在热力学分析的基础上，以铁尾矿和碳黑为原料，采用碳热还原氮化法合成了Si3N4粉。利用X射线衍射（XRD）、扫描电镜（SEM）等技术测定了产物的相组成和显微结构，研究了合成温度为1450 ℃，恒温时间8 h，N2流量600 mL/min条件下原料组成（配碳比（C和SiO2摩尔比））对合成过程的影响。结果表明，配碳比对合成过程的影响非常显著，在实验条件下配碳比为2最佳。当配碳比小于2时，随配碳比的增加，产物中Si3N4相迅速增加；当配碳比大于2时，随配碳比的增加，产物中Si3N4相开始减少，而SiC相逐渐增多。配碳比为2时，产物中Si3N4晶粒多为等轴柱状或短棒状βSi3N4。
Based on thermodynamic analysis, Si3N4 powders were synthesized by carbothermal reduction and nitridation from iron ore tailings and carbon black as raw materials. Phase composition and microstructure of products were determined by Xray diffraction (XRD) and scanning electron microscopy.For reaction temperature 1450 ℃, holding time 8 h, and N2 flow 600 mL/min, the effect of molar ratio of C and SiO2 on synthesis was studied. The results show that the molar ratio of C and SiO2 affects the synthesis process significantly, and the optimal ratio was 2. When the molar ratio was less than 2 Si3N4 phase in the product increased rapidly with the increase of molar ratio;When this molar ratio was more than 2 Si3N4 phase decreased while SiC phase rised with the increase of molar ratio. The favorable Si3N4 crystal mostly existed as equiaxed columnar or short rodlike βSi3N4 when the molar ratio was 2.
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