高岭石的热稳定性和热处理产物的DTA,IR和EPR研究

INVESTIGATION OF HEAT-STABILITY AND HEAT-TREATED PRODUCTS OF KAOLINITE WITH DTA,IR,AND EPR

本文利用DTA、IR和EPR等方法研究了高岭石的热稳定性及100—900℃热处理产物的系统特征。高岭石的热稳定性会因为堆垛层错缺陷浓度的增大而降低。根据IR和EPR实验,所有高岭石热处理过程中的变化包括:脱羟前、脱羟和脱羟后三个阶段。小于400℃时,产物成分和结构同原高岭石相同,≥400℃开始产物的堆垛层错浓度增大并有利于继续升温后的脱羟过程。变高岭石可能介于晶质和非晶质之间。此外,高岭石Ⅰ位Fe^(3+)和变高岭石结构中的Fe^(3+)可能有某些相似的特征。

Heat—stability and heat-treated products throughout the temperature 100—900℃ of kaolinite have been studied with DTA, IR, and EPR. Data show that heat-stability of kaolinite decreases as the concentration of stacking faults increases. EPR and IR results indicate that heat-treating process may be described as three stages: pre-dehydro-xylation,dehydroxylation,and post-dehydroxylation stage. The products treated below 400℃ are just the same as original. kaolinite in struscture and composition. It is nearly 400℃ when stacking fault concentration in products begin to increase and this may be helpful for dehydroxylation. Investigation implies that metakaolinite may be a material between crystalline and non-crystalline. In addition,EPR spectra of a series heat-treated products in the range of 100—900℃ suggest some similarities between I site Fe of kaolinite and Fe in matekaolinite and transition kaolinite.