GRAPHITE MELTING UNDER LASER-PULSE HEATING

For a long time, the solid/liquid/vapor triple point of graphite has been a subject of debate, and despite the progress in the experimental techniques adopted, the uncertainties became even greater in recent years. In the experiments described in this paper spherical graphite specimens were heated by four tetrahedrally oriented laser beams to produce a fairly uniform temperature on the surface. A sufficiently large amount of molten graphite was produced to make it possible to identify the liquid/solid transition by a conventional thermo-analytical method. The temperature was measured by multichannel pyrometry, which enabled a detailed analysis of the perturbations and errors to be carried out. The triple point of graphite was determined to be T(t) = 4100 + 50 K and p(t) = 110 +/- 10 bar.