Greatly enhanced microwave absorption properties of highly oriented flake carbonyl iron/epoxy resin composites under applied magnetic field

Oriented flake carbonyl iron/epoxy resin (FCI/EP) composites with enhanced microwave absorption properties were prepared by a magnetic field which was applied to make the plane of FCI parallel to each other. The morphology and the frequency-dependent electromagnetic and microwave absorption properties of the composites were investigated. The measurement results showed that the higher permeability and modest permittivity of the composites were obtained after orientation in the frequency range of 2-18 GHz. The calculated absorption properties indicated that the orientation plays an important role in decreasing the absorber thickness and broadening the absorption bandwidths. The oriented FCI/EP composites containing 75 wt% FCI show a wider absorption frequency range of 12.5 GHz from 5.5 to 18 GHz with reflection loss below -10 dB at thickness of 1.4 mm, while the bandwidth of the un-oriented one is only in a narrow frequency range of 1.4 GHz. This work offers a promising approach for the fabrication of magnetic absorbents for thin-thickness and microwave-absorbing materials with adjustable wider working frequencies range simply by magnetic field.