With the combination of the dielectric loss of the carbon layer with the magnetic loss of the ferromagnetic metal core, carbon-coated nickel （Ni（C）） nanoparticles are expected to be the promising microwave absorbe...With the combination of the dielectric loss of the carbon layer with the magnetic loss of the ferromagnetic metal core, carbon-coated nickel （Ni（C）） nanoparticles are expected to be the promising microwave absorbers. Microwave electromag- netic parameters and reflection loss in a frequency range of 2 GHz-18 GHz for paraffin-Ni（C） composites are investigated. The values of relative complex permittivity and permeability, the dielectric and magnetic loss tangent of paraffin-Ni（C） com- posites are measured, respectively, when the weight ratios of Ni（C） nanoparticles are equal to 10 wt%, 40 wt%, 50 wt%, 70 wt%, and 80 wt% in paraffin-Ni（C） composites. The results reveal that Ni（C） nanoparticles exhibit a peak of magnetic loss at about 13 GHz, suggesting that magnetic loss and a natural resonance could be found at that frequency. Based on the measured complex permittivity and permeability, the reflection losses of paraffin-Ni（C） composites with different weight ratios of Ni（C） nanoparticles and coating thickness values are simulated according to the transmission line theory. An ex- cellent microwave absorption is obtained. To be proved by the experimental results, the reflection loss of composite with a coating thickness of 2 mm is measured by the Arch method. The results indicate that the maximum reflection loss reaches -26.73 dB at 12.7 GHz, and below -10 dB, the bandwidth is about 4 GHz. The fact that the measured absorption position is consistent with the calculated results suggests that a good electromagnetic match and a strong microwave absorption can be established in Ni（C） nanoparticles. The excellent Ni（C） microwave absorber is prepared by choosing an optimum layer number and the weight ratio of Ni（C） nanoparticles in paraffin-Ni（C） composites.展开更多
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,...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。展开更多
基金supported by the Science and Technology Program of Guangdong Province,China(Grant Nos.2014B010106005,2013B051000077,and2015A050502047)the Science and Technology Program of Guangzhou City,China(Grant No.201508030018)
文摘With the combination of the dielectric loss of the carbon layer with the magnetic loss of the ferromagnetic metal core, carbon-coated nickel （Ni（C）） nanoparticles are expected to be the promising microwave absorbers. Microwave electromag- netic parameters and reflection loss in a frequency range of 2 GHz-18 GHz for paraffin-Ni（C） composites are investigated. The values of relative complex permittivity and permeability, the dielectric and magnetic loss tangent of paraffin-Ni（C） com- posites are measured, respectively, when the weight ratios of Ni（C） nanoparticles are equal to 10 wt%, 40 wt%, 50 wt%, 70 wt%, and 80 wt% in paraffin-Ni（C） composites. The results reveal that Ni（C） nanoparticles exhibit a peak of magnetic loss at about 13 GHz, suggesting that magnetic loss and a natural resonance could be found at that frequency. Based on the measured complex permittivity and permeability, the reflection losses of paraffin-Ni（C） composites with different weight ratios of Ni（C） nanoparticles and coating thickness values are simulated according to the transmission line theory. An ex- cellent microwave absorption is obtained. To be proved by the experimental results, the reflection loss of composite with a coating thickness of 2 mm is measured by the Arch method. The results indicate that the maximum reflection loss reaches -26.73 dB at 12.7 GHz, and below -10 dB, the bandwidth is about 4 GHz. The fact that the measured absorption position is consistent with the calculated results suggests that a good electromagnetic match and a strong microwave absorption can be established in Ni（C） nanoparticles. The excellent Ni（C） microwave absorber is prepared by choosing an optimum layer number and the weight ratio of Ni（C） nanoparticles in paraffin-Ni（C） composites.
文摘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。
