Composition Optimization of Iron-Nickel-Nanographite Particles for Tuning the Electromagnetic Parameters of Silicone Rubber Composites

The current study investigates iron (Fe)-nickel (Ni)-nanographite (NG) / silicone rubber composites for improved microwave absorption in 8–18 GHz range. Fe–Ni particles were produced in three different ratios (50:50, 60:40, and 75:25) using high-energy planetary ball mill. NG was also prepared from graphite using wet milling. The Fe–Ni combinations were then ball milled with NG at 75:25 ratio (Fe–Ni: NG) and coded as (Fe_0.75Ni_0.25)_0.75NG_0.25, (Fe_0.6Ni_0.4)_0.75NG_0.25, and (Fe_0.5Ni_0.5)_0.75NG_0.25. These hybrid nanoparticles were investigated for their structural and morphological properties. The thermomechanical, environmental and electromagnetic properties of silicone rubber composites with these nanoparticles (20% w/w) were studied. Around 60% improvement in tensile strength with 40% more elongation is achieved compared to the pure silicone rubber samples. (Fe_0.5Ni_0.5)_0.75NG_0.25 based sample shows good dynamic mechanical properties with almost 4 times increase in storage modulus and twice increase in loss modulus from − 20 °C to room temperature. The conducting nature of hybrid nanoparticles helps to reduce the electrical impedance up to two orders (from 10⁴ to 10² Ω). The composites with (Fe_0.75Ni_0.25)_0.75NG_0.25 have excellent mechanical characteristics and good dielectric and magnetic loss while the electromagnetic characteristics of (Fe_0.6Ni_0.4)_0.75NG_0.25 based composites have shown greater broad-spectrum absorption in 8–18 GHz range. Real and imaginary permittivity values are up to 50 and 8, respectively while real and imaginary permeability values are around 1 and 0.5, respectively. The results indicate that these flexible polymer nanocomposite sheets are a viable contender as microwave absorbers in a variety of stealth applications over wide range environmental conditions.