Thermal conductivity of nano modified pitch based carbon fibers

The addition of ultra dilute concentrations of MWNTs (≈0.3 wt%) to the ARHP mesophase pitch precursor has been shown, in our previous work, to improve the compressive strength of the carbon fibers. The objective of the present study was to determine if the thermal conductivity would be adversely affected for such fibers. The axial thermal conductivity (TC) of these fibers is reported based on two different methods: (1) laser/light flash analysis (LFA) on fiber/epoxy composites, and (2) correlation from electrical resistivity measurements on individual fibers. Both methods were verified with commercial grade carbon fibers, and then applied to experimental fibers containing 0 wt% and 0.3 wt% MWNTs. Carbon fibers containing no MWNTs (0 wt% MWNTs) displayed a TC of 330±120 W/m ^*K and 550±30 W/m ^*K, as measured using the LFA and electrical resistivity methods, respectively. The difference between results obtained by these two methods is believed to signify the difference between the bulk property of a fiber bundle, which may contain some fractured fibers, and that of an individual, undamaged fiber. Therefore, the LFA method signifies a lower TC limit, whereas the electrical resistivity method provides an upper bound. Finally, the nanomodified carbon fibers displayed TC values of 240±80 W/m ^*K and 570±40 W/m ^*K, as measured by the two methods. Interestingly, these values are not significantly smaller than those for carbon fibers containing no carbon nanotubes.