Carbon nanotube thermal interfaces enhanced with sprayed on nanoscale polymer coatings

Vertical carbon nanotube (CNT) forests bonded at room temperature with sprayed on nanoscale polymer coatings are found by measurement to produce thermal resistances that are on a par with those of conventional metallic solders. These results are achieved by reducing the high contact resistance at CNT tips, which has hindered the development of high performance thermal interface materials based on CNTs. A spray coating process is developed for depositing nanoscale coatings of polystyrene and poly-3-hexylthiophene onto CNT forests, as a bonding agent that mitigates thermal resistance by enhancing the area available for heat transfer at CNT contacts. Resistances as low as 4.9 ± 0.3 mm2 K W−1 are achieved for the entire polymer coated CNT interface structure. The suitability of the spray coating process for large-scale implementation and the role of polymer and CNT forest thickness in determining the thermal resistance are also examined. (paper)