Synthesis and characterization of nanosized urchin-like α-Fe2O3 and Fe3O4: Microwave electromagnetic and absorbing properties

Urchin-like alpha-Fe2O3 and Fe3O4 nanostructures were prepared from the precursor urchin-like alpha-FeOOH under reducing atmosphere. The dependence of reduction temperature on their morphology, microstructure, and microwave electromagnetic and absorbing characteristics were systematically studied. It is found that the reduction temperature plays an important role in the microstructure and electromagnetic characteristics of the resulting products. In present study, the urchin-like alpha-Fe2O3 with dual absorption peaks can be formed at the relatively low temperature (e.g. 300 degrees C). Urchin-like Fe3O4 can be obtained just at 350-400 degrees C, which presents excellent microwave absorption property, with the minimum reflection loss of -29.96 dB and below -20 dB in 3.76-8.15 GHz corresponding to 3-4 mm thickness. The excellent microwave-absorption properties are a consequence of a proper electromagnetic matching and enhanced absorbing abilities resulting from the urchin-like shape and inverse spinel-type crystal structure. (C) 2011 Elsevier B.V. All rights reserved.