Preparation and microwave absorption properties of spherical cobalt particles

Abstract:

Spherical cobalt particles with special morphology were successfully prepared on a large scale through a simple and low-cost liquid reduction method. The morphology, crystal structure, static magnetic properties and electromagnetic behavior of the cobalt particles were measured by SEM、XRD、VSM and vector network analyzer. The results show that saturation magnetization of 123 emu/g was obtained, less than that of hcp-Co single crystals, and the coercivity was 176 Oe, larger than that of bulk cobalt crystal. Furthermore, dual-nonlinear dielectric resonances were observed at 9.8 GHz and 15 GHz. The real part of permeability decreases with the frequency increasing, presenting excellent frequency dispersion property. Meanwhile, the imaginary part of permeability revealed a wide resonance peak over microwave frequency range. According to transmit-line theory, the reflection loss (RL) was predicted through the permittivity and permeability for a given frequency and absorber thickness. A maximum reflection loss of -13.2 dB was achieved at 12.4 GHz with a thickness of 5.5 mm, and the effective absorption bandwidth (≤ -10 dB) was 1.6 GHz, indicating the as-prepared cobalt particles have potential application as candidate for microwave absorption.

Key words:spherical cobalt particles; liquid reduction method; static magnetic properties; electromagnetic behavior; microwave absorpti