碳纳米管“捆绑”石墨烯的超耐压三维结构及其高导热复合材料的研究

Three-dimensional graphene (3DGr) has attracted more and more attentions in the fields of interfacial thermal conductiondue to theinterconnected structure and theextraordinarily high in-plane thermal conductivity of graphene. However, the ultra-low density of 3D graphene and the abundant gaps between graphene sheets led to its poor thermal conductivity. In this work, In the present study, carbon nanotubes were integrated into 3D graphene to reinforce its structure stability and bring it super-elasticity. And the gaps between graphene sheets would be sutured using Plasma Enhanced Chemical Vapor Deposition (PECVD). In addition, a ultra-thin polymer film was coated on graphene pore walls to reinforce the mechanical properties. The mechanism of the super-elasticity of 3DGr, growth mechanism of PECVD, and thermal conductive mechanism were studied. 3DGr showssuper-elasticity, high thermal conductivity and good mechanical properties, suggesting their promising potentials in thermal management of electronic and thermal protection of spacecraft. In addition, this project provides strong technical supports and theoretical basisfor preparing novel thermal interfacial materials.

三维石墨烯（3DGr）由于其相互连接的网络结构和石墨烯自身的超高热导率，使其在热界面材料（TIM）领域中引起广泛关注。但由于3DGr超低的密度、内部存在的大量片层间隙，导致其内部接触热阻过高、热导率极低。针对这一缺陷，本项目提出在3DGr中引入一维碳纳米管对石墨烯骨架进行“捆绑”加固，赋予其超耐压弹性，从而可通过简单的机械压缩使其致密化，进而大幅提高热导率；同时利用PECVD技术对3DGr中石墨烯片层间隙进行“缝合”修复，提高三维导热网络的连续性和完整性，降低内部接触热阻；另外在石墨烯骨架表面上复合聚合物薄层以提高3DGr的机械强度。项目重点研究3DGr中“捆绑”结构耐压弹性的作用机制、PECVD缝合片层间隙的生长机理和3DGr的热传导模型。这种具有高热导率、高强度的超耐压3DGr-TIM在热管理领域中具有可观的应用前景，同时还为研究新型三维高效TIM提供了理论基础和技术支撑。

传统的金属导热材料由于自身的缺陷，已不能满足当今电子器件导热散热的需求。而碳材料具有热导率高、热膨胀系数小、化学稳定性好等优异性能，在热管理领域越来越受到关注。三维石墨烯其内部具有连续的多孔网络结构，热流可沿着孔壁中石墨烯的二维晶面实现三维立体方向的连续传导，应用为热界面材料具有可观的应用前景。为解决目前三维石墨烯在界面热传导中的瓶颈问题，提高三维石墨烯的热导率、降低内部接触热阻，本研究在三维石墨烯中引入一维碳纳米管对石墨烯骨架进行捆绑加固以赋予三维石墨烯超强耐压弹性，使其可以通过大形变量压缩来降低孔隙率，提高热导率；同时采用改进的冷冻模板技术，调控三维石墨烯内部的孔结构，提高孔壁厚度，增强孔壁强度，从而进一步增强三维石墨烯的弹性，并通过PECVD技术在三维石墨烯的壁层表面原位生长，对石墨烯的表面缺陷进行修复，从而减小内部热阻；进一步通过在三维石墨烯壁层表面进行原位聚合，增强其可压缩性，使其能够在更致密的条件下进行热传导。这种三维石墨烯热界面材料可在致密的压缩状态下依然保持内部三维导热通道的连续性，获得热导率的提升和内部接触热阻降低。研究表明，所制备的三维石墨烯可形成规整的三维多孔结构，石墨烯层间隙和缺陷也得到了修复，展现出优异的耐压缩性能，其最高可回复压缩形变达到95%，并可耐受1000次压缩/回复，最高热导率达到122.5 W m-1K-1，最低界面热阻达到9.8 mm2KW-1。这一复合材料不仅自身展现出优异的界面热传导性能，并且还为开发更多新型三维弹性热界面材料提供了研究思路和理论基础。