The molten state of graphite: An experimental study

A subsecond laser heating technique has been successfully applied for graphite melting under controlled isobaric conditions. During the applied pulses, relatively large amounts of graphite were melted and subsequently solidified under good stability conditions of the liquid mass. The solid–liquid-vapor triple point was determined. From metallographic analysis of the quenched liquid, the expansion upon melting could be estimated. A mathematical model was then applied to analyze the measured thermograms and the thermal conductivity of liquid carbon was deduced. Both experimental observations and calculation results indicate a nonmetallic nature of liquid carbon in the pressure range of 110–2500 bar. Finally, an analysis of the melting line Tm(p) based on Simon’s empirical equation of state confirms the self-consistency of all results obtained.