Study On Preparation And Absorbing Properties Of Biomass Carbon Materials And Fe₃O₄/C Composites

Microwave absorption materials play an important role in electronic,environmental,medical and national defense security with the rapid increase of electronic communication frequency?such as the frequency increase from 0.9¹.8GHz in2G to dozens of GHz in 5G?,the emergence of related electromagnetic interference and microwave detection.Ultra-wideband absorption and low-density microwave absorbing materials have become an important topic in this field.For the microwave absorbing properties of single materials,their applications in the field of electromagnetic materials have been greatly limited due to their own shortcomings.Micro/nano carbon material has unique physical properties and is a light and wasting microwave absorbing material.Because biomass itself is hollow,cheap,abundant and renewable,it is a valuable raw material for synthetic carbon materials.Recently,there are many reports about the synthesis and characterization of carbon materials and composites.On the basis of previous research,a kind of carbon materials and Fe₃O₄/C composites,which have simple operation,cheap cost and natural renewable,was explored and studied.Firstly,the micro/nano carbon materials of different cavity size were prepared by high temperature carbonization.And then,the electromagnetic parameters of the materials were mediated through the design,doping and modification,and the electromagnetic loss properties of the materials are changed.Finally,dielectric loss,biomass carbon and magnetic loss materials were combined to prepare improved composite materials for absorbing properties.The contents of this paper are as follows:?1?Biomass carbon materials were obtained by carbonization of biomass fiber materials?catkin and floating flocculant of buttonwood?at high temperature.The prepared carbon material has the characteristics of hollow structure,good thermal conductivity,strong conductivity and light weight.The absorbing properties of biomass carbon materials?catkin and floating flocculant of buttonwood?were studied.When 27%mass ratio of carbon material?catkin?was mixed with paraffin with the thickness of3.0mm,the minimum reflection loss value is-45d B at 13GHz and the bandwidth of lower than-10dB is 8.5GHz.When the mass of carbon material?floating flocculant of buttonwood?is 35%and the thickness is 4.5mm,the minimum reflection loss is-35dB at7.8GHz.Biomass carbon materials?catkin and floating flocculant of buttonwood?showed good wave absorbing properties.?2?Sulfur doped carbon materials were obtained by high temperature carbonized biomass fiber material?catkin?with sulfur.The absorption performance of the carbon material after sulfur doping was studied.With the increase of the thickness of the sample,the absorption peak moves to the lower.When the mass fraction is 35%,the thickness is between 2.5-5.0mm,the peak value of the reflection loss is above-10dB,which shows good absorbing performance.?3?Fe₃O₄/C composites were prepared by high temperature carbonization and solvothermal method,and their absorbing properties were studied.When the thickness of the Fe₃O₄/C composite absorbing material is 1.5 mm,the absorption frequency is 17.4GHz,the minimum reflection loss is up to-24.1d B,and the effective absorption bandwidth?<-10 dB?is as high as 2.4GHz.The results show that Fe₃O₄/C composite absorbing material has high microwave absorbing ability in Ku band.In conclusion,the preparation and microwave absorbing properties of biomass carbon materials,sulfur doped carbon materials and Fe₃O₄/C composites were studied.These prepared materials have the characteristics of simple operation process,low cost and reproducible property.It has great reference value and practical significance for the preparation and absorbing properties of carbon materials and composites.