Melting of graphite

Abstract

The melting line of graphite has been investigated using a method of flash‐heating of small rod of graphite by discharging a bank of capacitors in a 6–8 anvil type high pressure apparatus. The changes of enthalpy of graphite up to the melting point were obtained from the heating energy inserted from a bank of capacitors, by making corrections for the heat losses due to thermal diffusion through the wall and the electrodes, which are surrounding the graphite rod. The melting temperatures of graphite were calculated from the enthalpy of graphite by using a data of specific heat Cp near the melting point. Melting temperatures increased from 4600 K at 10 MPa (the triple point of gas/graphite/liquid) to a maximum of 4800 K at 5.5 GPa, then decreased to 4600 K at 10 GPa. By an extrapolation of the line, the triple point of graphite/diamond/liquid is shown to be at about 4400 K and 14 GPa. The lower slope of melting line near the triple point is consistent with the positive slope for the melting line of diamond, which has been indicated in more recent experiment.