Phase transitions of carbon materials under high pressure

Abstract

Paradoxical experimental observations are explained by studying the high-pressure physical mechanics processes of graphite and carbon nanotubes (CNTs) and the macroscopic mechanics behaviors in the experiments of diamond anvil cells (DAC). The stress concentration on the graphite sample under non-hydrostatics compression in DAC experiments can produce a new phase that is hard enough to crack the superhard diamond. Those soft to hard phase transitions occur at the pressure of about 17 GPa for both graphite and CNTs, independent of the shape and the size of the indenter and the amount of the graphite layers. And a theoretical route is provided to industrially produce diamond and high strength CNTs-bundles composite at room temperature by using of high-pressure technology. Physical mechanics of nanomaterials in particular environment is also discussed. © 2007 Springer.