Complex permeability and electromagnetic wave absorption properties of amorphous alloy-epoxy composites

Electromagnetic wave absorption properties of amorphous alloy-epoxy composites have been investigated with various amorphous alloy particle sizes and fractions in the 45 MHz to 10 GHz frequency range. The fraction of amorphous alloy in amorphous alloy-epoxy composites varied from 30 to 60vol.% at a fixed amorphous alloy particle size and the size of amorphous alloy particles was varied from several mum to 125 mum at a fixed amorphous alloy particle fraction. Complex permeability (mu), permittivity, (epsilon) of composites and reflection loss were measured by the reflection/transmission technique. The composites with small sized amorphous alloy particles (<26 mum) and a small amount of particles (<50%) had good reflection loss values less than -20dB with thin thickness, (<1 cm). The decreasing amorphous alloy particle size and fraction in amorphous alloy-epoxy composites resulted in a high minimum reflection loss frequency and small minimum reflection loss thickness. Variations of minimum reflection loss frequency and thickness of composites resulted from variations of materials constants such complex permeability. permittivity, and resonance frequency. Changes in materials variables were due to the demagnetization effect and the eddy current effect, which operate differently in composites according to amorphous alloy particle size and fraction. (C) 2004 Elsevier B.V. All rights reserved.