Preparation And Electromagnetic Properties Of Co/rGO Materials And Its Close-packed Structure

The high conductivity of graphene means that it has a high permittivity,and its internal defects,edges,residual oxygen-containing functional groups,etc.can produce a variety of polarization relaxation,which is beneficial to the reduction and loss of electromagnetic waves.However,excellent electromagnetic wave absorption performance is required to satisfy impedance matching,single graphene has no magnetic loss,and magnetic permeability is very low.This experiment can not effectively change the permeability of the graphene by adjusting different process parameters,and the graphene itself is relatively high.The electrical constant will cause it to have a serious mismatch with a very low permeability,which causes most of the electromagnetic waves to enter the interior of the material when it is incident on the surface of the material and instead be reflected.Considering that ferromagnetic metals have higher saturation magnetization,they still have higher magnetic permeability levels and magnetic losses in the high frequency range.Nano-sized ferromagnetic particles have many interfacial effects which can improve the microwave absorbing properties of the material.In addition,the reflection loss of the ferromagnetic metal is generally in the low frequency region,and the reflection loss of the graphene is generally located in the high frequency region,so composition of the two materials is also beneficial to broadening the absorption band of the composite material.Based on this,Co/rGO composites were prepared using GO and Cobalt oxalate as raw materials,which combined the excellent properties of graphene and ferromagnetic particles and possessed good absorption properties.Different precursor preparation and calcination processes parameters can affect the size and distribution of Co nanoparticles.By regulating the process parameters,the precursor of Co-glycol chelate was obtained by liquid phase synthesis at 160°C for 1 h.Then the Co/rGO composite obtained by calcining it in hydrogen atmosphere at 600°C for 2h have suitable morphology characteristics and it has the superior electromagnetic performance of the maximum absorption of-59.8d B(matching thickness of 2.81mm)and the effective absorption bandwidth of 11.97 GHz.Graphene-based composite absorbers have a major drawback which is the low filling ratec.In order to improve the dispersibility and increase the filling rate,organosilane functionalization is performed using a KH550 silane coupling agent.The intrinsic silicon-oxygen bond is observed in the infrared spectrum.The stretching vibration peak indicates that the KH550 group was successfully introduced to complete the modification.by controlling the hydrolysis process of KH550,close-packed samples with high electromagnetic parameters can be obtained.The hydrolysis time was gradually extended,and the coercivity and electromagnetic parameters of KH550-Co/rGO basically met the law of decreasing first and then increasing.The product obtained after 6 hours of hydrolysis was assembled into a dense reactor and the real permeability was between 1.25 and 2.25.The imaginary part of the permeability changes from 0.25 to 0.75,which is higher overall.