高岭土煅烧活化温度的初选

Optimization of Calcined Temperature for Kaolin Activation

为得到高岭土的最佳活化温度,利用差热-热重(DSC-TG)、核磁共振(NMR)和红外光谱(IR)等测试方法对高岭土及其在不同温度(700,800,900,1000℃)条件下的煅烧产物进行了分析.结果表明:高岭土经900℃煅烧后所生成的偏高岭土反应活性最高;煅烧后的高岭土内部结构发生显著变化,结构水大量失去,Al的配位数发生转变,高活性的五配位铝(AlⅤ)大量生成;高岭土的振动特征吸收峰消失,出现了偏高岭土的振动特征吸收峰.实验证实:高岭土在900℃下煅烧后再经化学激发所得到的地聚合物其抗压强度最高,80℃下养护3,7 d后其抗压强度分别达到了33.8,35.3 MPa.SEM观察发现,其断裂面内部结构呈致密的珊瑚状三维空间形态.

To get the best activation temperature for kaolin, kaolin and its products calcined at different temperatures were analyzed by DSC-TG, NMR and IR. The results show that kaolin calcined at 900 ℃ has the higher activity than that calcined at 700, 800,1 000 ℃. Intenal structure of calcined kaolin changes notably, for example, the dehydration, Al-coordination conversion （from 6--coordinated into 5--coordinated） and many characteristic absorption peaks of metakaolin occur. Compressive experiment confirmes that geopolymer synthesized from kaolin calcined at 900℃ has higher compressive strength. The highest compressive strength of samples cured at 80 ℃ for 3,7 d reaches 33.8,35.3 MPa respectively. The coralloid 3--dimentional framework could be observed by examining the fracture surface.