The Preparation And The Electromagnetic Properties Of Quasi-one-dimensional Nickel Chains

Electromagnetic wave absorbing material has been one of the research hotspots in the fields of electromagnetic radiation pollution control,electromagnetic compatibility of electronic products and military stealth science and technology.In recent years,with the rapid development of electromagnetic shielding and radar detect technology,the performance of modern microwave absorbing material put forward higher requirements.The traditional electromagnetic wave absorption materials,such as carbonyl iron,ferrites and other absorbent materials,are increasingly difficult to meet the current needs.Low-dimensional transition metal absorbing materials have high permeability and excellent electromagnetic properties,has the potential to efficiently absorb electromagnetic energy.It is a kind of the developing electromagnetic wave absorption materials,attract more and more attention of domestic and foreign researchers.In this paper,the research object of the transition metal nickel(Ni)was synthesized via a mild wet chemistry method with hydrazine hydrate as reducing agent.The obtained quasi-one-dimensional nickel chains(Ni chains for short)shows uniform size and morphology.At the same time,using X-ray diffraction(XRD),scanning electron microscopy(SEM)and transmission electron microscopy(TEM)to study the microstructure and morphology of Ni chains,and reveals the growth mechanism.Using vibrating sample magnetometer(VSM)studies the hysteresis loop of Ni chains,and survey the saturation magnetization(Ms),residual magnetization(Mr)and coercive force(Hc).Compared to bulk Ni,the Ms of Ni chains decreased,but the Mr and Hc were increased significantly.Different mass ratios of Ni chains mixed in a paraffin wax matrix(10,20,30,40,50 and 60 wt%)were prepared to investigate the electromagnetic parameters and the microwave absorption properties in 2~18 GHz.Using vector network analyzer(VNA)to measure complex permittivity(?' and ? ")and complex permeability(?' and ?")of the Ni/wax samples,and calculate the reflection loss in the frequency range of 2 ~ 18 GHz.The study found that all Ni chains loadings of Ni/wax samples are present relaxation and resonance.At the same time,explores the impact of the Ni chains loading concentration and thickness of the samples on the properties of microwave absorption materials.The study found that with the change of the sample thickness and Ni chains loading concentration,there are significant differences of the microwave absorption performance of the samples.When the Ni loading concentration is 60 wt.%,the sample with thickness of 2 mm reached minimum reflection loss of-43.8 dB at 8.6 GHz,-10 dB absorbing bandwidth is 1.7 GHz;When the Ni chain nets loading concentration is 50 wt.%,the samples with thickness of 4 mm reaches a minimum reflection loss of-33.7 dB at 4.6 GHz,-10 dB level absorbing bandwidth is 1.5 GHz.Based on the electromagnetic parameters and the electromagnetic wave reflection loss,preliminary revealed the microwave absorption mechanism of the Ni chains.Electromagnetic wave absorption loss of the Ni chains mainly includes two categories,dielectric loss and magnetic loss.Among them,the dielectric loss mainly comes from dielectric relaxation,which caused by dipole polarization between the interface and the defect polarization in the crystal.Eddy-current,natural resonance and exchange resonance are the main source of the magnetic loss.Furthermore,the 3D chain nets struture increase the travel paths of electromagnetic wave in the sample and form multiple interface reflections and multiple scattering,which significantly enhanced attenuation capacity,beneficial to microwave absorption performance.Meanwhile,the good electromagnetic matching characteristic and(1/4?)thickness matching of the Ni chains is an important condition for the performance of high efficiency and multi-band absorbing.It is remain to be improvement for applied research of transition metal nickel in electromagnetic wave absorbing field,and the mechanism of electromagnetic wave energy attenuation remains to be further research and improvement.Contents of this paper have important guiding significance for the study of the electromagnetic wave absorption materials of transition metals nickel,and have laid a solid foundation for the subsequent in-depth study,promote development of the research of transition metal stealth materials.