Electromagnetic Wave Absorption Properties Of 3D Carbon Network Composites Decorated With Magnetic Nanoparticles

With the rapid development of electronic and information industry,environmental and health problems caused by electromagnetic radiation become more and more serious.In order to solve these problems,an effective way is to develop excellent electromagnetic wave?EMW?absorbing materials.Absorber materials,as an important part of EMW absorbing materials,determine the EMW absorption properties directly.In recent years,combining carbon materials with magnetic nanoparticles to prepare carbon-based magnetic absorbers has become a hot research topic at home and abroad.Nowadays,there have been a lot of reports on the research of carbon-based magnetic absorber.However,most carbon-based magnetic absorbers are mainly made of one and two carbon dimensional materials,and there are few researches on three-dimensional nano carbon materials.Besides,there are still some problems need to be solved for most carbon-based magnetic absorbers,such as narrow effective absorption bandwidth,high addition amount in the matrix,poor structural stability,complicated preparation process and low yields.In this paper,three-dimensional carbon networks decorated with Fe₃O₄nanoparticles?3DC/Fe₃O₄?and three-dimensional carbon networks decorated with CoFe₂O₄ nanoparticles?3DC/Fe₃O₄?were synthesized via freeze-drying and high-temperature calcination processes.The effects of raw materials and calcination process on the phase structure,microstructure,electromagnetic properties and EMW absorption performance of the composites were systematically investigated,and the EMW absorption mechanism was also analyzed.In order to increase the production of the absorber materials,the three-dimensional interconnected carbon nanosheets decorated with Fe₃O₄ nanoparticles?3D Fe₃O₄@CNS?was prepared via spray drying method combined with high-temperature calcination process.The phase structure,microstructure,electromagnetic properties and EMW absorption performance of 3D Fe₃O₄@CNS were investigated.The results show that the ratio of raw materials has an important effect on the microstructure,complex permittivity and EMW absorption properties of 3DC/Fe₃O₄composites.When the molecular ratio of Fe:C:NaCl is 1.5:20:150,3DC/Fe₃O₄ has an interconnected three-dimensional porous network structure,and Fe₃O₄ nanoparticles are evenly distributed on the carbon matrix.The 3DC/Fe₃O₄ composites exhibit excellent EMW absorption performance.The effective absorption bandwidth can reach up 5.95 GHz?11.2¹7.15 GHz?at the thickness of 3.0 mm with only 20 wt%filler loading in the paraffin matrix,which covers most range of Ku band.The minimum reflection loss?RL?of-37.8 dB was obtained at 6.95 GHz with the thickness of 5.5 mm.The calcination temperature has an important influence on the microstructure,complex permittivity and EMW absorption properties of 3DC/CoFe₂O₄ composites.When the calcination temperature was in the range of 600⁶50°C,3DC/CoFe₂O₄composites have an interconnected three-dimensional porous network structure,and CoFe₂O₄ nanoparticles are homogeneously distributed on the carbon.As the calcination temperature increases,the thickness of carbon network decreases gradually.When the calcination temperature is 630°C,the effective absorption bandwidth of 3DC/CoFe₂O₄ can reach up 6.63 GHz?11.37¹8 GHz?at the thickness of 2.5 mm,covering the Ku band.When the matching thickness is 3 mm,the effective absorption bandwidth of 7.31 GHz?9.16¹6.47 GHz?can be obtained.3D Fe₃O₄@CNS composite is composed of three-dimensional interconnected carbon nanosheets and Fe₃O₄ nanoparticles,which exhibits excellent EMW absorption performance.The minimum RL of-41.8 dB can be achieved at the thickness of 3 mm.The effective absorption bandwidth reaches up 7.99 GHz?9.67¹7.66 GHz?at the thickness of 2.8 mm with only 20 wt%filling amount in the paraffin matrix.