力学强韧的石墨烯基气凝胶各向异性结构的构筑及特性研究

The pristine graphene aerogels (GAs) tends to collapse due to its fragile inherent structure, resulting from the lack of cross-linking and disorderly restacking of individual graphene sheets. In this project, to overcome this problem, magnetic polymer nanofibers will be selected as key controllable factor to facilitate constructing interconnected network with high mechanical strength and high structure anisotropy for graphene based aerogels. The magnetic nanofibers and graphene sheets will orderly arrange and cross-link to each other in a certain orientation in the network of aerogel by magnetically manipulation. This project will study the gelation network evolution during macroscopically building of graphene aerogels from graphene oxides, thus elucidating the relationships between the cross-linking degree, ordered structure and tough mechanical properties of graphene aerogels. The preparation method for magnetic polymeric nanofibers with controllable structure and surface behavior will be developed. The effect of magnetic field manipulation on the inter-crosslinking behavior and orientation relationship between nanofibers and graphene sheets will also be explored so as to disclose the texturing formation mechanism of the anisotropic structure for graphene aerogels. Finally, the relationship models between ordered anisotropic structure and mechanical, electrical, as well as magnetic properties will be established for graphene based aerogels. We will further explore the anisotropic effect of elastic strain, straintronic resistance, magnetoresistance, microwave permeability, etc. This will provide a novel anisotropic material model for future development of flexible and multifunctional electric devices with complicated structure, and also contributes to a significant value of theory and application.

针对石墨烯气凝胶材料由于石墨烯片层缺乏交联、无序堆叠而引起的结构脆弱的问题，本课题结合前期基础，以磁性聚合物纳米纤维为调控因子，借助磁场取向技术，形成磁性纤维与石墨烯片层有序交联、取向排列的三维网络结构，从而实现力学强韧、微观有序、结构-性能各向异性石墨烯基气凝胶的宏观构筑。研究由氧化石墨烯向石墨烯气凝胶组装过程中凝胶网络结构的演变规律，阐明网络交联度、结构有序与结构强韧之间的关系；发展结构、表面特性和磁性能可控的磁性聚合物纳米纤维制备的新技术；研究磁场对纳米纤维与石墨烯片层在凝胶网络中的有序交联和空间取向的调控规律，揭示各向异性石墨烯基气凝胶的形成机理；建立石墨烯气凝胶各向异性有序结构与宏观力学性能、电性能、磁性能的构效关系模型，探索在力、电、磁等耦合场作用下的弹性形变、压阻、磁阻、电磁吸收等特性，为具有复杂结构和功能的柔性电子器件的开发提供新颖的材料模型和理论基础研究。

石墨烯气凝胶材料实现了由二维石墨烯片层向三维宏观结构的组装，在能量存储、吸附、催化和传感等领域有巨大应用潜力。针对石墨烯气凝胶由于石墨烯片层间缺乏交联、无序堆叠而引起的结构脆弱的问题，本项目以聚合物纳米纤维作为结构和功能强化控制因子，通过调控纳米纤维和石墨烯之间的相互作用和微观取向，实现了结构有序、力学性能优异的石墨烯基气凝胶的结构构筑，并对其潜在应用进行了研究。.本项目利用本课题组大规模制备的PVA-co-PE聚合物纤维作为基本构筑单元，加入小分子PVA作为交联剂，通过构筑主-客间氢键及表面疏水改性成功实现了对有机聚合物气凝胶的孔洞结构和表面性能的调控，应用广泛；基于上述研究，利用纳米纤维丰富的羟基与石墨烯含氧官能团之间的氢键相互作用，通过水热还原-后续冷冻干燥法形成了高度有序的石墨烯/纳米纤维复合三维网络结构。该结构具有以RGO片层为框架、聚合物纳米纤维为梁柱、PVA为粘合剂的特殊孔道构造。纳米纤维具有良好的柔性与韧性，支撑在石墨烯片层间类似于弹簧，在受压和变形时能起到隔离和能量耗散的作用，从而赋予石墨烯气凝胶优异的弹性。该气凝胶在超低应变（0.23%）下具有极高的灵敏度（GF=14387），应用于压阻式可穿戴压力传感器优势明显；通过聚合物纳米纤维成型制备过程中掺入硬磁性锶铁氧体粒子、金属磁性离子（Ni2+）在纳米纤维表面原位生长等技术制备了磁性聚合物纳米纤维，与GO片层在溶液中复合并经磁场取向，最终实现了多种结构有序和电磁性能优异的复合石墨烯气凝胶材料，验证了有序结构气凝胶材料在磁场/应变场下的显著磁阻效应；利用溶剂热还原-浸渍吸附法结合高温煅烧，制备了具有金属镍骨架和还原氧化石墨烯片层相互穿插包覆的Ni/rGO泡沫，提供多级孔洞结构和多重耗散磁/电损耗机制，从而对电磁波形成多次反射和衰减，显示优异的电磁吸波性能。.总之，本项目为有机气凝胶的便捷制备提供了新的思路，为具有复杂结构和功能的石墨烯基电子器件的开发提供了新颖的材料模型和理论研究基础。