Observed Dependence of the Low-Temperature Thermal and Electrical Conductivity of Graphite on Temperature, Type, Neutron Irradiation, and Bromination

The thermal conductivity of various graphites in the temperature interval 10° to 300°K has been determined and the effect of neutron irradiation and bromination investigated. The thermal conductivity of large crystallite natural graphite and of nonpitch-bonded graphite is found to vary as $T^2$ at low temperatures, as does the specific heat, in accordance with the simple theory of lattice heat conduction. This is in contrast to the anomalous $T^{2.7}$ dependence exhibited by various pitch-bonded graphites. The anomaly is explained in a subsequent paper in terms of the effect of ungraphitized pitch on the total thermal resistivity of pitch-bonded graphites.