Structural change of graphite by mechanical milling

Abstract

The crystal structure of graphite is characterized by layers, the large separation of which (3.35 Å) compared with the C-C bond length of 1.42 Å in the layers indicates relatively feeble binding between the atoms of different layers. X-ray diffraction patterns indicate that the layer structure of the graphite was transformed into amorphous-like one by mechanical milling. TEM image also shows that the layer structure of graphite has disappeared after milling. This suggests that the milling conducts a large amount of strains in the layers. The atomic distribution within 3Å in the radial distribution function RDF(r) observed by neutron diffraction indicates no drastic change in position. On the contrary, the coordination number of the 1st nearest neighbor gradually decreased with increasing milling time. The results allow us to conclude that the size of the graphite becomes smaller by milling and approaches to be about 30 Å in diameter in plane after 36 hours of milling.