Structural change of graphite subjected to mechanical milling

The synthesis of disordered carbon was attempted by a method of mechanical milling. Hexagonal graphite was employed as a starting material. X-ray diffraction patterns indicate that the hexagonal graphite, composed of layers, was transformed into amorphous-like carbon by mechanical milling. This transformation indicates that milling breaks down the layer structure of graphite. However, the atomic arrangement within 3 Angstrom in the radial distribution function, RDF(r), observed by neutron diffraction indicates no change in environment. On the contrary, the coordination number of the first nearest neighbour gradually decreased with increasing milling time. These results indicate that the mean size of the graphite crystallites becomes smaller on milling and approaches about 30 Angstrom diameter in the c axis direction after 36 h of milling. (C) 1998 Elsevier Science B.V. All rights reserved.