聚苯胺纳米棒垂直分布对石墨烯吸波性能提高作用机制

Graphene has grabbed considerable attention for microwave absorbing materials due to its varieties of remarkable properties, including low density, high specific surface area, large aspect ratios, charge carrier mobility, high mechanical properties as well as versatile processing. It’s well known that microwave absorbing performance of graphene can be improved by grafting polyaniline (PANI) nanorods, and PANI nanorods covalently graft on the surface of graphene sheets can make more significant improvement on microwave absorption performance. At present, the mechanism on microwave absorbing properties of the graphene-based composites is unclear. When PANI nanorods vertically grow on the surface of graphene by covalent bond, a conductive path between graphene and PANI nanorods is formed, which is benefit to the electronic transfer, thus increase the conduction loss. In the microwave field, the orientation polarization generated by the vertical distribution of PANI nanorods, the interfacial polarization generated by the heterogeneous media and special morphology of PANI nanorods have a great effect on the electromagnetic parameters. Therefore, the study on the distribution of covalently grafting PANI nanorods and the interaction between PANI nanorods and graphene will provide theoretical basis for improving microwave absorption performance, but this research has rarely been reported. In this study, PANI nanorods have been perpendicular grown on the different location of graphene surface by covalent bond, and the effect of covalent bond connection, PANI nanorods morphology, distribution and the layers of graphene sheets on the microstructures, aggregations, electrical conductivity, polarization degree and the electromagnetic parameters have been studied. These results will reveal the mechanism of improved microwave absorbing performance based on PANI nanorods perpendicular grown on the surface of graphene by covalent bond, clarity the regulation approach of microwave absorbing performance and provide a theoretical foundation for the development of new absorbing materials.

聚苯胺纳米棒连接到石墨烯表面可提高其吸波性能，而以共价键连接聚苯胺纳米棒时会使吸波效果更为显著，但其具体作用机制尚不清楚。聚苯胺纳米棒以共价键垂直连接到石墨烯表面，两者之间形成导电通路，有利于电子有效传递，增强材料传导损耗。微波电场作用下，聚苯胺纳米棒垂直排列所产生的取向极化、异质界面所产生的界面极化及聚苯胺纳米棒的特殊形貌均对材料电磁参数产生影响。因此，研究共价键连接聚苯胺纳米棒垂直分布与石墨烯相互作用对提高石墨烯吸波性能有重要理论意义，但这方面研究鲜有报道。本项目以共价键分别将聚苯胺纳米棒垂直连接到石墨烯表面不同位置，研究键和方式、聚苯胺纳米棒形貌、分布位置及石墨烯层数对材料微观形貌、聚集形态、电导率、极化程度、电磁参数的影响规律，揭示聚苯胺纳米棒以共价键垂直连接到石墨烯表面对其吸波性能提高的作用机制，阐明调控材料吸波性能的途径，为发展新型吸波材料奠定理论基础。

电子、通讯设备的广泛使用使电磁波辐射污染日益严重，因此研究电磁波吸收材料有着迫切的实际需要。质量轻和效率高是影响吸波材料应用的两个主要因素。相对于传统的吸波材料而言，石墨烯独特的二维结构使其具有质量轻、比表面积大、电子迁移率高、环境稳定性好等特点，是一种潜在的吸波材料。本项目分别将聚苯胺纳米棒以共价键垂直连接到石墨烯和层叠石墨烯表面，研究价键结构、聚苯胺纳米棒分布、电子传递和极化程度对材料吸波性能提高作用机制。所得结果如下：（1）聚苯胺纳米棒以共价键均匀连接到石墨烯表面，可形成导电通路，有利于电子在石墨烯和聚苯胺之间有效传递，增强材料传导损耗和吸波性能；（2）聚苯胺纳米棒定向排列在石墨烯表面，形成取向极化，改善石墨烯表面电子分布不均，增加石墨烯表面极化电子密度，提高其吸波性能；（3）聚苯胺纳米棒以共价键定向排列在石墨烯表面，与石墨烯之间形成大量界面，不同使异质界面积累的电荷产生场畸变，增强界面极化；（4）聚苯胺纳米棒特殊形貌可使入射到材料内部的电磁波发生多次散射，进而提高材料吸波性能。其关键数据如下：（1）将聚苯胺纳米棒以共价键均匀连接到石墨烯表面时，在厚度为3 mm时，吸波最大值可达-42.1 dB，高于单一石墨烯（-21.1 dB）。厚度为2 mm时，-10 dB以下的频带宽度从12 GHz到18 GHz（6 GHz）；（2）将聚苯胺纳米棒以共价键均匀连接到层叠石墨烯表面时，在厚度为2.5 mm时，吸波最大值可达-51.5 dB，高于非共价键连接的聚苯胺-层叠石墨烯（-34 dB），-10 dB以下的频带宽度从9.6 GHz到13.6 GHz（4 GHz）。