Structural evolution of a graphite–diamond mixture during ball milling

The structural evolution of a graphite–diamond mixture during high-energy ball milling was characterized by X-ray diffractometry, Raman spectroscopy, scanning electron microscopy and computer simulation. The milling behaviors of graphite and diamond were compared and studied. Graphite transformed into turbostratic carbon in the initial stage of milling and then into amorphous carbon with obvious sp2- and sp3-bonding, whereas diamond transformed into nano-diamond in the initial stage of milling and then into amorphous carbon with sp3-bonding. In the milling conditions used, graphite transformed via turbostratic carbon into amorphous carbon after having been milled for longer than about 30 h, but only a part of the diamond transformed into amorphous even after having been milled for 500 h.