Nanocrystalline structure and particle size effect on microwave permeability of FeNi powders prepared by mechanical alloying

In this paper, nanocrystalline FeNi alloy powders with different particle size were prepared by two-step mechanical alloying (MA), the first step of the processes is FeNi nanocrystalline alloying and the second step modifies particle size. As-milled powders were randomly dispersed in paraffin at a weight ratio of 5:1 for microwave complex permeability test and comparision in the frequency range of 0.5-18 GHz. It is observed and discussed that microwave complex permeability is prominently affected by FeNi microstructure and particle size. In this work, Fe0.85Ni0.15 nanocrystalline powders exhibit high value of complex permeability in 1-10 GHz, and the sample with particle size of 2.34 mu m possesses the maximum value as mu' = 6.32 at 1.81 GHz, mu '' = 3.45 at 4.09 GHz. This value may be useful for thin-thickness and wide-band microwave absorber. (c) 2004 Elsevier B.V. All rights reserved.