Anisotropy of thermal conductance in near-ideal graphite

Abstract

Measurements of thermal conductivities of a number of pyrolytic graphites are reported including values for annealed, hot pressed graphite (IFPA57). Thermal conductivities of IFPA57 in both basal plane and c-axis directions approach the values for ideal graphite at higher temperatures. A theoretical estimate of the anisotropy of thermal conduction in ideal graphite in the temperature range where umklapp scattering predominates shows fair agreement with the present experimental value. Such defects as are normally present in well-oriented graphite produce comparatively little effect on the c-axis thermal conductivity and exposure to neutron damage has a much smaller effect in the direction of the c axis, than in the basal plane direction.