Preparation And Electromagnetic Wave Absorption Properties Of Semiconductor/Carbon Composites

With the rapid development of science and technology,all kinds of wireless communication equipment are widely used in various fields.It brings great convenience to people's production and life.At the same time,electromagnetic(EM)radiation pollution becomes an increasingly severe problem in our daily life which threatens human health and affects the normal use of electronic devices.Therefore,the research on electromagnetic wave absorbing materials has become a hot topic.As part of the EM wave absorbing materials,carbon materials have many advantages,such as small density,strong loss,stable physical and chemical properties,but their further application is limited because of their large conductivity,poor impedance matching,narrow absorption band and other shortcomings.Therefore,the carbon material and the semiconductor material with the same low density but small dielectric constant are compounded in a certain way to prepare the semiconductor/carbon composite.The ZnO@ZnS@C composites were synthesized using hydrothermal treatment,sulfurized and carbonization.Compared with ZnO@ZnS,addition of carbon layer can effectively improve the conductivity of the material.It is found that with the further increase of carbonization temperature,the dielectric loss ability of the material is further improved,and the impedance matching property of the material is improved,so that the material shows excellent electromagnetic wave absorption performance.When the thickness is 2.6 mm,it shows a minimum RL value of-35.7 dB and a broad effective bandwidth of 4.6 GHz.The ZnO@ZnS@C composites achieved effective bandwidth of 8.7-12.0 GHz when samples were mixed with paraffin at 30 wt%.(1)The MnO@C nanorods were synthesized using hydrothermal method and carbonization process.Then the EM wave absorption properties of MnO@C nanorods were investigated in 2-18 GHz.The results showed that the MnO@C nanorods achieved excellent electromagnetic microwave absorption property.After carbonization at 700?,the minimum reflection loss(RL)of-69.4 dB at 30 wt%loading was observed at 9.4 GHz,and the bandwidth of RL less than-10 dB(90%absorption)covers 4.8 GHz at the thickness of 3.9 mm.When the MnO@C nanorods mixing with paraffin at 50 wt%,the effective bandwidth(RL<-10 dB)is 6.6 GHz at the thickness of 2.25 mm.After carbonization at 800 ?,a minimum reflection loss(RL)of-67.5 dB at 30 wt%loading was observed at 10.9 GHz of 2.9 mm,and the bandwidth of RL less than-10 dB(90%absorption)covers 4.8 GHz.With a thickness of 2.3 mm,the effective bandwidth covers 5,6 GHz.Through analysis,we can see that MnO@C nanorods have good microwave absorption,we believe the MnO@C nanorods can be promising candidates as highly effective microwave absorbers.(2)Carbon materials derived from metal organic frameworks(MOFs)have been used in various field.In this study,the obtained In2O3/C composites show excellent electromagnetic wave absorbing properties.When the In2O3/C nanorods mixing with paraffin at 50 wt%,the minimum reflection loss of-67.3 dB could be achieved with a thickness of 1.89 mm.And broad effective bandwidth of 5.5 GHz(11.9-17.4 GHz)can be reached with an absorbent thickness of 2.15 mm almost covered the whole Ku band.In this paper,we adjust the dielectric constant of the material to achieve good impedance matching and electromagnetic attenuation ability through compositing with semiconductor and carbon,thus excellent electromagnetic wave absorbing materials were obtained.