轻质中空“双面神”结构核壳微球的制备及其耐高温吸波机理的原位透射电子显微学研究

Lightweight and microwave absorption under high-temperature are the main challenges met by magnetic microwave absorber. This project is scheduled to fabricate hollow “Junas”-like core@shell composite absorber, utilizing the advantages of high-designable structure and electromagnetic parameters. A series of strategies regarding “surface modification”, “charge modulation at solution interface”, “selective growth based on controllable hydrolysis” and “gradient etching” will be established, based on which the multi-layered “Junas” microsphere with continuous matching of electromagnetic impedance will be designed and fabricated. The magnetic core will be selected from ferrites with high-Tc points, while the dielectric shell material will be chosen from ceramic oxide such as ZrO2, thus the absorption capability under high-temperature can be improved. Within “Junas” microsphere, multi-types of electromagnetic domains will be constructed to achieve strong coupling absorption. Based on in situ electron microscopy under multi-fields, from the viewpoint of crystal structure and at sub-angstrom resolution, the evolution mechanism of the atom arrangement, electron/moment/strain distribution on the applied electromagnetic field and temperature will be clarified. The pinning mechanism of dislocation defects on electromagnetic domain walls will be studied. The influence of interfacial polarization on the absorption performance of microspheres will be illustrated. A modulation strategy about breaking the Snoek frequency limit and Curie point of magnetic absorber based on microstructure will be proposed. This project can strengthen the understanding of absorption under high-temperature from microstructural point of view, and to solve the fundamental scientific issues faced by magnetic absorbers, and to support the development of stealth material technology.

轻质化和耐高温是磁性吸波材料面临的挑战。拟制备中空“双面神”结构的核壳复合吸波微球，发挥其结构与电磁参数可设计性强的优势。建立“表面修饰”、“溶液界面电荷调控”、“可控水解选择性生长”和“梯度刻蚀”等制备策略，据此设计并实现电磁阻抗连续渐变匹配的多壳层“双面神”结构微球。磁性核选择居里点高的铁氧体，最外介电壳层选择氧化锆等陶瓷材料，改善高温吸波能力。在“双面神”微球中，构建多种类型的电磁畴，实现强耦合吸波。运用原位多场电子显微学方法，从晶体结构角度在亚埃分辨揭示微球的原子结构、电子组态、磁矩排布与应变分布随外加电磁场和温度的演化机制。阐明位错等缺陷钉扎电磁畴界的机制。阐明界面极化对微球吸波性能的影响规律。提出突破传统磁性吸收剂Snoek极限频率和提高居里温度的显微结构调控策略。本项目可以从超显微结构角度加深对耐高温吸波机理的理解，解决磁性吸波材料面临的基础科学问题，支撑隐身材料技术的发展。

微波吸收（吸波）材料在信息安全、电磁屏蔽和隐身武器等领域具有重要应用。磁性吸波材料在实现薄涂层和增强吸收等方面存在优势，但保持吸波性能轻质化和耐高温是磁性吸波材料面临的挑战。本项目中通过“表面修饰”、“液相界面聚合调控”以及“梯度刻蚀”等制备策略，制备中空“双面神”结构的核壳复合吸波微球。通过双面神结构微球的多级结构调控，突破了Snoek频率极限，提升磁性吸波材料在高频下的微波损耗能力；通过各项异性调控以及多级磁耦合策略，保证了中空双面神微球的高饱和磁化强度；优化介电材料与磁组份的复合方式和表面结构，改善双面神结构吸波材料的频散效应，同时调控阻抗匹配，解决传统吸波材料吸波频带窄的问题。比如我们优化后的Fe@SiO2@C-Ni双面神材料表现出优异的微波吸收性能，有效吸收带宽为 8.2 GHz，反射损耗为-45.5 dB。同时，本项目自主建立了耦合磁、电、温多场的原位电镜平台，用于轻质中空“双面神”结构核壳微球研究，建立了核壳结构与耐高温吸波性能间的关联机制，从原子电子的超微观层次理解磁性复合吸波材料的电磁性能调控机理。以此平台为基础，综合运用多种先进显微学分析技术，如电子全息、电子能量损失谱、原位电、磁、脉冲驱动等，在原子分辨显微结构角度研究了吸波材料的电磁结构与性能的构效关系，实现了准确分析真实材料的晶体缺陷与电磁畴，并建立两者间联系。本项目的研究成果从超显微结构角度加深对耐高温吸波机理的理解，解决磁性吸波材料面临的基础科学问题，支撑隐身材料技术的发展。发表项目密切相关SCI一、二区论文60多篇，获教育部自然科学二等奖一项.