Thermal Conductivity of high performance yarn-like Carbon-nanotube Fibers
Vikas Prakash (Case Western Reserve Univ), Eric Mayhew (CWRU)
Eringen Medal Symposium in honor of G. Ravichandran
Tue 2:40 - 4:00
Salomon 001
The excellent thermal properties of individual multi walled carbon nanotubes (CNTs) have provided the impetus for researchers in developing high performance yarn-like carbon nanotube fibers. We present the results of thermal conductivity measurements in individual carbon nanotubes, CNT fibers, and CNT-polymer composite fibers. Thermal conductivity measurements are made using a T-type experimental configuration utilizing a Wollaston wire probe inside of a scanning electron microscope (SEM). In this technique a suspended platinum wire is used both as a heater and a thermal sensor. A specimen is attached to the midpoint of the suspended platinum wire using platinum electron-beam-induced deposition (for CNT strands) or conductive silver epoxy (for CNT fibers and CNT composite fibers), reducing the thermal contact resistance at the sample-platinum wire junction. During the experiment, the platinum wire is heated using an alternating current source while the third harmonic voltage across the suspended wire is measured by a lock-in amplifier. The thermal conductivity is deduced from an analytical model that relates the drop in the spatially-averaged temperature of the wire to the thermal resistance and thermal conductivity of the sample. Thermal conductivities are measured on individual CNT strands pulled from the fiber as well as the fibers themselves. The average thermal conductivity of the individual CNT strands is 8.9 ± 3.7 W/m-K. The highest measured thermal conductivity for an individual CNT is 14.3 ± 3.4 W/m-K. Thermal conductivity measurements are also made on CNT fibers and CNT composite fibers. The average thermal conductivity of the CNT fibers is 526 W/m-K with a standard deviation of 51 W/m-K, and the average thermal conductivity of the CNT composite fibers is 299 W/m-K with a standard deviation of 78.4 W/m-K. The significant difference in the thermal conductivity of the individual CNT strands and the CNT fibers warrants further investigation.