OBSERVATION OF TWO 4-COORDINATED AL SITES IN MONTMORILLONITE USING HIGH MAGNETIC FIELD STRENGTH 27AL MQMAS NMR

Abstract

Analyses of the layer structure of Na-montmorillonite have been performed using 27Al MAS and 27Al MQMAS NMR techniques. Results of 27Al MAS NMR measurements at higher magnetic field strength (16.4 T) suggest that the 4-coordinated Al site in Na-montmorillonite has two different structures. This was confirmed by the fact that two peaks corresponding to 4-coordinated Al are observed in the 27Al MQMAS NMR at high magnetic field strength. The ratio of two 4-coordinated Al sites was found to be affected by water in the interlayer space because the area ratio of cross peaks corresponding to two 4-coordinated Al sites changes with the water content.