Journal
POWDER TECHNOLOGY
Volume 269, Issue -, Pages 443-451Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.powtec.2014.09.045
Keywords
Iron oxides; Porous nanospheres; TEM; EM wave absorption properties
Categories
Funding
- Nature Science Foundation of China [50771082, 60776822]
- Excellent Doctorate Foundation
- Doctorate Foundation of Northwestern Polytechnical University
- Ministry of Education, P.R. China
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We reported a facile approach to prepare peculiar porous alpha-Fe2O3, gamma-Fe2O3 and Fe3O4 nanospheres by combining a facile hydrothermal route with a calcination process in Ar or H-2 atmosphere. The synthesized monodisperse potous alpha-Fe2O3 nanospheres with uniform average diameters of similar to 60 nm in fact contained randomly distributed pores. A close view further revealed that there are two types of pores, one is large mesopores (ca. 15-20 nm) in the center, and the other is small mesopores (ca. <10 nm) in the outside. After calcining in Ar or H-2, the obtained alpha-Fe2O3, gamma-Fe2O3 and Fe3O4 nanospheres preserved the similar morphology and particle size as the uncalcined alpha-Fe2O3 nanospheres, indicating the as-prepared alpha-Fe2O3 nanospheres are stable under Ar and H-2-annealing heat treatment Comparing with all the paraffin composites, it was found that the porous alpha-Fe2O3 nanosphere/paraffin composites exhibit a higher permittivity level. A minimum reflection loss (RL) of 25 dB was observed at similar to 13 GHz for the porous alpha-Fe2O3 nanosphere/paraffin composites with a thickness of 3.5 mm, and the effective absorption frequency (RL < 10 dB) ranged from 9.9 to 15.1 GHz. The composites exhibited better absorption properties than the magnetic porous gamma-Fe2O3 and Fe3O4 nanosphere/paraffin composites. (C) 2014 Elsevier B.V. All rights reserved.
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