单晶α-Si3N4纳米线宏量制备研究

本研究提出了一种宏量制备单晶α-Si₃N₄纳米线的方法。以造粒硅粉为原料, 通过在N₂-H₂混合气氛中直接氮化, 得到具有核壳结构的氮化产物(Si₃N₄纳米线@多孔Si₃N₄微米粉体), 氮化产物经过破碎、研磨、分离后即可获得Si₃N₄纳米线。检测结果表明, 制备的Si₃N₄纳米线直径为80~150 nm, 长径比为20~50, 其中纳米线含量>95wt%, α相/β相比为17.6, 收率为3.1%。进一步研究表明, 原料中微量Fe元素在还原气氛下具有催化作用, 纳米线由典型的气-液-固(VLS)生长机制控制。实验中对原料硅粉造粒后再氮化具有三大优点: 数量级地增大了Si₃N₄纳米线生长空间; 纳米线生长分布集中, 有利于后续高效分离; 显著提高了氮化速率。

Mass Production of α-silicon Nitride Single-crystalline Nanowires

α-silicon nitride single-crystalline nanowires were prepared by direct nitridation of granulation Si powders in N₂-H₂ mixture gas. The nitridation product has the core-shell structure (Si₃N₄ nanowires @porous Si₃N₄ powders), where Si₃N₄ nanowires can be effectively separated by crushing and grinding. The results show that the as-prepared α-Si₃N₄ nanowires are straight and uniform with diameters of 80-150 nm, length to diameter ratios of 20-50, purity higher than 95wt%, and yield of 3.1%. Further study indicates that growth of Si₃N₄ nanowires is controlled by the Vapor-Liquid-Solid (VLS) mechanism, where the trace Fe elements serves as catalyst in the reduction atmosphere. In this study, The process of the raw silicom powder granulation after nitriding shows three advantages: 1) remarkably increasing growth space of nanowires; 2) leading to concentrated distribution of nanowire, tacilitating subsequent separation; 3) remarkably increasing the nitridation rate.