The microwave electromagnetic and absorption properties of some porous iron powders

The porous iron powders were prepared by an activated carbon assisted route involving impregnation of activated carbon with concentrated metal nitrate solutions, calcination and subsequent hydrogen reduction. The prepared samples were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and nitrogen physisorption (physical adsorption). The complex relative dielectric permittivity (epsilon(r) = epsilon'-j epsilon) and magnetic permeability (mu(r) = mu'-j mu) of the powder-resin matrix composites were measured in the frequency range of 2-18 GHz. Morphological studies show that the prepared powder is flaky in appearance with a high specific surface area. For the porous magnetic fillers, the electromagnetic waves may occur repeatedly energy dissipation in the free space (pore) of the material, and resonance loss may be occurred. The porous microstructure in the materials under study has been found to be the main factor for the abnormal microwave response characteristics. The calculated results indicate that the prepared powder-resin composites exhibit good absorption performance in the 2-18 GHz range. (c) 2006 Elsevier B.V. All rights reserved.