Electromagnetic Wave Absorption Properties Of Hollow Carbon Spheres/Nitrogen-doped Carbon Nanotubes Composites

The development of the information age has brought great convenience to People’s Daily life.However,the use of a large number of electronic products produces a large number of electromagnetic waves in the environment,which brings electromagnetic radiation and electromagnetic interference and other pollution.Pollution from these electromagnetic waves affects the health of living things and the stability of electronic devices.In order to reduce the harm caused by electromagnetic radiation,the development of absorbing materials is necessary.In addition,it is also necessary to develop high performance electromagnetic wave absorbing materials to deal with the threat of electromagnetic leakage to information security and make it difficult for radar detection technology to detect military targets.In order to solve these problems,it is very urgent to develop and design electromagnetic wave absorbing materials which can realize "light weight,thin thickness,wide band and strong absorption".However,at present,the quality of most electromagnetic wave absorbing materials is still very high,which is not enough to fully meet the practical requirements.At the same time,the absorption intensity of electromagnetic wave materials still has a very large room for improvement.For electromagnetic wave absorbing materials,their structure and morphology have a great impact on the absorption performance.Layered hollow heterogeneous structures have attracted great interest due to their adjustable impedance matching and loss characteristics.However,manufacturing heterogeneous nanomaterials with layered and hollow characteristics is challenging.In this paper,heterogeneous nanomaterials with both layered and hollow characteristics were prepared by a series of methods.The specific research contents are as follows: 1.Nitrogenous carbon hollow spheres supported by nitrogenous carbon nanotubes embedded with Ni(Ni@NCNT/NCHS)were designed and synthesized by a hard template method,which is an excellent electromagnetic wave absorbing material.The morphology,composition and elements of the materials were analyzed by conventional characterization methods.The diameter of the nitrogen-doped carbon hollow sphere is about 400 nm and its thickness is about40 nm.The diameter of the doped carbon nanotubes is about 22.5 nm and its thickness is about5 nm.Ni exists on the surface of the nitrogen-doped carbon hollow sphere and the tip of the carbon nanotubes.2.The electromagnetic wave absorption performance of the material is tested and calculated by the vector network analyzer.When the thickness of the optimized structure is only 1.6mm and the addition amount is only 15 wt %,the minimum reflection loss can reach-64.75 d B and the effective absorption bandwidth is 4.17 GHz.3.Ni@NCNT/NCHS heterogeneous nanostructures with hollow and multistage characteristics: Heterogeneous structures composed of different substances can provide abundant heterogeneous interfaces.The layered structure formed by carbon nanotubes can make the material have a large number of holes.The hollow structure formed by carbon hollow spheres has the characteristics of large specific surface area and low density,so Ni@NCNT/NCHS shows efficient electromagnetic wave absorption performance.The experimental results show that the layered structure and the hollow structure significantly improve the electromagnetic wave absorption performance of Ni@NCNT/NCHS.This work provides an effective method to synthesize highly efficient electromagnetic wave absorbing materials with layered and hollow structures.