A MICRO-RAMAN INVESTIGATION OF HIGH-PRESSURE QUENCHED GRAPHITE

Polycrystalline pyrolytic graphite was compressed in a diamond anvil c ell to pressures up to 73 GPa. In situ Raman measurements reveal evide nce of a phase transition at 15-20 GPa, consistent with earlier static high-pressure experiments on graphite. The sample was quenched by rap id downloading of the cell to ambient pressure. Micro-Raman investigat ion of the quenched sample reveals a broad range of previously unobser ved intermediate carbon structures, sometimes coexisting with diamond. We also observe the quenching of the 'nanocrystalline' phase of graph ite.