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Abstract <p>It is crucial to improve the antioxidant ability and structural stability of high-performance rare earth (RE) metal nanoalloys for their potential wide applications. In this work, an efficient functional surface carbon modification method has been provided to fabricate high-stability RE alloy/carbon nanostructures as high-performance electromagnetic materials. Specifically, graphite-encapsulated Y<sub>2</sub>Co<sub>17</sub> nanoalloys constructed with high-purity Y<sub>2</sub>Co<sub>17</sub> nanoparticles entirely coated with dense ultrathin N-doped graphite carbon (NGC) nanolayers to form antioxidative Y<sub>2</sub>Co<sub>17</sub>@NGC nanostructures are fabricated by a precisely controlled calcium thermic reduction of well-designed crystalline CoO-Co-Y<sub>2</sub>O<sub>3</sub>/C precursors. Another similarly structured Y<sub>2</sub>Co<sub>17</sub>@defect-rich graphite carbon (DGC) nanostructure is obtained by replacing NGC in Y<sub>2</sub>Co<sub>17</sub>@NGC with DGC by the same calcium thermic reduction but adjusting the carbon sources in the precursors. The excellent oxidation resistance and stable structures for these graphite-encapsulated Y<sub>2</sub>Co<sub>17</sub> nanostructures facilitate the formation of ultrapure magnetic planar-anisotropy Y<sub>2</sub>Co<sub>17</sub> phase, which results in their good soft magnetism with ultrahigh saturation magnetization values of 112.1–113.3 A&#xa0;m<sup>2</sup>&#xa0;kg<sup>−1</sup>. Y<sub>2</sub>Co<sub>17</sub>@NGC nanostructures exhibit a favorable C band microwave absorption with a high minimum reflection loss (<i>RL</i><sub>min</sub>) value up to −80.16&#xa0;dB at 4.30&#xa0;GHz with a 4.03-mm-thick and Y<sub>2</sub>Co<sub>17</sub>@DGC nanostructures show a typical Ku band absorption with a <i>RL</i><sub>min</sub> value of −52.59&#xa0;dB at 16.71&#xa0;GHz with a 1.34&#xa0;mm thickness. The good switchable electromagnetic properties of these graphite-encapsulated Y<sub>2</sub>Co<sub>17</sub> nanostructures are demonstrated to arise from their different surface carbon defects. This work provides a surface carbon treatment strategy for fundamentally improving the oxidation resistance and structural stability of the easily oxidized RE nanoalloys and further constructing novelly structured functionalized RE alloy/carbon nanostructures.</p> Graphical Abstract <p></p>

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Ultrathin graphite-encapsulated Y2Co17 nanostructures with good structural stability and switchable microwave absorption

  • 期刊论文

  • 发表日期：

    2025年8月7日

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  • Jie Ma,
  • Han Zhang,
  • Bai Yang,
  • Xu-Feng Li,
  • Rong-Hai Yu,
  • Xi-Xiang Zhang,
  • Ran Li

摘要

Abstract

It is crucial to improve the antioxidant ability and structural stability of high-performance rare earth (RE) metal nanoalloys for their potential wide applications. In this work, an efficient functional surface carbon modification method has been provided to fabricate high-stability RE alloy/carbon nanostructures as high-performance electromagnetic materials. Specifically, graphite-encapsulated Y2Co17 nanoalloys constructed with high-purity Y2Co17 nanoparticles entirely coated with dense ultrathin N-doped graphite carbon (NGC) nanolayers to form antioxidative Y2Co17@NGC nanostructures are fabricated by a precisely controlled calcium thermic reduction of well-designed crystalline CoO-Co-Y2O3/C precursors. Another similarly structured Y2Co17@defect-rich graphite carbon (DGC) nanostructure is obtained by replacing NGC in Y2Co17@NGC with DGC by the same calcium thermic reduction but adjusting the carbon sources in the precursors. The excellent oxidation resistance and stable structures for these graphite-encapsulated Y2Co17 nanostructures facilitate the formation of ultrapure magnetic planar-anisotropy Y2Co17 phase, which results in their good soft magnetism with ultrahigh saturation magnetization values of 112.1–113.3 A m2 kg−1. Y2Co17@NGC nanostructures exhibit a favorable C band microwave absorption with a high minimum reflection loss (RLmin) value up to −80.16 dB at 4.30 GHz with a 4.03-mm-thick and Y2Co17@DGC nanostructures show a typical Ku band absorption with a RLmin value of −52.59 dB at 16.71 GHz with a 1.34 mm thickness. The good switchable electromagnetic properties of these graphite-encapsulated Y2Co17 nanostructures are demonstrated to arise from their different surface carbon defects. This work provides a surface carbon treatment strategy for fundamentally improving the oxidation resistance and structural stability of the easily oxidized RE nanoalloys and further constructing novelly structured functionalized RE alloy/carbon nanostructures.

Graphical Abstract