碳还原粉煤灰制备SiC/Al2 O3系复合材料

在氩气气氛下,以粉煤灰为原料,石墨为还原剂,研究碳还原粉煤灰制备SiC/Al₂O₃系复合材料的反应过程,并探索其制备的工艺条件.利用X射线衍射分析还原产物的物相变化规律,使用扫描电镜和能谱仪观察复合材料的微观结构.结果表明:在1673 K粉煤灰中石英相与碳反应生碳化硅,1773 K莫来石相基本分解完全.随着反应温度的升高,生成碳化硅和氧化铝含量增加,较合适的温度条件为1773~1873 K;保温时间的延长,有利于碳化硅和氧化铝的生成,较好的保温时间为3~4 h;增加配碳量对碳化硅和氧化铝的生成有促进作用,较合适的C/Si摩尔比为4~5.在制备出的SiC/Al₂O₃复合材料中碳化硅在产物中分散较为均匀,并且粒度小于20μm. 

Preparation of SiC/Al2O3 composite materials from coal fly ash

By using coal fly ash as a raw material and graphite as a reducer in the protective atmosphere of argon,SiC/Al₂O₃ composite materials were synthesized by carbothermal reduction.The reaction process of reduction of the coal fly ash was studied,and its influencing factors were investigated.The composition of products obtained at different temperatures was analyzed by X-ray diffraction,and the microstructure was observed by scanning electron microscopy and energy dispersive spectroscopy.The results show that the phases of quartz and mullite in the coal fly ash are almost completely reactive at 1673 and 1773 K,respectively.With increasing temperature,the contents of SiC and Al₂O₃ increase,and the suitable temperature condition is 1773 to 1873 K.The extension of holding time is good for the formation of SiC and Al₂O₃,and the appropriate holding time is 3 to 4 h.Increasing the carbon content has positive effect on the formation of SiC and Al₂O₃,and the optimum molar ratio of C/Si is 4 to 5.In the prepared SiC/Al₂O₃ composite materials,SiC is homogeneously dispersed in the products,and its granularity is less than 20 μm.