NER: Field-Aligned Nanotube Suspensions for the Active Control of Heat Transfer in Nanosystems

硅微电子等纳米级器件的持续小型化可能会增加热管理技术的重要性。纳米流体由悬浮在液体中的纳米颗粒或碳纳米管组成，在热管理系统中用于增强液体的热传输方面显示出前景。例如，碳纳米管悬浮液已被证明可以在体积分数仅为1%的情况下将基础液体的导热性提高2.5倍。迄今为止，对纳米管悬浮液的研究还没有充分利用碳纳米管的一个显著特性：热导率是各向异性的，沿着纳米管的轴向接近金刚石或石墨的热导率。通过将液体悬浮液中的碳纳米管与外加电场对齐，纳米流体有望显示出更大的导热性增强。此外，导热系数将是各向异性和可控的。通过外加电场改变悬浮碳纳米管的方向，应该可以在没有运动部件的情况下主动控制导热性和传热。对纳米管在液体悬浮液中的热性能进行了实验研究。本研究的主要目的是证明碳纳米管排列的可行性，并证明其热导率具有各向异性和可控性。热通量将测量不同的碳纳米管方向相对于温度梯度的纳米流体。进一步的实验将寻求测量热导张量与纳米管取向和对齐程度的关系。碳纳米管对准对热导率主动控制的可行性论证，将为下一代微处理器等纳米级系统的创新热管理策略打开大门。研究活动涉及研究生和本科生，也利用了罗格斯大学纳米材料科学与工程（NMSE）倡议的推广和课程开发工作。

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.