阻抗梯度碳基宽带吸波复合薄膜设计及吸波机理

Achieving lightweight，ultrathin, broadband and high-performance microwave absorption has been the goal of stealth technology all along, and it’s also quite valuable for various modern techniques, such as microwave attenuator and electronic countermeasures and safety. Graphene oxide exhibits a promising candidate in microwave absorption due to its exceptional modulability of microwave absorption properties originating from the controllable reduction degree from insulator to conductor. However, its high dielectric loss which leads to the impedance mismatch limits its practical application in broadband microwave absorption. In this project, we plan to focus research on the fabrication and microwave absorption mechanisms of impedance gradient layered graphene composite films for ultrathin broadband microwave absorption. Through the study of the electron relaxation polarization, electron-pinned defect dipole effect, interfacial polarization effect and electron-hopping conductance loss behaviors, we hope to get hold of a practical method of constraining the hopping electron loss to realize the matching of dielectric loss and permittivity. On the basis of the above work, emphasis will be laid on how to achieve the impedance gradient layered graphene composite films. It includes the researches on the interaction between the intralayer dielectric matching and interlamination impedance gradient matching of the layered materials, the regulatory mechanism of permittivity and impedance by reduction processes, and establishing the relationship between gradient and microwave absorption in aid of the inversion of the permittivity gradient function. The work will pave off an unique path for achieving lightweight，ultrathin, broadband and high-performance microwave absorption.

轻质、超薄、宽带、高效微波吸收一直是武器隐身和电磁防护领域追求的目标。石墨烯具有优异的电磁屏蔽性能，但是其高电导损耗导致其介电损耗和介电常数严重失配，制约了其在宽带吸波领域的应用。项目拟利用氧化石墨烯阻抗可调节的特点，开发一种阻抗渐变型石墨烯复合薄膜，通过研究掺杂和缺陷偶极钉扎效应、异质界面效应和跳跃电导损耗机理，探索抑制跳跃电导的有效方法，实现介电损耗与介电常数匹配；在此基础上，研究阻抗梯度复合薄膜的层内介电参数和层间渐变阻抗的双匹配关系与还原调控方法，揭示介电参数和阻抗调控机理，反演复合薄膜的介电渐变梯度函数，构建阻抗梯度与微波吸收的关系，获得具有实用价值的新型轻薄宽带吸波材料。

石墨烯因具有质轻、机械性能优异、比表面积大、电导率高等诸多优异的物理化学特性，受到吸波领域学者的广泛关注。然而，由于石墨烯的电导率较高，产生了较严重的阻抗失配，限制其在宽频吸波领域的应用。因此，为打破石墨烯在吸波领域存在的瓶颈，本项目旨在找到调控石墨烯介电性能的方法，改善因介电实部和虚部比例失衡造成的阻抗失配现象，开发一种有效吸收宽度在10GHz以上的阻抗渐变型复合薄膜。.本项目首先开展了石墨烯表面原子掺杂、还原度和结晶度等纳米级组织结构对石墨烯介电及吸波性能的影响研究，揭示了石墨烯介电弛豫损耗和电导损耗机理，形成石墨烯阻抗匹配理论。通过对不同石墨烯还原度的吸波性能的研究，证明了rGO在8-10GHz处产生的弛豫峰主要来自还原过程产生的缺陷，而非rGO表面残余含氧官能团或界面极化；对不同碳化温度的石墨烯的介电及吸波性能研究，揭示了合适的结晶度和缺陷密度对阻抗匹配优化和吸波性能的提升作用；研究不同氮掺杂含量对石墨烯的介电和吸波性能的影响，得出石墨烯氮掺杂含量可以有效调节材料与自由空间的阻抗匹配，进而获取优异的吸波性能。.制备了rGO/CNF、rGO/MoS2、rGO/PANI/PVA复合材料，掌握了石墨烯复合材料的吸波性能优化工艺，形成了高性能复合薄膜微波吸收理论，结果表明：当rGO填充量为10wt%、CNF浓度为0.75wt%时，材料最佳RL吸收峰在2.4mm下达-41.38dB；与纯rGO或MoS2相比,MoS2/rGO的吸波性能得到显著提升，揭示了界面极化的引入对介电及吸波性能的提升；由于PANI对EVA/rGO的介电“补偿”，制备了吸波性能优异的EVA/PANI/rGO三元复合薄片，成功改善了材料的阻抗匹配度，提高了衰减能力。.在上述研究基础上，提出全局NV-ETM-RCWA算法，分别构建了三层和四层周期性阻抗渐变结构，探究层间阻抗渐变理论，实现了2-18GHz全频带有效吸收(RL≤ 10dB)。