Order-disorder in 1:1 type clay minerals by solid-state ²⁷Al and ²⁹Si magic-angle-spinning NMR spectroscopy.

Study by ²⁷Al and ²⁹Si MAS-NMR showed the existence of short-range order in 1:1 dioctahedral layer-silicates; while XRD showed different degrees of long-range order-disorder. Spectra obtained on kaolinite and metakaolin clearly showed the transformation of some octahedral Al in kaolinite to tetrahedral coordination in metakaolin and also showed short-range Al and Si disorder in the latter. This suggests that structural re-arrangement on thermal treatment can be monitored by this technique. These results further suggest that MAS-NMR can detect short-range order, which is complimentary to the information that XRD provides regarding long-range order.-D.J.M.