Study On Preparation And Performance Of Modified Graphene Functional Particles And Structural Absorbing Composite

With the advent of the 5G era,more and more electronic devices and"clouds"are used in life,which will be accompanied by a large number of electromagnetic waves,resulting in serious electromagnetic pollution.In addition,communication equipment and detection instruments will also be used in the military field.Therefore,the role of absorbing materials in the field of life and military is more and more obvious.Structural absorbing materials have become an important research direction of absorbing materials,and also the development trend in the future.In order to achieve the dual requirements of material stealth and mechanical properties at the same time,in this paper,the reduced graphene oxide/ZnO micro rod with excellent absorbing properties is prepared by physical mixing method,which is used as the absorbing agent,the aramid fiber with excellent mechanical properties and light weight is used as the reinforcement fiber,and the epoxy resin with good processing performance is used as the matrix,and the composite is prepared by molding method.The main research contents and results are as follows:(1)The main research contents and results are as follows:ZnO microrods(ZnO-mrs)were prepared by water bath precipitation method,reduced graphene oxide(RGO)was prepared by chemical reduction method,and then the RGO/ZnO Mrs composite was successfully prepared by simple physical mixing method.By controlling the load of ZnO-mrs to adjust the dielectric constant of composite functional particles,it is found that when the mass ratio of RGO to ZnO-mrs is 1:3,the composite functional particles have the best electromagnetic wave absorption performance,the reflection loss is-38.5 dB at 15.4GHz,the effective absorption bandwidth(EAB)is 5.4 GHz(12.6-18 GHz),and the thickness of the material is only 2 mm.When the filling ratio is only 15 wt%,the composite particles of RGO/ZnO-mrs have good impedance matching and strong loss ability.The loss modes include conductive loss,interface polarization loss and dipole polarization loss.(2)RGO/ZnO-mrs was used as the absorbent,which was evenly dispersed into the mixture of epoxy resin and curing agent.The mixture was brushed on the surface of aramid fiber cloth,and the aramid fiber/epoxy resin composite was prepared by molding.Then the effects of different concentrations of RGO/ZnO-mrs on the mechanical properties and absorbing properties of composites were studied.The results show that as the particle concentration increases,the absorbing performance gradually increases and the mechanical properties gradually weaken.When the RGO/ZnO-mrs content is 7.5 wt%,the minimum reflection loss(RLmin)of the composite material reaches-28.2 dB at 6.5 GHz,the EAB reaches 2 GHz(5.7-7.7 GHz).At this time,the composite has an impact strength of 107kJ/m~2 and the bending strength of 160 MPa,the thickness of the composite material is 5 mm.The composite is greatly improved,but a lot of mechanical properties lost after adding functional particles RGO/ZnO-mrs.(3)A multi-layer alternating structure composite was designed in order to improve the absorbing performance and mechanical properties of composite,and keep the concentration of functional particles constant at 7.5 wt%.Alternating structure composites were prepared by brush coating and compression molding methods with 2 layers,4 layers and 6-layers,respectively.It was found that the alternating multi-layer structure can improve the mechanical properties and wave absorbing properties of the composite by comparing.The absorption and mechanical properties are optimal.At this time,the RLmin of the composite reaches-16.5 dB at 7.3 GHz,the EAB reaches 2.4 GHz(6.1-8.5 GHz),the impact strength is 167.35 kJ/m~2,and the bending strength is 161.13 MPa.The multi-layer alternating structure can significantly improve the performance of composite.In order to continue to improve the absorbing and mechanical properties of the composite,the surface of the aramid fiber was modified by KH550 with different amounts of functional particles RGO/ZnO-mrs,and we prepare 6 layers composite with alternating structure.The microwave absorption and mechanical properties of the composite were compared.It was found that multiple absorption peaks appeared in the reflection loss graph,this is because KH550 makes the functional particles more evenly distributed on the fiber surface lead to the wavelength loss caused by the abrupt change of the dielectric constant between the non-particle layers.At the same time,the modified aramid fiber and epoxy resin have better interface properties and improve the mechanical properties of the composite.When the RGO/ZnO-mrs content is 10 wt%,the composite’s performance is optimal.And the RLmin of the composite is-18.9 dB at 2.9 GHz,and the effective absorption band is 3.2 GHz(2.6-3.6 GHz,10.3-11.4 GHz,16.9-18 GHz),impact strength is 156.41 kJ/m~2,and bending strength is 158.73 MPa.