High-Resolution of Electron Microscopy of Montmorillonite and Montmorillonite/Epoxy Nanocomposites
AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
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Using high resolution transmission electron microscopy the structure and morphology of montmorillonite MMT, a material of current interest for use in polymer nanocomposites, was characterized. Using both imaging theory and experiment, the procedures needed to generate lattice images from MMT were established. These procedures involve careful control of the microscopes objective lens defocus to maximize contrast from features of certain size, as well as limiting the total dose of electrons received by the sample. Direct images of the MMT lattice were obtained from the neat Na MMT, organically modified MMT, and organically modified MMTepoxy nanocomposites. The degree of crystallinity and turbostratic disorder were characterized using electron diffraction and high resolution electron microscopy HREM. Also, the extent of the MMT sheets to bend when processed into an epoxy matrix was directly visualized. A minimum radius of curvature tolerable for a single MMT sheet during bending deformation was estimated to be 15 nm, and from this value a failure strain was calculated. HREM can be used to improve the understanding of the structure of polymer nanocomposites at the nanometer length scale.
- Geology, Geochemistry and Mineralogy