原位反应合成多孔莫来石质支撑体及其显微结构(英文)

MICROSTRUCTURE AND SYNTHESIS OF POROUS MULLITE-BASED SUPPORT FOR LIGHT-WEIGHT PROPPANT BY IN SITU REACTION SINTERING

采用粉煤灰、烧铝矾土和球黏土为原料,通过原位反应烧结合成球形多孔莫来石质支撑体。考察了烧结温度对多孔莫来石质支撑体相转变、晶粒尺寸、孔径分布和气孔率的影响,并对其莫来石化的机理进行了探讨。研究表明:在1300℃烧结温度下,二次莫来石在硅铝酸盐液相中通过溶解-沉淀机制开始成核,并于1400℃烧结发育成针状的晶粒;当烧结温度升至1500℃时,溶解在液相中的莫来石进行结构调整和生长,并最终在1550℃发生原位反应并形成刚性交错网络结构的柱状莫来石。在低温(<1400℃)烧结阶段,二次莫来石的成核和生长引起体积膨胀,导致气孔率随温度的升高而增大;在高温(≥1500℃)烧结阶段,大量玻璃相的存在使液相烧结占主导,气孔率因体积收缩呈下降趋势。支撑体的平均孔径随烧结温度的升高而增大,其原因是在高温烧结时莫来石生长消耗过多的SiO2使大量微孔联接形成大孔。

Sphere porous mullite-based support for lightweight proppant was fabricated by in situ reaction sintering from a powder mixture of coal fly ash,calcined bauxite and ball clay.The effects of sintering temperature on phase evolution,grain size,pore size distribution and porosity were investigated.Moreover,the mullitization mechanism is discussed.The secondary mullite nucleate inchoately through a solution-precipitation mechanism via amorphous aluminosilicate phase at 1 300 ℃.The needle-like mullite grains were formed at 1 400 ℃.The dissolution of mullite in the permanent liquid phase could improve the growth of mullite at 〉1 500 ℃.The stiff skeleton net-structure mullite can be formed in situ.At low sintering temperature（〈1 400 ℃）,the volume expan-sion resultes from the formation and growth of secondary mullite,leading to the enhancement of porosity with increasing temperature.At ≥1 500 ℃,the presence of excess liquid glassy phase and the occurrence of liquid phase sintering are do minant,which results in the shrinkage of specimen and the decrease of porosity.The mean pore size for the support increased with increasing temperature.This is due to the consumption of excess SiO2 and the formation of larger size pores.