Anisotropic thermal conductivity and permeability of compacted expanded natural graphite

The anisotropic thermal conductivities and permeabilities are investigated for discs and plates of compacted expanded natural graphite. The measuring directions of heat conductivity and permeability are both parallel and perpendicular to the pressing direction of compacted samples. An unexpected phenomenon is found in that the thermal conductivity sometimes decreases as the density of the material increases, and this phenomenon only occurs for thermal conduction parallel to the compressing direction. The results also indicate that the direction perpendicular to the compression direction shows higher thermal conductive properties and permeability values. Both anisotropic thermal conductivities and permeabilities are strongly dependent on density. Analysis shows that as a type of porous material, the ENG yields layers under the effect of pressure, and their orientation influences the values of heat conductivity and permeability of the different samples. (C) 2010 Elsevier Ltd. All rights reserved.