纳米梯度磁性颗粒膜的高频电磁特性研究

The magnetic electromagnetic wave absorbing material plays an indispensable role in many fields, such as communication, stealth, and electromagnetic wave interference shielding fields, and it has been paid attentions for many years. (1) The high-frequency electromagnetic properties of the gradient magnetic granular multilayered films which consist of the ferromagnetic metal alloy, ferromagnetic or non-ferromagnetic insulator will be studied in this project. (2) The influences of gradient composition on the high-frequency electromagnetic characteristics of the gradient films will be researched. The tune mechanism of high-frequency electromagnetic characteristics of gradient magnetic granular films will be illuminated based on microcosmic points included the size of nanoparticles, the exchange coupling effect and interface effect. The microwave magnetic permeability and resistivity computational models will be established. (3) The high permeability, high resistivity gradient magnetic granular films preparation technology with independent intellectual property rights will be obtained, which was adopted the method of gradient structure optimization and multiple composite materials, and used the exchange coupling between the magnetic particles and interlayer exchange coupling to tune the microwave permeability and dielectric property. And then ultra-thin, broadband, strong absorption of a new generation of nanoscale magnetic absorbing materials can be developed. Expected material performance of high frequency electromagnetic characteristics and its tune methods obtained from this project will provide theoretical basis and technical support for the application of nanometer thin layer broadband absorbent, and also provide effective solutions to solve the low-frequency band radar electromagnetic wave absorber and electromagnetic compatibility of electrical and electronic equipments.

吸收电磁波磁性材料在通讯、隐身、屏蔽电磁等方面具有不可或缺的作用，多年来一直倍受关注。（1）本项目将研究由铁磁金属合金、铁磁绝缘体和非磁绝缘体等构成的成分梯度磁性颗粒膜的高频电磁特性。（2）研究成分梯度对颗粒膜高频电磁特性的影响和调控；阐明纳米颗粒尺寸、界面效应对梯度磁性颗粒膜高频电磁特性调控机理，并建立磁性颗粒膜的复磁导率和电阻率理论模型。（3）采用梯度结构优化和多元材料复合方法，利用纳米磁性颗粒间交换耦合、层间交换耦合，调控梯度磁性颗粒膜的复磁导率及介电特性，获得具有自主知识产权的高复磁导率、高电阻率的梯度磁性颗粒膜，开发出超薄、宽频、强吸收的新一代纳米磁性吸波材料。本项目获得的高频电磁特性及其调控方法，将为纳米薄层宽频吸收剂的应用提供理论基础及技术支撑，也为解决雷达低频波段电磁波吸收提供有效方案。

电磁波吸收材料在通讯、隐身、屏蔽电磁干扰等方面具有不可缺少的作用，多年来一直倍受关注。随着探测手段的发展进步，新一代武器装备迫切需要一种具备“薄、轻、宽、强”等特性的高效吸收剂，然而目前国内传统的微米级磁性吸收剂的性能已经逼近Snoek理论极限。另一方面，近年来广泛使用1-6 GHz电磁波频率通信，如移动电话、智能运输系统、本地网络系统、电子自动收费系统等，由此产生的电磁波干扰问题，也变得越来越严重，急需开发新的抗电磁干扰的磁性材料。.1..在薄膜厚度方向上成分含量梯度渐变的颗粒膜结构。并以Kapton为衬底，通过成分和层数的优化设计，成功制备出了具有明显面内各向异性及良好软磁特性的FeCoB-SiO2成分梯度颗粒膜。它保持了较高的磁导率 ，其实部和虚部分别为276.3和441.4；同时，其ρ高达15.4 mΩ·cm，约为单层颗粒膜的ρ的4倍，比在SiO2衬底生长的FeCoB-SiO2颗粒膜的ρ高近一个数量级。2..在成分梯度颗粒膜磁谱虚部中发现双共振峰，且随着层数的增加，肩峰增强。分析提出双共振峰的现象起源于各成分层磁谱的加权平均。由于双共振峰的出现，8层梯度颗粒膜样品的Δf高达3.00 GHz (μ″≥140)，展宽了吸波频带，可满足“宽频”衰减特性的要求。铁磁共振谱观测到了成分梯度颗粒膜存在多个共振峰，分析认为，各成分层具有不同的Ms，成分梯度颗粒膜整体上呈现磁不均匀性，铁磁共振谱的结果与磁谱中双共振峰的结果一致。3..通过磁控溅射的方法，用聚酰亚胺Kapton作为衬底，共溅FeCoB靶、CoFe2O4靶制备厚度不同的FeCoB-CoFe2O4颗粒膜。Ar气压在0.3 Pa时制备的250 nm的FeCoB-CoFe2O4颗粒膜具有较好软磁特性（Ms~999.2 emu/cm3，Hce~2.79 Oe）、相对较高的ρ (~0.3 mΩ·cm)和较大的μ (μ’115.3， μ″411.4 )。