Spark plasma sintering and thermal conductivity of carbon nanotube bulk materials

Carbon nanotube (CNT) bulk samples were fabricated by spark plasma sintering (SPS), which, as a rapid consolidation technique, preserved the phase structure and diameter of cylindrical tubules of the CNTs even at high temperatures of up to $2000°\mathrm{C}$ . The thermal conductivity of the resultant bulk samples was measured by the conventional laser-flash method, and the corresponding thermal conductivity was found to be as low as $4.2\mathrm{W}∕\mathrm{m}∕\mathrm{K}$ at room temperature. This low thermal conductivity of the CNT bulk materials was explained on the basis of multiple physical elements including intensive tube–tube interactions. CNT bulk materials may find potential applications as thermoelectric materials that require low thermal conductivity, but high electrical conductivity.