石墨烯复合吸波材料的研究进展及未来发展方向

Progress and Future Developments of Graphene Composites Serving as Microwave Absorbing Materials

吸波材料是解决电磁波辐射污染的有效手段和影响雷达隐身的关键因素,该材料的研究对军用和民用都具有非常重要的意义,因此它一直是各国尖端科技的重要研究方向之一。自石墨烯被首次发现,学术界便掀起了对二维材料的研究热潮,相关学者开展了各类型石墨烯复合材料的研究,且在吸波领域的理论研究和新型吸波材料的开发取得了突出成果,短短几年时间内,石墨烯已经成为了新型复合吸波材料的研究热点。相比铁氧体、炭黑等传统吸波材料,石墨烯应用于吸波材料具有以下优势:(1)独特的二维材料性质、巨大的性能可调控工作表面;(2)良好的导电性以及特殊的边界效应。然而,单纯以石墨烯作为吸波剂的吸波材料,其性能测试结果与预期值存在显著差距,无法实现开发一种新型轻质、高效吸波材料的预期目标。因此,近三年来石墨烯复合吸波材料的研究重点主要集中在石墨烯二维结构的吸波机理和石墨烯/磁损耗型复合吸波材料的制备,研究者主要从选择合适的磁性纳米成分和优化制备工艺方面不断探索,并取得了丰硕的成果,深度挖掘出石墨烯对电磁波的潜在吸波性能。目前,通过优化石墨烯复合吸波材料组分已基本可以实现2～18 GHz频段范围内反射率小于-10 dB。对于石墨烯电磁波吸收机理的研究,主要依托其二维结构,应用密度泛函理论和原子-键电负性均衡理论模型来探索本征石墨烯和掺杂石墨烯的构型;在较高性能的石墨烯复合吸波材料制备过程中已取得成功应用的磁性纳米成分包括四氧化三铁、铁酸镍、硫化镉等。其中,以四氧化三铁、氧化铁为代表的铁氧体应用得最早;随着共沉淀法、溶剂热法等制备方法的不断成熟,各类新型磁性纳米颗粒可以与石墨烯复合,使之兼具磁损耗和电损耗能。近两年,相关学者将超材料的思想引入石墨烯复合吸波材料的研发中,以结构设计为手段,实现了新型透明石墨烯复合吸波材料的制备。此外,由于石墨烯自身的功能特性,石墨烯复合吸波材料大多也具有高效的热传导性能和良好的结构强度,可以实现材料的结构功能一体化。本文归纳总结了石墨烯复合吸波材料的研究历程和最新研究进展,介绍了石墨烯复合吸波材料的二维结构吸波机理、磁性掺杂成分的选择、大尺寸材料的制备工艺,分析了石墨烯复合吸波材料亟需解决的问题并展望其未来发展前景,以期为制备"宽薄轻强"的新型石墨烯复合吸波材料提供参考。

Microwave absorbing material is an effective measure to solve the electromagnetic radiation pollution and a key factor affecting radar stealth.Its research is of great significance for both military and civilian applications,which is as well as one of important research areas of high technology around the world.Since the first discovery of graphene,the research upsurge on 2D material in has been raised in the academic circles.Related scholars carried out the research of various types of graphene composites;they also have made some outstanding achievements in theoretical research of microwave absorbing field and development of new absorbing materials.Graphene has already become a research hotspot of new composite absorbing material in a few years.Compared with the traditional absorbing materials such as ferrite and carbon black,graphene has the following advantages:(1)unique two-dimensional material properties,huge performance can be controlled the working surface;(2)good conductivity and special boundary effect.Compared with Ferrite,carbon black and other traditional absorbing materials,graphene has following advantages:(1)the unique 2D material property and the performance of huge working surface can be controlled;(2)good electrical conductivity and special edge effect.However,there is a significant difference between the performance test results and the expected values of the absorbing materials with graphene as the absorbent,resulting in the expected goal of developing a new type of lightweight and high efficiency absorbing material can not be achieved.Therefore,in the past three years,the research focus of graphene composite absorbing materials has been mainly in absorbing mechanism of graphene 2D structure and preparation of graphene/magnetic loss composite absorbing materials.Researchers have been continuously explored new suitable magnetic nano-composition as well as optimized preparation technology,and achieved fruitful results.The potential wave absorbing property of graphene has been deeply excavated.At present,the reflectivity lower than-10 dB can basically realize within frequency band of 2-18 GHz by optimizing composition of graphene composite absorbing material.The researches on the wave absorbing mechanism of graphene were mainly relied on its 2D structure,using density functional theory(DFT)and atom-bond electronegativity equilibrium theory model for the investigatiiona of configurations of intrinsic graphene and doped graphene.During the preparation process of high-performance graphene composite absorbing material,magnetic nano-composition including ferroferric oxide,nickel ferrite,cadmium sulfide have been successfully applied.Ferrite that represented by ferroferric oxide and iron oxide was the earliest one.With advances in co-precipitation method,solvothermal method and other preparation methods,various new magnetic nanoparticles can be combined with graphene to make them have both magnetic loss and electrical energy loss.In recent two years,related scholars have introduced metamaterial into the research and development of graphene compo-site absorbing material and realized preparation of a new transparent graphene composite absorbing material by means of designing the sturcture.In addition,due to own functional property of graphene,most of the graphene composite absorbing materials also have high-efficiency thermal conductivity and good structural strength that can realize the integration of structure and function.This paper summarizes the research efforts and the latest research progress of graphene composite microwave absorbing materials,introduces their two-dimensional structural wave-absorption mechanism,the selection of magnetic doping components and preparation process of large-scale materials,respectively.Otherwise,we pay attention to the problems confronting the current state of the graphene composite microwave absorbing materials and look forward to their future development prospects,in order to provide a reference for the preparation of“wide,thin and light”new graphene composite microwave absorbing materials.