基于流态化技术硅粉直接氮化制备氮化硅粉

Preparation of silicon nitride powder by a direct nitridation process based on fluidization technology

提出了一种基于流态化技术,利用硅粉直接氮化制备氮化硅粉的新工艺。在常温下,以氮气为载气,将硅粉快速流化并夹带离开供料装置,硅粉和氮气组成的气-固两相流进入到预热器中,预热后的混合物从底部进入到高温悬浮床的高温区,以稀相气力输送的方式连续穿过高温悬浮床,在高温常压下发生燃烧合成反应,最后在出口经冷却装置冷却后,由收集装置收集,得到氮化产物。借助SEM、XRD、元素分析和FTIR等方法分析了氮化产物的形貌、物相组成、化学成分以及价键结构。实验结果表明:对于平均粒径为2.7μm的硅粉,在反应温度为1653K、反应时间为2.7min时,硅的转化率为53.4%,氮化产物为非晶氮化硅粉。通过理论预测,如果将反应温度升高至1723K,硅粉氮化7.1min后,其转化率可达99%。本文提出的方法可连续制备优质氮化硅粉,而且比现有的其他制备方法具有更高的生产效率。

A method for the preparation of silicon nitride powder by a direct nitridation process based on fluidization technology is described. At room temperature, using nitrogen as carrier gas, silicon powder was rapidly fluidized and the gas-solid two-phase mixture was carried from the feeding device into a preheater. The preheated mixture was then passed through a high-temperature suspended bed by a dilute phase pneumatic conveying process. Combustion synthesis at atmospheric pressure and high temperature afforded the nitridation products which were passed through a cooling device and collected. The morphology, phase composition, chemical composition and structure of the nitridation products were studied by SEM, XRD, elemental analysis and FTIR spectroscopy. In the case of silicon powder with particle size of 2.7μm, with a reaction temperature of 1653 K and reaction time of 2.7 minutes, the conversion of silicon was 53.4 %, and the products comprised amorphous silicon nitride powders. Theoretical predictions suggest that if the reaction temperature is increased to 1723 K, and the reaction time extended to 7.1 minutes, and the conversion of silicon should reach 99 %. The method presented here can be used for the continuous production of high-quality silicon nitride powders and has higher production efficiency than existing methods.