分子结连接的碳纳米管网络导热的多尺度研究

Individual carbon nanotube (CNT) has extraordinarily high thermal conductivity; however, the thermal conductivity of bulk CNT materials based on randomly oriented CNT networks is seriously limited due to the huge intertube thermal resistance. Therefore, joining CNTs together via covalently-bonded molecular junctions to reduce the intertube thermal resistance is a new way to enhance the thermal conductivity of random SWCNTs network. The objective of the project is to investigate the heat conduction of randomly oriented single-walled carbon nanotubes (SWCNTs) network interconnected by carbon-carbon-bonded junctions through a multiscale approach based on theoretical analysis, simulations and experiments. The machanism of heat transfer through the molecular junctions is probed. Specifically, atomistic and mesoscale modeling and simulation methods are proposed to calculate the thermal conductivity at two different scales of the SWCNT network. A theoretical multiscale model for estimating the thermal conductivity of SWCNT networks is proposed. Experimental studies of the synthesis and thermal conductivity measurements of welded bulk CNT samples will be conducted. The effect of the fraction of welded contacts and mass density on the thermal conductivity of the random SWCNT network will be revealed through the experimental results, theoretical prediction results and simulation results, and the method will be proposed to enhance the thermal conductivity of bulk CNTs based on randomly oriented CNTs via carbon-carbon-bonded molecular junctions. The outcome from this project has transformative impact in fully developing the potential of high thermal conductivity of CNTs materials and accelerating thermal management and thermal enhancement applications of CNT-based materials.

单个碳纳米管具有极强的导热性能，但对于碳纳米管随机网络材料，管间巨大的接触热阻却严重制约了其导热性能。因此，通过建立管间分子结连接以降低管间热阻，可以为提高碳纳米管随机网络材料导热性能提供新的途径。本项目针对管间碳碳键分子结连接的单壁碳纳米管随机网络结构的导热性能及机理进行理论、多尺度模拟和实验研究。在研究分子结的热输运机理的基础上，对分子结连接的单壁碳纳米管随机网络热导率的原子模拟、介观模拟及建模方法进行研究，并建立该网络结构的热导率多尺度理论预测模型；结合理论预测、模拟结果及单壁碳纳米管随机网络宏观体材料烧结及热导率测量实验，分析并揭示多尺度下烧结率、质量密度等对单壁碳纳米管随机网络导热性能的影响，并探索通过分子结连接来提高碳纳米管随机网络导热性能的方法。研究结果对于充分挖掘碳纳米管结构的导热性能优势和促进碳纳米管材料在热管理及强化传热领域的研究和应用具有非常重要的意义。

碳纳米管在热管理领域具有广泛的应用前景。与单个碳纳米管所具有的超强导热性能相比，碳纳米管随机网络材料热导率很低，主要原因之一是管间巨大的接触热阻严重制约了其导热性能。因此，通过建立管间分子结连接以降低管间热阻，可以为提高碳纳米管随机网络材料导热性能提供新的途径。本项目针对管间碳碳键分子结连接的单壁碳纳米管随机网络结构的导热性能及机理进行了理论、多尺度模拟和实验研究。通过分子动力学模拟分析了单壁碳纳米管管间热阻随管间热接触点的变化，构建了基于DPD和SPH的单壁碳纳米管随机网络结构的导热介观模拟模型，并通过实验研究了碳纳米管随机网络结构宏观体的导热及热电特性，揭示了质量密度、管长等对单壁碳纳米管随机网络导热性能的影响。并在此基础之上对碳纳米管-石墨烯分子结及其阵列的热整流特性进行了研究并揭示了其机理。本项目的研究对于促进碳纳米管材料在热管理及声子器件的应用起到了积极作用。