Electromagnetic properties of Co flaky particles prepared via-ball milling method

Flaky cobalt particles with different aspect ratio were produced with ball-milling method. The phase structure and morphology of the particles were identified by XRD analysis and SEM observation. The static magnetic and electromagnetic properties of the particles were measured and effects of shape, microstructure and filling fraction were investigated. Phase transition from fcc lattice to hcp lattice occur due to the drive of ball-milling is responsible for the largely increased coercivity. Particles with high aspect ratio are found to possess high permittivity and permeability, compelling the frequency of absorption peak to shift to low frequency. Coatings using cobalt particles milled for 20h as fillers present a RL peak of −33dB at 8GHz at the thickness of 2.5mm together with a broad effective absorbing (RL below −10dB) bandwidth covering 6–10GHz.