Preparation And Electromagnetic Wave Absorbing Property Of Graphene-based C/C Composite

In recent years,the issue arising from the radiation of electromagnetic(EM)waves is disturbing the lives of people and threatening military defense of country.Microwave absorbers have been widely studied due to their efficient attenuation towards EM waves.Among various kinds of microwave absorbers,graphene has also been considered to be a practical absorber because of its dispersion effects occurring in the real parts of permittivity constant.However,sole graphene still suffers from impedance mismatching,which hinders its practical application in the field of microwave absorption.Therefore,constructing graphene-based composites by incorporating secondary components has attracted considerable attention.Aiming at the high density and poor stability of current graphene-based absorbers,carbon/graphene composites are reporting consecutively.Although these microwave absorbers show much better performance,limited structural design of secondary carbon components makes them unpopular,and thus this study puts forward an idea on designing absorbers by incorporating graphene with secondary carbon components with certain structures,where the partical size of secondary carbon components is also be studied to adjust the dielectric parameters of composites.This study will provide new way for the design of efficient and light weight microwave absorbers.PCMs/r GO composites are successfully designed by an interfacial engineering of porous carbon microspheres(PCMs)an d reduced graphene oxide(r GO)and microwave absorbing property is also analyzed based on the measured EM parameters.As a result,the as-prepared PCMs/r GO composite exhibits obviously enhanced reflection loss characteristics(-58.1 d B at 8.6 GHz with the absorber thickness of 1.8 mm)in the frequency range of 2.0-18.0 GHz to reported carbon/graphene composites.EM parameters analysis reveals that this enhanced property is attributed to the well-matched characteristic impedance and interfacial polarizations.Carbon nanopolyhedrons decorated reduced graphene oxide(CNPs/r GO)composites have been successfully designed through in situ pyrolysis of ZIF-8/GO hybrids.It is found that GO can restrain the growth of ZIF-8 crystals and produce small-size CNPs after high-temperature pyrolysis,and the presence of CNPs will also suppress the re-stacking of r GO nanosheets.More importantly,the coupling of CNPs and r GO not only generates the desirable synergistic effects,but also accounts for the profitable interfacial polarization.Therefore,the electromagnetic parameters and microwave absorption properties of these composites can be rationally modulated in terms of the amount of GO.The optimized CNPs/r GO composite exhibits strong reflection loss(-66.2 d B at 6.2 GHz with the absorber thickness of 2.9 mm)and broad qualified bandwidth(over-10.0 d B in 3.2-18.0 GHz),which are superior to the above PCMs/r GO composite.