Thermal Transport through Individual Surface Modified Carbon Nanotubes and Their Contacts

CBET#1067213PI：Deyu Li通过单个表面改性碳纳米管及其接触件的热传输碳纳米管（CNT）由于其上级的机械、电气和热性能，已被广泛测试为纳米结构添加剂，以调节CNT-聚合物复合材料的性能。虽然CNT-聚合物复合材料的测量电导率可以比纯聚合物高7个数量级，但热导率的增加是温和的，并且远离基于经典颗粒混合理论的预测。这种明显的差异引起了极大的关注和研究。然而，迄今为止，一个彻底的理解仍然缺失，拟议的研究计划的目标是通过系统的测量在单个纳米结构水平，通过单个CNT的热传输，单个CNT之间的接触，和CNT和聚合物分子之间的界面理解。与传统的先将碳纳米管和聚合物混合固化成固体复合材料，然后测量其热导率的混合测量方法不同，本研究将对未改性的碳纳米管和表面改性的碳纳米管与聚合物分子通过非共价键或共价键连接进行测量。混合和测量方法导致不一致的结果，更重要的是，通过纳米结构和它们的接触的热传输必须从具有复合结构和形态的许多假设的散装样品的测量结果推断。因此，很难得出可靠的结论。 相反，拟议的实验研究将直接测量通过单个纳米结构及其接触的热传输，同时仔细表征所测量的样品结构和形态。我们相信，拟议的系统研究将导致坚实的实验数据，这将回答以下基本问题：（1）能量载体如何通过CNT-CNT接触传输以及接触电导如何与接触面积成比例（2）热能如何通过CNT（硬）和聚合物（软）材料之间的界面传输（3）聚合物分子如何影响通过CNT-CNT接触的能量传输基于所获得的基本理解，我们可以创建新的设计规则，用于使用CNT来调整CNT的输运性质，该项目的智力价值在于以前无法获得的通过表面改性的热传输实验数据。CNT、CNT-CNT接触和CNT-聚合物界面。 更重要的是，这些数据将导致新的或更深入的物理理解纳米级的热传输，可以回答许多基本的科学问题，通过各种纳米结构，涉及碳纳米管，其接触和碳纳米管聚合物的混合物的能量传输。提出的系统的研究将是特别有帮助的，以发现通过碳纳米管及其接触的CNT直径的函数的热传输的依赖性，这将揭示有趣的nanoconfinement效应对能量transfer.The更广泛的影响，包括新的设计规则的基础上获得的纳米级传输现象的见解，这可以用来调整CNT-聚合物复合材料的传输性能。这将导致高性能碳纳米管-聚合物杂化材料的技术进步，对于柔性微电子和热电/光伏能量转换等广泛应用至关重要。此外，拟议的综合研究和教育计划将在跨学科环境中教育研究生，研究成果将通过科学出版物和课堂教学广泛传播。研究的影响也将扩大到本科生，代表性不足，和K-12学生通过利用范德比尔特的各种教育和推广计划。

CBET#1067213PI: Deyu LiThermal Transport through Individual Surface Modified Carbon Nanotubes and Their Contacts Carbon nanotubes (CNTs), because of their superior mechanical, electrical and thermal properties, have been extensively tested as nanostructure additives to tune the properties of CNT-polymer composites. While the measured electrical conductivity of CNT-polymer composites can be seven orders of magnitude higher than that of pure polymers, the increase in thermal conductivity is mild and far from the prediction based on the classical particle mixing theory. This apparent dissimilarity attracted significant attention and studies. However, to date, a thorough understanding is still missing.The objective of the proposed research program is to understand, through systematic measurements at individual nanostructure level, thermal transport through individual CNTs, contacts between individual CNTs, and interfaces between CNTs and polymer molecules. The measurements will be performed with both non-modified CNTs and surface modified CNTs attached with polymer molecules via either non-covalent or covalent bonds.The proposed study is different from the traditional mix and measure approach, in which CNTs and polymers are first mixed and cured into solid composites and then the thermal conductivity of resulted materials is measured. The mix and measure approach leads to inconsistent results and more importantly, thermal transport through nanostructures and their contacts has to be inferred from the measured results of bulk samples with many assumptions of the composite structure and morphology. Therefore, it is difficult to draw solid conclusions. The proposed experimental studies, on the contrary, will directly measure thermal transport through individual nanostructures and their contacts, together with careful characterization of the measured samples structure and morphology. We believe that the proposed systematic study will lead to solid experimental data, which will answer the following fundamental questions: (1) How do energy carriers transport through CNT-CNT contacts and how does the contact conductance scale with the contact area (2) How does thermal energy transport through the interfaces between CNTs (hard) and polymer (soft) materials (3) How do polymer molecules affect energy transport through CNT-CNT contacts Based on the obtained fundamental understanding, we can create new design rules for using CNTs to tune the transport properties of CNT-polymer composites.The intellectual merit of the project resides in the previously unavailable experimental data of thermal transport through surface modified CNTs, CNT-CNT contacts and CNT-polymer interfaces. More importantly, these data will lead to new or deeper physical understanding of nanoscale thermal transport that can answer many fundamental scientific questions about energy transport through various nanostructures involving CNTs, their contacts and CNT-polymer hybrids. The proposed systematic studies will be especially helpful to discover the dependence of thermal transport through CNTs and their contacts as a function of the CNT diameter, which will disclose intriguing nanoconfinement effects on energy transport.The broader impacts include new design rules based on the obtained insights of nanoscale transport phenomena, which could be used to tune the transport properties of CNT-polymer composites. This will lead to technology advancement of high-performance CNT-polymer hybrid materials important for extensive applications such as flexible microelectronics and thermoelectric/photovoltaic energy conversion. In addition, the proposed integrated research and education plan will educate graduate students in an interdisciplinary environment and the research results will be widely disseminated through scientific publications and classroom instructions. The research impacts will also be extended to undergraduate, underrepresented, and K-12 students through leveraging Vanderbilt's various education and outreach programs.