Preparation And Properties Of Three-dimensional Graphene-based Composite Wave-absorbing Materials

Graphene has excellent physical and chemical properties,such as low density,light weight,large specific surface area and high electrical conductivity,and has good prospects for application in wave absorbing materials.Single graphene materials are poorly matched for resistance and have a single absorption mechanism,which can be complemented by designing microstructures or compounding materials with other loss mechanisms to create advantages.In the current research on graphene,the number of two-dimensional structures and binary composite materials are relatively large,and some of the absorbing materials with particularly excellent properties have complex preparation processes and preparation conditions.The aim of this paper is to investigate a relatively simple preparation process and conditions for the preparation of high performance wave absorbing materials,and to briefly analyze the role of each component.The research contents are as follows:（1）The magnetic hollow microspheres were prepared using polystyrene spheres as templates,with Si O₂,Ca O and Co Fe₂O₄ as the main components,where Si O₂ and Ca O mainly play a supporting role.The three-dimensional graphene/magnetic hollow microsphere binary composites were synthesized by hydrothermal method using graphene oxide slurry and magnetic hollow microspheres as raw materials.The characterization results show that the magnetic hollow microspheres and three-dimensional graphene form a nested microscopic morphology.This indicated that a composite material loaded with magnetic hollow microspheres and having a three-dimensional structure has been successfully synthesized.When the magnetic hollow microsphere loading rate was 50%,the absorbing performance of the material with a thickness of 2 mm reached-39.1 d B at 17 GHz.The material density was tested to be 0.120 g·cm^-3.The special morphology of hollow microspheres and three-dimensional graphene,such as large specific surface area and multi-layer porous folded structure,can effectively enhance the wave absorption performance of the material.（2）Based on the study of binary composites,graphene oxide/conducting polymer（polypyrrole）precursors were prepared by in situ polymerization methods.The precursors and magnetic hollow microspheres were synthesized as ternary composite wave absorbing materials by hydrothermal method.Characterization analysis showed that the magnetic hollow microspheres and 3D graphene formed a nested structure and the conducting polymer showed a scattered structure.This indicated that the ternary composite was successfully synthesized.Experimental test results showed that at a loading rate of 40%for the magnetic hollow microspheres and 50%for the conductive polymer,the material with a thickness of 2 mm achieves a wave absorption of-34.12d B at 18 GHz.The material density was tested to be 0.126 g·cm^-3.The addition of conductive polymers enhanced the dielectric and magnetic properties of the material.The multi-material composite intensified the polarization between the various interfaces and enhanced the dielectric loss,thus strengthening the wave absorption properties of the material.（3）Pyrrole/aniline copolymer nanoparticles were prepared by a redox method using pyrrole monomer and aniline monomer as raw materials.The copolymer nanoparticles,magnetic hollow microspheres and graphene oxide were synthesized as copolymerized terpolymer by hydrothermal method.The results of the characterization analysis illustrated that the magnetic hollow microspheres and three-dimensional（3D）graphene formed a nested structure,with the copolymer nanoparticles forming long chains of copolymer at each interface.This indicated that the ternary composite was successfully synthesized.When the magnetic hollow microsphere loading was 40%and the copolymer nanoparticle loading was 10%,the material with a thickness of 2 mm achieved a wave absorption performance of-38.1 d B at 18 GHz and a material density of 0.125 g·cm^-3.