An EELS study of the structural and chemical transformation of PAN polymer to solid carbon

The chemical and structural evolution of a regular polyacrylonitrile (PAN)-based carbon fibre precursor, is investigated by following the various steps of the carbon fibre preparation process (including stabilization and carbonization). Electron energy loss spectroscopy is mainly carried out together with high-resolution electron microscopy of the carbon materials subsequently obtained. Additional information is also obtained from X-ray photoemission spectroscopy and infrared spectroscopy. The goal is to reveal the role of the alignment of the precursor polymer chains and the role of the textural and structural features in the subsequent behaviour of heteroatoms, i.e. the evolution of content, location, and bonding-type of O and N relative to C during the fibre processing up to secondary carbonization. The consistency of the PAN carbonization mechanism proposed by Watt with the present result is discussed. In addition, structure and chemical bonding variation are discussed in relation to physical properties. (C) 2004 Elsevier Ltd. All rights reserved.