基于多磁共振的W型钡铁氧体梯度成分设计及宽频吸波机制研究

Microwave absorption materials with broad bandwidth show promising prospects, such as anti-electromagnetic pollution in the civil field and stealth technology in the military field. For now, the bandwidth is mainly broadened through material structure design, which is due to the summation of multi quarter-wave cancelled reflection loss peaks contributed by the EM waves transmitting different length within the materials. However, the thickness has to be increased or the shape has to be complicated designed to broaden the bandwidth. To address this issue, W-type barium ferrite with Fe3+ ions being gradient substituted by high valence ions is proposed in this work. The various Ha values and multi g values in W-type barium ferrite will lead to the formation of multi magnetic resonance peaks, improving the impedance matching and attenuation ability in frequency range of 2~40 GHz. Ultimately, broad bandwidth could be obtained in the thin absorbing material with uniform thickness, and remove the dependence of bandwidth on thickness and shape of the materials. The thermodynamic and kinetic synthesis conditions for different morphology and size of precursor powders will be studied. The influencing factors and function mechanisms for ions diffusion behavior during reheat treatment will also be expounded to realize subtle control of the ions concentration gradient distribution. Meanwhile, the influences of grain morphology and size, substitution sites of the doping ions and the concentration gradient distribution on multi magnetic resonances formation and dynamic permittivity behavior, and the controls of electromagnetic parameters on absorption properties will be investigated in detail, which lays scientific foundation for the controllable preparation of thin absorbing materials with wide bandwidth.

宽频吸波材料在民用电磁污染防治及军事隐身方面有广阔应用前景。通过材料结构设计，使电磁波在材料内部传输不同长度形成的四分之一波长干涉峰叠加，可获得宽频吸收。然而，这类吸波材料拓宽吸收频宽需要增加材料厚度或者设计复杂形状。本项目提出高价离子局域梯度浓度取代W型钡铁氧体的Fe3+，利用多g因子共存及局域变化的Ha形成多磁共振，提高2~40GHz的阻抗匹配及电磁波衰减能力，从而在厚度均一的薄层吸波材料中获得超宽频吸收，避免结构型宽频吸波材料厚度大及形状复杂的问题。研究不同形貌粒径的前驱体粉末的热力学和动力学合成条件，阐明热处理中离子扩散行为的影响因素及作用机理，从而实现掺杂离子局域梯度浓度分布方式的精细调控；揭示晶粒形貌粒径、掺杂离子取代Fe3+位置及其浓度梯度分布方式等因素对多磁共振形成及动态介电行为的影响机制，并明晰电磁参数对吸波性能的调节规律，为薄层超宽频吸波材料的可控制备奠定科学基础。

为解决日益严重的电磁污染问题和满足军事上多波段雷达波的吸收需求，本项目通过构建高价、梯度掺杂钡铁氧体以及硬/软磁耦合的复合铁氧体，利用多g因子共存、局域变化的磁晶各向异性场和硬/软磁交换耦合作用形成多磁共振，成功拓宽高频磁损耗范围, 从而同时显著提高2~40 GH的阻抗匹配及电磁波衰减能力，实现在厚度均一的薄层吸波材料中获得超宽频吸收(~20GHz)，避免传统宽频吸波材料厚度大及形状复杂的问题。本项目系统地表征和理解了梯度掺杂铁氧体的显微组织结构演变规律及化学非均质性特征，重点研究了掺杂离子梯度分布方式和吸收频宽的关联性，掌握了化学组分和热处理工艺对多磁共振形态的精细调控作用，分析了掺杂离子占位、界面电导不均匀性等对偶极子、界面极化强弱的影响规律，揭示了多磁共振形成及动态介电行为的可控调节机制，明晰了电磁参数与反射损耗峰强度与频率、匹配厚度以及吸收频宽的一一映射关系，最终建立了物相组分/制备工艺-梯度成分分布-吸收频宽的关联模型，为薄层超宽频吸波材料的可控制备提供了新方法并奠定了坚实的科学基础。

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