Research On Environmental Stability Of The Dual Left-handed Materials

The left-handed material(LHM)has some unusual characteristics compared with common material in nature due to their negative permittivity and negative permeability.This kind of artificial composite material has a wide application prospect in optics,material science,applied electromagnetics and other fields.The development of LHM trend to broadband,multiband and miniaturization.Therefore,the research on the miniaturized LHM with dual left-handed characteristics has become a hot spot.In this paper,a LHM structure with dual left-hand characteristics is designed and fabricated,which includes the combination of the split ring resonator(SRR)and the defected ground structure(DGS).At present,most of the recent attention has been focused on the theoretical analysis and design applications of LHM structures,application studies of LHM structures with the relevant exploration of operation environment being ignored.Based on the previous fabricated LHM structure,the environmental stability of the LHM with different conductive coatings is investigated.The main research contents include:1.The influence of temperature gradient shock on the left-handed characteristics and transmission characteristics of dual LHM structure is systematically investigated.The microstructure of the dual LHM surface before and after the temperature test is observed by scanning electron microscopy(SEM).The temperature gradient shock test in ambient air can cause the oxidation of the coated copper layer and thus lead to the decrease of the electrical conductivity of the dual LHM structure.As results,the transmission performance of the dual LHM structure is reduced,while the bandwidth of the dual LHM structure is broadened.However,the temperature test had little effect on the microscopic characteristics of the copper-plated dual LHM.As results,there is no obvious change in the center resonant frequency of the dual LHM.2.The humidity-heat environment tests were carried out on the coated copper and silver dual LHM.The effect of humidity-heat test on the left-handed transmission characteristics of LHM is investigated.As results,the humidity-heat test can destroy the microstructure of the copper-coated dual LHM in short time,while it has no obvious effect on the macroscopic characteristics.However,the humidity-heat test has little impact on the silver-plated dual LHM.The influence of humidity-heat environment on the transmission characteristics of dual LHM mainly focus on their transmission loss and bandwidth.The center frequency is almost unchanged under the humidity-heat test.3.The influence of salt spray test on the two conductive composite coatings consisting of silver and copper are contrastively investigated.It is found that the salt spray corrosion test can influence the microstructure of the coated copper and silver layers,which leading to the decrease of the electrical conductivity of the coated copper and silver layers.As results,the transmission performance of the dual LHM structure is reduced,while the bandwidth of the dual LHM structure is broadened.Moreover,at the same conditions,the salt spray corrosion test have less influence on the transmission characteristics of the silver-plated dual LHM structure than those of copper-plated dual LHM structure.Based on the great application prospect of dual LHM structure,the findings presented here offer an effective method to manipulate the performance of the dual LHM device by tuning the operation environments.