碳包覆镍纳米胶囊/石蜡复合材料电磁波吸收机制

Electromagnetic Wave Absorption of Carbon-coated Nickel Nanocapsules/Paraffin Composites

利用直流电弧等离子体法在甲烷气氛中制备碳包覆磁性镍纳米胶囊（Carbon-coated Ni nanocapsules,Ni（C）NCs）,将它作为电磁波吸收剂,按照质量比10%、20%、30%和40%与有机石蜡基体复合,在0.1～18GHz范围内测定其复介电常数和复磁导率,并对其电磁波响应特性及吸收机制进行了研究。研究结果表明,Ni（C）纳米胶囊具有明显的极化损耗特征,其介电常数在低频范围内随频率提高而急剧衰减,而磁导率具有宽化的多重共振峰;随着Ni（C）纳米胶囊添加量的增加,其介电常数逐渐增加,其复磁导率实部和虚部分别在0.1～8GHz、0.1～10GHz出现增加,而在8～18GHz和10～18GHz范围内出现实部减小和虚部平缓变化的特征。根据极化、涡流以及反射损耗的理论分析,发现Ni（C）纳米胶囊以介电损耗为主,并对相关机制进行了探讨。

The carbon-coated nickel nanocapsules（Ni（C）NCs）were prepared by DC arc-discharge method in CH4 atmosphere and mixed as electromagnetic absorber under various mass percentages（10%,20%,30% and 40%）with paraffin matrix to form composite wave absorbing materials,whose relative complex permeabilities and complex permittivities were measured within the frequency range of 0.1-18 GHz in order to investigate the electromagnetic characteristics and absorption mechanism of such Ni（C）nanocapsules/paraffin composites.The results revealed that Ni（C）nanocapsules exhibited significant characteristics of polarization losses and its dielectric constant drastically attenuated with increasing frequency in the low frequency range,while the magnetic permeability showed a broaden width with multiple resonance peaks.The increment of Ni（C）nanocapsules′mass fraction caused the gradual rise of dielectric constant,and meanwhile,rises of real and imaginary parts of complex permeability in the frequency range of0.1-8GHz and 0.1-10 GHz,respectively.However,in the frequency range of 8-18 GHz and 10-18 GHz,the real part reduced and imaginary part changed at an almost constant rate.We observed that electromagnetic loss of Ni（C）nanocapsules is mainly dominated by dielectric loss,and theoretically analyzed in detail thepolarization,eddy current and electromagnetic wave reflection,as well as the related mechanisms.