Enhanced microwave absorption of ZnO-coated planar anisotropy carbonyl-iron particles in quasimicrowave frequency band

For the aim of thin electromagnetic wave absorbers used in quasimicrowave frequency band, planar anisotropy carbonyl-iron (PACI) particles coated with ZnO nanoshells were prepared by ball milling technique and chemical precipitation method. Compared with the as-milled PACI/paraffin composite, lower dielectric constant was obtained for the composite containing PACI at ZnO particles, and hence a dramatic enhancement of reflection loss (RL) was obtained. The minimum RL of PACI at ZnO composite reaches -31.93 dB at 1.96 GHz with the matching thickness of 2.5 mm. Furthermore, the absorbing property is further improved after the PACI at ZnO composite was rotationally oriented in an external magnetic field. The minimum RL of the oriented PACI at ZnO composite reaches -40.06 dB and the matching thickness reduces to 2.2 mm with a slight variation of matching frequency. The PACI at ZnO core-shell particles exhibit great potential in application of the thin absorber in the 1-4 GHz frequency range. (C) 2011 Elsevier B.V. All rights reserved.