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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/Al_2O_3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/Al_2O_3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.
Under argon atmosphere, using fly ash as raw material and graphite as reductant, the reaction process of carbon-reduced fly ash to prepare SiC / Al_2O_3 composites was studied and the preparation conditions were explored.The reduction products were analyzed by X-ray diffraction The microstructure of the composites was observed by scanning electron microscopy and energy dispersive spectroscopy.The results show that the basic phase decomposition of 1773 K mullite phase is complete with the quartz and carbon-reactive silicon carbide in 1673 K fly ash With the increase of reaction temperature, the content of silicon carbide and alumina increased, the suitable temperature was 1773 ~ 1873 K. The prolongation of holding time was conducive to the formation of silicon carbide and alumina, and the better holding time was 3 ~ 4 h; increasing the amount of carbon added to promote the formation of silicon carbide and alumina, the more appropriate C / Si molar ratio of 4 to 5. In the prepared SiC / Al_2O_3 composite material in the product dispersion of silicon carbide is more uniform , And the particle size is less than 20 μm.