铁纳米线柔性透明电磁屏蔽薄膜的磁控构筑方法及性能研究

Flexible transparent electromagnetic shielding film is the basic strategic material of flexible electronic equipment. However, the commonly used silver nanowire electromagnetic shielding films have some limitations, such as shielding effectiveness and transmittance are difficult to balance, and easy to cause secondary electromagnetic radiation pollution. In this project, the soft magnetic properties and the high electromagnetic wave loss capability of iron nanowires are used to regulate the formation of ordered structure of iron nanowires by magnetic field to alleviate the contradiction between transmittance and shielding efficiency, and effectively avoid secondary pollution of electromagnetic environment. By studying the evolution law between the reaction conditions which induced by magnetic field and the structure of iron nanowires (diameter, aspect ratio), to reveal the growth mechanism of self-assembled iron nanowires induced by magnetic field, and clarify the relationship between iron nanowire structure and electromagnetic properties, based on this synthesis of high aspect ratio iron nanowires with excellent absorbing properties. Establishment of a method to construct ordered structure films using magnetic field to control the distribution of iron nanowires, and to explore the correlation model between magnetic field, film thickness, shielding efficiency and light transmittance, then the absorptive flexible transparent electromagnetic shielding film was developed by using particle swarm optimization (PSO) to optimize the ordered structure of iron nanowires with the objective of minimize the reflected electromagnetic wave and maximize the electromagnetic absorption and transmittance. The successful completion of this project is expected to provide theoretical exploration and technical reserves for the development of flexible transparent electromagnetic shielding films suitable for the next generation of flexible electronics in China.

柔性透明电磁屏蔽薄膜是柔性电子设备的基础性战略材料，然而常用的银纳米线电磁屏蔽薄膜存在屏蔽效能和透光率难以兼顾、容易造成二次电磁辐射污染等局限性。本项目利用铁纳米线的软磁性和高电磁波损耗能力，通过磁场调控铁纳米线形成有序结构来缓解透光率和屏蔽效能之间的矛盾，并有效避免电磁环境的二次污染。通过研究磁场诱导下反应条件与铁纳米线结构(直径、长径比)之间的演化规律，揭示磁场诱导自组装铁纳米线的生长机制，并理清铁纳米线结构与电磁性能的关系，合成具有优异吸波性能的高长径比铁纳米线；建立利用磁场调控铁纳米线分布构建有序结构膜层的方法，探索调控磁场、膜厚与屏蔽效能和透光率之间的关联模型，以反射电磁波极小而电磁吸收和透光率极大为目标，用粒子群算法研究铁纳米线有序结构的参数优化，研制出吸收型柔性透明电磁屏蔽薄膜。该课题的成功完成，可望为我国发展适用于下一代柔性电子的柔性透明电磁屏蔽薄膜提供理论探索和技术储备。

现有银/铜纳米线基柔性电磁屏蔽薄膜的透光率与屏蔽效能难以兼顾，且容易产生二次电磁辐射污染，无法满足柔性光电设备应用需求。本项目从金属纳米线吸波性能提升和分布状态优化入手，利用铁磁金属纳米线具有高电磁衰减能力和分布可磁场调控的优势，提出磁场调控铁磁纳米线分布构筑有序网络结构复合薄膜的设计思想，综合铁纳米线(Fe NWs)的高长径比、有序构筑和参数优化协同效应来提升复合薄膜的综合性能。研究了高长径比铁纳米线合成技术，采用磁场辅助诱导原位还原法合成出高长径比Fe NWs，通过电磁参数测试与合成工艺优化确定具有优异吸波性能的Fe NWs结构参数。在此基础上，利用海尔贝克阵列磁铁构筑有序分布结构PET/FeNWs/PEDOT复合薄膜，探究了Fe NWs面密度、层数、分布方式对屏蔽效能和透光率的影响规律。.在优化合成工艺下，Fe NWs的平均直径为60nm，长度为21μm，平均长径比可达350。当吸波涂层厚度为3mm，填充质量分数为20wt.%时，Fe NWs的最小反射损耗和有效吸收带宽(RL≤−10dB)分别可达-29.74dB 和 3.28GHz (3.84-7.12GHz)，表现出优异的电磁波衰减能力。利用Fe NWs构筑的有序结构可以显著提高薄膜的透光率和电磁屏蔽效率，当Fe NWs面密度为201.78mg/m2时，与随机分布Fe NWs薄膜相比，有序PET/Fe NWs/PEDOT的透射率和电磁屏蔽效能分别提高了49.1%和32.9%，达到75.78%和19.37dB。在相同的表面密度(201.78mg/m2)，交错角为45°的双层网络结构PET/Fe NWs/PEDOT薄膜在保持透光率基本不变的情况下，电磁屏蔽效能进一步提高73.2%，达到33.54dB。同时，Fe NWs复合薄膜还具有很高的柔韧性和结构稳定性，在3000次弯曲后任然可以保持97.4%的电磁屏蔽效能。此外，采用液相还原法和层-岛生长模式，成功合成了Fe@Ag NWs，在3.3mm时，最小反射损耗为-58.69dB并且有效吸收带宽达到6.71GHz，其具有在柔性透明电磁屏蔽薄膜应用的潜力。本项目通过优化Fe NWs分布，克服了传统金属纳米线柔性透明电磁屏蔽薄膜透光率和屏蔽效能难以兼顾的问题，在包括军事安全设备的液晶显示屏、高精度测量仪器的显示器和民用手机触屏等军民领域应用前景良好。