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<p>In this study, AlCoCrFeNi high-entropy alloys (HEAs) powder is passivation-modified with phosphoric acid passivation solution and annealed under nitrogen atmosphere. Magnetic high-entropy alloy composites exhibiting low magnetic loss at low frequencies and high wave-absorbing performance at high frequencies have been successfully synthesized. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) are used to study and analyze the phase changes, micro-morphology and surface element distribution of the composite materials. The magnetic permeability and magnetic loss of the composites at low frequencies are measured by B-H analyzer. The wave absorbing properties at high frequencies are characterized and tested using a vector network analyzer (VNA). It can be found that the physical phase of the high-entropy alloy composites after phosphoric acid passivation does not change significantly, but fine phosphate-containing passivation layers can be observed on the surface. The magnetic loss of the passivated composites at low frequencies is significantly reduced, with the lowest loss of 219.8 mW/cm<sup>3</sup> (1000&#xa0;kHz, <i>B</i><sub><i>m</i></sub> = 5mT) at 0.6 wt% phosphoric acid addition. The electromagnetic absorption performance is also improved to different degrees. The high-entropy alloy composites modified with 1.0 wt% phosphoric acid have the best absorption performance with the minimum reflection loss of − 36.494&#xa0;dB with a matching thickness of 2.5 mm and the maximum effective absorption bandwidth of 6.16&#xa0;GHz.</p>

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2–18 GHz broadband absorption achieved in phosphoric acid-passivated AlCoCrFeNi HEA: synergistic effects of magnetic loss and surface impedance matching

  • 期刊论文

  • 发表日期：

    2025年7月8日

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  • Hongyu Ding,
  • Yujie Yang,
  • Hao Li,
  • Zhenyu Zhang,
  • Zhihao Geng

摘要

In this study, AlCoCrFeNi high-entropy alloys (HEAs) powder is passivation-modified with phosphoric acid passivation solution and annealed under nitrogen atmosphere. Magnetic high-entropy alloy composites exhibiting low magnetic loss at low frequencies and high wave-absorbing performance at high frequencies have been successfully synthesized. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) are used to study and analyze the phase changes, micro-morphology and surface element distribution of the composite materials. The magnetic permeability and magnetic loss of the composites at low frequencies are measured by B-H analyzer. The wave absorbing properties at high frequencies are characterized and tested using a vector network analyzer (VNA). It can be found that the physical phase of the high-entropy alloy composites after phosphoric acid passivation does not change significantly, but fine phosphate-containing passivation layers can be observed on the surface. The magnetic loss of the passivated composites at low frequencies is significantly reduced, with the lowest loss of 219.8 mW/cm3 (1000 kHz, Bm = 5mT) at 0.6 wt% phosphoric acid addition. The electromagnetic absorption performance is also improved to different degrees. The high-entropy alloy composites modified with 1.0 wt% phosphoric acid have the best absorption performance with the minimum reflection loss of − 36.494 dB with a matching thickness of 2.5 mm and the maximum effective absorption bandwidth of 6.16 GHz.