Temperature dependence of the thermal conductivity of individual pitch-derived carbon fibers

The thermal conductivity of individual pitch-derived carbon fibers was measured in the temperature range 100–400 K by a T type method, in which a hot wire served both as a heating source and thermometer, and the electrical and thermal properties of the hot wire were measured by direct current heating. When a tested carbon fiber was attached to the center position of the hot wire, the thermal conductivity of the fiber was determined by a comparison of the average temperature rise of the hot wire with and without the fiber. Results show that the thermal conductivity of the fiber was limited by boundary scattering below 300 K, and saturated around 350 K at a value of about 800 W/(m·K). An unexpectedly high thermal conductivity of about 920 W/(m·K) was observed at around 400 K. The effect of the thermal contact resistance on the measurement was estimated by changing the length of the fiber in the same contact conditions and the radiation effect was also discussed. The uncertainty of the thermal conductivity was estimated to be ± 13%.