HRTEM and EELS studies of defects structure and amorphous-like graphite induced by ball-milling

Deformation structures and amorphization kinetics of graphite with high crystallinity upon ball-milling (BM) are studied by high-resolution transmission electron microscopy (HRTEM) and electron energy-loss spectroscopy (EELS). Basal plane stacking disorder, cleavage, delamination cracks; misorientation bands and low-angle (0002) twist boundaries are observed. The basal plane stacking disorder is probably produced by simultaneous shearing of all the lattice planes involved. Other defects such as half Frank loops or interstitial loops and significant bending and buckling of the basal planes are also frequently observed. Sustained shearing of (0002) planes acting in parallel with the increase of the Frank loops finally leads to the breakage of the hexagonal network in a very fine scale until an amorphous-like structure results. Although the amorphous-like phase exhibits amorphous halo diffraction patterns, HRTEM investigations indicate that it consists of highly curled small flakes with average basal plane diameter less than 5 nm and thickness (normal to the basal planes) less than 2 nm. EELS investigations demonstrate that its bonding is essentially sp(2). The present study clarifies the defect configuration appearing in heavily deformed graphite and also shows evidence that the amorphization of graphite is a defect-controlled process. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.