Experimental electrical resistivity of liquid carbon in the temperature range from 4800 to ∼20,000 K

Abstract

Specimens of high density pyrolytic graphite (2.2 g/cm 3) were placed inside thick-walled sapphire tubes and heated over several microseconds by an electric current of 68 kA. The electrical resistivity of the liquid carbon was measured in a constant volume heating process. The transition of liquid carbon from semi-metal properties (resistivity decreasing with increase of input energy) to metal-like behavior (resistivity increasing with increase of input energy) was obtained at a high input energy (25–75 kJ/g) and at a high, but not measured, pressure. The transition temperature, T, was roughly estimated through the C V value (heat capacity under constant volume). The relationship between the density and the transition temperature is as follows: for 1.88 g/cm 3 density, the transition temperature T = 6300 K, for 1.76 g/cm 3, T = 10,100 K, and for 1.1 g/cm 3, T = 13,500 K. The estimated temperature at the maximum input energy (75 kJ/g) for liquid metal-like carbon (just before the destruction of the sapphire tube) is 23,000 K, with a corresponding measured electrical resistivity of 3000 μΩ cm.