基于三维导热网络的高热导率石墨烯薄膜的研究

Graphene has great potential to solve the problems of low thermal conductivity, rigidity and bad weather resistance, due to its ultra-high thermal conductivity, super mechanical performance and corrosion resistance, which is beneficial to the thermal management for current ultra-fast high-power density electronic, optoelectronic, photonic devices. However, the thermal conductivity of graphene papers fabricated through layer by layer are anisotropy due to the weak intermolecular force, which limit its application as thermal interface materials that need heat conduct along the vertical direction. This project would synthesis high filling graphene composite material using 3D graphene as an isotropic skeleton and in-situ polymerization of polyacrylonitrile (PAN) as filler. Further, through hot-press, pre-oxidation, carbonization and joule welding, the PAN would transform into graphite crystallite and further construct a 3D thermal conductive net by crosslinking with graphene. A high density graphene based paper with high thermal conductivity in all directions was obtained. Then, the effect of fabrication techniques on the surface structure, morphology and thermal resistance of the sp2 crosslinked carbon structure will be systematically studied. Finally, the main purpose of this study is to demonstrate the construction mechanism of the 3D thermal conductive net and to provide theoretical basis and technical support for improving the three dimensional thermal conductivity of graphene.

石墨烯以其超高的热导率、优异的机械性能和耐腐蚀性能等优点，有望解决传统散热材料热导率低、柔性差、环境耐受性差等问题，对当前高功率密度集成电子设备的传热散热有积极意义。然而，层层自组装的石墨烯薄膜垂直面内方向较弱的分子间作用力使其热导率具有明显的各向异性，限制了其作为散热材料的应用。本项目拟采用三维石墨烯为骨架，利用其独特的各向同性结构，在其孔隙中原位生长填充聚丙烯腈（PAN），经过热压得到高致密石墨烯/PAN复合薄膜，进一步通过预氧化、碳化、焦耳热高温焊接实现PAN向石墨微晶转变，同时与石墨烯形成三维化学交联的共轭结构，得到具有三维导热网络的石墨烯薄膜，实现薄膜在三维方向均具有良好导热性能。同时，通过系统研究PAN填充量、热压、预氧化、碳化、焦耳热焊接对碳交联体微观结构形貌及界面热阻的影响规律，揭示sp2碳三维导热网络的构建机制，为提高石墨烯薄膜三维方向热传导能力提供理论依据和技术支持。

石墨烯在垂直方向热导率较低，是限制其在导热散热方面应用的瓶颈问题，本项目以各向同性的三维石墨烯为基础，通过在三维石墨烯孔隙中原位生长填充聚丙烯腈聚合物，通过热压得到高致密度薄膜。进一步，利用预氧化、碳化、焦耳热高温焊接等技术得到具有三维导热通道的石墨烯复合薄膜，与商用石墨纸相比，石墨烯复合薄膜具有更优异的力学、电学和垂直方向导热性能。