Synthesis And Electromagnetic Wave Absorption Properties Of Nitrogen-Doped Carbon Nanotubes Embedded With Iron-based Nanoparticles

The rapid development of electronic communication technology has provided great convenience to people's life and work,but the electromagnetic radiation has also affected people's health.In addition,the development of radar technology has also created crises for stealth weapons.Therefore,the research of electromagnetic wave absorbing materials with economic,environmental protection and high performance has aroused people's concern.The nitrogen-doped carbon nanotube composites with embedded iron-based nanoparticles(Fe/Fe3C@NCNTs)have good impedance matching characteristics and have both dielectric and magnetic loss mechanisms,and can effectively absorb incident electromagnetic waves.In this thesis,the wave absorbing principle of composite materials is also deeply studied.The contents of the study are as follows:The metal-organic frameworks containing Fe element were prepared by hydrothermal method and pyrolyzed to synthesize Fe/Fe3C@NCNTs,and the influence of pyrolysis temperature on the properties of composites was studied by setting the annealing temperature to 700??800? and 900?,respectively.The structure,morphology and composition of Fe/Fe3C@NCNTs were analyzed by means of transmission electron microscope,X-ray diffractometer and X-ray photoelectron spectrometer.It can be found that there are many interfaces between metal particles and carbon nanotubes,C-N and C-N groups and defects in the composites,which can cause interface polarization and dipole polarization and enhance the electromagnetic wave absorption performance of the materials.The three groups of Fe/Fe3C@NCNTs composites with different annealing temperatures were fully mixed with paraffin according to the addition amount of 40%,and the test samples were pressed into rings by mold.The electromagnetic parameters of the three groups of samples were obtained by network vector analyzer.The impedance coefficient(MZ),attenuation constant(?)and reflection loss(RL)were calculated by the formulas,and drew the relevant images.It is found that the nitrogen-doped carbon nanotube composites with embedded iron nanoparticles prepared at annealing temperature of 800?(Fe/Fe3C@NCNTs-800)shows excellent impedance matching and attenuation characteristics.At a thickness of 1.6 mm,the sample have the minimum reflection loss value of-50.8 dB for the electromagnetic wave with a frequency of 13.3 GHz,and the minimum reflection loss values within the thickness range of 1.5-2.5 mm are all less than-20 dB.And its maximum effective absorption bandwidth is 4.3 GHz(13.7-18 GHz)at a thickness of 1.4 mm.Therefore,the Fe/Fe3C@NCNTs-800 is very promising in the field of electromagnetic wave absorption.