Synthesis And Microwave-Absorption Properties Investigation Of Polyhedral Fe Nanocapsules

Al₂O₃ coated Fe polyhedral nanocapsules are prepared by arc-discharging a Fe-Al (8at%Al) alloy. HRTEM shows the as-prepared nanoparticles form in a core-shell structure and core consist of Fe, with the size of nanoparticles in range of 10⁵0nm and the thickness of the shell 2⁴nm. Al atoms in the Fe-Al alloy form the shell of Al₂O₃, which prevents the nanoparticles from a further oxidation. The shape of most Al₂O₃-coated Fe nanoparticle is hexagonal or quadrilateral. The electromagnetic characters are measured by Agilent 8722ES microwave network analyzer in the band of 2¹8GHz. The experiment results show thatε" of Al₂O₃ coated Fe polyhedral nanocapsules have a maximum in the band of 2⁴GHz, 8¹1GHz and 13¹6 GHz, whileμ" of Al₂O₃ coated Fe polyhedral nanocapsules have a maximum in the band of 10¹3GHz. The reflection loss RL(dB) of the nanocapsules are simulated with experimental date. The reflection loss RL(dB) of the nanocapsules 3mm in thickness reaches to -50.5dB at 7.9GHz, and EM absorption properties (RL<-20dB) in the 5.2¹6.1GHz range. The excellent microwave-absorption properties of as-prepared nanocapsules are ascribed to shape anisotropy and core/shell structure.Iron with particular shape anisotropic cubic morpholofy powders are successfully prepared by solvothermal process in the solvent of ethylenediamine, with the size in the range of 300⁵00nm. The electromagnetic characters are measured? in the band of 1¹8GHz.The results approve that the absorption is less than -10dB in the range of 2.4¹7GHz and the reflection loss RL(dB) reaches -21.2dB at 14.6GHz in the thickness of 1.5mm.?Al₂O₃/Fe₂O₃ composites coated cubic iron powders are synthesized by the method of seed deposition. After the seed deposition process, iron capsules are coated by Al₂O₃ with the shape of flocculent. Compared with uncoated powders, Al₂O₃/Fe₂O₃ composites coated cubic iron powders obviously have broader frequency ranges and higher reflection loss. The electromagnetic characters are measured? in the band of 1¹8GHz. The electromagnetic characters are also measured in the band of 1¹8GHz. The results showe that the absorption is less than -10dB in the range of 2.4¹8GHz and the reflection loss RL(dB) reaches -29.8dB at 16.3GHz in the thickness of 1.2mm. Therefore, Al₂O₃/Fe₂O₃ composites coated cubic iron is an excellent electromagnetic wave absorption material.