Fast and highly anisotropic thermal transport through vertically aligned carbon nanotube arrays

This letter reports on fast and highly anisotropic thermal transport through millimeter-tall, vertically aligned carbon nanotube arrays (VANTAs) synthesized by chemical vapor deposition on Si substrates. Thermal diffusivity measurements were performed for both longitudinal and transverse to the nanotube alignment direction, with longitudinal values as large as 2.1 +/- 0.2 cm(2)/s and anisotropy ratios as large as 72. Longitudinal thermal conductivities of 15.3 +/- 1.8 W/(m K) for porous 8 +/- 1 vol % VANTAs in air and 5.5 +/- 0.7 W/(m K) for epoxy-infiltrated VANTAs already exceed those of phase-changing thermal interface materials used in microelectronics. Data suggest that further improvements are possible through optimization of density and defects in the arrays.