High-field27Al Mas NMR Studies of the Formation of Metakaolinite by Flash Calcination of Kaolinite

Flash calcination was used to dehydroxylate kaolinite and produced calcines kinetically frozen at various stages during metakaolinite formation. High speed magic-angle spinning27Al NMR, in magnetic fields of 14.1 and 11.8 T, enabled new features to be observed in the metakaolinite spectrum. The dependence on magnetic field of simulated and experimental spectra is discussed, and the effects of a distribution of electric field gradients is examined. The evolution of the metakaolinite peaks is followed during dehydroxylation.