多级结构碳纳米材料构筑及其高性能聚合物电磁屏蔽纳米复合材料研究

Polymer based electromagnetic interference (EMI) shielding composites present promising potential applications in areas including electronics, automobile, aerospace and etc. However, it is still challenging to further improve shielding performance and to alleviate the seriously deteriorated mechanical properties due to the large filler contents. This project will fabricate strong three-dimensional (3D) graphene material with high electrical conductivity by strengthening the graphene interfaces with graphitized polymer precursors. Afterwards, metallic catalyst nanoparticles can be uniformly loaded on the obtained 3D graphene architectures by combining the advantages of supercritical CO2 in coating nanomaterials on inert substrates and of carbothermal reaction in reducing metal oxides. With controllable growth of carbon nanotubes (CNTs), strong and highly conductive hierarchically structured graphene-CNT hybrids could be constructed, which would provide valuable benefits for their polymer nanocomposites once the monomers and additives are impregnated. The influences of 3D graphene architectures, loaded catalysts, and CNT parameters on the properties of graphene-CNT hybrids will be explored and the relationship between microstructures of polymer nanocomposites and their macroscopic properties also be established. EMI shielding mechanisms and reinforcement effects of polymer nanocomposites will also be analyzed. Finally, this project will develop a novel method to prepare polymer nanocomposites simultaneously with excellent EMI shielding performance and outstanding mechanical properties.

聚合物基电磁屏蔽复合材料在电子、汽车和航空航天等领域具有重要的应用前景。但是，目前面临屏蔽性能提升困难和高填充所造成的力学性能严重劣化等问题。本项目拟采取以聚合物前驱体石墨化为基础的界面优化策略，强化石墨烯界面连接，突破制备高导电强韧三维结构石墨烯的关键技术；然后，结合超临界CO2利于纳米材料负载和碳热反应绿色高效还原的优势，在界面优化3D石墨烯惰性表面实现纳米尺度催化剂的均匀稳定负载和碳纳米管的可控生长，形成制备高强、高导电多级结构石墨烯-碳纳米管杂化材料新方法。最后通过真空辅助在杂化材料内部引入反应单体制备聚合物纳米复合材料，探明三维石墨烯结构特征、催化剂负载和碳纳米管形态结构对复合材料结构性能的影响规律，分析材料的电磁屏蔽机理和增强机理，建立聚合物纳米复合材料微观结构和宏观性能关系，为同时实现聚合物纳米复合材料电磁屏蔽功能化和高性能化提供新途径。

本项目开展了以石墨烯、碳纳米管和过渡金属碳氮化物为基本单元、构筑多级结构碳纳米材料和复合材料的多功能应用和性能优化的研究，取得了系列重要研究成果。具体总结如下：(1)为设计高性能高导电三维电磁屏蔽复合材料，我们使用聚苯乙烯微球为模板优化石墨烯导电网络，其电导率高达343 S m-1，实现优异电磁屏蔽性能（57.1 dB）。同时，采用原位气相生长碳纳米管的策略，完善气凝胶内部的导电网络，实现电导率由纯石墨烯气凝胶的60 S m-1提升至138 S m-1，获得55 dB的电磁屏蔽效能，比电磁屏蔽效能可达到4824.6 dB cm2/g。（2）为克服新型的过渡金属碳氮化物凝胶化能力差的弱点，采用以GO辅助水热成型和定向冷冻的策略制备三维Ti3C2Tx MXene气凝胶，并实现1085 S m-1的高电导率和超过50 dB的电磁屏蔽效能；并首次利用液-液界面组装的策略制备MXene基的结构液体，制备轻质、疏水、高电导率（376 S m-1）、高电磁屏蔽效能（0.4 vol%，34.5 dB）的MXene气凝胶。(3) 为增强二维纳米材料的界面相互作用，我们发展界面增强策略制备一系列多功能杂化气凝胶：首先，我们选用可石墨化的聚合物聚酰亚胺增强石墨烯界面相互作用，制备出超高导电性能(>1000 S m-1)，卓越电磁屏蔽效能(~83 dB)，90%应变下可压缩回弹和超强耐疲劳性能(50%应变下压缩1000次)的轻质超弹性石墨烯气凝胶。同时，引入聚酰亚胺来组装MXene片层，构建超弹性、耐疲劳、可逆拉伸性能以及优异吸波性能（-45.4 dB，有效吸收带宽5.1 GHz）的多功能3D MXene体系。进一步地，为充分保留MXene类金属的电导率，利用海藻酸钠辅助构建高效导电网络，在95 wt% Ti3C2Tx含量下，电导率可达2211 S/m，电磁屏蔽性能可达70.5 dB。此外，包覆PDMS层增强的导电网络（53.9 dB），压缩-释放循环500次后，仍保持48.2 dB的高电磁屏蔽效率。总之，本项目针对聚合物电磁屏蔽复合材料填料含量高和力学性能严重劣化问题，提出系列构筑三维高效导电/屏蔽结构网络策略，大幅降低填料用量、获得超高电导率，为聚合物电磁屏蔽复合材料的结构功能一体化设计与制备提供参考和技术支撑。