Synthesis And Microwave Absorbing Properties Of Graphene/CoO@Co/ZnO Nanocomposites

With the development of scientific and information technology,all kinds of digital and high frequency of electronic instruments with GHz frequency electromagnetic waves have being rapidly popularized and applied.Electromagnetic waves?EMW?plays an important role in ordinary civil communication and national defense construction,but it also brings more and more EMW radiation and interference.In order to eliminate or reduce these pollution,the development of new high performance of EMW absorption material is becoming more and more critical.These high performance of EMW absorbing materials needs to have wide absorption frequency range,thin coating,low density and strong absorption properties,but traditional single type of absorbing materials,such as graphene,ferrite,ZnO etc.are difficult to meet these requirements at the same time.As a result,the composite material have become the focus in the EMW absorbing materials.In this paper,we used a simple solvent hydrothermal and magnetic stirring method to incorporate the CoO@Co yolk-shell nanoparticles and ZnO nanoparticles with the physical and chemical properties of graphene sheets,and obtained G/y-Co O@Co/ZnO nanocomposites.After that,we analyzed their characterization and researched EMW absorbing property.The main research contents are as follows:1.Synthesis and characterization of the G/y-CoO@Co/ZnO nanocompositesG/Co₃O₄ nanocomposites were first fabricated by solvent hydrothermal method.After heating treatment under an Ar/H₂ flow based on the nanoscale Kirkendall effect can convert solid Co₃O₄ nanoparticles to yolk-shell CoO@Co nanoparticles.Finally,ZnO nanoparticles were intruded though a wet-chemical and magnetic stirring method to obtain the G/y-CoO@Co/ZnOnanocomposites.TheG/y-CoO@Co/ZnOnanocompositeswere characterized by transmission electron microscope,X-ray diffraction,X-ray photoelectron spectroscopy etc..The diameter and the CoO shell were merely 12.0 nm and 1.5 nm,respectively,while the diameter of ZnO nanoparticles were in the range of 4.0-10.0 nm.In addition,the magnetic properties of nanocomposite were measured by vibrating sample magnetometer,and the results showed that the G/y-Co O@Co/ZnO nanocomposites exhibited ferromagnetism properties.2.The research EMW absorbing property of G/y-Co O@Co/ZnO nanocompositesThe samples used for the EMW measurement were fabricated by mixing 20wt%of the nanocomposite with a paraffin matrix.Then,the electromagnetic parameters were analyzed by the vector network analyzer and the reflection loss of the nanocomposites with different thickness were calculated at the frequence of 2.0-18.0 GHz.The results showed that the minimal reflection loss value was up to-51.1 dB at 11.3 GHz with the thickness of 2.6 mm and the effective absorption bandwidth?below–10.0 dB?was 4.7 GHz?from 9.5 to 14.2GHz?.In addition,the reflection loss value ranging from 2.0 to 5.0 mm all belowed-20.0 dB.Therefore,the G/y-CoO@Co/ZnO nanocomposites exhibited excellent EMW absorption properties.3.The EMW absorption mechanism of the G/y-Co O@Co/ZnO nanocompositesIn order to study the mechanism of G/y-CoO@Co/ZnO nanocomposites nanocomposites,we use Matlab software to fit and calculate these electromagnetic parameters.After that we analysis and research absorption mechanism through the reflection loss?two-dimensional and three-dimensional map?,relative complex permittivity,relative complex permeability,loss tangent value,impedance matching and Cole-Cole semicircle curve theory.As a result,the G/y-CoO@Co/ZnO nanocomposites can not only have good application prospect in the field of EMW absorption,but also provide great reference value for the development of new efficient EMW absorption materials.