Microwave absorption study of low-density composites of barium hexaferrite and carbon black in X-band

The low-density composites based on carbon black (CB) nanopowder and barium hexaferrite (BaFe12O19) nanoparticles are synthesized and characterized for microwave absorption properties in X-band (8.2–12.4 GHz). Barium hexaferrite nanoparticles are developed using low-cost autocombustion method that resulted in low-density particles with uniform particle size distribution. Composites are developed by the ball-milling of BaFe12O19 with CB nanopowder in different weight ratios followed by heat-treatment process. The addition of CB in the composite resulted in enhanced electrical properties due to increase in the dipolar polarization between carbon and ferrite. As a result of increasing CB concentration in composite, the dielectric loss tangent increased from 0.31 to 0.366. On the contrary, the magnetic loss tangent decreased from 0.071 to 0.027, which is due to reduction of magneto-crystalline anisotropy of the composite with CB addition. The composite medium containing 80% CB and 20% BaFe12O19 showed excellent microwave absorption properties having minimum reflection loss of −56.266 dB at 11.98 GHz for an effective coating thickness of 1.85 mm. Also, the effective bandwidth of the composite having reflection loss of 90% (−10 dB) reached to 3.53 GHz (84% of X-band) for coating thickness 2.15 mm. The low reflection loss and wide bandwidth microwave absorption of the composite is due to the increased dielectric properties, which resulted in better impedance matching with free space and high electromagnetic (EM) attenuation.