Synthesis Of Magnetic Biomass Carbon Materials And Regulation Of Electromagnetic Loss Performance

In recent years,the rapid development of wireless networks,mobile phones and satellite systems has caused electromagnetic radiation and interference problems,and microwave absorbing materials have received more and more attention.At present,traditional microwave absorbing materials still have many limitations,and the development of "broadband,thin thickness,strong performance" microwave absorbing materials becomes very urgent.Biomass has the characteristics of fine structure and functional integration,and its dielectric loss is large;Nickel nanoparticles are characterized by strong anisotropy,high permeability,high saturation magnetization and high Snoek limit,and high magnetic loss.In this regard,this work combines biomass carbon materials and nickel nanoparticles,seeks appropriate size and quantity ratio to control electromagnetic loss ability and explore its corrosion resistance by controlling pyrolysis temperature and precursor concentration.The specific research work is as follows:Magnetic biomass carbon materials with high microwave absorption performance were successfully prepared by pyrolysis process,and the size of nickel nanoparticles was controlled by different pyrolysis temperatures.Macroscopically,it shows a highly porous and interconnected flower-like structure with microporous and nano-porous channels.Microscopically,nickel nanoparticles are coated in carbon matrix.The good size and quantity ratio between nickel nanoparticles monomer with an average particle size of 8.0 nm and aggregates with an average particle size of more than 100 nm produces coupling effect,causing strong dielectric loss and magnetic loss,and achieving the improvement of impedance matching and optimization of attenuation constant.For example,the effective absorption bandwidth of the representative sample is 4.24 GHz at 2.9 mm,and the best reflection loss is-41.91 d B at 3.4 mm.On the basis of the above research,in order to achieve the requirement of "thin thickness",the amount of nickel nanoparticles is controlled by increasing the concentration of precursor solution.With the increase of the loading amount of nickel nanoparticles,the morphology of the porous carbon skeleton remains stable at the macro level,and the quantity ratio at the micro level is further increased,improving the conductivity of magnetic biomass materials,further strengthening the dielectric loss performance and magnetic loss,resulting in the overall electromagnetic absorption capacity being improved.For example,the effective absorption bandwidth of the representative sample at 2.1 mm is 4.72 GHz,and the best reflection loss at 1.7mm is-56.07 d B.The morphology,structure and microwave absorption properties of the sample in low concentration strong acid,strong base and salt solution were investigated by static impregnation method.Due to the dual effects of chemical corrosion and electrochemical corrosion,the flower structure of biomass carbon interconnection in strong acid solution is seriously damaged,and the maximum reflection loss at 3.4mm is only-2.31 d B.Electrochemical corrosion occurs in strong alkali solution and salt solution.The salt solution has the weakest corrosion effect on magnetic biomass carbon material.The maximum reflection loss of the sample at 2.0mm is-13.21 d B,followed by strong alkali solution,and the maximum reflection loss at 2.7mm is-8.35 d B.That is,magnetic biomass carbon material has excellent corrosion resistance to salt solution,and certain corrosion resistance to strong alkali solution,and the strong acid solution is seriously damaged.