Detection of two silicon environments in kaolins by solid-state 29Si NMR

Abstract

An investigation of kaolins using solid-state 29Si NMR and X-ray crystallography is being carried out to study relationships between measured NMR parameters and X-ray determined properties. We report here some preliminary results of the 29Si NMR examination which provide new information on the structure of kaolins. Lippmaa and co-workers1 reported a single 29Si resonance for kaolinite at 39.75 MHz consistent with the existence of only one type of chemical environment for silicon as expected. We have examined highly crystalline samples of the three forms of kaolin by 29Si NMR at 59.61 MHz and resolved this peak into two components. This splitting of the 29Si resonance seems to be rationalized only by the presence, in fact, of two slightly different silicon environments in kaolins.