Study On The Effect Of Bonding Method On The Wave Absorption Performance Of Fe₃O₄-rGO Composites Particles

With the development of science and technology,the rapid renewal of electronic information technology products,in order to make weapons and equipment more adaptable to the battlefield environment,electromagnetic wave absorbing materials have been favored by researchers.At present,the characteristics of light weight,high efficiency,broadband and low load have become the hot spot of EMA material research.The research hotspots in the field of EWA materials are dominated by magnetic/electrical composite wave absorbing materials.At present,researchers have studied many combinations and ratios of different materials,but the influence of the combination of materials on the performance of EWA and the intrinsic mechanism of action have been little studied.The Fe₃O₄-reduced graphene oxide（Fe₃O₄-r GO）is a representative magnetic/electrical composite wave absorbing material and is relatively mature.In this study,the magnetic material Fe₃O₄ and the dielectric material GO were modified and functionalized respectively,and their effects on the EWA properties were investigated and the intrinsic mechanism was analyzed by constructing multiple bonding strategies to regulate the bonding between the magnetic and electric phases.The specific research contents are as follows:（1）Non-covalent bond:Fe₃O₄ nanoparticles were synthesized by co-precipitation method.Surface modification was performed using dopamine（PDA）;the optimal polymerization time and concentration ratio of PDA were determined by vibration magnetometer（VSM）and vector network analyzer（VNA）characterization to be 12 h and 2 g/L,respectively;the EWA properties of Fe₃O₄-r GO remained basically stable when the PDA concentration was greater than 2 g/L.By X-ray photoelectron spectroscopy（XPS）characterization,it was demonstrated thatπ-πbonds were formed between the benzene ring of PDA and the six-membered ring of GO,and the magnetic Fe₃O₄ nanoparticles and GO nanosheets were combined by the force ofπ-πconjugation.The non-covalently bound Fe₃O₄-r GO composite particles were characterized by Raman spectroscopy（Raman）,X-ray diffractometer（XRD）,Fourier infrared spectroscopy（FT-IR）,XPS,VSM,and VNA tests for their compositional structures as well as wave absorption properties.It was found that when the non-covalently bound Fe₃O₄-r GO composite particles were filled with 50 wt%in the paraffin matrix,the composite had the best EWA performance with a maximum effective absorption bandwidth of(EAB_max;RL<-10 d B)5.71 GHz（12.29-18.00 GHz）and a maximum reflection loss(RL_min)value of-46.34 d B.（2）Covalent bond:The amino groups（-NH₂）were grafted onto the surface of Fe₃O₄nanoparticles by chemical modification to obtain aminated ferric tetroxide（Fe₃O₄-NH₂）.Graphene oxide（GO）was modified using activators.The best reaction time of 10 h for the preparation of Fe₃O₄-NH₂ was determined by FT-IR,TG,VSM and other tests,and the best Fe₃O₄ to GO ratio was determined by Raman,VNA,four-probe conductivity measurements and other tests.The successful synthesis of the covalently bound Fe₃O₄-r GO was confirmed by XRD,XPS and FT-IR characterization.The microscopic morphology of the composite particles was characterized by SEM and TEM,and the particle size of Fe₃O₄ loaded on the r GO nanosheets was about 20 nm.The EAB_max of the Fe₃O₄-r GO/paraffin composite with 40 wt%filling ratio reached 6.36 GHz（11.64-18.00 GHz）,and RL_min=-47.46 d B was obtained at 10.68GHz.（3）Electrostatic coupling:The electrostatically coupled Fe₃O₄-r GO composite wave absorbing particles were prepared and characterized using the well-established process of the group.The Fe₃O₄-r GO wave-absorbing particles filled with resin matrix composites were prepared,and the electric and magnetic field distributions of Fe₃O₄-r GO composite particles bonded by different bonding methods（non-covalent,covalent,and electrostatic coupling）were compared and analyzed by using CST Microwave Studio（CST）simulation software,and the electron motion in the material system was observed through simulation.The reasons for the performance differences were analyzed.The results show thatλ/4 resonance is the main factor causing the energy loss.At the same time,in the case of covalent bonding,the electron migration rate in the composite material and the magnetic field intensity cooperate with each other,resulting in the best impedance matching and the best performance.