石墨烯三维结构的可控构筑及其高导热聚合物复合材料研究

High thermally conductive polymer composites are of great value in the field of heat dissipation of electronics and heat exchange. This project aims to prepare oriented graphene aerogels by directional freeze-drying large-size graphene oxide suspension or graphitizable polymer solution followed by high-temperature graphitization, which can act as efficient and continuous conductive network when applied in thermally conductive polymer composites. The influence of the microstructure on the thermal conductivity of the polymer composite will be investigated, including the pore size, wall thickness and stacking of graphene sheets and interfacial interaction between the graphene and polymer matrix. It is determined to reveal the relationship between the structure and performance of the oriented graphene aerogels, and establish a structure-performance model, which could optimize the structure of the oriented graphene aerogels. Interfacial thermal resistance, thermal contact resistance, defects in graphene lattice and boundary phonon scattering, which are harmful to the thermal conductivity of composites, will be minimized, and the ultra-high in-plane thermal conductivity of graphene will be fully utilized. In this way, high thermal conductivity of composites at low graphene loading could be realized, overcoming the problems that polymer based thermally conductive composites often need high filler loadings. In addition, it may solve the problem of low thermal conductivity of thermal interface materials in thickness direction, which is vital to the modern electronics.

聚合物导热复合材料在电子产品散热以及热能交换领域具有重要的应用价值。本课题拟采用大片氧化石墨烯、可石墨化聚合物等作为构筑基元，通过定向冷冻干燥和高温石墨化处理制备孔壁高度取向并且平整而致密的石墨烯气凝胶，并以此作为连续而高效的导热通道构筑聚合物导热复合材料。研究并揭示石墨烯气凝胶各项结构特征如构筑基元尺寸、孔壁厚度及致密性以及石墨烯同基体之间界面相互作用等因素对复合材料导热性能的影响机制，构建结构-性能关系模型，指导结构调控，优化导热网络热传导性能。在最小化界面热阻、接触热阻、石墨烯面内缺陷以及边缘声子散射等不利因素对复合材料导热性能制约的同时，最大化发挥石墨烯超高面内热传导能力。从而突破复合材料高导热需要高填充的普遍规律，实现低填充、高导热特性，并同时解决热界面材料及薄壁材料困扰已久的厚度方向热导率低的问题，促进现代电子元器件进一步发展。

项目采用氧化石墨烯、石墨微片和可石墨化聚合物聚酰亚胺等作为构筑基元，结合室温干燥、定向冷冻干燥以及高温石墨化处理等方式制备自由分散、层状取向、蜂窝状取向以及同心圆环状取向等多种结构形态的石墨烯气凝胶，并以此作为连续而高效的导热通道构筑聚合物导热复合材料。项目研究并揭示了石墨烯气凝胶各项结构特征如构筑基元、孔壁厚度及致密性以及石墨烯同基体之间界面相互作用等因素对复合材料导热性能的影响机制，构建了结构-性能关系模型。通过降低界面热阻、接触热阻、石墨烯面内缺陷以及边缘声子散射等不利因素对复合材料导热性能制约，通过石墨烯取向最大化发挥石墨烯超高面内热传导能力，从而突破复合材料高导热需要高填充的普遍规律，实现低填充、高导热特性，在提高复合材料热导率的同时，显著提高复合材料的力学性能，并同时解决热界面材料及薄壁材料困扰已久的厚度方向热导率低的问题。