The thermal and electrical conductivities of deposited carbon

Abstract

Details are given of a method used to deposit carbon from hydrocarbons at high temperatures for the production of small tubular specimens. The density had been found to vary systematically with the temperature of deposition, and the present work relates to measurements of thermal conductivity and electrical resistivity made over the range 20 to 200° C on commercial graphite and deposited carbons formed at temperatures of 1800, 1900, 2000 and 2100° C. The thermal conductivities of the specimens deposited at 2000 and 2100° C were found to be exceptionally high. At 50° C the value for material deposited at 2000° C was approximately 20% greater than that of copper; for material deposited at 2100° C it was approximately 40% greater than that of copper. These measurements were made in a direction parallel to the axis of the tube for which direction the deposited carbon showed a pronounced layered structure. This, and an associated high electrical resistance normal to its plane, made it difficult to determine the electrical resistivity of the sample deposited at 2100° C. The high thermal conductivity appears to result from the high lattice conductivity of this material, the electronic component being only of the order of 1%.