The Preparation And Electromagnetic Wave Absorption Properties Of Nickel/Carbon-Based Nanocomposites

Absorbing materials can absorb the incident electromagnetic wave and converted it into heat.It is of great significance to reduce the electromagnetic pollution as well as to improve the operational capability of the military.Carbon materials have no magnetic loss when they absorb electromagnetic wave,but their quality are lighter.The saturation magnetization and permeability of nano-magnetic metals are bigger that can lead to strong absorption of electromagnetic wave by magnetic loss.However,their densities are generally large.Therefore,the preparation of nano-magnetic metals and carbon composites are of great importance.In this paper,on the basis of the existing literature,solvothermal method and microwave synthesis method are used to prepare nickel-carbon nanocomposites.Their structures are characterized by a series analysis methods and the electromagnetic wave absorption performances are analyzed by the microwave vector network analyzer.(1)Based on automatic microwave synthesis of combinatorial chemistry workstation,Ni-CNTs nanocomposites are prepared.The morphology of composites are characterized by SEM and TEM and the results show that Ni particles more evenly attached on the surface of CNTs with thickness of 10 nm.In microwave synthesis,sp2 carbon can be activated to sp3 carbon.At the same time,Ni particles are liquefied due to overheating and fall on the surface of CNTs to form stable Ni-C chemical bonds.In this paper,the formation of Ni-C chemical bonds is proved by XPS and Raman.And the electromagnetic wave absorption properties of Ni-CNTs nanocomposites are measured by the microwave vector network analyzer.It turned out that the bonded Ni-CNTs nanocomposites have higher electromagnetic wave absorption properties in comparison with CNTs or Ni.When the matching thickness is 2 mm,the Ni-CNTs nanocomposites have best wave absorption performance and the minimum reflection loss is-30 dB at 13.7 GHz,which means that more than 99%EM wave energy can be attenuated by the absorber.(2)Using solvothermal method to prepare the Ni/C porous one-dimensional nanorods.The tests prove that the Ni-NTA precursors are formed by complexing nickel ion and NTA at first.The precursors are nanorods with diameter of 150 nm.After heat treatment,the precursors can be completely converted into Ni/C nanorods which are composed of numerous core-shell-like Ni/C nanoparticles.The core of nickel is about 10 nm in diameter and the thickness of carbon shell is about 2 nm.The probable growth mechanism has been proposed by studying the composition of the solvent,reaction time and reaction temperature.The electromagnetic wave absorption properties of one-dimensional Ni/C nanorods were measured by the microwave vector network analyzer and it turned out that the materials have optimal absorption performance with matching thickness of 3.5 mm.In 2-18 GHz,the lowest reflection loss is up to-40 dB at 10.5 GHz which means that more than 99%EM wave energies can be attenuated by the absorber.In addition,the effective absorption bandwidth with reflection loss less than-10 dB is up to 4.0 GHz.