Key Findings
The study demonstrates that a FeCoNiCr-based high-entropy alloy (4E5-r), processed via magnetic-field annealing (MFA), achieves an ultra-strong reflection loss of -72.30 dB and a maximum effective absorption bandwidth (EABmax) of 4.40 GHz at a thickness of 1.59 mm. The material maintains high thermal stability, with the EABmax retaining 92.7% of its value at 85 °C. These results were validated through integration into flexible antennas and strain sensors.
Technical Details
The synthesis followed a two-step thermal treatment process:
- Rapid Joule Heating: FeCoNi, FeCoNiCr, and FeCoNiCrCu nanoparticles were synthesized on graphene oxide at 1800 °C for 500 ms.
- Magnetic-Field Annealing: Samples were annealed at 600 °C for 0.5 h under magnetic fields of 0, 0.5, or 0.95 T to induce chemical short-range order (SRO).
Analysis revealed that the 0.5 T MFA sample (4E5-r) optimized the balance between dielectric loss (tanδe,max 0.651) and magnetic loss (tanδm,max 0.154), resulting in an impedance ratio |Zin/Z0| of 0.9996. Electronic structure calculations and atomic modeling indicated that Co-centered rearrangement—specifically Co-Co enrichment and Co-Cr/Co-Fe depletion—drives the redistribution of charge and spin polarization, which controls the electromagnetic response.
Background & Context
Developing electromagnetic wave absorbers for 5G/6G and radar requires materials that are thin, heat-resistant, and effective below 6 GHz. Traditional HEA absorbers face three primary challenges: the “low-frequency dilemma” where long wavelengths require excessive thickness, the coupling of composition and conductivity, and a lack of understanding regarding how SRO affects electromagnetic properties.
Significance & Outlook
The research establishes a “composition-process” dependency chain, proving that MFA can be used as a precise variable to balance microwave responses. Beyond material synthesis, the team integrated the alloy into a U-shaped microstrip patch antenna (2.0 mm thickness) achieving S11 of -55.882 dB, and developed a metasurface with a predicted RLmin of -18.55 dB near 4.69 GHz for chip integration and crosstalk suppression.
Source: https://www.sohu.com/a/1092959957_122940509
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