进液相Si的润湿铺展，加速其蒸发汽化，协同强化Si的气相氮化，实现α-Si3N4粉体的低成本制备。揭示气相氮化燃烧反应的过程机制，澄清Si/SiO2/Si3N4三元高温界面反应机理及润湿行为，通过优化工艺，制备出α相含量≥95%、氧含量≤1.5wt.%、残余Si含量≤0.1wt.%、粒度D50≤1μm的Si3N4粉体。在此基础上，气压烧结制备出高强韧氮化硅陶瓷（抗弯强度≥1000MPa、断裂韧性≥6MPa·m1/2），实现α-Si3N4粉体烧结制品的应用验证。.通过本项目研究，发展一种α-Si3N4粉体的低成本燃烧合成制备新技术，为我国氮化硅粉体制备技术的升级换代提供重要技术和理论支撑。

The project aims to develop a novel stable and clean combustion synthesis technology for the preparation of α-Si3N4 powder. Photovoltaic waste cutting silicon is used as raw powder for the fabrication of low-cost α-Si3N4 powder by enhanced gas phase nitridation of Si. In the combustion process the SiO2 film on the surface of fine Si powder is used as a green catalyst to improve the gasification of Si, and the evaporation and gasification of liquid Si is accelerated by using H2 to remove the SiO2 film on the surface of Si3N4 diluent powder to improve its high-temperature wettability in the meanwhile. The gas phase nitridation reaction mechanism in the combustion process is revealed, the high temperature reaction mechanism and wetting behavior of Si/SiO2/Si3N4 ternary interface is clarified. Si3N4 powder with α phase content ≥95wt.%, oxygen content ≤1.5wt.%, residual Si content ≤0.1wt% and particle size D50≤1μm is prepared by optimizing the combustion process. Base on that, high-strength and tough silicon nitride ceramics with bending strength≥1000MPa and fracture toughness ≥6MPa·m1/2 are prepared by gas pressure sintering, which realizes the application of the as-prepared α-Si3N4 powder. .Benefiting from this project, a novel combustion synthesis technology for low-cost α-Si3N4 powder was developed, which provides important technical and theoretical support for the upgrading of the preparation technology of Si3N4 powder in China.