Controllable Synthesis And Electromagnetic Wave Absorption Performance Investigation Of Micro-nano Composite Materials

The electromagnetic(EM)wave absorbing materials play an important role in defending electromagnetic radiation pollution and promoting the stealth performance of weapons.Nowadays,materials with single absorbing mechanism can hardly meet the demands of novel EM wave absorbing materials.Researches on novel EM wave absorbing materials tend to broadband,compounded and light-weight properties.Fabricating composites to realize the synergistic effect of different attenuation mechanism and controlling electromagnetism parameters to reach a better impedance matching are the keys to develop high-performance EM wave absorbing materials.In this study,ZnO-Ni-C and CoSnO3 micro-nano composites were prepared through facile liquid phase reaction method.Then,ZnO-Ni-C/RGO and CoSnO3/RGO composites were prepared by the wrapping of reduced graphene oxides(RGO).By regulating the component and structure of composites,we obtained the EM absorption performance of composites.The main contents and results are as follows:(1)In a typical procedure,we utilized zinc nitrate hexahydrate(Zn(NO3)2·6H2O),hexamethylenetetramine(HMT,(CH2)6N4)and tripotassium citrate Monohydrate(K3C6H5O7·H2O)to prepare zinc citrate microspheres via a facile water bath method.Field emission scanning electron microscopy(SEM)and transmission electron microscopy(TEM)were employed to represent the morphologies of microspheres.The solid spheres occupied smooth surfaces are well dispersed with an average diameter of 1.25 ?m.Then zinc citrate microspheres were added into the nickel nitrate solution for an aging treatment to prepare the spherical,yolk-shell and hollow structure zinc-nickel citrate microspheres.To further improve the EM wave absorption properties of microspheres,graphene oxides(GO)were used to wrap the yolk-shell microspheres.By the simple mechanical agitation and freeze drying processes,ZnO-Ni-C/RGO composite was prepared.Above all,the yolk-shell ZnO-Ni-C/RGO composite materials showed the best attenuation performance of the three kinds of microsphere composites.The minimum RL of yolk-shell ZnO-Ni-C/RGO is-47.9 dB at 16 GHz with a thickness of 2.0 mm and the effective attenuation bandwidth surpassed-10 dB in a broad range of 5.44 GHz.(2)CoSnO3 nanocubes and CoSnO3/RGO composites were produced through a facile aqueous solution method at room temperature.As the results showed,the EM absorption performance of CoSnO3 nanocubes was really poor.The minimum value of RL was only-3 dB.However,CoSnO3/RGO composites produced by the CoSnO3 grown in-situ on GO sheets showed much better attenuation performance.The minimum reflection loss of CoSnO3/RGO composites was-21.2 dB and the effective attenuation bandwidth was 4.4 GHz.