Effect of attrition time on the microwave permeability of magnetic Fe-Si-Al flakes

Fe-Si-Al particles with irregular shapes have been successfully milled into flaky shapes by attrition for 10, 20, and 30 h, respectively. The attrition time has very small effect on the static magnetic properties, but shows strong effects on the high frequency properties (permittivity and permeability). With increasing the attrition time, the values of permeability can be obviously enhanced, especially at lower frequencies. The high frequency permittivity values of flakes milled for 30 h are much larger than those of particles milled for 10 or 20 h. A multiple relaxation processes model has been used to study the permeability dispersion behaviors. Analysis show the variation of shape anisotropy could be the main cause for the observed changes in permeability dispersion behaviors. However, the electromagnetic wave absorption properties of composites filled with these flaky shape Fe-Si-Al particles are found deteriorated when the particles have been milled for longer time. (C) 2012 American Institute of Physics. [doi:10.1063/1.3673813]