NMR探讨粉煤灰研磨过程中铝氧多面体的变化

采用²⁷Al魔角旋转核磁共振和二维三量子魔角旋转（2D 3QMAS）核磁共振方法对研磨前后粉煤灰中铝氧多面体结构进行了探讨. 结果表明：粉煤灰中铝氧多面体主要以四面体和八面体形式存在. 分析认为铝氧四面体和八面体有多种结构环境形式，导致它们宽化峰的出现. 经过机械研磨后，处于玻璃体硅氧四面体网络中的四配位结构相对稳定，只有微小的变化；网络外作为调整离子的六配位多面体有一部分脱离网络向结构环境对称性状态转变. 从2D图谱中还可以辨别出原先少量的五配位不稳定结构在研磨后消失.

STRUCTURES OF ALUMINUM-OXIDE POLYHEDRON IN FLY ASH BEFORE AND AFTER GRINDING STUDIED BY SOLID STATE NMR

The structures of aluminum-oxide polyhedron in fly ash and their changes after a grinding process were studied by ~(27)Al MAS and 2D 3QMAS NMR. The results showed that tetrahedron and octahedron are the main forms of aluminum-oxide polyhedron in raw fly ash, and they exist in a multi-structural surrounding. Only slight changes were observed for the tetrahedron structures after grinding, indicating that they are stable, probably because they exist in a three dimensional structural net of SiO_4]~(4-). The results also showed that, after grinding, part of the octahedron structures broken away from the net, and transformed and distributed in a symmetrical structural surrounding. The results from the 2D 3QMAS experiments showed that a small amount of hexahedron structures originally existed in the raw fly ash was damaged after grinding.