Synthesis and Study of Electromagnetic Wave Absorption Performance of Nano Medium-Entropy FeCoNi Magnetic Alloy Particles with Varying Ni Element Contents

To investigate the influence of Ni element content on the absorptive properties of nano medium-entropy FeCoNi alloy particles, five groups of nano medium-entropy FeCoNi alloy particles was synthesized with varying Ni element contents by chemical liquid-phase reduction, and the microstructure characteristics, magnetic and absorptive properties were studied. The results show that the synthesized nano medium-entropy FeCoNi alloy particles have a spherical geometry and face-centered cubic crystal structure, with a slight increase in particle size as the Ni element content increases, averaging radius 100–200 nm. The alloy particles exhibit soft magnetic properties, with decreasing saturation magnetization intensity, coercivity, and residual magnetization as the Ni element content increases. The real and imaginary parts of the dielectric constant and complex magnetic permeability of the prepared FeCoNi alloy particles show an increasing followed by a decreasing trend with the increase of Ni element content, maximum values was with Ni element content of x = 0.8. As the electromagnetic frequency increases, the real part of the complex magnetic permeability of the alloy particles follows a decreasing trend, and the imaginary part of the magnetic permeability at a Ni element content of x = 0.8 is lower than that of the other alloy particles. The dielectric loss gradually increases with the rise of electromagnetic wave frequency, with polarization relaxation was the primary loss mechanism. At a Ni element content of x = 0.8, the alloy particle sample demonstrates the widest effective absorption bandwidth 4.48 GHz with sample thickness of 1.4 mm and the maximum reflection loss 44.2 dB with thickness of 1.6 mm. Similarly, with Ni element content of x = 1, the alloy particle sample exhibits the largest effective absorption bandwidth 5.36 GHz at thickness 1.6 mm and the maximum reflection loss 32.5 dB at thickness of 1.8 mm.