超细碳酸钙微晶结构与热分解特性

研究了不同晶粒粒径,不同团聚状态的3种超细碳酸钙样品的热分解状况.应用三维球对称相界面迁移机理和CoatsandRedfern方程与应用Kissinger非机理方程得到的动力学参数基本一致,与普通碳酸钙相比,超细碳酸钙显示出60～80kJ·mol^-1的表观活化能降.3种超细碳酸钙样品的X射线衍射的数据分析表明,超细碳酸钙样品晶格中存在较大的畸变应力.我们认为,这可能是导致其反常热分解特性的原因.同时,对样品的TEM,SEM的观察揭示了微结构的团聚状态对热分解活化能的影响.

The Crystal Structure of Ultra-fine CaCO3 and Its Thermal Decomposition

The thermal decomposition of three ultra-fine CaCO3 having different particle sizes and agglomeration states was investigated. The kinetic parameters obtained by using the contracting volume mechanism R3 and Coats and Redfern′s equation were in good agreement with those using Kissinger nonmechanism equation. Furthermore, the result showed that a considerable diminution of the activation energy Ea up to 60～80 kJ·mol-1 is observed in the case of ultra-fine calcite. The Voigt analysis of the Xray diffraction data for the samples showed that abnormally large strain existed in the lattice of these samples. We suggest that this may be the reason of their abnormal decomposition behavior. At the same time, we observed that the conglomeration states revealed by TEM and SEM images result in the minute difference between those ultra-fine CaCO3.