二维导电材料复合体系的有序构建及其电磁屏蔽和吸波性能研究

As recent studies showed, 2D transitional metal carbides (MXenes) possessed excellent electromagnetic interference (EMI) shielding performance and unique microwave absorbing properties. In order to further tap into the potential of MXenes as microwave absorber, and develop lightweight high-efficiency EMI shielding and microwave absorbing materials, this project proposed to construct ordered 2D conductive materials-based hybrid systems with tunable components and controllable thickness by layer-by-layer self-assembly to adjust EMI shielding effectiveness (SE) and microwave absorbing effect. In order to make MXenes charged, ionizable groups were covalently grafted onto the surface of MXenes. After ionization in the solution, charged MXenes can absorb the substances with opposite charge to form multilayer stacked structure by alternative deposition. By tuning the components and thickness of multilayer structure, controllable conductivity and dielectric properties can be obtained, which will determine the EMI shielding effectiveness of multilayer film and the ratio of absorption loss to reflection loss, thus to enable specific applications. For instance, when negatively charged carbon nanotubes/graphene oxides were employed to assemble with positively charged MXenes by alternative deposition, as-prepared multilayer films would have good conductivity and be suitable for EMI shielding, and when polyelectrolytes/dielectric materials were used to prepare multilayer film together with MXenes via layer-by-layer self-assembly, as-obtained films should be better microwave absorbing materials due to better impedance matching. In addition, this project will take use of the full advantages of layer-by-layer self-assembly technique in precisely controlling the layer thickness and physical properties of the multilayer film, to study the relationship of EMI shielding effectiveness and film parameters, and then try to establish the functional relation between them.

基于二维过渡金属碳化物（MXenes）展现的优异的电磁屏蔽性能及独特的吸波性质，为了进一步挖掘该类材料在电磁波吸收上的潜力，开发出超薄轻质高效的电磁屏蔽材料和吸波隐身材料，本项目提出基于层层自组装方式构建成分可调厚度可控的有序二维导电材料复合体系以调节薄膜的电磁屏蔽效能及吸波性能的研究方案。通过共价改性技术在MXenes表面引进可电离基团，然后依靠静电相互作用与异电性材料进行层层交替组装，构建多层有序堆垛结构。通过控制异质膜层的成分和厚度，调节材料的导电及介电性质，进而调控材料的电磁屏蔽效能及吸收反射损耗之比，以实现不同的材料功能。如MXenes与碳纳米管石墨烯等导电材料组装制备高效电磁屏蔽材料；与聚电解质或介电材料组装制备吸波材料。此外，本项目也将充分发挥层层自组装技术在精确控制膜层厚度及调控薄膜性能上的优势，研究自组装薄膜电磁屏蔽效能与薄膜参数的对应关系，并尝试建立二者间的函数关系式。

二维MXene材料因其优异的导电性、好的水溶液分散性、大的比表面积和可调的物化性能，在许多领域展示了良好的应用前景，然而其较差的水氧稳定性和不太好的有机溶剂及高分子基体分散性极大限制了其应用领域。本项目针对MXene材料存在的这些突出问题，从MXene的制备、改性和基本物化性能研究出发，聚焦于MXene在水氧环境下的稳定性研究以及MXene基薄膜材料的制备、性能和应用研究，提出了MXene在光热条件下水性环境中的氧化机制和化学稳定性改进方案和措施，主要包括低温保存、疏水改性、表面活性剂保护及表面共价接枝等。然后我们重点调研了MXene基多元高分子自组装薄膜的几种制备方法，包括静电自组装、喷涂、喷雾旋涂和真空抽滤等，以及所制备薄膜材料在柔性传感及电磁屏蔽领域的应用。通过调控薄膜组分和优化薄膜参数，我们进一步改善了薄膜材料的机械性能、压阻性能和电磁屏蔽效能。各种薄膜参数与薄膜性能的对应关系被初步建立，这将为MXene基薄膜材料的性能优化和广泛应用提供了数据参考和技术支持。