针对当前民用、军用对电磁防护的迫切性以及传统磁性材料Snoek极限的限制，本项目提出用Fe/C/MxFe3-xO(M=Co，Ni)异质纳米磁环设计和制备“高Snoek极限、宽频带-高吸收”微波吸收材料。这是考虑到：从纳米尺度上设计和控制异质纳米磁环的结构、尺寸、组成和分布有可能赋予其特殊的电、磁功能。纳米磁环的AB效应、等离子体结构、特殊的极化和耦合模式有望带来令人憧憬的微波吸收特性；控制环的双各向异性和界面特性，有望突破Snoek极限的限制，改善匹配特性，获得“宽频带-高吸收”的材料。为此，本项目建立合成异质磁环的微波水热-还原工艺和固相还原/碳化/熟化法及其调控技术；获得异质纳米磁环；揭示结构、尺寸、组成及分布对其静磁、微波电磁特性、Snoek值的影响规律；探索其微波激励机制及突破Snoek极限的新途径，获得“宽频带-高吸收”纳米磁环。因而该研究具有重要的民用、军用意义和学术价值。

According to the urgent need of the electromagnetic protection in current civil and military fields, as well as the Snoek’s limit of magnetic absorbing materials, the proposed project is aiming to design and prepare Fe/C/MxFe3-xO(M=Co，Ni) heterostructure nanorings as microwave absorbing materials with high Snoek’s limit and broadband - high absorption. The aforesaid project is based on the following reasons: Designing and controlling over the structure, size, composition, and distribution of the Fe/C/MxFe3-xO (M = Co, Ni) heterostructure nanorings in the nanoscale may give them unique electric and magnetic functions. Owing to Aharonov–Bohm (AB) effect, plasmonic structure, unique polarization and coulping modes, magnetic nanorings can expectantly bring some longing microwave characteristics (i.e., electromagnetic field enhancement, multiple resonance, interference and radiation loss). In this case, Snoek’s limit can be expectantly broken via controlling the interaction between layers of heterostructure nanorings, as well as its surface and interface anisotropy. Moreover, owing to the improved matching and absorbing properties, the “broad band - high absorption” microwave absorbing materials can also be obtained. Therefore, in this project, the microwave –assisted hydrothermal-reduction and solid phase reduction/carbonization/Oswald ripening methods can be developed for selective preparation of Fe/C/MxFe3-xO (M = Co, Ni) heterostructure nanorings; control technology for modulating the microstructure and properties of the above NRs can be established. Moreover, laws about the microstructure, size, composition, and distribution of the heterostructure nanorings influencing on their static magnetic, microwave electromagnetic properties, and Snoek value will be revealed; the microwave excitation mechanism and the new approach for breaking Snoek’s limit will be explored; the heterostructure magnetic nanomaterials with “broadband - high absorption” will be obtained. Therefore, it is of civil significance, military significance, and academic interest.