摘要
Te mechanism of negative permittivity/permeability is still unclear in the random metamaterials,where the precise control of microstructure and electromagnetic properties is also a challenge due to its random characteristic.Here silver was introduced into porous SiO_(2) microsphere matrix by a self-assemble and template method to construct the random metamaterials.Te distribution of silver was restricted among the interstices of SiO_(2) microspheres,which lead to the precise regulation of electrical percolation(from hoping to Drude-type conductivity)with increasing silver content.Negative permittivity came from the plasma-like behavior of silver network,and its value and frequency dispersion were further adjusted by Lorentz-type dielectric response.During this process,the frequency of epsilon-near-zero(ENZ)could be adjusted accordingly.Negative permeability was well explained by the magnetic response of eddy current in silver micronetwork.Te calculation results indicated that negative permeability has a linear relation with ω^(0.5),showing a relaxation-type spectrum,diferent from the“magnetic plasma”of periodic metamaterials.Electromagnetic simulations demonstrated that negative permittivity materials and ENZ materials,with the advantage of enhanced absorption(40dB)and intelligent frequency selection even in a thin thickness(0.1 mm),could have potentials for electromagnetic attenuation and shielding.Tis work provides a clear physical image for the theoretical explanation of negative permittivity and negative permeability in random metamaterials,as well as a novel strategy to precisely control the microstructure of random metamaterials.
出处
《Research》
EI
CAS
2019年第1期1226-1236,共11页
研究（英文）
基金
The authors thank Xueyan Fu for her advice on electromagnetic simulation using Computer Simulation Technology sofware.Te authors thank Yao Liu,Guohua Fan,Yunpeng Qu,and Yuliang Jiang for their advice for doing experiments and measurements.The authors acknowledge the support of the National Natural Science Foundation of China[Grants nos.51601105,51871146,and 51803119]
the Young Elite Scientists Sponsorship Program by CAST(Grant no.2017QNRC001)
the Innovation Program of Shanghai Municipal Education Commission.
