Investigating the structure of non-graphitising carbons using electron energy loss spectroscopy in the transmission electron microscope

Abstract

We have investigated the structure and bonding in phenolic resin-based carbons as a function of heat treatment using a combination of high resolution transmission electron microscopy, electron energy loss spectroscopy, X-ray diffraction, gas adsorption and density measurements. On heat treatment, the initially amorphous material transforms to a micro-porous material containing small graphitic packets enclosing elongated pores, with a relatively small change in density but an appreciable change in planar carbon sp 2-content as well as the development of significant curvature in the graphitic layers. The results from the different characterisation techniques are discussed and wherever possible, cross-correlated. They are also compared with proposed models for the microstructural development in non-graphitising carbons and also with the corresponding data obtained from graphitisable carbons. Overall the data provides strong evidence for a fullerene-based model for the microstructural development in non-graphitising carbons and more generally, the interpretation of the current EELS data has important implications for the spatially localised analysis of poorly crystalline carbon materials.