Electromagnetic characteristics and microwave absorption properties of carbon-encapsulated cobalt nanoparticles in 2–18-GHz frequency range
Electromagnetic characteristics and microwave absorption properties of carbon-encapsulated cobalt nanoparticles in 2–18-GHz frequency range
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DOI：
10.1016/j.carbon.2014.08.044
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发表时间：
2014-12
期刊：
影响因子：
10.9
通讯作者：
Danfeng Zhang;Fangxing Xu;Jin Lin;Zhenda Yang;M. Zhang
中科院分区：
文献类型：
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作者：
Danfeng Zhang;Fangxing Xu;Jin Lin;Zhenda Yang;M. Zhang
采用弧光放电法制备了直径为10~50 nm的碳包覆钴纳米粒子(Co(C))。内部晶体钴核完全被外层碳壳包裹，外层碳壳由无定形碳和15-20层类石墨碳组成。在2-18 GHz频率下，研究了Co(C)在10、40、50、70和80wt.%(分别为2、10、15、29和41g.%)的石蜡中的电磁特性。Co(C)独特的核壳结构和碳壳结构是产生高复介电常数的主要原因。复磁导率(μ)的实部随频率的增加而减小，μ的虚部随频率的增加而减小，表明碳包覆金属钴芯获得了良好的绝缘效果。主要的电磁吸收机制是介电损耗。对于3 mm的Co(C)/石蜡复合材料，计算的最小反射损耗(RL)在7.54千兆赫时为−52分贝，Co(C)为50%。Co(C)/环氧涂层在3 mm处加载量为40wt%时的测量RL与计算的RL吻合较好。Co(C)的电磁性能可以通过控制Co(C)的浓度和涂层厚度来调节。
Carbon-encapsulated cobalt nanoparticles (Co(C)) with a diameter of 10–50 nm were synthesized by an arc discharge method. The inner crystal cobalt core was completely encapsulated by an outer carbon shell, which consisted of both amorphous carbon and 15–20 layers of graphite-like carbon. The electromagnetic characteristics of Co(C) embedded in paraffin at 10, 40, 50, 70, and 80 wt.% (2, 10, 15, 29, and 41 vol.%, respectively) at 2–18 GHz were investigated. The distinctive core–shell microstructure of Co(C) and the carbon shells were mainly responsible for the high complex permittivity. The real part of complex permeability (μ) decreased and the imaginary part ofμremained small with increasing frequency, which revealed that good insulation between the metallic cobalt cores was achieved by carbon encapsulation. The major electromagnetic absorption mechanism was dielectric loss. The minimum calculated reflection loss (RL) was −52 dB at 7.54 GHz with 50 wt.% Co(C) for a 3-mm Co(C)/paraffin composite. The measured RL of a Co(C)/epoxy coating with 40 wt.% loading at 3 mm showed good agreement with that of calculated RL. The electromagnetic property of Co(C) can be tailored through both control Co(C) concentrations and coating thickness.