Study On The Electromagnetic Properties Of Carbonyl Iron Powder And Their Composites

The tracking capabilities of modern military system have gotten more powerful as the improvingmilitary science and technology and the application of absorbing material to evade radar detection isan efficient method for self-protection. In the thesis, carbonyl iron powder and its composites areprepared, the structural features, electromagnetic parameters and electromagnetic waves absorptionproperties of as-prepared materials are also investigated.1. In order to improve electromagnetic parameters of CI, we prepared flake/shaped carbonyl ironpowder （FCI） using a mechanical milling method, the influence of process control agents and millingtime on the morphology, electromagnetic and related microwave absorption properties of CI arestudied. The result shows uniform FCI are achieved under the condition that solvent C as processcontrol agents and milling time is set at18h. SEM analysis demonstrates the morphology of CIchanging from globular to flaky after ball milling, and the saturation magnetization and permeabilityof FCI higher than that of spherical carbonyl iron powder （SCI）. Especially, the enhancement for theimage part of the permeability helps to reinforce magnetic loss and improve impedance matching ofabsorbing materials. When the matching thickness of2.0⁴.0mm, the effective absorption bandwidthof FCI （<-10dB） could cover2.82¹6.9GHz and the maximum absorption peak can reach-33.97dB.2. Flake-Shaped carbonyl iron powder/Cr₂O₃composites （FCI/Cr₂O₃） were prepared by amechanical milling method, the influence of different addition amounts of Cr₂O₃on the morphology,electromagnetic and related microwave absorption properties of materials are also investigated. Theintroduction of Cr₂O₃alter the impedance matching characteristics of composites and the maximumabsorption peak moves to higher frequency as the addition amounts of Cr₂O₃increases. When thematching thickness of2.0mm, the range of reflectivity of pure FCI below-10dB is7.7¹2.7GHzwhile the effective absorption bandwidth of FCI/Cr₂O₃（<-10dB） could cover both X and Kufrequency range.3. In order to further optimize the impedance matching characteristics and enhance absorptionperformance, flake-Shaped carbonyl iron powder/ZnO （FCI/ZnO） composites were prepared by amechanical milling method, the influence of different addition amounts of ZnO on the morphology,electromagnetic and related microwave absorption properties of materials are also investigated. Theresult shows that the as-prepared FCI/ZnO composites exhibited better dielectric loss and magneticloss properties in the range2¹8GHz, the absorption intensity and effective absorption bandwidth arealso enhanced. When the addition amounts of ZnO is0.1g and matching thickness is2.0mm, theeffective absorption bandwidth of FCI-ZnO composites is7.09GHz, and the range of reflectivity below-20dB appeared at7.7¹2.7GHz.4. Carbonyl iron powder-reduced graphene oxide composites are prepared by a chemical method.We investigated different addition amounts of graphene on the morphology, electromagnetic andrelated microwave absorption properties of materials. The introduction of graphene not only optimizesthe impedance matching characteristics, but also enhances the dielectric loss of composites. When thematching thickness is3.0mm, the bandwidth of reflectivity below-10dB and-10dB is4.43GHz and1.34GHz, and the maximum absorption peak can reach-52.46dB. In addition composites also havethe characteristics of low density, which means this composite could be used as a light-weightmaterials and more efficient absorber.