Investigation on electromagnetic characteristics, microwave absorption, thermal and mechanical properties of ferromagnetic cobalt-polystyrene composites in the X-band (8.4-12.4 GHz)

The electromagnetic, thermal and mechanical properties of ferromagnetic cobalt-polystyrene composites in the X-band (8.4-12.4 GHz) are investigated in order to explore their usage for wide band microwave absorbers. The cobalt-polystyrene composites are prepared by mechanical blending method using automated injection molding equipment. The microwave absorption properties of cobalt-polystyrene (Co-PS) composites with different cobalt weight ratios are investigated in order to determine the optimum weight ratio for design of efficient microwave absorbers. In order to understand the electromagnetic absorption process at micro level, the X-ray diffraction (XRD) and scanning electron microscopy (SEM) of various samples are carried out to obtain information about the existence and dispersion of Co filler in the Co-PS composite samples, respectively. The thermal stability of the synthesized Co-PS composites is analyzed using the thermo gravimetric analysis (TGA), while the surface hardness is measured using Shore D hardness tool. The tensile and flexural tests are performed to find out the mechanical properties of the molded composites. The complex permittivity (3) and permeability (m) of the Co-PS composites are extracted from the scattering data obtained using the vector network analyzer (VNA) measurements in the X-band of microwave frequency. The reflection losses (RL) in the composites are calculated using the complex permittivity and permeability parameters. The minimum reflection loss (maximum absorption) of -19.85 dB (98.96%) at 10.22 GHz is achieved for 30 wt% Co-PS composite with thickness of 5 mm, and this value reaches to -31.6 dB (99.93%) at 9.04 GHz with thickness of 10 mm. For 5 wt% Co-PS composite, the minimum reflection loss of -4.90 dB (67.66%) at 10.72 GHz is achieved with thickness of 5 mm. The experimental results reveal that the microwave absorption properties of the synthesized composites in the X-band can be improved by changing the ferromagnetic cobalt weight ratios in the composite.