Experimental investigation of the thermal properties of carbon at high temperatures and moderate pressures

A consistent procedure for plotting the carbon melting and boiling coexistence curves based on published data and the authors' experimental results is proposed. The parameters of a triple point are predicted to differ markedly from the currently accepted values: p_t ≈1 bar and T_t ≈ 4000 K. Two types of experimental facilities were used, with laser heating of samples in one and direct ohmic heating in the other. The existence of a carbyne region (a stable linear polymer consisting of carbon atoms) in the carbon phase diagram is discussed. Results on the direct solid-phase graphite – carbyne transition are presented, and this is shown to occur under certain conditions in the form of a thermal explosion.