29Si and 27Al MAS NMR study of the thermal transformations of kaolinite from North China
The thermal transformations of kaolinite have been studied using 27Al and 29Si magic angle spinning nuclear magnetic resonance (MAS NM R), X-ray diffraction (XRD), differential thermal analysis (DTA) and thermogravimetric analysis (TG). The experimental results show that this sample is a pure kaolinite which contains ~3% carbonaceous material as impurity. 27Al and 29Si MAS NMR spectra show that the microstructural evolution of the thermal transformation of kaolinite at 450-1050°C is similar to that of the kaolinite-mullite reaction series previously published by many authors. 29Si MAS NMR spectra of mullite at 1190 and deg;C display two resonances at ~-87 and-92 ppm, corresponding to sillimanite-type geometry around Si and the typical Si environment of mullite, respectively. At 1350°C, the splitting of (hk0) and (kh0) of mullite occurs, indicating that the primary mullite transforms into orthorhombic mullite. Simultaneously, the resonance at ~-92 ppm splits into two signals at ~-90 and -94 ppm. 27Al MAS NMR spectra of the mullite consist of three signals centred at ~-4, 45 and 60 ppm, corresponding to octahedral, distorted tetrahedral and tetrahedral Al sites, respectively.
No Reference information available - sign in for access.
No Citation information available - sign in for access.
No Supplementary Data.
No Article Media
Document Type: Research Article
Publication date: 2003-12-01