Continued miniaturization of nanoscale devices like Si microelectronics is likely to increase the importance of thermal management technologies. Nanofluids, consisting of nanoparticles or carbon nanotubes suspended in liquids, have shown promise for enhancing the thermal transport of liquids used in thermal management systems. Carbon nanotube suspensions, for example, have been demonstrated to increase the thermal conductivity of base liquids by up to 2.5 x for a volume fraction of only 1%. Studies to date on nanotube suspensions have not exploited one of the remarkable properties of carbon nanotubes: the thermal conductivity is anisotropic and approaches that of diamond or graphite along the axis of the nanotube. By aligning carbon nanotubes in liquid suspension with an applied electric field, the nanofluid is expected to show even greater enhancement of thermal conductivity. Moreover, the thermal conductivity will be anisotropic and controllable. By changing the orientation of the suspended carbon nanotubes with an applied electric field, it should be possible to actively control thermal conductivity and heat transfer with no moving parts.
Experiments are proposed on the thermal properties of aligned nanotubes in liquid suspension. The primary objectives of the proposed research are to demonstrate the feasibility of aligning carbon nanotubes, and to show that the thermal conductivity is anisotropic and controllable. Heat flux will be measured across the nanofluid for varying carbon-nanotube orientations relative to a temperature gradient. Further experiments will seek to measure the thermal conductivity tensor versus nanotubes orientation and degree of alignment.
Demonstration of the feasibility of carbon-nanotube alignment for active control of thermal conductivity will open the door to innovative thermal management strategies for nanoscale systems such as next-generation microprocessors. The research activities involve graduate and undergraduate students, and also leverages the outreach and curriculum development efforts of the Nanomaterials Science and Engineering (NMSE) Initiative at Rutgers University.
