Facile sample preparation method allowing TEM characterization of the stacking structures and interlayer spaces of clay minerals

Abstract

Transmission electron microscopy (TEM) is an essential and irreplaceable technique for studying the micromorphology and microstructure of clay minerals. However, observing layer stacking and detecting the interlayer spaces of clay minerals by TEM are still major challenges, due to the difficulty of finding suitable fields of view for clay planes along the [00l] direction. A simple and effective sample pretreatment method was proposed here for TEM characterization of clay mineral stacking structures and interlayer spaces. Using this method, clay mineral-bearing ultrathin slices, in which clay minerals particles showed an orientated arrangement, were prepared based on the resin embedding method. The (00l) plane of clay minerals was exposed toward electron beams during TEM analysis, and fields of view along the [00l] direction were observed, accordingly. This method is thus particularly useful for the observation of stacking information and detection of interlayer regions in clay minerals. The validity of this method is exemplified by its application to pure kaolinite and clay mineral-rich shale samples which contains several clay minerals and the clay mineral-organic matter complexes.