基于FeCo纳米片构筑双壳层纳米复合物的可控合成及其微波吸收机理研究

Magntic/dielectric nanocomposties have been considered as excellent microwave absorbents becasuse of magnetic and dielectric loss.However,the Magntic/dielectric nanocomposties have no microwave absorption properties in the S frequency range with a thickness smaller than 3mm.On basis of electromagnetic wave loss mechanism and quarter-wave matching model, the enhancement of the complex permittivity and complex permeability and impedance matching in the GHz frequency range is vital for improving the microwave absorption properties in the S frequency range.The FeCo nanosheets with easy-plane anisotropy have higher Snoeck limit. ZnO as a middle shell not only depress the oxidation and aggregation of FeCo nanosheets, but also possess favorable dielectric properties and induce interfacial polarization from the formation double shell, improving the dielectric loss of magnetic nanocomposites. Ferromagnetic-dielectric oxides as outside shell have preferable dielectric loss as well as suppress the decrease of the complex permeability of nanocomposties. This strategy could restrain the decrease of the complex permeability of magnetic nanocomposties。 We intend to fabricate the microwave absorption properties of FeCo@ZnO @ La1-xAg(k)xMnO3 double-shell sheets nanocomposites,which could solve the above-stated problems.. We will systematically study the effects of composition,content,and morphology of nanocomposites on the magnetic,electric,electromagnetic parameters,microwave impendence matching,and microwave absorption properties, deeply investigate the microwave absorption mechanism, broaden absorption bandwidth,and enhance microwave absorption properties with the aim of developing new-style microwave absorbents.

因兼具磁、介电损耗，磁/介电纳米复合物被认为具有优异的吸波性能。但该吸波剂在较薄的涂层厚度（3mm内）范围内，在S波段无损耗特征。根据电磁波损耗机制和四分之一波长匹配模型分析，在GHz频段，提高纳米复合材料的复磁导率、复介电系数和电磁阻抗匹配，是实现其在S波段增强微波吸收性能的关键。易面磁各向异性的铁钴纳米片具有高Snoek极限；中间壳层氧化锌，不仅限制铁钴纳米片的团聚和氧化，而且其自身的介电性能和产生双壳层的界面极化增强介电损耗；外壳层铁磁介电氧化物，既能减小纳米复合物磁导率的降低，同时具有较强的介电损耗。本项目构筑FeCo@ZnO @ La1-xAg(k)xMnO3双壳层纳米片复合物，有望解决上述问题。系统研究该纳米复合物的组成、含量、形貌与其磁性、电性、电磁参数及阻抗匹配特性和微波吸收性能的关系，深入揭示其微波吸收机制，拓宽吸收频带、提高微波吸收性能，发展新型纳米复合吸波材料。

电磁吸波材料能够有效吸收衰减电磁波，被广泛应用于民用和军事领域。研发宽频和强吸收吸波材料是该领域的发展需求。本项目开展吸波材料的设计合成和性能研究，研究了FeCo@ZnO复合物、FeCo/ZnO/La0.7Ba0.3MnO3、LaMnO3+d二维层状纳米材料、LaOCl/C纳米复合物、具有纳米孔的Co3O4纳米纤维和纳米片、三元LaOCl/C/MnO纳米复合物、Ni@C/NC壳核纳米复合物和Fe@Fe3O4复合物。通过设计单相组分的微观形貌、不同组分的有效组合及其微观形貌，能够有效调控介电损耗、磁损耗、介电/磁损耗的有效复合，揭示吸波剂的内在特征与其电磁参数、吸波性能的构效关系。FeCo@ZnO复合物体系的介电系数随着ZnO含量的增加而增加，存在三重介电共振峰；复磁导率随着ZnO含量的降低而降低。适当ZnO含量促使磁损耗与介电损耗达到最优匹配，涂层厚度为1.5 mm，反射损耗(RL)可达-34.8 dB，有限带宽（RL<-10dB）为5.1 GHz。通过La0.7Ba0.3MnO3的复合，当层厚为2 mm时，该复合物在11.6 GHz处的RL值为-34 dB，单层有效吸波频带（RL<-10 dB）达到4.8 GHz。LaOCl/C纳米复合物，LaOCl纳米颗粒均匀地镶嵌在C片层里，提出了LaOCl/C纳米复合物的合成机理。通过控制LaOCl/C纳米复合物的C含量，能够有效调控LaOCl/C纳米复合物的复介电系数。LaOCl/C纳米复合物最佳的反射损耗为-32 dB，匹配厚度为1.5 mm;有效带宽（RL<-20 dB）为14.2 GHz，覆盖3.2-18 GHz频段范围。具有纳米孔的Co3O4纳米纤维和纳米片，纳米片优异的吸波性能归因于其多孔的微观结构促进的几何效应、介电损耗和阻抗匹配。Fe@Fe3O4复合物，界面极化、偶极子极化和铁磁共振赋予了其电磁匹配和强烈的电磁衰减能力，1.5mm厚度的反射损耗为-33dB。通过本项目的实施，揭示了吸波剂的介电性能、磁性与其形貌密切相关。各向异性形貌和多元复合材料能够增强空间电荷极化和界面极化，增强介电损耗和磁损耗。优异的吸波性能需要满足阻抗匹配和电磁衰减两个特性。在电磁匹配条件下，充分增大磁损耗和介电损耗，实现宽频强吸收。