Electromagnetic wave absorption properties of iron/rare earth oxide composites dispersed by amorphous carbon powder

The Sludge powders of Nd-Fe-B sintered magnets were oxidized at 250-325 degrees C for 2 h and then the alpha-Fe/Fe2B/Nd2O3/amorphous carbon (a-C) nanocomposite powders were prepared by ball-milling the sludge with the a-C powder for 12-40 h. The resin composites of 75 mass% of these nanocomposite powders showed excellent electromagnetic wave absorption properties in GHz range. The effective absorption of RL <-20 dB were observed in a range of 7.6-18.0 GHz and the minimum absorption peaks around -58.5 dB appeared at 12.0 GHz with matching thickness of 1.9 mm for the samples heated at 300 degrees C for 2 h and then ball-milled with 4.8 mass% a-C for 30 h. (c) 2005 Published by Elsevier B.V.