Multicomponent-Multiphase Equation of State for Carbon

Abstract

The PANDA code is used to build a tabular equation of state (EOS) table for carbon. The model includes three solid phases (graphite, diamond, and metallic) and a fluid phase mixture containing three molecular components (C 1 , C 2 , and C 3). Separate EOS tables were first constructed for each solid phase and for each molecular species in the fluid phase. Next, a mixture/chemical equilibrium model was used to construct a single multicomponent EOS table for the fluid phase from those for the individual chemical species. Finally, the phase diagram and multiphase EOS were determined from the Helmholtz free energies. The model gives good agreement with experimental thermophysical data, static compression data, known phase boundaries, and shock-wave measurements. This EOS covers a wide range of densities (0-100 g/cm 3) and temperatures (0-1.0×10 8 K). The new EOS table can be accessed through the SNL-SESAME library as material number 7830.

Experimental investigation of linear thermal expansion of pyrolytic graphite at high temperatures

“…Dependence of the relative density of pyrolytic graphite on temperature in comparison with the literature data [2,3,5]. Thus, the average volume coefficient of thermal expansion at the temperature interval 3300-4800 K can be calculated as ̅ = ┴ + 2 ║ = 5,76 * 10 (3) Assuming that the approximation of the CTE of pyrographite in a direction perpendicular to the layers near the melting point is closer to the experimental data obtained than the approximation by the constant, one can obtain the density and expansion at this temperature.…”

“…Hence the CTE of pyrolytic graphite in a direction parallel to the layers in the temperature range 3300-4800 K can be taken equal to ║ = 4,65 * 10 . From the obtained dependences of the relative expansion of pyrolytic graphite in directions perpendicular and parallel to the basal plane one can calculate the dependence of graphite density on temperature in the temperature range 3000-4800 K. Figures 7 shows the relative density of pyrographite versus temperature in comparison with literature data [2,3,5]. Experimental points correspond to a pressure of 1 kbar (i.e.…”

“…The existing experimental data on the volumetric expansion of graphite in the temperature range up to the melting temperature are either calculated [3,4] or obtained in experiments in non-isobaric conditions, as in [5]. The difficulty of isobaric experiments with graphite is explained by the abovementioned features, as well as by the active sublimation of carbon, which intensifies at the temperatures above 3000 K. Thereby it was required to develop an experimental technique that makes it possible to obtain data on the thermal expansion of graphite materials in the temperature range 3300-5000 K.…”

“…Pyrolytic graphite with a density of 2.18 g/cm 3 was investigated. The properties of this material made it possible to measure thermal expansion up to the melting point without destroying the samples.…”

“…Thus, the average volume coefficient of thermal expansion at the temperature interval 3300-4800 K can be calculated as ̅ = ┴ + 2 ║ = 5,76 * 10 (3) Assuming that the approximation of the CTE of pyrographite in a direction perpendicular to the layers near the melting point is closer to the experimental data obtained than the approximation by the constant, one can obtain the density and expansion at this temperature. Taking into account the fact that the initial density of the graphite under study was 2.18 g/cm 3 , the density of this graphite at the beginning of melting is 1.82 g/cm 3 , and the volume change is 16.5%.…”