Electromagnetic Microwave Absorption of α-Fe Microstructure Produced by Disproportionation Reaction of Sm 2 Fe 7 Compound

Abstract

The electromagnetic wave absorption properties of a magnetic powder with a fine α-Fe structure, produced by the disproportionation of Sm 2 Fe 17 , were investigated in the GHz frequency range. A fine, sub-micrometre α-Fe/SmH 2 structure was formed from the Sm 2 Fe 17 compound after disproportionation in a hydrogen atmosphere. The grain size of the α-Fe phase was calculated by X-ray diffraction line broadening analysis, to he about 30nm. In this way, a magnetic powder with a line structure of α-Fe was obtained. This powder was then heated in air in order to oxidize the SmH 2 , with the result that an α-Fe/SmO two-phase microstructure was obtained. Toroidally shaped epoxyresin composites were made from this powder, and the microwave absorption properties of these samples were measured. As a result, the disproportionated samples (heated in hydrogen at 873 K for 1 hour, milled for 30 minutes and oxidized at 473 K for 2 hours in the air) exhibited electromagnetic wave absorption (R.L. < -20 dB) in the frequency range 0.75 to 1.3 GHz, for absorber thicknesses ranging from 12.5 to 7.5 mm, respectively. An undisproportionated sample did not show any electromagnetic wave absorption in this frequency range.