蒙脱土的高温相变及微观结构表征

用X射线衍射仪和扫描电子显微镜,对阳离子交换容量为0.90 mmol/g,粒径≤74μm,纯度为80%～90%的钙基蒙脱土粉体,在不同温度下的焙烧产物进行了物相分析和结构表征。结果表明:钙基蒙脱土经过800℃焙烧后,蒙脱土的衍射峰消失,出现非晶质相,粉体颗粒边缘有部分熔融迹象;经1 000℃焙烧后,出现镁铝硅酸盐相,蒙脱土粉体颗粒边缘熔化,相互黏结成块,但是非常疏松;经1 200℃焙烧后,镁铝硅酸盐发生分解,生成堇青石和少量方石英,蒙脱土颗粒熔融、再结晶成块,致密度较高,但是表面有气孔。

Phases Transition and Microstructure of Montmorillonite at High Temperature

Calcium montmorillonite powder with a cation exchange capacity(CEC) 0.90 mmol/g,particle size≤74μm and purity 80%～90%was roasted at different temperatures.The phases compositions of roasted products were analyzed by X-ray diffraction and the microstructures of roasted products were observed by scanning electron microscopy.The results showed that roasted at 800℃the diffraction peaks of calcium montmorillonite disappear.But amorphous phase appears,and the edge of the particles of the powder shows the signs of partial melting.The magnesium aluminum silicate phase appears roasted at 1 000℃.The edges of montmorillonite particles are melted and bonded into loose blocks with each other.Roasted at 1 200℃,the magnesium aluminum silicate phase is resolved into cordierite and cristobalite.The montmorillonite particles are completely melted and recrystallized into blocks with higher density,but have many pores on the surface.