Synthesis and microwave absorption properties of hierarchical Fe micro-sphere assembly by nano-plates

Self-assembly of flakes to form three-dimensional flower-like structure is an effective way to strengthen electromagnetic absorption capability. However, it still remains a great challenge to synthesis of such structure, especially the preparation of flower-like Fe particles. In this paper, hierarchical flower-like alpha-Fe particles with a diameter of similar to 3 mu m are prepared by combining a simple in situ reduction method and assisted with an appropriate external magnetic field at normal atmosphere. A possible mechanism for the formation of flower-like structure related to the synergy of magnetic field and hydrogen bubble which generated by in-situ reduction reaction is proposed. The electromagnetic properties of flower-like alpha-Fe-paraffin composites were measured with the coaxial reflection/transmission technique at 2 -18 GHz. The minimal reflection loss value of -33.1 dB is obtained at 17.46 GHz. Moreover, the effective absorption bandwidth with reflection loss exceeding 10 dB is up to 6.2 GHz (7.7-13.9 GHz) at a thickness of 3 mm, which covers whole of the X-band (8-12 GHz) and part of the Ku-band (12-18 GHz). These excellent absorbing performances suggesting that the flower-like alpha-Fe particles synthesized here could be an extremely promising electromagnetic absorbing material. (C) 2017 Published by Elsevier B.V.