Synthesis Of Bowl-like Carbon Nanoparticle And Its Application For Microwave Absorption

With the wide use of various electronics in modern society these days,the radiation and prevention of electromagnetic waves have gradually been put on the agenda,and plenty of studies and researches have been conducted to develop a new type of practical active absorbing materials or electromagnetic shielding materials in many countries.Generally speaking,in order to avoid the risk of secondary pollution to the environment from the electromagnetic microwave shielding materials,absorbing materials is more practicable and environmentally friendly.The absorption ability of almost microwave absorbing materials comes from its electromagnetic properties,mainly including dielectric loss and magnetic loss.As the name suggests,the absorbers equipped with the magnetic loss ability is mainly based on some magnetic metals.Therefore,compared to the dielectric-loss absorbers,magnetic-loss absorbers are poor for antioxidation,along with portability and thermal stability.The novel carbon nanomaterials,such as graphene,have promising dielectric properties,as well as the potential to become excellent absorbing materials.In recent years,many studies have shown that the microstructure of materials could have a positive influence on the microwave absorption performance.With the assistance of the inducer F127 and the surfactant TMB,the bowl shaped polydopamine nanoparticles are formed through polymerization of dopamine.The bowl-like carbon nanoparticles then are obtained by carbonization under high temperature after hydrothermal reaction for reinforce the microstructure.By adjusting the amount of TMB,a series of bowl-like carbon nanoparticles with different micromorphology are obtained.Via scanning electron microscopy(SEM)and transmission electron microscopy(TEM),the microstructure of the nanoparticles gradually changes from spherical structure to bowl-like structure with rising the volume of TMB,and finally turns back to spherical structure with obviously shrinking diameter.Nanoparticles are analyzed by Raman spectrometer,X ray photoelectron spectroscopy and infrared spectroscopy,and demonstrates there is no great difference in the degree of graphitization,the crystallinity of carbon and element containing.Therefore,we eliminate the influence of the element structure and the crystallinity of carbon on the absorbing performance.In addition,we regulate the working conditions of the material with the best absorption effect.The experiment shows that the material which is carbonized under 800 ~oC and mixes up with paraffin with 20%mass fraction,shows the best absorption performance.After testing the wave absorption performance under the optimum conditions,the bowl-like materials are tested as the best absorbers:the strongest reflection loss is-45.3 dB with only 1.5 mm thickness,and the bandwidth of effective absorption(RL<-10 dB)covers 4.2 GHz.Once the bowl-like structure exists in the absorbers,the wave absorption ability will enhance a lot.This excellent wave absorbing property is due to the unique structure of the material,because the bowl like structure can generate lots of caves and channels which come from bowl-like particles’randomly stacking,which is beneficial to the formation of the interface polarization,and also give rise to high possibility for electromagnetic wave to reflect multiply in the material.Their perfect electromagnetic properties enhance the microwave absorbing properties.These all make bowl-like carbon nanoparticle a promising electromagnetic microwave absorption material.