Temperature dependence of the resistivity of carbon fibers

An anomalous temperature dependence of the resistivity rho (T) of carbon fi bers in the temperature range from II to 350 K was considered. The fibers w ere obtained from polyacrylonitrile thermally treated at 1400, 1600, 1800, 2000, 2200, 2400, and 2600 degreesC. A heterogeneous model of electric cond uction was developed, which closely described the experimental temperature dependence of the conductivity of the carbon fibers under study, including the temperature range where the temperature coefficient d rho /dT is positi ve. It was demonstrated that the basic assumption of the model about the ex istence of several phases in the material reflects the realization of sever al different mechanisms of charge transfer in complex materials.