Aerospace and Mechanical Engineering and ‡Center for Sustainable Energy at Notre Dame, University of Notre Dame , Notre Dame, Indiana 46556, United States.
ACS Nano. 2013 Sep 24;7(9):7592-600. doi: 10.1021/nn401714e. Epub 2013 Aug 19.
Reversible thermal conductivity regulation at the nanoscale is of great interest to a wide range of applications such as thermal management, phononics, sensors, and energy devices. Through a series of large-scale molecular dynamics simulations, we demonstrate a thermal conductivity regulation utilizing the phase transition of polyethylene nanofibers, enabling a thermal conductivity tuning factor of as high as 12, exceeding all previously reported values. The thermal conductivity change roots from the segmental rotations along the polymer chains, which introduce along-chain morphology disorder that significantly interrupts phonon transport along the molecular chains. This phase transition, which can be regulated by temperature, strain, or their combinations, is found to be fully reversible in the polyethylene nanofibers and can happen at a narrow temperature window. The phase change temperature can be further tuned by engineering the diameters of the nanofibers, making such a thermal conductivity regulation scheme adaptable to different application needs. The findings can stimulate significant research interest in nanoscale heat transfer control.
在纳米尺度上实现热导率的可逆调控对于广泛的应用领域具有重要意义，例如热管理、声子学、传感器和能源器件。通过一系列大规模分子动力学模拟，我们展示了一种利用聚乙烯纳米纤维的相变来调节热导率的方法，实现了高达 12 的热导率调节因子，超过了所有先前报道的值。热导率的变化源于聚合物链上的链段旋转，这会引入沿链的形态无序，从而显著中断分子链上的声子输运。这种可以通过温度、应变或它们的组合来调节的相变，在聚乙烯纳米纤维中被发现是完全可逆的，并且可以在很窄的温度窗口内发生。通过工程化纳米纤维的直径，可以进一步调整相变温度，使这种热导率调节方案能够适应不同的应用需求。这一发现可以激发人们对纳米尺度传热控制的极大研究兴趣。
