机械活化含不同镁源的混合物合成堇青石

Synthesis of cordierite from different MgO source-containing mixtures via mechanical activation

分别以轻烧氧化镁、氢氧化镁、碱式碳酸镁为镁源,以三水铝石和无定形二氧化硅为铝源和硅源,按堇青石的理论组成配制成3种不同的混合料,经0、1、3、10、20、40 h机械活化后,在1 200、1 250、1 300、1 350℃空气气氛中煅烧3 h合成堇青石,用XRD分析机械活化前后物料的物相组成和结晶度以及合成产物的相组成。研究结果表明:1)以轻烧氧化镁为镁源的物料经40 h机械活化后仍未完全无定形化,而以氢氧化镁或碱式碳酸镁为镁源的物料经20或10 h机械活化后就完全无定形化;2)机械活化对3种物料的堇青石初始生成温度影响不大,在1 350℃煅烧3 h后,未机械活化的3种物料均未完全生成堇青石,而机械活化一定时间后的3种物料均形成了纯相堇青石,表明机械活化降低了堇青石的完全生成温度。

Three kinds of mixtures were prepared according to the theory composition of cordierite using light burned magnesia,magnesium hydroxide and basic magnesium carbonate as MgO sources,gibbsite and fumed silica as Al2O3 source and SiO2 source, respectively. The mixtures were mechanically milled for 0,1,3,10,20 and 40 h and heat-treated at 1 200 ℃,1 2.50 ℃,1 300 ℃ and 1 350 ℃ in air,respectively,to synthesize cordierite. The phase compositions and crystallinity of these mixtures before and after milling, and phase compositions of the synthesized products were characterized by XRD. The results show that： （]）the light burned magnesia-containing mixture is not entirely amorphous after 40 h milling ,while the magnesium hydroxide-containing mixture or the basic magnesium carbonateontaining mixture totally transforms into amorphous status after milling for 20 h or 10 h,respectively; （2）the influence of mechanical activation on incipient temperature of cordierite formation can be ignored ;after heat-treating at 1350 ℃ for 3 h, pure cordierite is obtained from these milled mixtures, while the mixtures without mechanical activation don＇ t transform into cordierite completely, showing that mechanical activation decreases the complete temperature of cordierite formation.